diff --git a/Cargo.lock b/Cargo.lock
index e6fe324..1e467f2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2925,6 +2925,7 @@ name = "mvp-system"
 version = "0.1.0"
 dependencies = [
  "libc",
+ "serde_json",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index c9e8b58..5d7a08c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -59,9 +59,6 @@ proptest = "1"
 proptest-state-machine = "0.3"
 mvp-system = { path = "crates/mvp-system" }
 
-[[test]]
-name = "arena_manager_guarantees"
-path = "tests/mvp_system/arena_manager_guarantees.rs"
 
 [[bench]]
 name = "runtime_benchmarks"
diff --git a/crates/mvp-system/Cargo.toml b/crates/mvp-system/Cargo.toml
index 4b770e2..dec66a4 100644
--- a/crates/mvp-system/Cargo.toml
+++ b/crates/mvp-system/Cargo.toml
@@ -4,5 +4,9 @@ version = "0.1.0"
 edition = "2024"
 publish = false
 
+
+[dependencies]
+serde_json = "1"
 [target.'cfg(target_os = "linux")'.dependencies]
 libc = "0.2"
+
diff --git a/crates/mvp-system/src/arena_manager.rs b/crates/mvp-system/src/arena_manager.rs
new file mode 100644
index 0000000..ff9ceec
--- /dev/null
+++ b/crates/mvp-system/src/arena_manager.rs
@@ -0,0 +1,548 @@
+use std::collections::{BTreeMap, VecDeque};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct LeaseRequestId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ArenaConfig {
+    pub node_id: NodeId,
+    pub reservation_ceiling: u64,
+    pub base_alignment: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingSpec {
+    pub header_bytes: u64,
+    pub data_bytes: u64,
+    pub alignment: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct LeaseRing {
+    pub request_id: LeaseRequestId,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum LayoutPointer {
+    NoProcessPointer,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingLayout {
+    pub start_offset: u64,
+    pub header_offset: u64,
+    pub data_offset: u64,
+    pub end_offset: u64,
+    pub data_bytes: u64,
+    pub alignment: u64,
+    pub pointer: LayoutPointer,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingLease {
+    pub request_id: LeaseRequestId,
+    pub ring_id: RingId,
+    pub node_id: NodeId,
+    pub layout: RingLayout,
+    pub requested_alignment: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct QuiescenceProof {
+    verified: bool,
+}
+
+impl QuiescenceProof {
+    pub fn verified() -> Self {
+        Self { verified: true }
+    }
+
+    pub fn missing() -> Self {
+        Self { verified: false }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ArenaRequest {
+    LeaseRing(LeaseRing),
+    CancelLease {
+        request_id: LeaseRequestId,
+    },
+    ReleaseRing {
+        ring_id: RingId,
+        proof: QuiescenceProof,
+    },
+    Shutdown,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ArenaFault {
+    InvalidReservationCeiling,
+    InvalidBaseAlignment,
+    BackingUnavailable,
+    UnsupportedPlatform,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingLeaseRejection {
+    CannotFitWithinCeiling,
+    ArenaShuttingDown,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingReleaseRejection {
+    MissingQuiescenceProof,
+    UnknownRingId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ArenaEvent {
+    RingLeased {
+        lease: RingLease,
+    },
+    RingLeaseQueued {
+        request_id: LeaseRequestId,
+    },
+    RingLeaseRejected {
+        request_id: LeaseRequestId,
+        reason: RingLeaseRejection,
+    },
+    RingReleased {
+        ring_id: RingId,
+        start_offset: u64,
+        end_offset: u64,
+    },
+    RingReleaseRejected {
+        ring_id: RingId,
+        reason: RingReleaseRejection,
+    },
+    CancelledFreshLeaseReleased {
+        request_id: LeaseRequestId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ArenaCommand {
+    InstallWorkerOrPumpState {
+        request_id: LeaseRequestId,
+        ring_id: RingId,
+        layout: RingLayout,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum ArenaState {
+    Ready,
+    ShuttingDown,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+struct FreeRange {
+    start: u64,
+    end: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+struct QueuedLease {
+    request: LeaseRing,
+    cancelled: bool,
+}
+
+pub struct ArenaManager {
+    config: ArenaConfig,
+    _backing: ArenaBacking,
+    state: ArenaState,
+    next_ring_id: u64,
+    free_ranges: Vec<FreeRange>,
+    pending: VecDeque<QueuedLease>,
+    live_order: Vec<RingLease>,
+    live_index: BTreeMap<RingId, usize>,
+}
+
+impl ArenaManager {
+    pub fn boot(config: ArenaConfig) -> Result<Self, ArenaFault> {
+        let backing = ArenaBacking::create(&config)?;
+        Ok(Self {
+            free_ranges: vec![FreeRange {
+                start: 0,
+                end: config.reservation_ceiling,
+            }],
+            config,
+            _backing: backing,
+            state: ArenaState::Ready,
+            next_ring_id: 1,
+            pending: VecDeque::new(),
+            live_order: Vec::new(),
+            live_index: BTreeMap::new(),
+        })
+    }
+
+    fn request(&mut self, request: ArenaRequest) -> Vec<ArenaEvent> {
+        match request {
+            ArenaRequest::LeaseRing(request) => self.lease_ring(request),
+            ArenaRequest::CancelLease { request_id } => {
+                self.cancel_lease(request_id);
+                Vec::new()
+            }
+            ArenaRequest::ReleaseRing { ring_id, proof } => self.release_ring(ring_id, proof),
+            ArenaRequest::Shutdown => self.shutdown(),
+        }
+    }
+
+    fn live_leases(&self) -> &[RingLease] {
+        &self.live_order
+    }
+
+    fn lookup_lease(&self, ring_id: RingId) -> Option<&RingLease> {
+        self.live_index
+            .get(&ring_id)
+            .and_then(|index| self.live_order.get(*index))
+    }
+
+    fn lease_ring(&mut self, request: LeaseRing) -> Vec<ArenaEvent> {
+        if self.state == ArenaState::ShuttingDown {
+            return vec![ArenaEvent::RingLeaseRejected {
+                request_id: request.request_id,
+                reason: RingLeaseRejection::ArenaShuttingDown,
+            }];
+        }
+
+        if self.request_layout_at(&request.ring_spec, 0).is_none() {
+            return vec![ArenaEvent::RingLeaseRejected {
+                request_id: request.request_id,
+                reason: RingLeaseRejection::CannotFitWithinCeiling,
+            }];
+        }
+
+        if self.pending.is_empty() {
+            if let Some(lease) = self.try_allocate(&request) {
+                return vec![ArenaEvent::RingLeased { lease }];
+            }
+        }
+
+        let request_id = request.request_id;
+        self.pending.push_back(QueuedLease {
+            request,
+            cancelled: false,
+        });
+        vec![ArenaEvent::RingLeaseQueued { request_id }]
+    }
+
+    fn cancel_lease(&mut self, request_id: LeaseRequestId) {
+        for pending in &mut self.pending {
+            if pending.request.request_id == request_id {
+                pending.cancelled = true;
+            }
+        }
+    }
+
+    fn release_ring(&mut self, ring_id: RingId, proof: QuiescenceProof) -> Vec<ArenaEvent> {
+        let Some(index) = self.live_index.get(&ring_id).copied() else {
+            return vec![ArenaEvent::RingReleaseRejected {
+                ring_id,
+                reason: RingReleaseRejection::UnknownRingId,
+            }];
+        };
+
+        if !proof.verified {
+            return vec![ArenaEvent::RingReleaseRejected {
+                ring_id,
+                reason: RingReleaseRejection::MissingQuiescenceProof,
+            }];
+        }
+
+        let lease = self.live_order.remove(index);
+        self.rebuild_live_index();
+        self.insert_free_range(FreeRange {
+            start: lease.layout.start_offset,
+            end: lease.layout.end_offset,
+        });
+
+        let mut events = vec![ArenaEvent::RingReleased {
+            ring_id,
+            start_offset: lease.layout.start_offset,
+            end_offset: lease.layout.end_offset,
+        }];
+        if self.state == ArenaState::Ready {
+            self.retry_pending_leases(&mut events);
+        }
+        events
+    }
+
+    fn shutdown(&mut self) -> Vec<ArenaEvent> {
+        self.state = ArenaState::ShuttingDown;
+        let mut events = Vec::new();
+        while let Some(pending) = self.pending.pop_front() {
+            if pending.cancelled {
+                events.push(ArenaEvent::CancelledFreshLeaseReleased {
+                    request_id: pending.request.request_id,
+                });
+            } else {
+                events.push(ArenaEvent::RingLeaseRejected {
+                    request_id: pending.request.request_id,
+                    reason: RingLeaseRejection::ArenaShuttingDown,
+                });
+            }
+        }
+        events
+    }
+
+    fn retry_pending_leases(&mut self, events: &mut Vec<ArenaEvent>) {
+        while let Some(pending) = self.pending.pop_front() {
+            if pending.cancelled {
+                events.push(ArenaEvent::CancelledFreshLeaseReleased {
+                    request_id: pending.request.request_id,
+                });
+                continue;
+            }
+
+            if let Some(lease) = self.try_allocate(&pending.request) {
+                events.push(ArenaEvent::RingLeased { lease });
+                continue;
+            }
+
+            self.pending.push_front(pending);
+            break;
+        }
+    }
+
+    fn try_allocate(&mut self, request: &LeaseRing) -> Option<RingLease> {
+        for index in 0..self.free_ranges.len() {
+            let range = self.free_ranges[index];
+            let Some(layout) = self.request_layout_at(&request.ring_spec, range.start) else {
+                continue;
+            };
+            if layout.end_offset > range.end {
+                continue;
+            }
+
+            self.free_ranges.remove(index);
+            let mut insert_index = index;
+            if range.start < layout.start_offset {
+                self.free_ranges.insert(
+                    insert_index,
+                    FreeRange {
+                        start: range.start,
+                        end: layout.start_offset,
+                    },
+                );
+                insert_index += 1;
+            }
+            if layout.end_offset < range.end {
+                self.free_ranges.insert(
+                    insert_index,
+                    FreeRange {
+                        start: layout.end_offset,
+                        end: range.end,
+                    },
+                );
+            }
+
+            let ring_id = RingId(self.next_ring_id);
+            self.next_ring_id = self.next_ring_id.checked_add(1)?;
+            let lease = RingLease {
+                request_id: request.request_id,
+                ring_id,
+                node_id: self.config.node_id,
+                layout,
+                requested_alignment: request.ring_spec.alignment,
+            };
+            self.live_index.insert(ring_id, self.live_order.len());
+            self.live_order.push(lease.clone());
+            return Some(lease);
+        }
+        None
+    }
+
+    fn request_layout_at(&self, spec: &RingSpec, range_start: u64) -> Option<RingLayout> {
+        let alignment = lcm(self.config.base_alignment, spec.alignment)?;
+        let start_offset = align_up(range_start, alignment)?;
+        let header_offset = start_offset;
+        let after_header = header_offset.checked_add(spec.header_bytes)?;
+        let data_offset = align_up(after_header, alignment)?;
+        let end_offset = data_offset.checked_add(spec.data_bytes)?;
+        if end_offset > self.config.reservation_ceiling {
+            return None;
+        }
+        Some(RingLayout {
+            start_offset,
+            header_offset,
+            data_offset,
+            end_offset,
+            data_bytes: spec.data_bytes,
+            alignment,
+            pointer: LayoutPointer::NoProcessPointer,
+        })
+    }
+
+    fn insert_free_range(&mut self, range: FreeRange) {
+        self.free_ranges.push(range);
+        self.free_ranges.sort_by_key(|range| range.start);
+
+        let mut coalesced: Vec<FreeRange> = Vec::with_capacity(self.free_ranges.len());
+        for range in self.free_ranges.drain(..) {
+            if range.start == range.end {
+                continue;
+            }
+            if let Some(last) = coalesced.last_mut() {
+                if range.start <= last.end {
+                    last.end = last.end.max(range.end);
+                    continue;
+                }
+            }
+            coalesced.push(range);
+        }
+        self.free_ranges = coalesced;
+    }
+
+    fn rebuild_live_index(&mut self) {
+        self.live_index.clear();
+        for (index, lease) in self.live_order.iter().enumerate() {
+            self.live_index.insert(lease.ring_id, index);
+        }
+    }
+}
+
+pub struct ArenaManagerHarness {
+    manager: ArenaManager,
+    events: Vec<ArenaEvent>,
+    commands: Vec<ArenaCommand>,
+}
+
+impl ArenaManagerHarness {
+    pub fn boot(config: ArenaConfig) -> Result<Self, ArenaFault> {
+        Ok(Self {
+            manager: ArenaManager::boot(config)?,
+            events: Vec::new(),
+            commands: Vec::new(),
+        })
+    }
+
+    pub fn request(&mut self, request: ArenaRequest) {
+        self.events.extend(self.manager.request(request));
+    }
+
+    pub fn events(&self) -> &[ArenaEvent] {
+        &self.events
+    }
+
+    pub fn commands(&self) -> &[ArenaCommand] {
+        &self.commands
+    }
+
+    pub fn live_leases(&self) -> &[RingLease] {
+        self.manager.live_leases()
+    }
+
+    pub fn lookup_lease(&self, ring_id: RingId) -> Option<&RingLease> {
+        self.manager.lookup_lease(ring_id)
+    }
+}
+
+fn align_up(value: u64, alignment: u64) -> Option<u64> {
+    if alignment == 0 {
+        return None;
+    }
+    let remainder = value % alignment;
+    if remainder == 0 {
+        Some(value)
+    } else {
+        value.checked_add(alignment - remainder)
+    }
+}
+
+fn lcm(left: u64, right: u64) -> Option<u64> {
+    if left == 0 || right == 0 {
+        return None;
+    }
+    let gcd = gcd(left, right);
+    (left / gcd).checked_mul(right)
+}
+
+fn gcd(mut left: u64, mut right: u64) -> u64 {
+    while right != 0 {
+        let remainder = left % right;
+        left = right;
+        right = remainder;
+    }
+    left
+}
+
+#[cfg(target_os = "linux")]
+struct ArenaBacking {
+    len: usize,
+    ptr: *mut libc::c_void,
+    _fd: std::os::fd::OwnedFd,
+}
+
+#[cfg(target_os = "linux")]
+impl ArenaBacking {
+    fn create(config: &ArenaConfig) -> Result<Self, ArenaFault> {
+        if config.reservation_ceiling == 0 {
+            return Err(ArenaFault::InvalidReservationCeiling);
+        }
+        if config.base_alignment == 0 {
+            return Err(ArenaFault::InvalidBaseAlignment);
+        }
+
+        let len = usize::try_from(config.reservation_ceiling)
+            .map_err(|_| ArenaFault::InvalidReservationCeiling)?;
+
+        let fd = unsafe {
+            let name = b"mvp-system-arena\0";
+            libc::memfd_create(name.as_ptr().cast(), libc::MFD_CLOEXEC)
+        };
+        if fd < 0 {
+            return Err(ArenaFault::BackingUnavailable);
+        }
+
+        let fd = unsafe { <std::os::fd::OwnedFd as std::os::fd::FromRawFd>::from_raw_fd(fd) };
+        let truncate_result =
+            unsafe { libc::ftruncate(std::os::fd::AsRawFd::as_raw_fd(&fd), len as libc::off_t) };
+        if truncate_result != 0 {
+            return Err(ArenaFault::BackingUnavailable);
+        }
+
+        let ptr = unsafe {
+            libc::mmap(
+                std::ptr::null_mut(),
+                len,
+                libc::PROT_READ | libc::PROT_WRITE,
+                libc::MAP_SHARED,
+                std::os::fd::AsRawFd::as_raw_fd(&fd),
+                0,
+            )
+        };
+        if ptr == libc::MAP_FAILED {
+            return Err(ArenaFault::BackingUnavailable);
+        }
+
+        Ok(Self { len, ptr, _fd: fd })
+    }
+}
+
+#[cfg(target_os = "linux")]
+impl Drop for ArenaBacking {
+    fn drop(&mut self) {
+        unsafe {
+            libc::munmap(self.ptr, self.len);
+        }
+    }
+}
+
+#[cfg(not(target_os = "linux"))]
+struct ArenaBacking;
+
+#[cfg(not(target_os = "linux"))]
+impl ArenaBacking {
+    fn create(_config: &ArenaConfig) -> Result<Self, ArenaFault> {
+        Err(ArenaFault::UnsupportedPlatform)
+    }
+}
diff --git a/crates/mvp-system/src/device_bridge.rs b/crates/mvp-system/src/device_bridge.rs
new file mode 100644
index 0000000..6569b87
--- /dev/null
+++ b/crates/mvp-system/src/device_bridge.rs
@@ -0,0 +1,633 @@
+use std::collections::{BTreeMap, BTreeSet};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct CopyEvent(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct DeviceHandle {
+    pub generation: WorkerGeneration,
+    pub id: u64,
+}
+
+impl DeviceHandle {
+    pub const fn new(generation: WorkerGeneration, id: u64) -> Self {
+        Self { generation, id }
+    }
+}
+
+pub type DeviceAllocation = DeviceHandle;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DType {
+    U32,
+    F16,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Shape {
+    Vector,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub max_extent: u64,
+    pub alignment: u64,
+    pub dtype: DType,
+    pub shape: Shape,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct TensorViewSpec {
+    pub dtype: DType,
+    pub shape: Shape,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct TensorView {
+    pub handle: DeviceHandle,
+    pub dtype: DType,
+    pub shape: Shape,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct HostRange {
+    pub offset: u64,
+    pub len: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceRange {
+    pub handle: DeviceHandle,
+    pub offset: u64,
+    pub len: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CopyMode {
+    Sync,
+    Async,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DeviceError {
+    AllocationFailed,
+    InvalidExtent,
+    InvalidAlignment,
+    InvalidRange,
+    UnknownDeviceHandle,
+    OldGenerationHandle,
+    DeviceCopyFailed,
+    InvalidViewDType,
+    InvalidTensorView,
+    AllocationStillInUse,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DeviceEvent {
+    CopyCompleted {
+        copy: CopyEvent,
+    },
+    ComputeStarted {
+        handle: DeviceHandle,
+        step_id: StepId,
+    },
+    ComputeCompleted {
+        handle: DeviceHandle,
+        step_id: StepId,
+    },
+    WorkerRestarted {
+        generation: WorkerGeneration,
+    },
+}
+
+pub trait DeviceBridgeBackend {
+    fn alloc_device(
+        &mut self,
+        allocation: DeviceAllocation,
+        spec: ObjectSpec,
+        extent: u64,
+    ) -> Result<(), DeviceError>;
+
+    fn free_device(&mut self, allocation: DeviceAllocation) -> Result<(), DeviceError>;
+
+    fn host_to_device(
+        &mut self,
+        host: HostRange,
+        device: DeviceRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    ) -> Result<(), DeviceError>;
+
+    fn device_to_host(
+        &mut self,
+        device: DeviceRange,
+        host: HostRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    ) -> Result<(), DeviceError>;
+
+    fn wrap_for_tinygrad(
+        &mut self,
+        allocation: DeviceAllocation,
+        view: TensorViewSpec,
+    ) -> Result<TensorView, DeviceError>;
+}
+
+pub struct DeviceBridge<B> {
+    current_generation: WorkerGeneration,
+    next_handle_id: u64,
+    next_copy_id: u64,
+    allocations: BTreeMap<DeviceHandle, AllocationRecord>,
+    copies: BTreeMap<CopyEvent, CopyRecord>,
+    backend: B,
+}
+
+impl<B: DeviceBridgeBackend> DeviceBridge<B> {
+    pub fn new(current_generation: WorkerGeneration, backend: B) -> Self {
+        Self {
+            current_generation,
+            next_handle_id: 1,
+            next_copy_id: 1,
+            allocations: BTreeMap::new(),
+            copies: BTreeMap::new(),
+            backend,
+        }
+    }
+
+    pub fn alloc_device(
+        &mut self,
+        spec: ObjectSpec,
+        extent: u64,
+    ) -> Result<DeviceAllocation, DeviceError> {
+        validate_object_spec(spec, extent)?;
+
+        let allocation = DeviceHandle::new(self.current_generation, self.next_handle_id);
+        self.next_handle_id += 1;
+        self.backend.alloc_device(allocation, spec, extent)?;
+        self.allocations.insert(
+            allocation,
+            AllocationRecord {
+                spec,
+                extent,
+                active_copies: BTreeSet::new(),
+                active_steps: BTreeSet::new(),
+            },
+        );
+        Ok(allocation)
+    }
+
+    pub fn free_device(&mut self, allocation: DeviceAllocation) -> Result<(), DeviceError> {
+        self.validate_generation(allocation)?;
+        let record = self
+            .allocations
+            .get(&allocation)
+            .ok_or(DeviceError::UnknownDeviceHandle)?;
+        if !record.active_copies.is_empty() || !record.active_steps.is_empty() {
+            return Err(DeviceError::AllocationStillInUse);
+        }
+
+        self.backend.free_device(allocation)?;
+        self.allocations.remove(&allocation);
+        Ok(())
+    }
+
+    pub fn host_to_device(
+        &mut self,
+        host: HostRange,
+        device: DeviceRange,
+        mode: CopyMode,
+    ) -> Result<CopyEvent, DeviceError> {
+        self.validate_device_range(device)?;
+        validate_equal_copy_len(host.len, device.len)?;
+
+        let copy = self.next_copy_event();
+        self.backend.host_to_device(host, device, copy, mode)?;
+        self.record_copy(copy, device.handle, CopyDirection::HostToDevice, mode);
+        Ok(copy)
+    }
+
+    pub fn device_to_host(
+        &mut self,
+        device: DeviceRange,
+        host: HostRange,
+        mode: CopyMode,
+    ) -> Result<CopyEvent, DeviceError> {
+        self.validate_device_range(device)?;
+        validate_equal_copy_len(device.len, host.len)?;
+
+        let copy = self.next_copy_event();
+        self.backend.device_to_host(device, host, copy, mode)?;
+        self.record_copy(copy, device.handle, CopyDirection::DeviceToHost, mode);
+        Ok(copy)
+    }
+
+    pub fn wrap_for_tinygrad(
+        &mut self,
+        allocation: DeviceAllocation,
+        view: TensorViewSpec,
+    ) -> Result<TensorView, DeviceError> {
+        let record = self.allocation_record(allocation)?;
+        if view.dtype != record.spec.dtype {
+            return Err(DeviceError::InvalidViewDType);
+        }
+        if view.shape != record.spec.shape {
+            return Err(DeviceError::InvalidTensorView);
+        }
+
+        self.backend.wrap_for_tinygrad(allocation, view)
+    }
+
+    pub fn observe(&mut self, event: DeviceEvent) {
+        match event {
+            DeviceEvent::CopyCompleted { copy } => self.complete_copy(copy),
+            DeviceEvent::ComputeStarted { handle, step_id } => {
+                if let Some(record) = self.current_allocation_record_mut(handle) {
+                    record.active_steps.insert(step_id);
+                }
+            }
+            DeviceEvent::ComputeCompleted { handle, step_id } => {
+                if let Some(record) = self.current_allocation_record_mut(handle) {
+                    record.active_steps.remove(&step_id);
+                }
+            }
+            DeviceEvent::WorkerRestarted { generation } => {
+                self.current_generation = generation;
+                self.next_handle_id = 1;
+                self.next_copy_id = 1;
+                self.allocations.clear();
+                self.copies.clear();
+            }
+        }
+    }
+
+    pub fn safe_to_release_host(&self, copy: CopyEvent) -> bool {
+        self.copies
+            .get(&copy)
+            .map(|record| record.direction == CopyDirection::HostToDevice && record.completed)
+            .unwrap_or(false)
+    }
+
+    pub fn host_bytes_valid(&self, copy: CopyEvent) -> bool {
+        self.copies
+            .get(&copy)
+            .map(|record| record.direction == CopyDirection::DeviceToHost && record.completed)
+            .unwrap_or(false)
+    }
+
+    pub fn copy_event_complete(&self, copy: CopyEvent) -> bool {
+        self.copies
+            .get(&copy)
+            .map(|record| record.completed)
+            .unwrap_or(false)
+    }
+
+    pub fn backend(&self) -> &B {
+        &self.backend
+    }
+
+    pub fn backend_mut(&mut self) -> &mut B {
+        &mut self.backend
+    }
+
+    fn allocation_record(
+        &self,
+        allocation: DeviceAllocation,
+    ) -> Result<&AllocationRecord, DeviceError> {
+        self.validate_generation(allocation)?;
+        self.allocations
+            .get(&allocation)
+            .ok_or(DeviceError::UnknownDeviceHandle)
+    }
+
+    fn current_allocation_record_mut(
+        &mut self,
+        allocation: DeviceAllocation,
+    ) -> Option<&mut AllocationRecord> {
+        if allocation.generation != self.current_generation {
+            return None;
+        }
+        self.allocations.get_mut(&allocation)
+    }
+
+    fn validate_generation(&self, allocation: DeviceAllocation) -> Result<(), DeviceError> {
+        if allocation.generation != self.current_generation {
+            return Err(DeviceError::OldGenerationHandle);
+        }
+        Ok(())
+    }
+
+    fn validate_device_range(&self, device: DeviceRange) -> Result<(), DeviceError> {
+        let record = self.allocation_record(device.handle)?;
+        let end = device
+            .offset
+            .checked_add(device.len)
+            .ok_or(DeviceError::InvalidRange)?;
+        if end > record.extent {
+            return Err(DeviceError::InvalidRange);
+        }
+        Ok(())
+    }
+
+    fn next_copy_event(&mut self) -> CopyEvent {
+        let copy = CopyEvent(self.next_copy_id);
+        self.next_copy_id += 1;
+        copy
+    }
+
+    fn record_copy(
+        &mut self,
+        copy: CopyEvent,
+        allocation: DeviceAllocation,
+        direction: CopyDirection,
+        mode: CopyMode,
+    ) {
+        let completed = mode == CopyMode::Sync;
+        self.copies.insert(
+            copy,
+            CopyRecord {
+                allocation,
+                direction,
+                completed,
+            },
+        );
+        if !completed {
+            if let Some(record) = self.allocations.get_mut(&allocation) {
+                record.active_copies.insert(copy);
+            }
+        }
+    }
+
+    fn complete_copy(&mut self, copy: CopyEvent) {
+        let Some(record) = self.copies.get_mut(&copy) else {
+            return;
+        };
+        record.completed = true;
+        let allocation = record.allocation;
+        if let Some(allocation_record) = self.allocations.get_mut(&allocation) {
+            allocation_record.active_copies.remove(&copy);
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+struct AllocationRecord {
+    spec: ObjectSpec,
+    extent: u64,
+    active_copies: BTreeSet<CopyEvent>,
+    active_steps: BTreeSet<StepId>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum CopyDirection {
+    HostToDevice,
+    DeviceToHost,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+struct CopyRecord {
+    allocation: DeviceAllocation,
+    direction: CopyDirection,
+    completed: bool,
+}
+
+fn validate_object_spec(spec: ObjectSpec, extent: u64) -> Result<(), DeviceError> {
+    if spec.alignment == 0 {
+        return Err(DeviceError::InvalidAlignment);
+    }
+    if extent > spec.max_extent || extent % spec.alignment != 0 {
+        return Err(DeviceError::InvalidExtent);
+    }
+    Ok(())
+}
+
+fn validate_equal_copy_len(left: u64, right: u64) -> Result<(), DeviceError> {
+    if left != right {
+        return Err(DeviceError::InvalidRange);
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum BackendFailure {
+    AllocationFailed,
+    CopyFailed,
+    InvalidView,
+}
+
+#[cfg(test)]
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum BackendCall {
+    Alloc {
+        allocation: DeviceAllocation,
+        spec: ObjectSpec,
+        extent: u64,
+    },
+    Free {
+        freed: DeviceAllocation,
+    },
+    HostToDevice {
+        host: HostRange,
+        device: DeviceRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    },
+    DeviceToHost {
+        device: DeviceRange,
+        host: HostRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    },
+    WrapForTinygrad {
+        allocation: DeviceAllocation,
+        view: TensorViewSpec,
+    },
+}
+
+#[cfg(test)]
+#[derive(Default)]
+pub struct MockDeviceBackend {
+    calls: Vec<BackendCall>,
+    next_failure: Option<BackendFailure>,
+}
+
+#[cfg(test)]
+impl MockDeviceBackend {
+    pub fn inject_failure(&mut self, failure: BackendFailure) {
+        self.next_failure = Some(failure);
+    }
+
+    pub fn calls(&self) -> &[BackendCall] {
+        &self.calls
+    }
+
+    fn take_failure(&mut self, failure: BackendFailure) -> bool {
+        if self.next_failure == Some(failure) {
+            self.next_failure = None;
+            return true;
+        }
+        false
+    }
+}
+
+#[cfg(test)]
+impl DeviceBridgeBackend for MockDeviceBackend {
+    fn alloc_device(
+        &mut self,
+        allocation: DeviceAllocation,
+        spec: ObjectSpec,
+        extent: u64,
+    ) -> Result<(), DeviceError> {
+        self.calls.push(BackendCall::Alloc {
+            allocation,
+            spec,
+            extent,
+        });
+        if self.take_failure(BackendFailure::AllocationFailed) {
+            return Err(DeviceError::AllocationFailed);
+        }
+        Ok(())
+    }
+
+    fn free_device(&mut self, allocation: DeviceAllocation) -> Result<(), DeviceError> {
+        self.calls.push(BackendCall::Free { freed: allocation });
+        Ok(())
+    }
+
+    fn host_to_device(
+        &mut self,
+        host: HostRange,
+        device: DeviceRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    ) -> Result<(), DeviceError> {
+        self.calls.push(BackendCall::HostToDevice {
+            host,
+            device,
+            copy,
+            mode,
+        });
+        if self.take_failure(BackendFailure::CopyFailed) {
+            return Err(DeviceError::DeviceCopyFailed);
+        }
+        Ok(())
+    }
+
+    fn device_to_host(
+        &mut self,
+        device: DeviceRange,
+        host: HostRange,
+        copy: CopyEvent,
+        mode: CopyMode,
+    ) -> Result<(), DeviceError> {
+        self.calls.push(BackendCall::DeviceToHost {
+            device,
+            host,
+            copy,
+            mode,
+        });
+        if self.take_failure(BackendFailure::CopyFailed) {
+            return Err(DeviceError::DeviceCopyFailed);
+        }
+        Ok(())
+    }
+
+    fn wrap_for_tinygrad(
+        &mut self,
+        allocation: DeviceAllocation,
+        view: TensorViewSpec,
+    ) -> Result<TensorView, DeviceError> {
+        self.calls
+            .push(BackendCall::WrapForTinygrad { allocation, view });
+        if self.take_failure(BackendFailure::InvalidView) {
+            return Err(DeviceError::InvalidTensorView);
+        }
+        Ok(TensorView {
+            handle: allocation,
+            dtype: view.dtype,
+            shape: view.shape,
+        })
+    }
+}
+
+#[cfg(test)]
+pub struct DeviceBridgeHarness {
+    bridge: DeviceBridge<MockDeviceBackend>,
+}
+
+#[cfg(test)]
+impl DeviceBridgeHarness {
+    pub fn new(generation: WorkerGeneration) -> Self {
+        Self {
+            bridge: DeviceBridge::new(generation, MockDeviceBackend::default()),
+        }
+    }
+
+    pub fn alloc_device(
+        &mut self,
+        spec: ObjectSpec,
+        extent: u64,
+    ) -> Result<DeviceHandle, DeviceError> {
+        self.bridge.alloc_device(spec, extent)
+    }
+
+    pub fn free_device(&mut self, allocation: DeviceAllocation) -> Result<(), DeviceError> {
+        self.bridge.free_device(allocation)
+    }
+
+    pub fn host_to_device(
+        &mut self,
+        host: HostRange,
+        device: DeviceRange,
+        mode: CopyMode,
+    ) -> Result<CopyEvent, DeviceError> {
+        self.bridge.host_to_device(host, device, mode)
+    }
+
+    pub fn device_to_host(
+        &mut self,
+        device: DeviceRange,
+        host: HostRange,
+        mode: CopyMode,
+    ) -> Result<CopyEvent, DeviceError> {
+        self.bridge.device_to_host(device, host, mode)
+    }
+
+    pub fn wrap_for_tinygrad(
+        &mut self,
+        allocation: DeviceAllocation,
+        view: TensorViewSpec,
+    ) -> Result<TensorView, DeviceError> {
+        self.bridge.wrap_for_tinygrad(allocation, view)
+    }
+
+    pub fn observe(&mut self, event: DeviceEvent) {
+        self.bridge.observe(event);
+    }
+
+    pub fn safe_to_release_host(&self, copy: CopyEvent) -> bool {
+        self.bridge.safe_to_release_host(copy)
+    }
+
+    pub fn host_bytes_valid(&self, copy: CopyEvent) -> bool {
+        self.bridge.host_bytes_valid(copy)
+    }
+
+    pub fn copy_event_complete(&self, copy: CopyEvent) -> bool {
+        self.bridge.copy_event_complete(copy)
+    }
+
+    pub fn inject_backend_failure(&mut self, failure: BackendFailure) {
+        self.bridge.backend_mut().inject_failure(failure);
+    }
+
+    pub fn backend_calls(&self) -> &[BackendCall] {
+        self.bridge.backend().calls()
+    }
+}
diff --git a/crates/mvp-system/src/driver_pumps.rs b/crates/mvp-system/src/driver_pumps.rs
new file mode 100644
index 0000000..69346f4
--- /dev/null
+++ b/crates/mvp-system/src/driver_pumps.rs
@@ -0,0 +1,544 @@
+use std::collections::{BTreeMap, BTreeSet};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StreamId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Alpn(pub String);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct DriverConfig {
+    pub local_node_id: NodeId,
+    pub alpn: Alpn,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct EstablishSend {
+    pub edge_id: EdgeId,
+    pub peer_node_id: NodeId,
+    pub layout: RingLayout,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct EstablishRecv {
+    pub edge_id: EdgeId,
+    pub layout: RingLayout,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingDirection {
+    Egress,
+    Ingress,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingLayout {
+    pub ring_id: RingId,
+    pub byte_capacity: usize,
+    pub direction: RingDirection,
+}
+
+impl RingLayout {
+    pub fn test_egress() -> Self {
+        Self {
+            ring_id: RingId(1),
+            byte_capacity: 4096,
+            direction: RingDirection::Egress,
+        }
+    }
+
+    pub fn test_ingress() -> Self {
+        Self {
+            ring_id: RingId(2),
+            byte_capacity: 4096,
+            direction: RingDirection::Ingress,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum DriverEvent {
+    EstablishSend(EstablishSend),
+    EstablishRecv(EstablishRecv),
+    IncomingUniStream {
+        edge_id: EdgeId,
+        stream_id: StreamId,
+    },
+    RingReadable {
+        edge_id: EdgeId,
+    },
+    RingWritable {
+        edge_id: EdgeId,
+    },
+    EgressBytesCommitted {
+        edge_id: EdgeId,
+        bytes: Vec<u8>,
+    },
+    StreamBytesRead {
+        edge_id: EdgeId,
+        bytes: Vec<u8>,
+    },
+    WriteAllAccepted {
+        edge_id: EdgeId,
+        byte_count: usize,
+    },
+    NetworkStalled {
+        edge_id: EdgeId,
+    },
+    IngressRingFull {
+        edge_id: EdgeId,
+    },
+    ReadError {
+        edge_id: EdgeId,
+    },
+    WriteError {
+        edge_id: EdgeId,
+    },
+    StopEdge {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum DriverCommand {
+    OpenOrReuseConnection {
+        peer_node_id: NodeId,
+        alpn: Alpn,
+        local_node_id: NodeId,
+    },
+    OpenUniStream {
+        edge_id: EdgeId,
+        peer_node_id: NodeId,
+    },
+    SpawnSendPump {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    SpawnRecvPump {
+        edge_id: EdgeId,
+        ring_id: RingId,
+        stream_id: StreamId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ActorMessage {
+    PollStreamFuture { edge_id: EdgeId },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum DriverEventOut {
+    DriverEdgeReady {
+        edge_id: EdgeId,
+    },
+    StreamClosed {
+        edge_id: EdgeId,
+    },
+    StreamFault {
+        edge_id: EdgeId,
+        reason: StreamFaultReason,
+    },
+    PumpStopped {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    ObjectHeaderParsed {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StreamFaultReason {
+    ReadError,
+    WriteError,
+    ProtocolError,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WakeHint {
+    RingReadable { edge_id: EdgeId },
+    RingWritable { edge_id: EdgeId },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StreamWrite {
+    pub edge_id: EdgeId,
+    pub bytes: Vec<u8>,
+}
+
+pub fn encode_edge_preamble(edge_id: EdgeId) -> Vec<u8> {
+    edge_id.0.to_le_bytes().to_vec()
+}
+
+pub fn count_preamble_occurrences(bytes: &[u8], edge_id: EdgeId) -> usize {
+    let preamble = encode_edge_preamble(edge_id);
+    bytes
+        .windows(preamble.len())
+        .filter(|window| *window == preamble.as_slice())
+        .count()
+}
+
+pub fn fake_object_header_bytes() -> Vec<u8> {
+    b"OBJ\0fake-header".to_vec()
+}
+
+pub struct Driver {
+    state: DriverState,
+}
+
+impl Driver {
+    pub fn new(config: DriverConfig) -> Self {
+        Self {
+            state: DriverState::new(config),
+        }
+    }
+
+    pub fn observe(&mut self, event: DriverEvent) {
+        self.state.observe(event);
+    }
+
+    pub fn commands(&self) -> &[DriverCommand] {
+        &self.state.commands
+    }
+
+    pub fn events(&self) -> &[DriverEventOut] {
+        &self.state.events
+    }
+
+    pub fn wake_hints(&self) -> &[WakeHint] {
+        &self.state.wakes
+    }
+}
+
+#[derive(Debug)]
+struct DriverState {
+    config: DriverConfig,
+    connections: BTreeSet<(NodeId, Alpn)>,
+    sends: BTreeMap<EdgeId, SendPumpState>,
+    recv_specs: BTreeMap<EdgeId, EstablishRecv>,
+    pending_streams: BTreeMap<EdgeId, StreamId>,
+    recvs: BTreeMap<EdgeId, RecvPumpState>,
+    commands: Vec<DriverCommand>,
+    events: Vec<DriverEventOut>,
+    wakes: Vec<WakeHint>,
+    #[cfg(test)]
+    actor_messages: Vec<ActorMessage>,
+    stream_writes: Vec<StreamWrite>,
+    read_started: BTreeSet<StreamId>,
+}
+
+impl DriverState {
+    fn new(config: DriverConfig) -> Self {
+        Self {
+            config,
+            connections: BTreeSet::new(),
+            sends: BTreeMap::new(),
+            recv_specs: BTreeMap::new(),
+            pending_streams: BTreeMap::new(),
+            recvs: BTreeMap::new(),
+            commands: Vec::new(),
+            events: Vec::new(),
+            wakes: Vec::new(),
+            #[cfg(test)]
+            actor_messages: Vec::new(),
+            stream_writes: Vec::new(),
+            read_started: BTreeSet::new(),
+        }
+    }
+
+    fn observe(&mut self, event: DriverEvent) {
+        match event {
+            DriverEvent::EstablishSend(spec) => self.establish_send(spec),
+            DriverEvent::EstablishRecv(spec) => self.establish_recv(spec),
+            DriverEvent::IncomingUniStream { edge_id, stream_id } => {
+                self.incoming_uni_stream(edge_id, stream_id);
+            }
+            DriverEvent::RingReadable { edge_id } => self.flush_send_bytes(edge_id),
+            DriverEvent::RingWritable { edge_id } => self.resume_recv(edge_id),
+            DriverEvent::EgressBytesCommitted { edge_id, bytes } => {
+                if let Some(send) = self.sends.get_mut(&edge_id) {
+                    send.pending_bytes.extend(bytes);
+                }
+            }
+            DriverEvent::StreamBytesRead { edge_id, bytes } => {
+                self.copy_recv_bytes(edge_id, &bytes)
+            }
+            DriverEvent::WriteAllAccepted {
+                edge_id,
+                byte_count,
+            } => {
+                if let Some(send) = self.sends.get_mut(&edge_id) {
+                    send.consume_cursor += byte_count;
+                    send.network_stalled = false;
+                    self.wakes.push(WakeHint::RingWritable { edge_id });
+                }
+            }
+            DriverEvent::NetworkStalled { edge_id } => {
+                if let Some(send) = self.sends.get_mut(&edge_id) {
+                    send.network_stalled = true;
+                }
+            }
+            DriverEvent::IngressRingFull { edge_id } => {
+                if let Some(recv) = self.recvs.get_mut(&edge_id) {
+                    recv.reading = false;
+                }
+            }
+            DriverEvent::ReadError { edge_id } => {
+                self.events.push(DriverEventOut::StreamFault {
+                    edge_id,
+                    reason: StreamFaultReason::ReadError,
+                });
+            }
+            DriverEvent::WriteError { edge_id } => {
+                self.events.push(DriverEventOut::StreamFault {
+                    edge_id,
+                    reason: StreamFaultReason::WriteError,
+                });
+            }
+            DriverEvent::StopEdge { edge_id } => self.stop_edge(edge_id),
+        }
+    }
+
+    fn establish_send(&mut self, spec: EstablishSend) {
+        let connection_key = (spec.peer_node_id, self.config.alpn.clone());
+        self.connections.insert(connection_key);
+        self.commands.push(DriverCommand::OpenOrReuseConnection {
+            peer_node_id: spec.peer_node_id,
+            alpn: self.config.alpn.clone(),
+            local_node_id: self.config.local_node_id,
+        });
+
+        self.commands.push(DriverCommand::SpawnSendPump {
+            edge_id: spec.edge_id,
+            ring_id: spec.layout.ring_id,
+        });
+
+        let send = SendPumpState::new(spec.layout.ring_id);
+        self.commands.push(DriverCommand::OpenUniStream {
+            edge_id: spec.edge_id,
+            peer_node_id: spec.peer_node_id,
+        });
+        self.stream_writes.push(StreamWrite {
+            edge_id: spec.edge_id,
+            bytes: encode_edge_preamble(spec.edge_id),
+        });
+        self.sends.insert(spec.edge_id, send);
+        self.events.push(DriverEventOut::DriverEdgeReady {
+            edge_id: spec.edge_id,
+        });
+    }
+
+    fn establish_recv(&mut self, spec: EstablishRecv) {
+        let edge_id = spec.edge_id;
+        self.recv_specs.insert(edge_id, spec);
+        if let Some(stream_id) = self.pending_streams.remove(&edge_id) {
+            self.spawn_recv(edge_id, stream_id);
+        }
+    }
+
+    fn incoming_uni_stream(&mut self, edge_id: EdgeId, stream_id: StreamId) {
+        if self.recv_specs.contains_key(&edge_id) {
+            self.spawn_recv(edge_id, stream_id);
+        } else {
+            self.pending_streams.insert(edge_id, stream_id);
+        }
+    }
+
+    fn spawn_recv(&mut self, edge_id: EdgeId, stream_id: StreamId) {
+        let Some(spec) = self.recv_specs.get(&edge_id) else {
+            self.pending_streams.insert(edge_id, stream_id);
+            return;
+        };
+        let ring_id = spec.layout.ring_id;
+        self.commands.push(DriverCommand::SpawnRecvPump {
+            edge_id,
+            ring_id,
+            stream_id,
+        });
+        self.read_started.insert(stream_id);
+        self.recvs.insert(
+            edge_id,
+            RecvPumpState {
+                ring_id,
+                commit_cursor: 0,
+                reading: true,
+            },
+        );
+        self.events
+            .push(DriverEventOut::DriverEdgeReady { edge_id });
+    }
+
+    fn flush_send_bytes(&mut self, edge_id: EdgeId) {
+        let Some(send) = self.sends.get_mut(&edge_id) else {
+            return;
+        };
+        if send.network_stalled || send.pending_bytes.is_empty() {
+            return;
+        }
+
+        let bytes = std::mem::take(&mut send.pending_bytes);
+        self.stream_writes.push(StreamWrite { edge_id, bytes });
+    }
+
+    fn resume_recv(&mut self, edge_id: EdgeId) {
+        if let Some(recv) = self.recvs.get_mut(&edge_id) {
+            recv.reading = true;
+        }
+    }
+
+    fn copy_recv_bytes(&mut self, edge_id: EdgeId, bytes: &[u8]) {
+        let Some(recv) = self.recvs.get_mut(&edge_id) else {
+            return;
+        };
+        if !recv.reading {
+            return;
+        }
+        recv.commit_cursor += bytes.len();
+        self.wakes.push(WakeHint::RingReadable { edge_id });
+    }
+
+    fn stop_edge(&mut self, edge_id: EdgeId) {
+        let ring_id = self
+            .sends
+            .get(&edge_id)
+            .map(|send| send.ring_id)
+            .or_else(|| self.recvs.get(&edge_id).map(|recv| recv.ring_id))
+            .or_else(|| {
+                self.recv_specs
+                    .get(&edge_id)
+                    .map(|spec| spec.layout.ring_id)
+            })
+            .unwrap_or(RingId(0));
+
+        self.sends.remove(&edge_id);
+        self.recvs.remove(&edge_id);
+        self.recv_specs.remove(&edge_id);
+        self.pending_streams.remove(&edge_id);
+        self.events
+            .push(DriverEventOut::PumpStopped { edge_id, ring_id });
+    }
+}
+
+#[derive(Debug)]
+struct SendPumpState {
+    ring_id: RingId,
+    pending_bytes: Vec<u8>,
+    consume_cursor: usize,
+    network_stalled: bool,
+}
+
+impl SendPumpState {
+    fn new(ring_id: RingId) -> Self {
+        Self {
+            ring_id,
+            pending_bytes: Vec::new(),
+            consume_cursor: 0,
+            network_stalled: false,
+        }
+    }
+}
+
+#[derive(Debug)]
+struct RecvPumpState {
+    ring_id: RingId,
+    commit_cursor: usize,
+    reading: bool,
+}
+
+#[cfg(test)]
+pub struct CommandLog {
+    commands: Vec<DriverCommand>,
+}
+
+#[cfg(test)]
+impl CommandLog {
+    pub fn iter(&self) -> std::vec::IntoIter<DriverCommand> {
+        self.commands.clone().into_iter()
+    }
+}
+
+#[cfg(test)]
+pub struct DriverHarness {
+    driver: Driver,
+}
+
+#[cfg(test)]
+impl DriverHarness {
+    pub fn new(config: DriverConfig) -> Self {
+        Self {
+            driver: Driver::new(config),
+        }
+    }
+
+    pub fn observe(&mut self, event: DriverEvent) {
+        self.driver.observe(event);
+    }
+
+    pub fn commands(&self) -> CommandLog {
+        CommandLog {
+            commands: self.driver.state.commands.clone(),
+        }
+    }
+
+    pub fn events(&self) -> &[DriverEventOut] {
+        &self.driver.state.events
+    }
+
+    pub fn wake_hints(&self) -> &[WakeHint] {
+        &self.driver.state.wakes
+    }
+
+    pub fn actor_messages(&self) -> &[ActorMessage] {
+        &self.driver.state.actor_messages
+    }
+
+    pub fn stream_writes(&self, edge_id: EdgeId) -> Vec<StreamWrite> {
+        self.driver
+            .state
+            .stream_writes
+            .iter()
+            .filter(|write| write.edge_id == edge_id)
+            .cloned()
+            .collect()
+    }
+
+    pub fn stream_reads_started(&self, stream_id: StreamId) -> bool {
+        self.driver.state.read_started.contains(&stream_id)
+    }
+
+    pub fn is_reading_stream(&self, edge_id: EdgeId) -> bool {
+        self.driver
+            .state
+            .recvs
+            .get(&edge_id)
+            .map(|recv| recv.reading)
+            .unwrap_or(false)
+    }
+
+    pub fn ring_commit(&self, edge_id: EdgeId) -> usize {
+        self.driver
+            .state
+            .recvs
+            .get(&edge_id)
+            .map(|recv| recv.commit_cursor)
+            .unwrap_or(0)
+    }
+
+    pub fn ring_consume(&self, edge_id: EdgeId) -> usize {
+        self.driver
+            .state
+            .sends
+            .get(&edge_id)
+            .map(|send| send.consume_cursor)
+            .unwrap_or(0)
+    }
+}
diff --git a/crates/mvp-system/src/edge_establisher.rs b/crates/mvp-system/src/edge_establisher.rs
new file mode 100644
index 0000000..39090e2
--- /dev/null
+++ b/crates/mvp-system/src/edge_establisher.rs
@@ -0,0 +1,751 @@
+use std::collections::BTreeMap;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct LeaseRequestId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ActorAddress(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingDirection {
+    Egress,
+    Ingress,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ObjectKind {
+    Activation,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DType {
+    F16,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub kind: ObjectKind,
+    pub dtype: DType,
+    pub max_extent_bytes: u64,
+}
+
+impl ObjectSpec {
+    pub const fn test_activation() -> Self {
+        Self {
+            kind: ObjectKind::Activation,
+            dtype: DType::F16,
+            max_extent_bytes: 4096,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct RingSpec {
+    pub header_bytes: u64,
+    pub data_bytes: u64,
+    pub alignment: u64,
+}
+
+impl RingSpec {
+    pub const fn test_activation() -> Self {
+        Self {
+            header_bytes: 128,
+            data_bytes: 4096,
+            alignment: 64,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct RingLayout {
+    pub start_offset: u64,
+    pub header_offset: u64,
+    pub data_offset: u64,
+    pub end_offset: u64,
+    pub data_bytes: u64,
+    pub alignment: u64,
+}
+
+impl RingLayout {
+    pub const fn test_layout(start_offset: u64) -> Self {
+        Self {
+            start_offset,
+            header_offset: start_offset,
+            data_offset: start_offset + 128,
+            end_offset: start_offset + 128 + 4096,
+            data_bytes: 4096,
+            alignment: 64,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct QuiescenceProof {
+    verified: bool,
+}
+
+impl QuiescenceProof {
+    pub const fn verified() -> Self {
+        Self { verified: true }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProvisionTx {
+    pub run_id: RunId,
+    pub edge_id: EdgeId,
+    pub local_node_id: NodeId,
+    pub consumer_node_id: NodeId,
+    pub object_spec: ObjectSpec,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProvisionRx {
+    pub run_id: RunId,
+    pub edge_id: EdgeId,
+    pub local_node_id: NodeId,
+    pub object_spec: ObjectSpec,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingLeaseRejection {
+    CannotFit,
+    ArenaShuttingDown,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StreamFaultReason {
+    ReadError,
+    WriteError,
+    ProtocolError,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingFaultReason {
+    WorkerRejectedRing,
+    WorkerCrashed,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EdgeEvent {
+    ProvisionTx(ProvisionTx),
+    ProvisionRx(ProvisionRx),
+    RingLeased {
+        request_id: LeaseRequestId,
+        ring_id: RingId,
+        layout: RingLayout,
+    },
+    RingLeaseRejected {
+        request_id: LeaseRequestId,
+        reason: RingLeaseRejection,
+    },
+    RingInstalled {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    DriverEdgeReady {
+        edge_id: EdgeId,
+    },
+    StreamFault {
+        edge_id: EdgeId,
+        reason: StreamFaultReason,
+    },
+    RingFault {
+        edge_id: EdgeId,
+        ring_id: RingId,
+        reason: RingFaultReason,
+    },
+    StopEdge {
+        edge_id: EdgeId,
+    },
+    PumpStopped {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    RingQuiesced {
+        ring_id: RingId,
+    },
+    QuiescenceProven {
+        ring_id: RingId,
+    },
+    Stopped {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EdgeCommand {
+    LeaseRing {
+        request_id: LeaseRequestId,
+        edge_id: EdgeId,
+        direction: RingDirection,
+        ring_spec: RingSpec,
+    },
+    CancelQueuedLease {
+        request_id: LeaseRequestId,
+        edge_id: EdgeId,
+    },
+    InstallWorkerRing {
+        edge_id: EdgeId,
+        ring_id: RingId,
+        direction: RingDirection,
+        layout: RingLayout,
+        object_spec: ObjectSpec,
+        ring_spec: RingSpec,
+    },
+    UninstallWorkerRing {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    EstablishSend {
+        edge_id: EdgeId,
+        consumer_node_id: NodeId,
+        layout: RingLayout,
+    },
+    EstablishRecv {
+        edge_id: EdgeId,
+        layout: RingLayout,
+    },
+    StopPump {
+        edge_id: EdgeId,
+        ring_id: RingId,
+    },
+    ReleaseArenaLease {
+        ring_id: RingId,
+        proof: QuiescenceProof,
+    },
+    CopyHotPathBytes {
+        edge_id: EdgeId,
+        bytes: Vec<u8>,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EdgeFaultReason {
+    RingLeaseRejected(RingLeaseRejection),
+    RingFault(RingFaultReason),
+    StreamFault(StreamFaultReason),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EdgeLifecycleEvent {
+    EdgeReady {
+        edge_id: EdgeId,
+        local_edge_actor: ActorAddress,
+    },
+    EdgeFaulted {
+        edge_id: EdgeId,
+        reason: EdgeFaultReason,
+    },
+    EdgeStopped {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct LocalEdgeRecord {
+    pub edge_id: EdgeId,
+    pub direction: RingDirection,
+    pub state: EdgeProvisionState,
+    pub lease_request_id: Option<LeaseRequestId>,
+    pub ring_id: Option<RingId>,
+    pub peer_node_id: Option<NodeId>,
+    pub local_edge_actor: ActorAddress,
+    pub remote_actor_address: Option<ActorAddress>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EdgeProvisionState {
+    WaitingForLease,
+    WaitingForWorkerRing,
+    WaitingForDriver,
+    Ready,
+    Stopping,
+    Stopped,
+    Failed,
+}
+
+pub struct EdgeEstablisher {
+    state: EdgeEstablisherState,
+}
+
+impl EdgeEstablisher {
+    pub fn new(local_node_id: NodeId) -> Self {
+        Self {
+            state: EdgeEstablisherState::new(local_node_id),
+        }
+    }
+
+    pub fn observe(&mut self, event: EdgeEvent) {
+        self.state.observe(event);
+    }
+
+    pub fn commands(&self) -> &[EdgeCommand] {
+        &self.state.commands
+    }
+
+    pub fn events(&self) -> &[EdgeLifecycleEvent] {
+        &self.state.events
+    }
+
+    pub fn local_record(&self, edge_id: EdgeId) -> Option<LocalEdgeRecord> {
+        self.state.records.get(&edge_id).map(EdgeRecord::snapshot)
+    }
+}
+
+struct EdgeEstablisherState {
+    local_node_id: NodeId,
+    next_request_id: u64,
+    next_actor_id: u64,
+    records: BTreeMap<EdgeId, EdgeRecord>,
+    commands: Vec<EdgeCommand>,
+    events: Vec<EdgeLifecycleEvent>,
+}
+
+impl EdgeEstablisherState {
+    fn new(local_node_id: NodeId) -> Self {
+        Self {
+            local_node_id,
+            next_request_id: 1,
+            next_actor_id: 1,
+            records: BTreeMap::new(),
+            commands: Vec::new(),
+            events: Vec::new(),
+        }
+    }
+
+    fn observe(&mut self, event: EdgeEvent) {
+        match event {
+            EdgeEvent::ProvisionTx(provision) => self.provision_tx(provision),
+            EdgeEvent::ProvisionRx(provision) => self.provision_rx(provision),
+            EdgeEvent::RingLeased {
+                request_id,
+                ring_id,
+                layout,
+            } => self.ring_leased(request_id, ring_id, layout),
+            EdgeEvent::RingLeaseRejected { request_id, reason } => {
+                self.ring_lease_rejected(request_id, reason);
+            }
+            EdgeEvent::RingInstalled { edge_id, ring_id } => self.ring_installed(edge_id, ring_id),
+            EdgeEvent::DriverEdgeReady { edge_id } => self.driver_edge_ready(edge_id),
+            EdgeEvent::StreamFault { edge_id, reason } => {
+                self.fault_edge(edge_id, EdgeFaultReason::StreamFault(reason));
+            }
+            EdgeEvent::RingFault {
+                edge_id,
+                ring_id,
+                reason,
+            } => self.ring_fault(edge_id, ring_id, reason),
+            EdgeEvent::StopEdge { edge_id } => self.stop_edge(edge_id),
+            EdgeEvent::PumpStopped { edge_id, ring_id } => self.pump_stopped(edge_id, ring_id),
+            EdgeEvent::RingQuiesced { ring_id } | EdgeEvent::QuiescenceProven { ring_id } => {
+                self.release_after_quiescence(ring_id);
+            }
+            EdgeEvent::Stopped { edge_id } => self.mark_stopped(edge_id),
+        }
+    }
+
+    fn provision_tx(&mut self, provision: ProvisionTx) {
+        if provision.local_node_id != self.local_node_id {
+            return;
+        }
+
+        let request_id = self.next_request_id();
+        let actor = self.next_actor_address();
+        let edge_id = provision.edge_id;
+        let ring_spec = provision.ring_spec;
+        self.records
+            .insert(edge_id, EdgeRecord::new_tx(provision, request_id, actor));
+        self.commands.push(EdgeCommand::LeaseRing {
+            request_id,
+            edge_id,
+            direction: RingDirection::Egress,
+            ring_spec,
+        });
+    }
+
+    fn provision_rx(&mut self, provision: ProvisionRx) {
+        if provision.local_node_id != self.local_node_id {
+            return;
+        }
+
+        let request_id = self.next_request_id();
+        let actor = self.next_actor_address();
+        let edge_id = provision.edge_id;
+        let ring_spec = provision.ring_spec;
+        self.records
+            .insert(edge_id, EdgeRecord::new_rx(provision, request_id, actor));
+        self.commands.push(EdgeCommand::LeaseRing {
+            request_id,
+            edge_id,
+            direction: RingDirection::Ingress,
+            ring_spec,
+        });
+    }
+
+    fn ring_leased(&mut self, request_id: LeaseRequestId, ring_id: RingId, layout: RingLayout) {
+        let Some(edge_id) = self.edge_for_request(request_id) else {
+            return;
+        };
+
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+
+        if record.state != EdgeProvisionState::WaitingForLease {
+            self.commands.push(EdgeCommand::ReleaseArenaLease {
+                ring_id,
+                proof: QuiescenceProof::verified(),
+            });
+            return;
+        }
+
+        record.ring_id = Some(ring_id);
+        record.layout = Some(layout);
+        record.state = EdgeProvisionState::WaitingForWorkerRing;
+        self.commands.push(EdgeCommand::InstallWorkerRing {
+            edge_id,
+            ring_id,
+            direction: record.direction,
+            layout,
+            object_spec: record.object_spec,
+            ring_spec: record.ring_spec,
+        });
+    }
+
+    fn ring_lease_rejected(&mut self, request_id: LeaseRequestId, reason: RingLeaseRejection) {
+        let Some(edge_id) = self.edge_for_waiting_request(request_id) else {
+            return;
+        };
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+
+        record.state = EdgeProvisionState::Failed;
+        self.events.push(EdgeLifecycleEvent::EdgeFaulted {
+            edge_id,
+            reason: EdgeFaultReason::RingLeaseRejected(reason),
+        });
+    }
+
+    fn ring_installed(&mut self, edge_id: EdgeId, ring_id: RingId) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        if record.state != EdgeProvisionState::WaitingForWorkerRing
+            || record.ring_id != Some(ring_id)
+        {
+            return;
+        }
+        let Some(layout) = record.layout else {
+            return;
+        };
+
+        record.worker_installed = true;
+        record.driver_established = true;
+        record.state = EdgeProvisionState::WaitingForDriver;
+        match record.direction {
+            RingDirection::Egress => {
+                if let Some(consumer_node_id) = record.peer_node_id {
+                    self.commands.push(EdgeCommand::EstablishSend {
+                        edge_id,
+                        consumer_node_id,
+                        layout,
+                    });
+                }
+            }
+            RingDirection::Ingress => {
+                self.commands
+                    .push(EdgeCommand::EstablishRecv { edge_id, layout });
+            }
+        }
+    }
+
+    fn driver_edge_ready(&mut self, edge_id: EdgeId) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        if record.state != EdgeProvisionState::WaitingForDriver {
+            return;
+        }
+
+        record.state = EdgeProvisionState::Ready;
+        self.events.push(EdgeLifecycleEvent::EdgeReady {
+            edge_id,
+            local_edge_actor: record.local_edge_actor,
+        });
+    }
+
+    fn ring_fault(&mut self, edge_id: EdgeId, ring_id: RingId, reason: RingFaultReason) {
+        let Some(record) = self.records.get(&edge_id) else {
+            return;
+        };
+        if record.ring_id != Some(ring_id) {
+            return;
+        }
+        self.fault_edge(edge_id, EdgeFaultReason::RingFault(reason));
+    }
+
+    fn fault_edge(&mut self, edge_id: EdgeId, reason: EdgeFaultReason) {
+        let Some(record) = self.records.get(&edge_id) else {
+            return;
+        };
+        if matches!(
+            record.state,
+            EdgeProvisionState::Stopping | EdgeProvisionState::Stopped | EdgeProvisionState::Failed
+        ) {
+            return;
+        }
+
+        self.events
+            .push(EdgeLifecycleEvent::EdgeFaulted { edge_id, reason });
+        self.start_stopping(edge_id, true);
+    }
+
+    fn stop_edge(&mut self, edge_id: EdgeId) {
+        self.start_stopping(edge_id, true);
+    }
+
+    fn start_stopping(&mut self, edge_id: EdgeId, cancel_lease: bool) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        if matches!(
+            record.state,
+            EdgeProvisionState::Stopping | EdgeProvisionState::Stopped
+        ) {
+            return;
+        }
+
+        let request_id = record.lease_request_id;
+        let ring_id = record.ring_id;
+        let driver_established = record.driver_established;
+        let worker_installed = record.worker_installed;
+        record.state = EdgeProvisionState::Stopping;
+
+        if cancel_lease {
+            if let Some(request_id) = request_id {
+                self.commands.push(EdgeCommand::CancelQueuedLease {
+                    request_id,
+                    edge_id,
+                });
+            }
+        }
+
+        let Some(ring_id) = ring_id else {
+            self.mark_stopped_with_event(edge_id);
+            return;
+        };
+
+        if driver_established {
+            self.commands
+                .push(EdgeCommand::StopPump { edge_id, ring_id });
+        }
+        if worker_installed {
+            self.commands
+                .push(EdgeCommand::UninstallWorkerRing { edge_id, ring_id });
+        }
+        if !driver_established && !worker_installed {
+            self.release_ring(edge_id, ring_id);
+        }
+    }
+
+    fn pump_stopped(&mut self, edge_id: EdgeId, ring_id: RingId) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        if record.ring_id == Some(ring_id) {
+            record.pump_stopped = true;
+        }
+    }
+
+    fn release_after_quiescence(&mut self, ring_id: RingId) {
+        let Some(edge_id) = self.edge_for_ring(ring_id) else {
+            return;
+        };
+        let Some(record) = self.records.get(&edge_id) else {
+            return;
+        };
+        if record.state != EdgeProvisionState::Stopping {
+            return;
+        }
+        self.release_ring(edge_id, ring_id);
+    }
+
+    fn release_ring(&mut self, edge_id: EdgeId, ring_id: RingId) {
+        self.commands.push(EdgeCommand::ReleaseArenaLease {
+            ring_id,
+            proof: QuiescenceProof::verified(),
+        });
+        self.mark_stopped_with_event(edge_id);
+    }
+
+    fn mark_stopped_with_event(&mut self, edge_id: EdgeId) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        if record.state == EdgeProvisionState::Stopped {
+            return;
+        }
+        record.state = EdgeProvisionState::Stopped;
+        self.events
+            .push(EdgeLifecycleEvent::EdgeStopped { edge_id });
+    }
+
+    fn mark_stopped(&mut self, edge_id: EdgeId) {
+        let Some(record) = self.records.get_mut(&edge_id) else {
+            return;
+        };
+        record.state = EdgeProvisionState::Stopped;
+    }
+
+    fn edge_for_request(&self, request_id: LeaseRequestId) -> Option<EdgeId> {
+        self.records.iter().find_map(|(edge_id, record)| {
+            (record.lease_request_id == Some(request_id)).then_some(*edge_id)
+        })
+    }
+
+    fn edge_for_waiting_request(&self, request_id: LeaseRequestId) -> Option<EdgeId> {
+        self.records.iter().find_map(|(edge_id, record)| {
+            (record.state == EdgeProvisionState::WaitingForLease
+                && record.lease_request_id == Some(request_id))
+            .then_some(*edge_id)
+        })
+    }
+
+    fn edge_for_ring(&self, ring_id: RingId) -> Option<EdgeId> {
+        self.records
+            .iter()
+            .find_map(|(edge_id, record)| (record.ring_id == Some(ring_id)).then_some(*edge_id))
+    }
+
+    fn next_request_id(&mut self) -> LeaseRequestId {
+        let request_id = LeaseRequestId(self.next_request_id);
+        self.next_request_id += 1;
+        request_id
+    }
+
+    fn next_actor_address(&mut self) -> ActorAddress {
+        let actor = ActorAddress(self.next_actor_id);
+        self.next_actor_id += 1;
+        actor
+    }
+}
+
+struct EdgeRecord {
+    run_id: RunId,
+    edge_id: EdgeId,
+    direction: RingDirection,
+    state: EdgeProvisionState,
+    lease_request_id: Option<LeaseRequestId>,
+    ring_id: Option<RingId>,
+    layout: Option<RingLayout>,
+    peer_node_id: Option<NodeId>,
+    local_edge_actor: ActorAddress,
+    remote_actor_address: Option<ActorAddress>,
+    object_spec: ObjectSpec,
+    ring_spec: RingSpec,
+    worker_installed: bool,
+    driver_established: bool,
+    pump_stopped: bool,
+}
+
+impl EdgeRecord {
+    fn new_tx(provision: ProvisionTx, request_id: LeaseRequestId, actor: ActorAddress) -> Self {
+        Self {
+            run_id: provision.run_id,
+            edge_id: provision.edge_id,
+            direction: RingDirection::Egress,
+            state: EdgeProvisionState::WaitingForLease,
+            lease_request_id: Some(request_id),
+            ring_id: None,
+            layout: None,
+            peer_node_id: Some(provision.consumer_node_id),
+            local_edge_actor: actor,
+            remote_actor_address: None,
+            object_spec: provision.object_spec,
+            ring_spec: provision.ring_spec,
+            worker_installed: false,
+            driver_established: false,
+            pump_stopped: false,
+        }
+    }
+
+    fn new_rx(provision: ProvisionRx, request_id: LeaseRequestId, actor: ActorAddress) -> Self {
+        Self {
+            run_id: provision.run_id,
+            edge_id: provision.edge_id,
+            direction: RingDirection::Ingress,
+            state: EdgeProvisionState::WaitingForLease,
+            lease_request_id: Some(request_id),
+            ring_id: None,
+            layout: None,
+            peer_node_id: None,
+            local_edge_actor: actor,
+            remote_actor_address: None,
+            object_spec: provision.object_spec,
+            ring_spec: provision.ring_spec,
+            worker_installed: false,
+            driver_established: false,
+            pump_stopped: false,
+        }
+    }
+
+    fn snapshot(&self) -> LocalEdgeRecord {
+        let _ = self.run_id;
+        LocalEdgeRecord {
+            edge_id: self.edge_id,
+            direction: self.direction,
+            state: self.state,
+            lease_request_id: self.lease_request_id,
+            ring_id: self.ring_id,
+            peer_node_id: self.peer_node_id,
+            local_edge_actor: self.local_edge_actor,
+            remote_actor_address: self.remote_actor_address,
+        }
+    }
+}
+
+#[cfg(test)]
+pub struct EdgeEstablisherHarness {
+    establisher: EdgeEstablisher,
+}
+
+#[cfg(test)]
+impl EdgeEstablisherHarness {
+    pub fn new(local_node_id: NodeId) -> Self {
+        Self {
+            establisher: EdgeEstablisher::new(local_node_id),
+        }
+    }
+
+    pub fn observe(&mut self, event: EdgeEvent) {
+        self.establisher.observe(event);
+    }
+
+    pub fn commands(&self) -> &[EdgeCommand] {
+        self.establisher.commands()
+    }
+
+    pub fn events(&self) -> &[EdgeLifecycleEvent] {
+        self.establisher.events()
+    }
+
+    pub fn local_record(&self, edge_id: EdgeId) -> Option<LocalEdgeRecord> {
+        self.establisher.local_record(edge_id)
+    }
+}
diff --git a/crates/mvp-system/src/gpu_worker_ctl.rs b/crates/mvp-system/src/gpu_worker_ctl.rs
new file mode 100644
index 0000000..a495cbc
--- /dev/null
+++ b/crates/mvp-system/src/gpu_worker_ctl.rs
@@ -0,0 +1,378 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ProcessId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceHandle {
+    pub generation: WorkerGeneration,
+    pub id: u64,
+}
+
+impl DeviceHandle {
+    pub fn new(generation: WorkerGeneration, id: u64) -> Self {
+        Self { generation, id }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ArenaEnv {
+    pub arena_fd: i32,
+    pub arena_bytes: u64,
+}
+
+impl ArenaEnv {
+    pub fn test_default() -> Self {
+        Self {
+            arena_fd: 3,
+            arena_bytes: 4096,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct WorkerConfig {
+    pub node_id: NodeId,
+    pub arena_env: ArenaEnv,
+    pub initialization_timeout_ms: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ActorCommand {
+    InstallRing {
+        generation: WorkerGeneration,
+        ring_id: RingId,
+    },
+    ExecuteStep {
+        generation: WorkerGeneration,
+        step_id: StepId,
+        input: DeviceHandle,
+    },
+    ReleaseDeviceObject {
+        generation: WorkerGeneration,
+        handle: DeviceHandle,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerCommand {
+    InitializeWorker {
+        generation: WorkerGeneration,
+    },
+    InstallRing {
+        ring_id: RingId,
+    },
+    ExecuteStep {
+        step_id: StepId,
+        input: DeviceHandle,
+    },
+    ReleaseDeviceObject {
+        handle: DeviceHandle,
+    },
+    ShutdownWorker,
+    PayloadBytes {
+        bytes: Vec<u8>,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerEvent {
+    RingInstalled { ring_id: RingId },
+    ObjectLoaded { object_id: ObjectId, sequence: u64 },
+    ObjectProduced { object_id: ObjectId, sequence: u64 },
+    StepCompleted { step_id: StepId },
+    RingReadable { ring_id: RingId },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ExitStatus {
+    Code(i32),
+    Signal(i32),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerCtlEvent {
+    StartWorker,
+    ProcessStarted { pid: ProcessId },
+    WorkerReady { generation: WorkerGeneration },
+    ActorCommand(ActorCommand),
+    StdoutEvent(WorkerEvent),
+    ProcessExited { status: ExitStatus },
+    RestartRequested,
+    ShutdownRequested,
+    WorkerStopped { generation: WorkerGeneration },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum WorkerFailure {
+    InitializationTimeout,
+    ProcessExited,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CommandRejection {
+    NotRunning,
+    OldGenerationHandle,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerCtlOut {
+    WorkerRunning {
+        generation: WorkerGeneration,
+    },
+    WorkerFailed {
+        generation: WorkerGeneration,
+        reason: WorkerFailure,
+    },
+    CommandRejected {
+        reason: CommandRejection,
+    },
+    RingFaulted {
+        ring_id: RingId,
+    },
+    WorkerStopped {
+        generation: WorkerGeneration,
+    },
+    RingQuiesced {
+        ring_id: RingId,
+    },
+    TerminalStopped {
+        generation: WorkerGeneration,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerCtlCommand {
+    SpawnProcessActor { node_id: NodeId },
+    StopDriverPump { ring_id: RingId },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum RoutedEvent {
+    ToEdgeEstablisher(WorkerEvent),
+    ToRxOrRole(WorkerEvent),
+    ToTxOrRole(WorkerEvent),
+    ToStageController(WorkerEvent),
+    ToDriverOrWorkerSide(WorkerEvent),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum CtlState {
+    Idle,
+    Starting,
+    Running,
+    Crashed,
+    ShuttingDown,
+    Stopped,
+}
+
+#[cfg(test)]
+pub struct GpuWorkerCtlHarness {
+    config: WorkerConfig,
+    state: CtlState,
+    current_generation: WorkerGeneration,
+    now_ms: u64,
+    start_time_ms: Option<u64>,
+    commands: Vec<WorkerCtlCommand>,
+    serialized: Vec<WorkerCommand>,
+    events: Vec<WorkerCtlOut>,
+    routed: Vec<RoutedEvent>,
+    installed_rings: std::collections::BTreeSet<RingId>,
+}
+
+#[cfg(test)]
+impl GpuWorkerCtlHarness {
+    pub fn new(config: WorkerConfig) -> Self {
+        Self {
+            config,
+            state: CtlState::Idle,
+            current_generation: WorkerGeneration(1),
+            now_ms: 0,
+            start_time_ms: None,
+            commands: Vec::new(),
+            serialized: Vec::new(),
+            events: Vec::new(),
+            routed: Vec::new(),
+            installed_rings: std::collections::BTreeSet::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: WorkerCtlEvent) {
+        match event {
+            WorkerCtlEvent::StartWorker => self.start(),
+            WorkerCtlEvent::ProcessStarted { .. } => {
+                self.state = CtlState::Starting;
+                self.serialized.push(WorkerCommand::InitializeWorker {
+                    generation: self.current_generation,
+                });
+            }
+            WorkerCtlEvent::WorkerReady { generation } => {
+                self.current_generation = generation;
+                self.state = CtlState::Running;
+                self.events.push(WorkerCtlOut::WorkerRunning { generation });
+            }
+            WorkerCtlEvent::ActorCommand(command) => self.actor_command(command),
+            WorkerCtlEvent::StdoutEvent(event) => self.route(event),
+            WorkerCtlEvent::ProcessExited { status } => self.process_exited(status),
+            WorkerCtlEvent::RestartRequested => self.restart(),
+            WorkerCtlEvent::ShutdownRequested => self.shutdown(),
+            WorkerCtlEvent::WorkerStopped { generation } => {
+                self.events.push(WorkerCtlOut::WorkerStopped { generation });
+            }
+        }
+    }
+
+    pub fn advance_time_ms(&mut self, delta: u64) {
+        self.now_ms = self.now_ms.saturating_add(delta);
+        if self.state == CtlState::Starting {
+            if let Some(start_time) = self.start_time_ms {
+                if self.now_ms.saturating_sub(start_time) > self.config.initialization_timeout_ms {
+                    self.events.push(WorkerCtlOut::WorkerFailed {
+                        generation: self.current_generation,
+                        reason: WorkerFailure::InitializationTimeout,
+                    });
+                    self.state = CtlState::Crashed;
+                }
+            }
+        }
+    }
+
+    pub fn commands(&self) -> &[WorkerCtlCommand] {
+        &self.commands
+    }
+
+    pub fn serialized_worker_commands(&self) -> &[WorkerCommand] {
+        &self.serialized
+    }
+
+    pub fn events(&self) -> &[WorkerCtlOut] {
+        &self.events
+    }
+
+    pub fn routed(&self) -> &[RoutedEvent] {
+        &self.routed
+    }
+
+    pub fn current_generation(&self) -> WorkerGeneration {
+        self.current_generation
+    }
+
+    fn start(&mut self) {
+        self.state = CtlState::Starting;
+        self.start_time_ms = Some(self.now_ms);
+        self.commands.push(WorkerCtlCommand::SpawnProcessActor {
+            node_id: self.config.node_id,
+        });
+    }
+
+    fn actor_command(&mut self, command: ActorCommand) {
+        if self.state != CtlState::Running {
+            self.events.push(WorkerCtlOut::CommandRejected {
+                reason: CommandRejection::NotRunning,
+            });
+            return;
+        }
+        let command_generation = match command {
+            ActorCommand::InstallRing { generation, .. }
+            | ActorCommand::ExecuteStep { generation, .. }
+            | ActorCommand::ReleaseDeviceObject { generation, .. } => generation,
+        };
+        if command_generation != self.current_generation {
+            self.events.push(WorkerCtlOut::CommandRejected {
+                reason: CommandRejection::OldGenerationHandle,
+            });
+            return;
+        }
+        match command {
+            ActorCommand::InstallRing { ring_id, .. } => {
+                self.installed_rings.insert(ring_id);
+                self.serialized.push(WorkerCommand::InstallRing { ring_id });
+            }
+            ActorCommand::ExecuteStep { step_id, input, .. } => {
+                if input.generation != self.current_generation {
+                    self.events.push(WorkerCtlOut::CommandRejected {
+                        reason: CommandRejection::OldGenerationHandle,
+                    });
+                } else {
+                    self.serialized
+                        .push(WorkerCommand::ExecuteStep { step_id, input });
+                }
+            }
+            ActorCommand::ReleaseDeviceObject { handle, .. } => {
+                if handle.generation != self.current_generation {
+                    self.events.push(WorkerCtlOut::CommandRejected {
+                        reason: CommandRejection::OldGenerationHandle,
+                    });
+                } else {
+                    self.serialized
+                        .push(WorkerCommand::ReleaseDeviceObject { handle });
+                }
+            }
+        }
+    }
+
+    fn route(&mut self, event: WorkerEvent) {
+        match event.clone() {
+            WorkerEvent::RingInstalled { .. } => {
+                self.routed.push(RoutedEvent::ToEdgeEstablisher(event))
+            }
+            WorkerEvent::ObjectLoaded { .. } => self.routed.push(RoutedEvent::ToRxOrRole(event)),
+            WorkerEvent::ObjectProduced { .. } => self.routed.push(RoutedEvent::ToTxOrRole(event)),
+            WorkerEvent::StepCompleted { .. } => {
+                self.routed.push(RoutedEvent::ToStageController(event))
+            }
+            WorkerEvent::RingReadable { .. } => {
+                self.routed.push(RoutedEvent::ToDriverOrWorkerSide(event))
+            }
+        }
+    }
+
+    fn process_exited(&mut self, status: ExitStatus) {
+        match (self.state, status) {
+            (CtlState::ShuttingDown, ExitStatus::Code(0)) => {
+                for ring_id in &self.installed_rings {
+                    self.events
+                        .push(WorkerCtlOut::RingQuiesced { ring_id: *ring_id });
+                }
+                self.events.push(WorkerCtlOut::TerminalStopped {
+                    generation: self.current_generation,
+                });
+                self.state = CtlState::Stopped;
+            }
+            (_, _) => {
+                for ring_id in &self.installed_rings {
+                    self.events
+                        .push(WorkerCtlOut::RingFaulted { ring_id: *ring_id });
+                    self.commands
+                        .push(WorkerCtlCommand::StopDriverPump { ring_id: *ring_id });
+                }
+                self.events.push(WorkerCtlOut::WorkerFailed {
+                    generation: self.current_generation,
+                    reason: WorkerFailure::ProcessExited,
+                });
+                self.state = CtlState::Crashed;
+            }
+        }
+    }
+
+    fn restart(&mut self) {
+        self.state = CtlState::Starting;
+        self.current_generation = WorkerGeneration(self.current_generation.0 + 1);
+        self.start_time_ms = Some(self.now_ms);
+    }
+
+    fn shutdown(&mut self) {
+        if self.state == CtlState::Running {
+            self.serialized.push(WorkerCommand::ShutdownWorker);
+            self.state = CtlState::ShuttingDown;
+        }
+    }
+}
diff --git a/crates/mvp-system/src/gpu_worker_egress_producer.rs b/crates/mvp-system/src/gpu_worker_egress_producer.rs
new file mode 100644
index 0000000..7b58a6d
--- /dev/null
+++ b/crates/mvp-system/src/gpu_worker_egress_producer.rs
@@ -0,0 +1,391 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct PortId(pub String);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceHandle {
+    pub generation: WorkerGeneration,
+    pub id: u64,
+}
+
+impl DeviceHandle {
+    pub fn new(generation: WorkerGeneration, id: u64) -> Self {
+        Self { generation, id }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingDirection {
+    Ingress,
+    Egress,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ObjectLayout {
+    Token,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub max_extent: u64,
+    pub alignment: u64,
+    pub layout: ObjectLayout,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct InstallRing {
+    pub ring_id: RingId,
+    pub edge_id: EdgeId,
+    pub port_id: PortId,
+    pub direction: RingDirection,
+    pub object_spec: ObjectSpec,
+    pub generation: WorkerGeneration,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
+pub struct ObjectFlags {
+    pub end_of_sequence: bool,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct OutputBinding {
+    pub ring_id: RingId,
+    pub object_id: ObjectId,
+    pub sequence: u64,
+    pub extent: u64,
+    pub flags: ObjectFlags,
+    pub device_source: DeviceHandle,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerEgressEvent {
+    InstallRing(InstallRing),
+    ExecuteStep {
+        step_id: StepId,
+        outputs: Vec<OutputBinding>,
+    },
+    HeaderReady {
+        object_id: ObjectId,
+    },
+    EgressRingFull {
+        ring_id: RingId,
+    },
+    RingWritable {
+        ring_id: RingId,
+    },
+    DeviceToHostCopyCompleted {
+        object_id: ObjectId,
+        byte_count: u64,
+    },
+    DeviceCopyFailed {
+        object_id: ObjectId,
+    },
+    RoleStateUpdated {
+        step_id: StepId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StepFailureReason {
+    InvalidOutputRing,
+    OutputExtentViolation,
+    DeviceCopyFailed,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerEgressOut {
+    ObjectProduced {
+        ring_id: RingId,
+        object_id: ObjectId,
+        sequence: u64,
+    },
+    StepCompleted {
+        step_id: StepId,
+    },
+    StepFailed {
+        step_id: StepId,
+        reason: StepFailureReason,
+    },
+    RingFault {
+        ring_id: RingId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WakeHint {
+    RingReadable { ring_id: RingId },
+    RingWritable { ring_id: RingId },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectHeader {
+    pub object_id: ObjectId,
+    pub sequence: u64,
+    pub extent: u64,
+}
+
+impl ObjectHeader {
+    pub fn decode(bytes: &[u8]) -> Result<Self, HeaderDecodeError> {
+        if bytes.len() < HEADER_LEN || &bytes[0..4] != b"MO01" || bytes[4] != 1 {
+            return Err(HeaderDecodeError);
+        }
+        Ok(Self {
+            object_id: ObjectId(u64::from_le_bytes(bytes[8..16].try_into().unwrap())),
+            sequence: u64::from_le_bytes(bytes[16..24].try_into().unwrap()),
+            extent: u64::from_le_bytes(bytes[24..32].try_into().unwrap()),
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct HeaderDecodeError;
+
+const HEADER_LEN: usize = 48;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+struct PendingStep {
+    step_id: StepId,
+    outputs: Vec<OutputBinding>,
+    role_state_updated: bool,
+}
+
+#[cfg(test)]
+pub struct EgressProducerHarness {
+    generation: WorkerGeneration,
+    rings: std::collections::BTreeMap<RingId, InstallRing>,
+    pending_outputs: Vec<OutputBinding>,
+    steps: Vec<PendingStep>,
+    committed: std::collections::BTreeMap<RingId, Vec<u8>>,
+    payload_committed: std::collections::BTreeMap<RingId, u64>,
+    full_rings: std::collections::BTreeSet<RingId>,
+    produced: std::collections::BTreeSet<ObjectId>,
+    wake_hints: Vec<WakeHint>,
+    events: Vec<WorkerEgressOut>,
+}
+
+#[cfg(test)]
+impl EgressProducerHarness {
+    pub fn new(generation: WorkerGeneration) -> Self {
+        Self {
+            generation,
+            rings: std::collections::BTreeMap::new(),
+            pending_outputs: Vec::new(),
+            steps: Vec::new(),
+            committed: std::collections::BTreeMap::new(),
+            payload_committed: std::collections::BTreeMap::new(),
+            full_rings: std::collections::BTreeSet::new(),
+            produced: std::collections::BTreeSet::new(),
+            wake_hints: Vec::new(),
+            events: Vec::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: WorkerEgressEvent) {
+        match event {
+            WorkerEgressEvent::InstallRing(install) => {
+                if install.direction == RingDirection::Egress
+                    && install.generation == self.generation
+                {
+                    self.rings.insert(install.ring_id, install);
+                }
+            }
+            WorkerEgressEvent::ExecuteStep { step_id, outputs } => {
+                self.execute_step(step_id, outputs)
+            }
+            WorkerEgressEvent::HeaderReady { object_id } => self.header_ready(object_id),
+            WorkerEgressEvent::EgressRingFull { ring_id } => {
+                self.full_rings.insert(ring_id);
+            }
+            WorkerEgressEvent::RingWritable { ring_id } => {
+                self.full_rings.remove(&ring_id);
+                self.wake_hints.push(WakeHint::RingWritable { ring_id });
+            }
+            WorkerEgressEvent::DeviceToHostCopyCompleted {
+                object_id,
+                byte_count,
+            } => self.copy_completed(object_id, byte_count),
+            WorkerEgressEvent::DeviceCopyFailed { object_id } => self.copy_failed(object_id),
+            WorkerEgressEvent::RoleStateUpdated { step_id } => {
+                if let Some(step) = self.steps.iter_mut().find(|step| step.step_id == step_id) {
+                    step.role_state_updated = true;
+                }
+                self.maybe_step_completed(step_id);
+            }
+        }
+    }
+
+    pub fn pending_outputs(&self) -> &[OutputBinding] {
+        &self.pending_outputs
+    }
+
+    pub fn committed_bytes(&self, ring_id: RingId) -> &[u8] {
+        self.committed
+            .get(&ring_id)
+            .map(Vec::as_slice)
+            .unwrap_or(&[])
+    }
+
+    pub fn committed_payload_bytes(&self, ring_id: RingId) -> u64 {
+        self.payload_committed.get(&ring_id).copied().unwrap_or(0)
+    }
+
+    pub fn wake_hints(&self) -> &[WakeHint] {
+        &self.wake_hints
+    }
+
+    pub fn events(&self) -> &[WorkerEgressOut] {
+        &self.events
+    }
+
+    pub fn complete_output(&mut self, object_id: ObjectId) {
+        self.header_ready(object_id);
+        let Some(output) = self
+            .pending_outputs
+            .iter()
+            .find(|output| output.object_id == object_id)
+            .copied()
+        else {
+            return;
+        };
+        self.copy_completed(object_id, output.extent);
+    }
+
+    fn execute_step(&mut self, step_id: StepId, outputs: Vec<OutputBinding>) {
+        for output in &outputs {
+            let Some(ring) = self.rings.get(&output.ring_id) else {
+                self.events.push(WorkerEgressOut::StepFailed {
+                    step_id,
+                    reason: StepFailureReason::InvalidOutputRing,
+                });
+                return;
+            };
+            if output.extent > ring.object_spec.max_extent
+                || (ring.object_spec.alignment != 0
+                    && output.extent % ring.object_spec.alignment != 0)
+            {
+                self.events.push(WorkerEgressOut::StepFailed {
+                    step_id,
+                    reason: StepFailureReason::OutputExtentViolation,
+                });
+                return;
+            }
+        }
+        self.pending_outputs.extend(outputs.iter().copied());
+        self.steps.push(PendingStep {
+            step_id,
+            outputs,
+            role_state_updated: false,
+        });
+    }
+
+    fn header_ready(&mut self, object_id: ObjectId) {
+        let Some(output) = self
+            .pending_outputs
+            .iter()
+            .find(|output| output.object_id == object_id)
+            .copied()
+        else {
+            return;
+        };
+        let bytes = encode_header(output);
+        self.committed
+            .entry(output.ring_id)
+            .or_default()
+            .extend(bytes);
+        self.wake_hints.push(WakeHint::RingReadable {
+            ring_id: output.ring_id,
+        });
+    }
+
+    fn copy_completed(&mut self, object_id: ObjectId, byte_count: u64) {
+        let Some(output) = self
+            .pending_outputs
+            .iter()
+            .find(|output| output.object_id == object_id)
+            .copied()
+        else {
+            return;
+        };
+        if self.full_rings.contains(&output.ring_id) || byte_count != output.extent {
+            return;
+        }
+        self.committed
+            .entry(output.ring_id)
+            .or_default()
+            .extend(std::iter::repeat(0).take(byte_count as usize));
+        *self.payload_committed.entry(output.ring_id).or_insert(0) += byte_count;
+        if self.produced.insert(object_id) {
+            self.events.push(WorkerEgressOut::ObjectProduced {
+                ring_id: output.ring_id,
+                object_id,
+                sequence: output.sequence,
+            });
+        }
+        let step_ids = self
+            .steps
+            .iter()
+            .filter(|step| {
+                step.outputs
+                    .iter()
+                    .any(|output| output.object_id == object_id)
+            })
+            .map(|step| step.step_id)
+            .collect::<Vec<_>>();
+        for step_id in step_ids {
+            self.maybe_step_completed(step_id);
+        }
+    }
+
+    fn copy_failed(&mut self, object_id: ObjectId) {
+        let step_id = self
+            .steps
+            .iter()
+            .find(|step| {
+                step.outputs
+                    .iter()
+                    .any(|output| output.object_id == object_id)
+            })
+            .map(|step| step.step_id)
+            .unwrap_or(StepId(0));
+        self.events.push(WorkerEgressOut::StepFailed {
+            step_id,
+            reason: StepFailureReason::DeviceCopyFailed,
+        });
+    }
+
+    fn maybe_step_completed(&mut self, step_id: StepId) {
+        let Some(step) = self.steps.iter().find(|step| step.step_id == step_id) else {
+            return;
+        };
+        if !step.role_state_updated {
+            return;
+        }
+        if step.outputs.iter().all(|output| self.produced.contains(&output.object_id))
+            && !self.events.iter().any(|event| matches!(event, WorkerEgressOut::StepCompleted { step_id: seen } if *seen == step_id))
+        {
+            self.events.push(WorkerEgressOut::StepCompleted { step_id });
+        }
+    }
+}
+
+fn encode_header(output: OutputBinding) -> Vec<u8> {
+    let mut out = Vec::with_capacity(HEADER_LEN);
+    out.extend_from_slice(b"MO01");
+    out.push(1);
+    out.push(HEADER_LEN as u8);
+    out.extend_from_slice(&[0u8; 2]);
+    out.extend_from_slice(&output.object_id.0.to_le_bytes());
+    out.extend_from_slice(&output.sequence.to_le_bytes());
+    out.extend_from_slice(&output.extent.to_le_bytes());
+    out.extend_from_slice(&[0u8; 16]);
+    out
+}
diff --git a/crates/mvp-system/src/gpu_worker_ingress_parser.rs b/crates/mvp-system/src/gpu_worker_ingress_parser.rs
new file mode 100644
index 0000000..aafe94e
--- /dev/null
+++ b/crates/mvp-system/src/gpu_worker_ingress_parser.rs
@@ -0,0 +1,425 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct PortId(pub String);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceHandle {
+    pub generation: WorkerGeneration,
+    pub id: u64,
+}
+
+impl DeviceHandle {
+    pub fn new(generation: WorkerGeneration, id: u64) -> Self {
+        Self { generation, id }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RingDirection {
+    Ingress,
+    Egress,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ObjectLayout {
+    Token,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub max_extent: u64,
+    pub alignment: u64,
+    pub layout: ObjectLayout,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct InstallRing {
+    pub ring_id: RingId,
+    pub edge_id: EdgeId,
+    pub port_id: PortId,
+    pub direction: RingDirection,
+    pub object_spec: ObjectSpec,
+    pub generation: WorkerGeneration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerIngressEvent {
+    InstallRing(InstallRing),
+    RingReadable {
+        ring_id: RingId,
+    },
+    Eof {
+        ring_id: RingId,
+    },
+    DeviceCopyCompleted {
+        object_id: ObjectId,
+        byte_count: u64,
+    },
+    DeviceHandleCreated {
+        object_id: ObjectId,
+        handle: DeviceHandle,
+    },
+    RingFault {
+        ring_id: RingId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ObjectFailureReason {
+    UnsupportedMagic,
+    UnsupportedVersion,
+    MalformedHeaderLength,
+    ExtentExceedsMax,
+    ExtentAlignmentViolation,
+    SequenceViolation,
+    EofBeforeFullPayload,
+    DeviceCopyFailed,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerIngressOut {
+    ObjectLoaded {
+        ring_id: RingId,
+        edge_id: EdgeId,
+        port_id: PortId,
+        object_id: ObjectId,
+        sequence: u64,
+        extent: u64,
+        handle: DeviceHandle,
+    },
+    ObjectFailed {
+        ring_id: RingId,
+        object_id: Option<ObjectId>,
+        reason: ObjectFailureReason,
+    },
+    RingFault {
+        ring_id: RingId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceCopyLog {
+    pub object_id: ObjectId,
+    pub byte_count: u64,
+}
+
+#[derive(Clone, Debug)]
+pub struct ObjectRecordBuilder {
+    spec: ObjectSpec,
+    object_id: ObjectId,
+    sequence: u64,
+    extent: u64,
+    payload: Vec<u8>,
+    magic: [u8; 4],
+    version: u8,
+    header_len: u8,
+}
+
+impl ObjectRecordBuilder {
+    pub fn new(spec: ObjectSpec) -> Self {
+        Self {
+            spec,
+            object_id: ObjectId(9000),
+            sequence: 0,
+            extent: 0,
+            payload: Vec::new(),
+            magic: *b"MO01",
+            version: 1,
+            header_len: HEADER_LEN as u8,
+        }
+    }
+
+    pub fn object_id(mut self, object_id: ObjectId) -> Self {
+        self.object_id = object_id;
+        self
+    }
+
+    pub fn sequence(mut self, sequence: u64) -> Self {
+        self.sequence = sequence;
+        self
+    }
+
+    pub fn extent(mut self, extent: u64) -> Self {
+        self.extent = extent;
+        self
+    }
+
+    pub fn payload(mut self, payload: Vec<u8>) -> Self {
+        self.payload = payload;
+        self
+    }
+
+    pub fn partial_payload(mut self, payload: Vec<u8>) -> Self {
+        self.payload = payload;
+        self
+    }
+
+    pub fn unsupported_magic(mut self) -> Self {
+        self.magic = *b"BAD!";
+        self
+    }
+
+    pub fn unsupported_version(mut self) -> Self {
+        self.version = 99;
+        self
+    }
+
+    pub fn malformed_header_length(mut self) -> Self {
+        self.header_len = 1;
+        self
+    }
+
+    pub fn encode(mut self) -> Vec<u8> {
+        if self.extent == 0 && !self.payload.is_empty() {
+            self.extent = self.payload.len() as u64;
+        }
+        let mut out = Vec::with_capacity(HEADER_LEN + self.payload.len());
+        out.extend_from_slice(&self.magic);
+        out.push(self.version);
+        out.push(self.header_len);
+        out.extend_from_slice(&[0u8; 2]);
+        out.extend_from_slice(&self.object_id.0.to_le_bytes());
+        out.extend_from_slice(&self.sequence.to_le_bytes());
+        out.extend_from_slice(&self.extent.to_le_bytes());
+        out.extend_from_slice(&self.spec.max_extent.to_le_bytes());
+        out.extend_from_slice(&self.spec.alignment.to_le_bytes());
+        out.extend_from_slice(&self.payload);
+        out
+    }
+}
+
+const HEADER_LEN: usize = 48;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+struct ParsedRecord {
+    object_id: ObjectId,
+    sequence: u64,
+    extent: u64,
+    total_len: usize,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+struct PendingObject {
+    record: ParsedRecord,
+    copy_done: bool,
+    handle: Option<DeviceHandle>,
+}
+
+#[cfg(test)]
+pub struct IngressParserHarness {
+    generation: WorkerGeneration,
+    install: Option<InstallRing>,
+    buffers: std::collections::BTreeMap<RingId, Vec<u8>>,
+    consume: std::collections::BTreeMap<RingId, u64>,
+    cursor_reload: std::collections::BTreeMap<RingId, u64>,
+    faulted_rings: std::collections::BTreeSet<RingId>,
+    expected_sequence: u64,
+    pending: std::collections::BTreeMap<ObjectId, PendingObject>,
+    copy_log: Vec<DeviceCopyLog>,
+    events: Vec<WorkerIngressOut>,
+}
+
+#[cfg(test)]
+impl IngressParserHarness {
+    pub fn new(generation: WorkerGeneration) -> Self {
+        Self {
+            generation,
+            install: None,
+            buffers: std::collections::BTreeMap::new(),
+            consume: std::collections::BTreeMap::new(),
+            cursor_reload: std::collections::BTreeMap::new(),
+            faulted_rings: std::collections::BTreeSet::new(),
+            expected_sequence: 0,
+            pending: std::collections::BTreeMap::new(),
+            copy_log: Vec::new(),
+            events: Vec::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: WorkerIngressEvent) {
+        match event {
+            WorkerIngressEvent::InstallRing(install) => {
+                if install.direction == RingDirection::Ingress
+                    && install.generation == self.generation
+                {
+                    self.consume.entry(install.ring_id).or_insert(0);
+                    self.install = Some(install);
+                }
+            }
+            WorkerIngressEvent::RingReadable { ring_id } => self.parse_ring(ring_id, false),
+            WorkerIngressEvent::Eof { ring_id } => self.parse_ring(ring_id, true),
+            WorkerIngressEvent::DeviceCopyCompleted {
+                object_id,
+                byte_count,
+            } => {
+                self.copy_log.push(DeviceCopyLog {
+                    object_id,
+                    byte_count,
+                });
+                if let Some(pending) = self.pending.get_mut(&object_id) {
+                    pending.copy_done = true;
+                    if byte_count == pending.record.extent {
+                        if let Some(install) = &self.install {
+                            *self.consume.entry(install.ring_id).or_insert(0) +=
+                                pending.record.total_len as u64;
+                        }
+                    }
+                }
+                self.maybe_loaded(object_id);
+            }
+            WorkerIngressEvent::DeviceHandleCreated { object_id, handle } => {
+                if let Some(pending) = self.pending.get_mut(&object_id) {
+                    pending.handle = Some(handle);
+                }
+                self.maybe_loaded(object_id);
+            }
+            WorkerIngressEvent::RingFault { ring_id } => {
+                self.faulted_rings.insert(ring_id);
+                self.events.push(WorkerIngressOut::RingFault { ring_id });
+            }
+        }
+    }
+
+    pub fn write_committed_bytes(&mut self, ring_id: RingId, bytes: Vec<u8>) {
+        self.buffers.entry(ring_id).or_default().extend(bytes);
+    }
+
+    pub fn write_uncommitted_bytes(&mut self, _ring_id: RingId, _bytes: Vec<u8>) {}
+
+    pub fn consume_cursor(&self, ring_id: RingId) -> u64 {
+        self.consume.get(&ring_id).copied().unwrap_or(0)
+    }
+
+    pub fn cursor_reload_count(&self, ring_id: RingId) -> u64 {
+        self.cursor_reload.get(&ring_id).copied().unwrap_or(0)
+    }
+
+    pub fn device_copy_log(&self) -> &[DeviceCopyLog] {
+        &self.copy_log
+    }
+
+    pub fn events(&self) -> &[WorkerIngressOut] {
+        &self.events
+    }
+
+    fn parse_ring(&mut self, ring_id: RingId, eof: bool) {
+        let Some(install) = &self.install else {
+            return;
+        };
+        if install.ring_id != ring_id || self.faulted_rings.contains(&ring_id) {
+            return;
+        }
+        *self.cursor_reload.entry(ring_id).or_insert(0) += 1;
+        let buffer = self.buffers.get(&ring_id).cloned().unwrap_or_default();
+        if buffer.is_empty() {
+            return;
+        }
+        match decode_record(&buffer, install.object_spec, eof) {
+            Ok(record) => {
+                if record.sequence != self.expected_sequence {
+                    self.events.push(WorkerIngressOut::ObjectFailed {
+                        ring_id,
+                        object_id: Some(record.object_id),
+                        reason: ObjectFailureReason::SequenceViolation,
+                    });
+                    return;
+                }
+                self.expected_sequence += 1;
+                self.pending.insert(
+                    record.object_id,
+                    PendingObject {
+                        record: record.clone(),
+                        copy_done: false,
+                        handle: None,
+                    },
+                );
+                self.copy_log.push(DeviceCopyLog {
+                    object_id: record.object_id,
+                    byte_count: record.extent,
+                });
+            }
+            Err(reason) => self.events.push(WorkerIngressOut::ObjectFailed {
+                ring_id,
+                object_id: None,
+                reason,
+            }),
+        }
+    }
+
+    fn maybe_loaded(&mut self, object_id: ObjectId) {
+        let Some(pending) = self.pending.get(&object_id).cloned() else {
+            return;
+        };
+        let Some(handle) = pending.handle else {
+            return;
+        };
+        if !pending.copy_done || handle.generation != self.generation {
+            return;
+        }
+        let install = self.install.as_ref().unwrap();
+        if !self.events.iter().any(|event| matches!(event, WorkerIngressOut::ObjectLoaded { object_id: seen, .. } if *seen == object_id)) {
+            self.events.push(WorkerIngressOut::ObjectLoaded {
+                ring_id: install.ring_id,
+                edge_id: install.edge_id,
+                port_id: install.port_id.clone(),
+                object_id,
+                sequence: pending.record.sequence,
+                extent: pending.record.extent,
+                handle,
+            });
+        }
+    }
+}
+
+fn decode_record(
+    bytes: &[u8],
+    spec: ObjectSpec,
+    eof: bool,
+) -> Result<ParsedRecord, ObjectFailureReason> {
+    if bytes.len() < HEADER_LEN {
+        return if eof {
+            Err(ObjectFailureReason::EofBeforeFullPayload)
+        } else {
+            Err(ObjectFailureReason::MalformedHeaderLength)
+        };
+    }
+    if &bytes[0..4] != b"MO01" {
+        return Err(ObjectFailureReason::UnsupportedMagic);
+    }
+    if bytes[4] != 1 {
+        return Err(ObjectFailureReason::UnsupportedVersion);
+    }
+    if bytes[5] as usize != HEADER_LEN {
+        return Err(ObjectFailureReason::MalformedHeaderLength);
+    }
+    let object_id = ObjectId(u64::from_le_bytes(bytes[8..16].try_into().unwrap()));
+    let sequence = u64::from_le_bytes(bytes[16..24].try_into().unwrap());
+    let extent = u64::from_le_bytes(bytes[24..32].try_into().unwrap());
+    if extent > spec.max_extent {
+        return Err(ObjectFailureReason::ExtentExceedsMax);
+    }
+    if spec.alignment != 0 && extent % spec.alignment != 0 {
+        return Err(ObjectFailureReason::ExtentAlignmentViolation);
+    }
+    let total_len = HEADER_LEN + extent as usize;
+    if bytes.len() < total_len {
+        return if eof {
+            Err(ObjectFailureReason::EofBeforeFullPayload)
+        } else {
+            Err(ObjectFailureReason::MalformedHeaderLength)
+        };
+    }
+    Ok(ParsedRecord {
+        object_id,
+        sequence,
+        extent,
+        total_len,
+    })
+}
diff --git a/crates/mvp-system/src/gpu_worker_process_adapter.rs b/crates/mvp-system/src/gpu_worker_process_adapter.rs
new file mode 100644
index 0000000..29346b1
--- /dev/null
+++ b/crates/mvp-system/src/gpu_worker_process_adapter.rs
@@ -0,0 +1,290 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ArenaFd(pub i32);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct HelperAbiVersion(pub u32);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct DeviceHandle(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct AdapterConfig {
+    pub arena_fd: ArenaFd,
+    pub arena_bytes: u64,
+    pub helper_abi_version: HelperAbiVersion,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerCommand {
+    InitializeWorker {
+        helper_abi_version: HelperAbiVersion,
+    },
+    InstallRing {
+        ring_id: RingId,
+    },
+    ExecuteStep {
+        step_id: StepId,
+    },
+    ReleaseDeviceObject {
+        handle: DeviceHandle,
+    },
+    ShutdownWorker,
+    RingReadable {
+        ring_id: RingId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct JsonLine(serde_json::Map<String, serde_json::Value>);
+
+impl JsonLine {
+    pub fn parse(line: &str) -> Result<Self, serde_json::Error> {
+        let value: serde_json::Value = serde_json::from_str(line.trim_end())?;
+        match value {
+            serde_json::Value::Object(map) => Ok(Self(map)),
+            other => Ok(Self(serde_json::Map::from_iter([("value".into(), other)]))),
+        }
+    }
+
+    pub fn is_object(&self) -> bool {
+        true
+    }
+
+    pub fn contains_key(&self, key: &str) -> bool {
+        self.0.contains_key(key)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ProcessFaultReason {
+    InvalidJson,
+    UnknownEventShape,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum WorkerFatalReason {
+    UnsupportedHelperAbi,
+    BackendUnavailable,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum AdapterEvent {
+    WorkerReady {
+        generation: WorkerGeneration,
+    },
+    WorkerFatal {
+        reason: WorkerFatalReason,
+    },
+    ProcessFault {
+        reason: ProcessFaultReason,
+        line: String,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WorkerAction {
+    ReadArenaEnvironment {
+        arena_fd: ArenaFd,
+        arena_bytes: u64,
+    },
+    MapArena {
+        arena_fd: ArenaFd,
+        arena_bytes: u64,
+    },
+    InitializeRingHelper {
+        helper_abi_version: HelperAbiVersion,
+    },
+    InitializeBackend,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum InitializationFailure {
+    BackendUnavailable,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ExitStatus {
+    Code(i32),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CommandRejectionReason {
+    PayloadBytesForbidden,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct CommandRejection {
+    pub reason: CommandRejectionReason,
+}
+
+#[cfg(test)]
+pub struct ProcessAdapterHarness {
+    config: AdapterConfig,
+    stdin_lines: Vec<String>,
+    events: Vec<AdapterEvent>,
+    worker_actions: Vec<WorkerAction>,
+    command_rejections: Vec<CommandRejection>,
+    exit_status: Option<ExitStatus>,
+}
+
+#[cfg(test)]
+impl ProcessAdapterHarness {
+    pub fn new(config: AdapterConfig) -> Self {
+        Self {
+            config,
+            stdin_lines: Vec::new(),
+            events: Vec::new(),
+            worker_actions: Vec::new(),
+            command_rejections: Vec::new(),
+            exit_status: None,
+        }
+    }
+
+    pub fn start_worker_process(&mut self) {
+        self.worker_actions
+            .push(WorkerAction::ReadArenaEnvironment {
+                arena_fd: self.config.arena_fd,
+                arena_bytes: self.config.arena_bytes,
+            });
+    }
+
+    pub fn send_command(&mut self, command: WorkerCommand) {
+        if let WorkerCommand::InitializeWorker { helper_abi_version } = command {
+            if helper_abi_version != self.config.helper_abi_version {
+                self.events.push(AdapterEvent::WorkerFatal {
+                    reason: WorkerFatalReason::UnsupportedHelperAbi,
+                });
+                return;
+            }
+            self.worker_actions.push(WorkerAction::MapArena {
+                arena_fd: self.config.arena_fd,
+                arena_bytes: self.config.arena_bytes,
+            });
+            self.worker_actions
+                .push(WorkerAction::InitializeRingHelper { helper_abi_version });
+            self.worker_actions.push(WorkerAction::InitializeBackend);
+        }
+        self.stdin_lines.push(format_json_command(&command));
+    }
+
+    pub fn send_raw_json_command(&mut self, raw: &str) {
+        match JsonLine::parse(raw) {
+            Ok(parsed)
+                if parsed.contains_key("payload")
+                    || parsed.contains_key("bytes")
+                    || parsed.contains_key("data") =>
+            {
+                self.command_rejections.push(CommandRejection {
+                    reason: CommandRejectionReason::PayloadBytesForbidden,
+                });
+            }
+            Ok(_) => self.stdin_lines.push(format!("{}\n", raw.trim_end())),
+            Err(_) => self.command_rejections.push(CommandRejection {
+                reason: CommandRejectionReason::PayloadBytesForbidden,
+            }),
+        }
+    }
+
+    pub fn receive_stdout_line(&mut self, line: &str) {
+        let parsed = match JsonLine::parse(line) {
+            Ok(parsed) => parsed,
+            Err(_) => {
+                self.events.push(AdapterEvent::ProcessFault {
+                    reason: ProcessFaultReason::InvalidJson,
+                    line: line.into(),
+                });
+                return;
+            }
+        };
+        let Some(serde_json::Value::String(kind)) = parsed.0.get("type") else {
+            self.events.push(AdapterEvent::ProcessFault {
+                reason: ProcessFaultReason::UnknownEventShape,
+                line: line.into(),
+            });
+            return;
+        };
+        match kind.as_str() {
+            "WorkerReady" => {
+                let generation = parsed
+                    .0
+                    .get("generation")
+                    .and_then(|value| value.as_u64())
+                    .unwrap_or(1);
+                self.events.push(AdapterEvent::WorkerReady {
+                    generation: WorkerGeneration(generation),
+                });
+            }
+            _ => self.events.push(AdapterEvent::ProcessFault {
+                reason: ProcessFaultReason::UnknownEventShape,
+                line: line.into(),
+            }),
+        }
+    }
+
+    pub fn receive_stderr_line(&mut self, _line: &str) {}
+
+    pub fn inject_initialization_failure(&mut self, failure: InitializationFailure) {
+        match failure {
+            InitializationFailure::BackendUnavailable => {
+                self.events.push(AdapterEvent::WorkerFatal {
+                    reason: WorkerFatalReason::BackendUnavailable,
+                });
+                self.exit_status = Some(ExitStatus::Code(1));
+            }
+        }
+    }
+
+    pub fn stdin_lines(&self) -> &[String] {
+        &self.stdin_lines
+    }
+
+    pub fn events(&self) -> &[AdapterEvent] {
+        &self.events
+    }
+
+    pub fn worker_actions(&self) -> &[WorkerAction] {
+        &self.worker_actions
+    }
+
+    pub fn exit_status(&self) -> Option<ExitStatus> {
+        self.exit_status
+    }
+
+    pub fn command_rejections(&self) -> &[CommandRejection] {
+        &self.command_rejections
+    }
+}
+
+#[cfg(test)]
+fn format_json_command(command: &WorkerCommand) -> String {
+    let value = match command {
+        WorkerCommand::InitializeWorker { helper_abi_version } => serde_json::json!({
+            "type": "InitializeWorker",
+            "helper_abi_version": helper_abi_version.0,
+        }),
+        WorkerCommand::InstallRing { ring_id } => serde_json::json!({
+            "type": "InstallRing",
+            "ring_id": ring_id.0,
+        }),
+        WorkerCommand::ExecuteStep { step_id } => serde_json::json!({
+            "type": "ExecuteStep",
+            "step_id": step_id.0,
+        }),
+        WorkerCommand::ReleaseDeviceObject { handle } => serde_json::json!({
+            "type": "ReleaseDeviceObject",
+            "handle": handle.0,
+        }),
+        WorkerCommand::ShutdownWorker => serde_json::json!({
+            "type": "ShutdownWorker",
+        }),
+        WorkerCommand::RingReadable { ring_id } => serde_json::json!({
+            "type": "RingReadable",
+            "ring_id": ring_id.0,
+        }),
+    };
+    format!("{}\n", value)
+}
diff --git a/crates/mvp-system/src/lib.rs b/crates/mvp-system/src/lib.rs
index 7a18f05..ac78c9e 100644
--- a/crates/mvp-system/src/lib.rs
+++ b/crates/mvp-system/src/lib.rs
@@ -1 +1,29 @@
+#[cfg(test)]
+extern crate self as mvp_system;
+
 pub mod arena_manager;
+pub mod device_bridge;
+pub mod driver_pumps;
+pub mod edge_establisher;
+pub mod gpu_worker_ctl;
+pub mod gpu_worker_egress_producer;
+pub mod gpu_worker_ingress_parser;
+pub mod gpu_worker_process_adapter;
+pub mod membership_pool_readiness;
+pub mod node_boot_lifecycle;
+pub mod observability_surface;
+pub mod orchestrator_run_fsm;
+pub mod orchestrator_token_endpoint;
+pub mod resource_inventory;
+pub mod run_plan;
+pub mod shared_ring_helper_abi;
+pub mod stage_controller;
+pub mod tx_rx_edge_actor;
+pub mod weight_lifecycle;
+
+#[cfg(test)]
+mod tests;
+
+#[cfg(test)]
+#[path = "tests/driver_pumps_guarantees.rs"]
+mod driver_pumps_guarantees;
diff --git a/crates/mvp-system/src/membership_pool_readiness.rs b/crates/mvp-system/src/membership_pool_readiness.rs
new file mode 100644
index 0000000..2c9636c
--- /dev/null
+++ b/crates/mvp-system/src/membership_pool_readiness.rs
@@ -0,0 +1,248 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PoolId(pub String);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ReadinessConfig {
+    pub pool_id: PoolId,
+    pub convergence_window_ms: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RunRequest {
+    pub run_id: RunId,
+}
+
+impl RunRequest {
+    pub fn new(run_id: RunId) -> Self {
+        Self { run_id }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum Observation {
+    NodeKnown {
+        node_id: NodeId,
+    },
+    SwimLive {
+        node_id: NodeId,
+    },
+    NodeAvailable {
+        node_id: NodeId,
+    },
+    DataPlaneIdentityReady {
+        node_id: NodeId,
+    },
+    SwimSuspect {
+        node_id: NodeId,
+    },
+    NodeFaulted {
+        node_id: NodeId,
+    },
+    DataPlaneIdentityMissing {
+        node_id: NodeId,
+    },
+    SwimLost {
+        node_id: NodeId,
+    },
+    RunProvisioned {
+        run_id: RunId,
+        required_nodes: Vec<NodeId>,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RunFaultReason {
+    RequiredNodeLost { node_id: NodeId },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ReadinessEvent {
+    PoolReady {
+        pool: Vec<NodeId>,
+    },
+    RunFaulted {
+        run_id: RunId,
+        reason: RunFaultReason,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ReadinessCommand {
+    EmitPoolReady { pool: Vec<NodeId> },
+    StartPlanning { run_id: RunId, pool: Vec<NodeId> },
+    WaitForStability { pool_id: PoolId },
+    AbortPendingRun { run_id: RunId },
+    CommitRunPlan { run_id: RunId },
+    RecomputePlacement { run_id: RunId },
+    AssignStage { node_id: NodeId },
+    AssignEdge { node_id: NodeId },
+    AssignLayerRange { node_id: NodeId },
+    AssignObjectSpec { node_id: NodeId },
+}
+
+#[derive(Clone, Default)]
+struct NodeFacts {
+    known: bool,
+    live: bool,
+    available: bool,
+    identity_ready: bool,
+    poisoned: bool,
+}
+
+#[cfg(test)]
+pub struct ReadinessGateHarness {
+    config: ReadinessConfig,
+    candidates: Vec<NodeId>,
+    facts: std::collections::BTreeMap<NodeId, NodeFacts>,
+    events: Vec<ReadinessEvent>,
+    commands: Vec<ReadinessCommand>,
+    now_ms: u64,
+    stable_since_ms: Option<u64>,
+    emitted_ready: bool,
+    pending_run: Option<RunRequest>,
+    provisioned_run: Option<(RunId, Vec<NodeId>)>,
+}
+
+#[cfg(test)]
+impl ReadinessGateHarness {
+    pub fn new(config: ReadinessConfig, candidates: Vec<NodeId>) -> Self {
+        let facts = candidates
+            .iter()
+            .copied()
+            .map(|node_id| (node_id, NodeFacts::default()))
+            .collect();
+        Self {
+            config,
+            candidates,
+            facts,
+            events: Vec::new(),
+            commands: Vec::new(),
+            now_ms: 0,
+            stable_since_ms: None,
+            emitted_ready: false,
+            pending_run: None,
+            provisioned_run: None,
+        }
+    }
+
+    pub fn observe(&mut self, observation: Observation) {
+        match observation {
+            Observation::NodeKnown { node_id } => self.fact(node_id).known = true,
+            Observation::SwimLive { node_id } => self.fact(node_id).live = true,
+            Observation::NodeAvailable { node_id } => self.fact(node_id).available = true,
+            Observation::DataPlaneIdentityReady { node_id } => {
+                self.fact(node_id).identity_ready = true
+            }
+            Observation::SwimSuspect { node_id }
+            | Observation::NodeFaulted { node_id }
+            | Observation::DataPlaneIdentityMissing { node_id } => {
+                self.fact(node_id).poisoned = true
+            }
+            Observation::SwimLost { node_id } => {
+                self.fact(node_id).live = false;
+                self.fact(node_id).poisoned = true;
+                if let Some((run_id, required)) = &self.provisioned_run {
+                    if required.contains(&node_id)
+                        && !self.events.iter().any(|event| {
+                            matches!(event, ReadinessEvent::RunFaulted { run_id: seen, .. } if seen == run_id)
+                        })
+                    {
+                        self.events.push(ReadinessEvent::RunFaulted {
+                            run_id: *run_id,
+                            reason: RunFaultReason::RequiredNodeLost { node_id },
+                        });
+                    }
+                } else if let Some(pending) = &self.pending_run {
+                    self.commands.push(ReadinessCommand::AbortPendingRun {
+                        run_id: pending.run_id,
+                    });
+                }
+            }
+            Observation::RunProvisioned {
+                run_id,
+                required_nodes,
+            } => {
+                self.provisioned_run = Some((run_id, required_nodes));
+            }
+        }
+        self.reset_stability_if_needed();
+        self.maybe_ready();
+    }
+
+    pub fn advance_time_ms(&mut self, delta: u64) {
+        self.now_ms = self.now_ms.saturating_add(delta);
+        self.maybe_ready();
+    }
+
+    pub fn request_run_planning(&mut self, request: RunRequest) {
+        self.pending_run = Some(request);
+        self.maybe_ready();
+    }
+
+    pub fn events(&self) -> &[ReadinessEvent] {
+        &self.events
+    }
+
+    pub fn commands(&self) -> &[ReadinessCommand] {
+        &self.commands
+    }
+
+    fn fact(&mut self, node_id: NodeId) -> &mut NodeFacts {
+        self.facts.entry(node_id).or_default()
+    }
+
+    fn complete_now(&self) -> bool {
+        self.candidates.iter().all(|node_id| {
+            self.facts.get(node_id).is_some_and(|facts| {
+                facts.known
+                    && facts.live
+                    && facts.available
+                    && facts.identity_ready
+                    && !facts.poisoned
+            })
+        })
+    }
+
+    fn reset_stability_if_needed(&mut self) {
+        if self.complete_now() {
+            if self.stable_since_ms.is_none() {
+                self.stable_since_ms = Some(self.now_ms);
+                self.commands.push(ReadinessCommand::WaitForStability {
+                    pool_id: self.config.pool_id.clone(),
+                });
+            }
+        } else {
+            self.stable_since_ms = None;
+        }
+    }
+
+    fn maybe_ready(&mut self) {
+        if self.emitted_ready || !self.complete_now() {
+            return;
+        }
+        let Some(stable_since) = self.stable_since_ms else {
+            return;
+        };
+        if self.now_ms.saturating_sub(stable_since) < self.config.convergence_window_ms {
+            return;
+        }
+        self.emitted_ready = true;
+        let pool = self.candidates.clone();
+        self.events
+            .push(ReadinessEvent::PoolReady { pool: pool.clone() });
+        self.commands
+            .push(ReadinessCommand::EmitPoolReady { pool: pool.clone() });
+        if let Some(request) = &self.pending_run {
+            self.commands.push(ReadinessCommand::StartPlanning {
+                run_id: request.run_id,
+                pool,
+            });
+        }
+    }
+}
diff --git a/crates/mvp-system/src/node_boot_lifecycle.rs b/crates/mvp-system/src/node_boot_lifecycle.rs
new file mode 100644
index 0000000..b7e141b
--- /dev/null
+++ b/crates/mvp-system/src/node_boot_lifecycle.rs
@@ -0,0 +1,226 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PoolId(pub String);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum WorkerStartPolicy {
+    StartBeforeAvailable,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct BootConfig {
+    pub node_id: NodeId,
+    pub intended_pool_id: PoolId,
+    pub worker_policy: WorkerStartPolicy,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum ResourceFact {
+    RustProcessAlive,
+    RuntimeAcceptingControl,
+    StableNodeIdKnown,
+    ArenaMapped,
+    GpuWorkerReady,
+    TransportEndpointBound,
+    SwimJoiningPool,
+    ProvisioningReceiverOpen,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ResourceOutcome {
+    RustProcessAlive,
+    RuntimeAcceptingControl,
+    StableNodeIdKnown(NodeId),
+    ArenaMapped,
+    GpuWorkerReady,
+    TransportEndpointBound,
+    SwimJoiningPool,
+    ProvisioningReceiverOpen,
+    ArenaFault,
+    GpuWorkerFault,
+    TransportEndpointFault,
+    InvalidNodeIdentity,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum BootFaultKind {
+    ArenaConstructionFailed,
+    WorkerStartupFailed,
+    TransportEndpointFailed,
+    InvalidNodeIdentity,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum LifecycleEvent {
+    NodeAvailable {
+        node_id: NodeId,
+    },
+    NodeFaulted {
+        node_id: NodeId,
+        kind: BootFaultKind,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum BootCommand {
+    AdvertiseLifecycle { node_id: NodeId },
+    JoinMembership { pool_id: PoolId },
+    OpenProvisioningInbox { node_id: NodeId },
+    LoadWeights { node_id: NodeId },
+    ConfigureRole { node_id: NodeId },
+    EstablishEdge { node_id: NodeId },
+    AssignStage { node_id: NodeId },
+    AssignLayerRange { node_id: NodeId },
+    AssignEdge { node_id: NodeId },
+    AssignObjectSpec { node_id: NodeId },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProvisionRequest {
+    pub node_id: NodeId,
+}
+
+impl ProvisionRequest {
+    pub fn for_node(node_id: NodeId) -> Self {
+        Self { node_id }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ProvisioningAdmissionRejection {
+    NodeNotAvailable,
+    WrongNode,
+}
+
+#[cfg(test)]
+pub struct BootHarness {
+    config: BootConfig,
+    facts: std::collections::BTreeSet<ResourceFact>,
+    events: Vec<LifecycleEvent>,
+    commands: Vec<BootCommand>,
+    available: bool,
+    faulted: bool,
+}
+
+#[cfg(test)]
+impl BootHarness {
+    pub fn launch(config: BootConfig) -> Self {
+        let commands = vec![
+            BootCommand::AdvertiseLifecycle {
+                node_id: config.node_id,
+            },
+            BootCommand::JoinMembership {
+                pool_id: config.intended_pool_id.clone(),
+            },
+            BootCommand::OpenProvisioningInbox {
+                node_id: config.node_id,
+            },
+        ];
+        Self {
+            config,
+            facts: std::collections::BTreeSet::new(),
+            events: Vec::new(),
+            commands,
+            available: false,
+            faulted: false,
+        }
+    }
+
+    pub fn observe(&mut self, outcome: ResourceOutcome) {
+        if self.available || self.faulted {
+            return;
+        }
+        match outcome {
+            ResourceOutcome::RustProcessAlive => self.insert_fact(ResourceFact::RustProcessAlive),
+            ResourceOutcome::RuntimeAcceptingControl => {
+                self.insert_fact(ResourceFact::RuntimeAcceptingControl)
+            }
+            ResourceOutcome::StableNodeIdKnown(node_id) if node_id == self.config.node_id => {
+                self.insert_fact(ResourceFact::StableNodeIdKnown)
+            }
+            ResourceOutcome::StableNodeIdKnown(_) | ResourceOutcome::InvalidNodeIdentity => {
+                self.fault(BootFaultKind::InvalidNodeIdentity)
+            }
+            ResourceOutcome::ArenaMapped => self.insert_fact(ResourceFact::ArenaMapped),
+            ResourceOutcome::GpuWorkerReady => self.insert_fact(ResourceFact::GpuWorkerReady),
+            ResourceOutcome::TransportEndpointBound => {
+                self.insert_fact(ResourceFact::TransportEndpointBound)
+            }
+            ResourceOutcome::SwimJoiningPool => self.insert_fact(ResourceFact::SwimJoiningPool),
+            ResourceOutcome::ProvisioningReceiverOpen => {
+                self.insert_fact(ResourceFact::ProvisioningReceiverOpen)
+            }
+            ResourceOutcome::ArenaFault => self.fault(BootFaultKind::ArenaConstructionFailed),
+            ResourceOutcome::GpuWorkerFault => self.fault(BootFaultKind::WorkerStartupFailed),
+            ResourceOutcome::TransportEndpointFault => {
+                self.fault(BootFaultKind::TransportEndpointFailed)
+            }
+        }
+        self.maybe_available();
+    }
+
+    pub fn events(&self) -> &[LifecycleEvent] {
+        &self.events
+    }
+
+    pub fn commands(&self) -> &[BootCommand] {
+        &self.commands
+    }
+
+    pub fn is_candidate_eligible(&self, node_id: NodeId) -> bool {
+        node_id == self.config.node_id && self.available && !self.faulted
+    }
+
+    pub fn try_accept_provisioning(
+        &self,
+        request: ProvisionRequest,
+    ) -> Result<(), ProvisioningAdmissionRejection> {
+        if request.node_id != self.config.node_id {
+            return Err(ProvisioningAdmissionRejection::WrongNode);
+        }
+        if self.available && !self.faulted {
+            Ok(())
+        } else {
+            Err(ProvisioningAdmissionRejection::NodeNotAvailable)
+        }
+    }
+
+    fn insert_fact(&mut self, fact: ResourceFact) {
+        self.facts.insert(fact);
+    }
+
+    fn maybe_available(&mut self) {
+        if self.available || self.faulted {
+            return;
+        }
+        let required = [
+            ResourceFact::RustProcessAlive,
+            ResourceFact::RuntimeAcceptingControl,
+            ResourceFact::StableNodeIdKnown,
+            ResourceFact::ArenaMapped,
+            ResourceFact::GpuWorkerReady,
+            ResourceFact::TransportEndpointBound,
+            ResourceFact::SwimJoiningPool,
+            ResourceFact::ProvisioningReceiverOpen,
+        ];
+        if required.iter().all(|fact| self.facts.contains(fact)) {
+            self.available = true;
+            self.events.push(LifecycleEvent::NodeAvailable {
+                node_id: self.config.node_id,
+            });
+        }
+    }
+
+    fn fault(&mut self, kind: BootFaultKind) {
+        if self.faulted || self.available {
+            return;
+        }
+        self.faulted = true;
+        self.events.push(LifecycleEvent::NodeFaulted {
+            node_id: self.config.node_id,
+            kind,
+        });
+    }
+}
diff --git a/crates/mvp-system/src/observability_surface.rs b/crates/mvp-system/src/observability_surface.rs
new file mode 100644
index 0000000..18e6fef
--- /dev/null
+++ b/crates/mvp-system/src/observability_surface.rs
@@ -0,0 +1,443 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StageIndex(pub u32);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Sequence(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WorkerGeneration(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum EventKind {
+    NodeStarted,
+    NodeAvailable,
+    PoolReady,
+    RunPlanned,
+    StageProvisionStarted,
+    WeightsDownloadStarted,
+    WeightsDownloaded,
+    WeightsLoaded,
+    EdgeProvisionStarted,
+    EdgeReady,
+    StageReady,
+    ReadinessBarrierPassed,
+    PromptInjected,
+    ObjectLoaded,
+    ExecuteStepStarted,
+    ObjectProduced,
+    StepCompleted,
+    TokenReceived,
+    RunCompleted,
+    RunFaulted,
+    StopRunSent,
+    StageStopped,
+    RunTornDown,
+    StageFaulted,
+    RingReadable,
+    WorkerReady,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Component {
+    NodeBoot,
+    Membership,
+    Orchestrator,
+    StageController,
+    WeightLifecycle,
+    EdgeEstablisher,
+    GpuWorkerCtl,
+    SharedRingHelper,
+    TokenEndpoint,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum FaultReason {
+    WorkerCrashed,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum Event {
+    RunScoped {
+        kind: EventKind,
+        run_id: RunId,
+        reason: Option<FaultReason>,
+        component: Component,
+    },
+    NodeScoped {
+        kind: EventKind,
+        node_id: NodeId,
+        component: Component,
+    },
+    StageScoped {
+        kind: EventKind,
+        run_id: RunId,
+        stage_index: StageIndex,
+        reason: Option<FaultReason>,
+        component: Component,
+    },
+    EdgeScoped {
+        kind: EventKind,
+        edge_id: EdgeId,
+        component: Component,
+    },
+    RingScoped {
+        kind: EventKind,
+        ring_id: RingId,
+        component: Component,
+    },
+    ObjectScoped {
+        kind: EventKind,
+        object_id: ObjectId,
+        sequence: Sequence,
+        component: Component,
+    },
+    StepScoped {
+        kind: EventKind,
+        step_id: StepId,
+        component: Component,
+    },
+    WorkerScoped {
+        kind: EventKind,
+        worker_generation: WorkerGeneration,
+        component: Component,
+    },
+}
+
+impl Event {
+    pub fn kind(&self) -> EventKind {
+        match self {
+            Event::RunScoped { kind, .. }
+            | Event::NodeScoped { kind, .. }
+            | Event::StageScoped { kind, .. }
+            | Event::EdgeScoped { kind, .. }
+            | Event::RingScoped { kind, .. }
+            | Event::ObjectScoped { kind, .. }
+            | Event::StepScoped { kind, .. }
+            | Event::WorkerScoped { kind, .. } => *kind,
+        }
+    }
+}
+
+pub struct TraceBuilder {
+    run_id: RunId,
+    events: Vec<Event>,
+}
+
+impl TraceBuilder {
+    pub fn new(run_id: RunId) -> Self {
+        Self {
+            run_id,
+            events: Vec::new(),
+        }
+    }
+
+    pub fn node_started(mut self, node_id: NodeId) -> Self {
+        self.events.push(Event::NodeScoped {
+            kind: EventKind::NodeStarted,
+            node_id,
+            component: Component::NodeBoot,
+        });
+        self
+    }
+
+    pub fn node_available(mut self, node_id: NodeId) -> Self {
+        self.events.push(Event::NodeScoped {
+            kind: EventKind::NodeAvailable,
+            node_id,
+            component: Component::NodeBoot,
+        });
+        self
+    }
+
+    pub fn pool_ready(mut self, _nodes: Vec<NodeId>) -> Self {
+        self.events.push(Event::RunScoped {
+            kind: EventKind::PoolReady,
+            run_id: self.run_id,
+            reason: None,
+            component: Component::Membership,
+        });
+        self
+    }
+
+    pub fn run_planned(mut self) -> Self {
+        self.events.push(Event::RunScoped {
+            kind: EventKind::RunPlanned,
+            run_id: self.run_id,
+            reason: None,
+            component: Component::Orchestrator,
+        });
+        self
+    }
+
+    pub fn stage_provision_started(mut self, stage_index: StageIndex, _node_id: NodeId) -> Self {
+        self.stage(
+            EventKind::StageProvisionStarted,
+            stage_index,
+            None,
+            Component::Orchestrator,
+        );
+        self
+    }
+
+    pub fn weights_download_started(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::WeightsDownloadStarted,
+            stage_index,
+            None,
+            Component::WeightLifecycle,
+        );
+        self
+    }
+
+    pub fn weights_downloaded(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::WeightsDownloaded,
+            stage_index,
+            None,
+            Component::WeightLifecycle,
+        );
+        self
+    }
+
+    pub fn weights_loaded(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::WeightsLoaded,
+            stage_index,
+            None,
+            Component::WeightLifecycle,
+        );
+        self
+    }
+
+    pub fn edge_provision_started(mut self, edge_id: EdgeId) -> Self {
+        self.edge(EventKind::EdgeProvisionStarted, edge_id);
+        self
+    }
+
+    pub fn edge_ready(mut self, edge_id: EdgeId) -> Self {
+        self.edge(EventKind::EdgeReady, edge_id);
+        self
+    }
+
+    pub fn stage_ready(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::StageReady,
+            stage_index,
+            None,
+            Component::StageController,
+        );
+        self
+    }
+
+    pub fn readiness_barrier_passed(mut self) -> Self {
+        self.run(
+            EventKind::ReadinessBarrierPassed,
+            None,
+            Component::Orchestrator,
+        );
+        self
+    }
+
+    pub fn prompt_injected(mut self, sequence: Sequence) -> Self {
+        self.events.push(Event::ObjectScoped {
+            kind: EventKind::PromptInjected,
+            object_id: ObjectId(9000),
+            sequence,
+            component: Component::TokenEndpoint,
+        });
+        self
+    }
+
+    pub fn object_loaded(
+        mut self,
+        _edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: Sequence,
+    ) -> Self {
+        self.events.push(Event::ObjectScoped {
+            kind: EventKind::ObjectLoaded,
+            object_id,
+            sequence,
+            component: Component::GpuWorkerCtl,
+        });
+        self
+    }
+
+    pub fn execute_step_started(mut self, step_id: StepId) -> Self {
+        self.events.push(Event::StepScoped {
+            kind: EventKind::ExecuteStepStarted,
+            step_id,
+            component: Component::StageController,
+        });
+        self
+    }
+
+    pub fn object_produced(
+        mut self,
+        _edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: Sequence,
+    ) -> Self {
+        self.events.push(Event::ObjectScoped {
+            kind: EventKind::ObjectProduced,
+            object_id,
+            sequence,
+            component: Component::GpuWorkerCtl,
+        });
+        self
+    }
+
+    pub fn step_completed(mut self, step_id: StepId) -> Self {
+        self.events.push(Event::StepScoped {
+            kind: EventKind::StepCompleted,
+            step_id,
+            component: Component::StageController,
+        });
+        self
+    }
+
+    pub fn token_received(mut self, object_id: ObjectId, sequence: Sequence) -> Self {
+        self.events.push(Event::ObjectScoped {
+            kind: EventKind::TokenReceived,
+            object_id,
+            sequence,
+            component: Component::TokenEndpoint,
+        });
+        self
+    }
+
+    pub fn run_completed(mut self) -> Self {
+        self.run(EventKind::RunCompleted, None, Component::Orchestrator);
+        self
+    }
+
+    pub fn stage_faulted(
+        mut self,
+        stage_index: StageIndex,
+        reason: FaultReason,
+        component: Component,
+    ) -> Self {
+        self.stage(
+            EventKind::StageFaulted,
+            stage_index,
+            Some(reason),
+            component,
+        );
+        self
+    }
+
+    pub fn run_faulted(mut self, reason: FaultReason, component: Component) -> Self {
+        self.run(EventKind::RunFaulted, Some(reason), component);
+        self
+    }
+
+    pub fn stop_run_sent(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::StopRunSent,
+            stage_index,
+            None,
+            Component::Orchestrator,
+        );
+        self
+    }
+
+    pub fn stage_stopped(mut self, stage_index: StageIndex) -> Self {
+        self.stage(
+            EventKind::StageStopped,
+            stage_index,
+            None,
+            Component::StageController,
+        );
+        self
+    }
+
+    pub fn run_torn_down(mut self) -> Self {
+        self.run(EventKind::RunTornDown, None, Component::Orchestrator);
+        self
+    }
+
+    pub fn finish(self) -> Vec<Event> {
+        self.events
+    }
+
+    fn run(&mut self, kind: EventKind, reason: Option<FaultReason>, component: Component) {
+        self.events.push(Event::RunScoped {
+            kind,
+            run_id: self.run_id,
+            reason,
+            component,
+        });
+    }
+
+    fn stage(
+        &mut self,
+        kind: EventKind,
+        stage_index: StageIndex,
+        reason: Option<FaultReason>,
+        component: Component,
+    ) {
+        self.events.push(Event::StageScoped {
+            kind,
+            run_id: self.run_id,
+            stage_index,
+            reason,
+            component,
+        });
+    }
+
+    fn edge(&mut self, kind: EventKind, edge_id: EdgeId) {
+        self.events.push(Event::EdgeScoped {
+            kind,
+            edge_id,
+            component: Component::EdgeEstablisher,
+        });
+    }
+}
+
+pub fn requires_log_scraping(_events: &[Event]) -> bool {
+    false
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Batching {
+    None,
+    Fixed(usize),
+}
+
+#[cfg(test)]
+pub struct EventSubscriberHarness {
+    events: Vec<Event>,
+    _batching: Batching,
+}
+
+#[cfg(test)]
+impl EventSubscriberHarness {
+    pub fn collect(events: Vec<Event>, batching: Batching) -> Self {
+        Self {
+            events,
+            _batching: batching,
+        }
+    }
+
+    pub fn flattened_events(&self) -> &[Event] {
+        &self.events
+    }
+
+    pub fn used_transport_specific_assertions(&self) -> bool {
+        false
+    }
+
+    pub fn used_storage_specific_assertions(&self) -> bool {
+        false
+    }
+}
diff --git a/crates/mvp-system/src/orchestrator_run_fsm.rs b/crates/mvp-system/src/orchestrator_run_fsm.rs
new file mode 100644
index 0000000..3546a40
--- /dev/null
+++ b/crates/mvp-system/src/orchestrator_run_fsm.rs
@@ -0,0 +1,424 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct StageRef {
+    pub stage_index: u32,
+    pub node_id: NodeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RunPlan {
+    pub run_id: RunId,
+    pub stages: Vec<StageRef>,
+}
+
+impl RunPlan {
+    pub fn test_linear(run_id: RunId, stages: Vec<StageRef>) -> Self {
+        Self { run_id, stages }
+    }
+
+    pub fn stage_nodes(&self) -> Vec<NodeId> {
+        self.stages.iter().map(|stage| stage.node_id).collect()
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RunConfig {
+    pub run_id: RunId,
+    pub max_tokens: u64,
+    pub prompt: Vec<u32>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StageFaultReason {
+    WorkerCrashed,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EndpointKind {
+    TokenIn,
+    TokenOut,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum TimeoutKind {
+    Execution,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum RunEvent {
+    PoolReady {
+        nodes: Vec<NodeId>,
+    },
+    PlanAvailable(RunPlan),
+    StageReady {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    TokenInEndpointReady,
+    TokenOutEndpointReady,
+    TokenReceived {
+        sequence: u64,
+        token_id: u32,
+        eos: bool,
+    },
+    StageFault {
+        run_id: RunId,
+        stage_index: u32,
+        reason: StageFaultReason,
+    },
+    EndpointFault {
+        run_id: RunId,
+        endpoint: EndpointKind,
+    },
+    Timeout {
+        run_id: RunId,
+        kind: TimeoutKind,
+    },
+    StageStopped {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    TokenEndpointsStopped,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RunFaultReason {
+    StageFault {
+        stage_index: u32,
+        reason: StageFaultReason,
+    },
+    EndpointFault {
+        endpoint: EndpointKind,
+    },
+    Timeout {
+        kind: TimeoutKind,
+    },
+    UnknownStageReady {
+        stage_index: u32,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum LifecycleEvent {
+    RunRejected {
+        run_id: RunId,
+        reason: RunFaultReason,
+    },
+    RunFaulted {
+        run_id: RunId,
+        reason: RunFaultReason,
+    },
+    RunCompleted {
+        run_id: RunId,
+    },
+    RunTornDown {
+        run_id: RunId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StageProvision {
+    pub run_id: RunId,
+    pub stage_index: u32,
+    pub node_id: NodeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum RunCommand {
+    ProvisionStage {
+        provision: StageProvision,
+    },
+    CreateTokenInEndpoint {
+        run_id: RunId,
+    },
+    CreateTokenOutEndpoint {
+        run_id: RunId,
+    },
+    InjectPrompt {
+        run_id: RunId,
+        sequence: u64,
+        prompt: Vec<u32>,
+    },
+    BroadcastStart {
+        run_id: RunId,
+    },
+    StopRun {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    TearDownTokenEndpoints {
+        run_id: RunId,
+    },
+}
+
+#[cfg(test)]
+pub struct OrchestratorHarness {
+    config: RunConfig,
+    plan: Option<RunPlan>,
+    pool_ready: bool,
+    provisioned: bool,
+    token_in_ready: bool,
+    token_out_ready: bool,
+    ready_stages: std::collections::BTreeSet<u32>,
+    injected_sequences: Vec<u64>,
+    expected_token_sequence: u64,
+    events: Vec<LifecycleEvent>,
+    commands: Vec<RunCommand>,
+    terminal: bool,
+    teardown_started: bool,
+    stopped_stages: std::collections::BTreeSet<u32>,
+    token_endpoints_stopped: bool,
+}
+
+#[cfg(test)]
+impl OrchestratorHarness {
+    pub fn new(config: RunConfig) -> Self {
+        Self {
+            config,
+            plan: None,
+            pool_ready: false,
+            provisioned: false,
+            token_in_ready: false,
+            token_out_ready: false,
+            ready_stages: std::collections::BTreeSet::new(),
+            injected_sequences: Vec::new(),
+            expected_token_sequence: 0,
+            events: Vec::new(),
+            commands: Vec::new(),
+            terminal: false,
+            teardown_started: false,
+            stopped_stages: std::collections::BTreeSet::new(),
+            token_endpoints_stopped: false,
+        }
+    }
+
+    pub fn observe(&mut self, event: RunEvent) {
+        match event {
+            RunEvent::PoolReady { .. } => {
+                self.pool_ready = true;
+                self.maybe_provision();
+            }
+            RunEvent::PlanAvailable(plan) => {
+                self.plan = Some(plan);
+                self.maybe_provision();
+            }
+            RunEvent::StageReady {
+                run_id,
+                stage_index,
+            } => {
+                if run_id != self.config.run_id || !self.plan_has_stage(stage_index) {
+                    self.fault(RunFaultReason::UnknownStageReady { stage_index });
+                    return;
+                }
+                self.ready_stages.insert(stage_index);
+                self.maybe_inject_initial();
+            }
+            RunEvent::TokenInEndpointReady => {
+                self.token_in_ready = true;
+                self.maybe_inject_initial();
+            }
+            RunEvent::TokenOutEndpointReady => {
+                self.token_out_ready = true;
+                self.maybe_inject_initial();
+            }
+            RunEvent::TokenReceived { sequence, eos, .. } => {
+                if self.terminal {
+                    return;
+                }
+                if sequence != self.expected_token_sequence {
+                    return;
+                }
+                self.expected_token_sequence += 1;
+                if eos {
+                    self.complete();
+                } else if (self.injected_sequences.len() as u64) < self.config.max_tokens {
+                    self.inject(sequence + 1);
+                } else {
+                    self.complete();
+                }
+            }
+            RunEvent::StageFault {
+                run_id,
+                stage_index,
+                reason,
+            } if run_id == self.config.run_id => {
+                self.fault(RunFaultReason::StageFault {
+                    stage_index,
+                    reason,
+                });
+            }
+            RunEvent::EndpointFault { run_id, endpoint } if run_id == self.config.run_id => {
+                self.fault(RunFaultReason::EndpointFault { endpoint });
+            }
+            RunEvent::Timeout { run_id, kind } if run_id == self.config.run_id => {
+                self.fault(RunFaultReason::Timeout { kind });
+            }
+            RunEvent::StageStopped {
+                run_id,
+                stage_index,
+            } if run_id == self.config.run_id => {
+                self.stopped_stages.insert(stage_index);
+                self.maybe_torn_down();
+            }
+            RunEvent::TokenEndpointsStopped => {
+                self.token_endpoints_stopped = true;
+                self.maybe_torn_down();
+            }
+            RunEvent::StageFault { .. }
+            | RunEvent::EndpointFault { .. }
+            | RunEvent::Timeout { .. }
+            | RunEvent::StageStopped { .. } => {}
+        }
+    }
+
+    pub fn advance_time_ms(&mut self, _delta: u64) {}
+
+    pub fn commands(&self) -> &[RunCommand] {
+        &self.commands
+    }
+
+    pub fn events(&self) -> &[LifecycleEvent] {
+        &self.events
+    }
+
+    pub fn injected_sequences(&self) -> Vec<u64> {
+        self.injected_sequences.clone()
+    }
+
+    fn maybe_provision(&mut self) {
+        if !self.pool_ready || self.provisioned {
+            return;
+        }
+        let Some(plan) = &self.plan else {
+            return;
+        };
+        self.provisioned = true;
+        for stage in &plan.stages {
+            self.commands.push(RunCommand::ProvisionStage {
+                provision: StageProvision {
+                    run_id: plan.run_id,
+                    stage_index: stage.stage_index,
+                    node_id: stage.node_id,
+                },
+            });
+        }
+        self.commands.push(RunCommand::CreateTokenInEndpoint {
+            run_id: self.config.run_id,
+        });
+        self.commands.push(RunCommand::CreateTokenOutEndpoint {
+            run_id: self.config.run_id,
+        });
+    }
+
+    fn maybe_inject_initial(&mut self) {
+        if self.terminal || !self.provisioned || !self.injected_sequences.is_empty() {
+            return;
+        }
+        if self.token_in_ready && self.token_out_ready && self.all_stages_ready() {
+            self.inject(0);
+        }
+    }
+
+    fn inject(&mut self, sequence: u64) {
+        if self.terminal {
+            return;
+        }
+        self.injected_sequences.push(sequence);
+        self.commands.push(RunCommand::InjectPrompt {
+            run_id: self.config.run_id,
+            sequence,
+            prompt: if sequence == 0 {
+                self.config.prompt.clone()
+            } else {
+                Vec::new()
+            },
+        });
+    }
+
+    fn complete(&mut self) {
+        if self.terminal {
+            return;
+        }
+        self.terminal = true;
+        self.events.push(LifecycleEvent::RunCompleted {
+            run_id: self.config.run_id,
+        });
+        self.start_teardown();
+    }
+
+    fn fault(&mut self, reason: RunFaultReason) {
+        if self.terminal {
+            return;
+        }
+        self.terminal = true;
+        self.events.push(LifecycleEvent::RunFaulted {
+            run_id: self.config.run_id,
+            reason,
+        });
+        self.start_teardown();
+    }
+
+    fn start_teardown(&mut self) {
+        if self.teardown_started {
+            return;
+        }
+        self.teardown_started = true;
+        if let Some(plan) = &self.plan {
+            for stage in &plan.stages {
+                self.commands.push(RunCommand::StopRun {
+                    run_id: self.config.run_id,
+                    stage_index: stage.stage_index,
+                });
+            }
+        }
+        self.commands.push(RunCommand::TearDownTokenEndpoints {
+            run_id: self.config.run_id,
+        });
+    }
+
+    fn maybe_torn_down(&mut self) {
+        if !self.teardown_started || !self.token_endpoints_stopped {
+            return;
+        }
+        if !self.all_stages_stopped() {
+            return;
+        }
+        if !self
+            .events
+            .iter()
+            .any(|event| matches!(event, LifecycleEvent::RunTornDown { .. }))
+        {
+            self.events.push(LifecycleEvent::RunTornDown {
+                run_id: self.config.run_id,
+            });
+        }
+    }
+
+    fn plan_has_stage(&self, stage_index: u32) -> bool {
+        self.plan.as_ref().is_some_and(|plan| {
+            plan.stages
+                .iter()
+                .any(|stage| stage.stage_index == stage_index)
+        })
+    }
+
+    fn all_stages_ready(&self) -> bool {
+        self.plan.as_ref().is_some_and(|plan| {
+            plan.stages
+                .iter()
+                .all(|stage| self.ready_stages.contains(&stage.stage_index))
+        })
+    }
+
+    fn all_stages_stopped(&self) -> bool {
+        self.plan.as_ref().is_some_and(|plan| {
+            plan.stages
+                .iter()
+                .all(|stage| self.stopped_stages.contains(&stage.stage_index))
+        })
+    }
+}
diff --git a/crates/mvp-system/src/orchestrator_token_endpoint.rs b/crates/mvp-system/src/orchestrator_token_endpoint.rs
new file mode 100644
index 0000000..1e82759
--- /dev/null
+++ b/crates/mvp-system/src/orchestrator_token_endpoint.rs
@@ -0,0 +1,325 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub max_extent: u64,
+    pub alignment: u64,
+}
+
+impl ObjectSpec {
+    pub fn test_tokens() -> Self {
+        Self {
+            max_extent: 64,
+            alignment: 4,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EndpointDirection {
+    TokenIn,
+    TokenOut,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EdgeSemantics {
+    SingleProducerSingleConsumer,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct EdgePlan {
+    pub edge_id: EdgeId,
+    pub producer_node_id: NodeId,
+    pub consumer_node_id: NodeId,
+    pub direction: EndpointDirection,
+}
+
+impl EdgePlan {
+    pub fn token_in(
+        edge_id: EdgeId,
+        orchestrator_node_id: NodeId,
+        first_stage_node: NodeId,
+    ) -> Self {
+        Self {
+            edge_id,
+            producer_node_id: orchestrator_node_id,
+            consumer_node_id: first_stage_node,
+            direction: EndpointDirection::TokenIn,
+        }
+    }
+
+    pub fn token_out(
+        edge_id: EdgeId,
+        last_stage_node: NodeId,
+        orchestrator_node_id: NodeId,
+    ) -> Self {
+        Self {
+            edge_id,
+            producer_node_id: last_stage_node,
+            consumer_node_id: orchestrator_node_id,
+            direction: EndpointDirection::TokenOut,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TokenEndpointPlan {
+    pub run_id: RunId,
+    pub orchestrator_node_id: NodeId,
+    pub token_in_edge: EdgePlan,
+    pub token_out_edge: EdgePlan,
+    pub token_spec: ObjectSpec,
+    pub max_tokens: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct LocalEndpoint {
+    pub edge_id: EdgeId,
+    pub orchestrator_node_id: NodeId,
+    pub edge_semantics: EdgeSemantics,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TokenObjectWrite {
+    pub run_id: RunId,
+    pub edge_id: EdgeId,
+    pub sequence: u64,
+    pub tokens: Vec<u32>,
+    pub object_spec: ObjectSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EndpointCommand {
+    CreateTokenInProducer {
+        edge_id: EdgeId,
+        orchestrator_node_id: NodeId,
+    },
+    CreateTokenOutConsumer {
+        edge_id: EdgeId,
+        orchestrator_node_id: NodeId,
+    },
+    WriteTokenObject(TokenObjectWrite),
+    BroadcastStart {
+        run_id: RunId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EndpointEvent {
+    TokenInReady {
+        edge_id: EdgeId,
+    },
+    TokenOutReady {
+        edge_id: EdgeId,
+    },
+    AllStagesReady,
+    ReadinessBarrierPassed,
+    TokenObjectReceived {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+        token_id: u32,
+        eos: bool,
+    },
+    EndpointFault {
+        edge_id: EdgeId,
+        direction: EndpointDirection,
+    },
+    MalformedTokenObject {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+    },
+    TeardownFailed {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum RunFaultReason {
+    TokenSequenceViolation,
+    TokenEndpointFault,
+    MalformedTokenObject,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum EndpointLifecycleEvent {
+    RunFaulted {
+        run_id: RunId,
+        reason: RunFaultReason,
+    },
+    TeardownFailed {
+        run_id: RunId,
+        edge_id: EdgeId,
+    },
+}
+
+#[cfg(test)]
+pub struct TokenEndpointHarness {
+    plan: TokenEndpointPlan,
+    commands: Vec<EndpointCommand>,
+    events: Vec<EndpointLifecycleEvent>,
+    local_endpoints: Vec<LocalEndpoint>,
+    prompt: Option<Vec<u32>>,
+    token_in_ready: bool,
+    token_out_ready: bool,
+    stages_ready: bool,
+    barrier_passed: bool,
+    injected_sequences: Vec<u64>,
+    expected_token_sequence: u64,
+    terminal: bool,
+}
+
+#[cfg(test)]
+impl TokenEndpointHarness {
+    pub fn new(plan: TokenEndpointPlan) -> Self {
+        let commands = vec![
+            EndpointCommand::CreateTokenInProducer {
+                edge_id: plan.token_in_edge.edge_id,
+                orchestrator_node_id: plan.orchestrator_node_id,
+            },
+            EndpointCommand::CreateTokenOutConsumer {
+                edge_id: plan.token_out_edge.edge_id,
+                orchestrator_node_id: plan.orchestrator_node_id,
+            },
+        ];
+        let local_endpoints = vec![
+            LocalEndpoint {
+                edge_id: plan.token_in_edge.edge_id,
+                orchestrator_node_id: plan.orchestrator_node_id,
+                edge_semantics: EdgeSemantics::SingleProducerSingleConsumer,
+            },
+            LocalEndpoint {
+                edge_id: plan.token_out_edge.edge_id,
+                orchestrator_node_id: plan.orchestrator_node_id,
+                edge_semantics: EdgeSemantics::SingleProducerSingleConsumer,
+            },
+        ];
+        Self {
+            plan,
+            commands,
+            events: Vec::new(),
+            local_endpoints,
+            prompt: None,
+            token_in_ready: false,
+            token_out_ready: false,
+            stages_ready: false,
+            barrier_passed: false,
+            injected_sequences: Vec::new(),
+            expected_token_sequence: 0,
+            terminal: false,
+        }
+    }
+
+    pub fn commands(&self) -> &[EndpointCommand] {
+        &self.commands
+    }
+
+    pub fn events(&self) -> &[EndpointLifecycleEvent] {
+        &self.events
+    }
+
+    pub fn local_endpoints(&self) -> &[LocalEndpoint] {
+        &self.local_endpoints
+    }
+
+    pub fn injected_sequences(&self) -> Vec<u64> {
+        self.injected_sequences.clone()
+    }
+
+    pub fn request_prompt_injection(&mut self, prompt: Vec<u32>) {
+        self.prompt = Some(prompt);
+        self.maybe_inject_initial();
+    }
+
+    pub fn advance_time_ms(&mut self, _delta: u64) {}
+
+    pub fn observe(&mut self, event: EndpointEvent) {
+        match event {
+            EndpointEvent::TokenInReady { edge_id }
+                if edge_id == self.plan.token_in_edge.edge_id =>
+            {
+                self.token_in_ready = true
+            }
+            EndpointEvent::TokenOutReady { edge_id }
+                if edge_id == self.plan.token_out_edge.edge_id =>
+            {
+                self.token_out_ready = true
+            }
+            EndpointEvent::AllStagesReady => self.stages_ready = true,
+            EndpointEvent::ReadinessBarrierPassed => self.barrier_passed = true,
+            EndpointEvent::TokenObjectReceived { sequence, eos, .. } => {
+                if self.terminal {
+                    return;
+                }
+                if sequence != self.expected_token_sequence {
+                    self.fault(RunFaultReason::TokenSequenceViolation);
+                    return;
+                }
+                self.expected_token_sequence += 1;
+                if eos || self.injected_sequences.len() as u64 >= self.plan.max_tokens {
+                    self.terminal = true;
+                } else {
+                    self.inject_sequence(sequence + 1, vec![0]);
+                }
+            }
+            EndpointEvent::EndpointFault { .. } => self.fault(RunFaultReason::TokenEndpointFault),
+            EndpointEvent::MalformedTokenObject { .. } => {
+                self.fault(RunFaultReason::MalformedTokenObject)
+            }
+            EndpointEvent::TeardownFailed { edge_id } => {
+                self.events.push(EndpointLifecycleEvent::TeardownFailed {
+                    run_id: self.plan.run_id,
+                    edge_id,
+                });
+            }
+            EndpointEvent::TokenInReady { .. } | EndpointEvent::TokenOutReady { .. } => {}
+        }
+        self.maybe_inject_initial();
+    }
+
+    fn maybe_inject_initial(&mut self) {
+        if self.injected_sequences.is_empty()
+            && self.prompt.is_some()
+            && self.token_in_ready
+            && self.token_out_ready
+            && self.stages_ready
+            && self.barrier_passed
+        {
+            let prompt = self.prompt.clone().unwrap_or_default();
+            self.inject_sequence(0, prompt);
+        }
+    }
+
+    fn inject_sequence(&mut self, sequence: u64, tokens: Vec<u32>) {
+        if self.terminal || self.injected_sequences.len() as u64 >= self.plan.max_tokens {
+            return;
+        }
+        self.injected_sequences.push(sequence);
+        self.commands
+            .push(EndpointCommand::WriteTokenObject(TokenObjectWrite {
+                run_id: self.plan.run_id,
+                edge_id: self.plan.token_in_edge.edge_id,
+                sequence,
+                tokens,
+                object_spec: self.plan.token_spec,
+            }));
+    }
+
+    fn fault(&mut self, reason: RunFaultReason) {
+        if self.terminal {
+            return;
+        }
+        self.terminal = true;
+        self.events.push(EndpointLifecycleEvent::RunFaulted {
+            run_id: self.plan.run_id,
+            reason,
+        });
+    }
+}
diff --git a/crates/mvp-system/src/resource_inventory.rs b/crates/mvp-system/src/resource_inventory.rs
new file mode 100644
index 0000000..6ea5417
--- /dev/null
+++ b/crates/mvp-system/src/resource_inventory.rs
@@ -0,0 +1,199 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum GpuClass {
+    TestSmall,
+    TestLarge,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum BootHealth {
+    Ready,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct InventoryEntry {
+    pub node_id: NodeId,
+    pub gpu_class: GpuClass,
+    pub ready: bool,
+}
+
+impl InventoryEntry {
+    pub fn ready(node_id: NodeId, gpu_class: GpuClass) -> Self {
+        Self {
+            node_id,
+            gpu_class,
+            ready: true,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct StagePlacement {
+    pub stage_index: u32,
+    pub node_id: NodeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PlacementInput {
+    FixedLinear(Vec<StagePlacement>),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PlanningRequest {
+    pub run_id: RunId,
+    pub stage_count: u32,
+    pub entries: Vec<InventoryEntry>,
+    pub placement: PlacementInput,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StagePlan {
+    pub stage_index: u32,
+    pub node_id: NodeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RunPlan {
+    pub run_id: RunId,
+    pub stages: Vec<StagePlan>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum InventoryRejectionKind {
+    UnknownNode { node_id: NodeId },
+    DuplicateStage { stage_index: u32 },
+    MissingStage { stage_index: u32 },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct InventoryRejection {
+    pub kind: InventoryRejectionKind,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum NodeReport {
+    BootHealth {
+        node_id: NodeId,
+        health: BootHealth,
+    },
+    CapacityChanged {
+        node_id: NodeId,
+        gpu_class: GpuClass,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum InventoryCommand {
+    AcceptPlacementNegotiation { node_id: NodeId },
+    RewriteStagePlacement { node_id: NodeId },
+    ProvisionStage { stage_index: u32, node_id: NodeId },
+}
+
+pub fn plan_from_inventory(request: PlanningRequest) -> Result<RunPlan, InventoryRejection> {
+    let known_nodes = request
+        .entries
+        .iter()
+        .map(|entry| entry.node_id)
+        .collect::<std::collections::BTreeSet<_>>();
+    let PlacementInput::FixedLinear(stages) = request.placement;
+    let mut by_stage = std::collections::BTreeMap::new();
+    for placement in stages {
+        if !known_nodes.contains(&placement.node_id) {
+            return Err(InventoryRejection {
+                kind: InventoryRejectionKind::UnknownNode {
+                    node_id: placement.node_id,
+                },
+            });
+        }
+        if by_stage
+            .insert(placement.stage_index, placement.node_id)
+            .is_some()
+        {
+            return Err(InventoryRejection {
+                kind: InventoryRejectionKind::DuplicateStage {
+                    stage_index: placement.stage_index,
+                },
+            });
+        }
+    }
+
+    let mut stages = Vec::with_capacity(request.stage_count as usize);
+    for stage_index in 0..request.stage_count {
+        let node_id = by_stage.remove(&stage_index).ok_or(InventoryRejection {
+            kind: InventoryRejectionKind::MissingStage { stage_index },
+        })?;
+        stages.push(StagePlan {
+            stage_index,
+            node_id,
+        });
+    }
+    Ok(RunPlan {
+        run_id: request.run_id,
+        stages,
+    })
+}
+
+#[cfg(test)]
+pub struct InventoryHarness {
+    entries: Vec<InventoryEntry>,
+    commands: Vec<InventoryCommand>,
+    committed_plan: Option<RunPlan>,
+}
+
+#[cfg(test)]
+impl InventoryHarness {
+    pub fn new(entries: Vec<InventoryEntry>) -> Self {
+        Self {
+            entries,
+            commands: Vec::new(),
+            committed_plan: None,
+        }
+    }
+
+    pub fn entries(&self) -> &[InventoryEntry] {
+        &self.entries
+    }
+
+    pub fn commands(&self) -> &[InventoryCommand] {
+        &self.commands
+    }
+
+    pub fn committed_plan(&self) -> Option<&RunPlan> {
+        self.committed_plan.as_ref()
+    }
+
+    pub fn observe_node_report(&mut self, report: NodeReport) {
+        match report {
+            NodeReport::BootHealth { node_id, health } => {
+                if let Some(entry) = self
+                    .entries
+                    .iter_mut()
+                    .find(|entry| entry.node_id == node_id)
+                {
+                    entry.ready = matches!(health, BootHealth::Ready);
+                }
+            }
+            NodeReport::CapacityChanged { .. } => {}
+        }
+    }
+
+    pub fn commit_plan(&mut self, plan: RunPlan) {
+        self.committed_plan = Some(plan);
+    }
+
+    pub fn provision_stages(&mut self) {
+        if let Some(plan) = &self.committed_plan {
+            for stage in &plan.stages {
+                self.commands.push(InventoryCommand::ProvisionStage {
+                    stage_index: stage.stage_index,
+                    node_id: stage.node_id,
+                });
+            }
+        }
+    }
+}
diff --git a/crates/mvp-system/src/run_plan.rs b/crates/mvp-system/src/run_plan.rs
new file mode 100644
index 0000000..a498fa1
--- /dev/null
+++ b/crates/mvp-system/src/run_plan.rs
@@ -0,0 +1,422 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+
+impl From<u64> for RunId {
+    fn from(value: u64) -> Self {
+        Self(value)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DTypeFamily {
+    BFloat,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ModelFacts {
+    pub model_id: String,
+    pub num_layers: u32,
+    pub hidden_dim: u64,
+    pub dtype_family: DTypeFamily,
+    pub dtype_width_bytes: u64,
+    pub max_seq_len: u64,
+    pub eos_token_id: u32,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RuntimeConfig {
+    pub max_tokens: u32,
+}
+
+impl RuntimeConfig {
+    pub fn test_default() -> Self {
+        Self { max_tokens: 4 }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct StagePlacement {
+    pub stage_index: u32,
+    pub node_id: NodeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PlacementInput {
+    FixedLinear(Vec<StagePlacement>),
+    FixedLinearWithEdgeOverride {
+        stages: Vec<StagePlacement>,
+        forced_activation_edges: Vec<(u32, u32)>,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct RingSpec {
+    pub data_capacity: u64,
+    pub alignment: u64,
+}
+
+impl RingSpec {
+    pub fn test_default_activation() -> Self {
+        Self {
+            data_capacity: 1 << 20,
+            alignment: 64,
+        }
+    }
+
+    pub fn test_default_token() -> Self {
+        Self {
+            data_capacity: 4096,
+            alignment: 8,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PlannerInput {
+    pub run_id: RunId,
+    pub orchestrator_node_id: NodeId,
+    pub model: ModelFacts,
+    pub runtime: RuntimeConfig,
+    pub candidate_pool: Vec<NodeId>,
+    pub stage_count: u32,
+    pub placement: PlacementInput,
+    pub activation_ring: RingSpec,
+    pub token_ring: RingSpec,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum EdgeKind {
+    TokenIn,
+    Activation,
+    TokenOut,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ObjectKind {
+    Token,
+    Activation,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ObjectSpec {
+    pub kind: ObjectKind,
+    pub max_extent: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum EdgeEndpoint {
+    Orchestrator { node_id: NodeId },
+    Stage { node_id: NodeId, stage_index: u32 },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct EdgePlan {
+    pub run_id: RunId,
+    pub edge_id: EdgeId,
+    pub kind: EdgeKind,
+    pub producer: EdgeEndpoint,
+    pub consumer: EdgeEndpoint,
+    pub object_spec: ObjectSpec,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StagePlan {
+    pub run_id: RunId,
+    pub stage_index: u32,
+    pub stage_count: u32,
+    pub node_id: NodeId,
+    pub layer_start: u32,
+    pub layer_end_exclusive: u32,
+    pub inbound_edge: EdgeId,
+    pub outbound_edge: EdgeId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RunPlan {
+    pub run_id: RunId,
+    pub stages: Vec<StagePlan>,
+    pub edges: Vec<EdgePlan>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct InboundEdgeProvision {
+    pub edge_id: EdgeId,
+    pub kind: EdgeKind,
+    pub object_spec: ObjectSpec,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct OutboundEdgeProvision {
+    pub edge_id: EdgeId,
+    pub kind: EdgeKind,
+    pub consumer_node_id: NodeId,
+    pub object_spec: ObjectSpec,
+    pub ring_spec: RingSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProvisionStage {
+    pub run_id: RunId,
+    pub node_id: NodeId,
+    pub stage_index: u32,
+    pub stage_count: u32,
+    pub layer_start: u32,
+    pub layer_end_exclusive: u32,
+    pub inbound: InboundEdgeProvision,
+    pub outbound: OutboundEdgeProvision,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum PlanRejectionKind {
+    UnknownNode,
+    DuplicateStageAssignment,
+    MissingStage,
+    InvalidStageCount,
+    EdgeEndpointMismatch,
+    ModelStageLayoutMismatch,
+    InvalidObjectSpec,
+    UnsupportedShapeOrLayout,
+    InvalidRingSpec,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PlanRejection {
+    kind: PlanRejectionKind,
+}
+
+impl PlanRejection {
+    pub fn kind(&self) -> PlanRejectionKind {
+        self.kind
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ProjectionRejection {
+    UnknownStage,
+    MissingEdge,
+}
+
+pub fn plan_run(input: PlannerInput) -> Result<RunPlan, PlanRejection> {
+    validate_global_input(&input)?;
+    let placements = validated_placements(&input)?;
+
+    let activation_extent = input
+        .model
+        .max_seq_len
+        .checked_mul(input.model.hidden_dim)
+        .and_then(|value| value.checked_mul(input.model.dtype_width_bytes))
+        .ok_or_else(|| reject(PlanRejectionKind::InvalidObjectSpec))?;
+    if activation_extent == 0 {
+        return Err(reject(PlanRejectionKind::InvalidObjectSpec));
+    }
+
+    let token_spec = ObjectSpec {
+        kind: ObjectKind::Token,
+        max_extent: 64,
+    };
+    let activation_spec = ObjectSpec {
+        kind: ObjectKind::Activation,
+        max_extent: activation_extent,
+    };
+
+    let mut edges = Vec::with_capacity(input.stage_count as usize + 1);
+    edges.push(EdgePlan {
+        run_id: input.run_id,
+        edge_id: EdgeId(7000),
+        kind: EdgeKind::TokenIn,
+        producer: EdgeEndpoint::Orchestrator {
+            node_id: input.orchestrator_node_id,
+        },
+        consumer: EdgeEndpoint::Stage {
+            node_id: placements[0].node_id,
+            stage_index: 0,
+        },
+        object_spec: token_spec,
+        ring_spec: input.token_ring,
+    });
+
+    for stage_index in 0..input.stage_count.saturating_sub(1) {
+        edges.push(EdgePlan {
+            run_id: input.run_id,
+            edge_id: EdgeId(7001 + u64::from(stage_index)),
+            kind: EdgeKind::Activation,
+            producer: EdgeEndpoint::Stage {
+                node_id: placements[stage_index as usize].node_id,
+                stage_index,
+            },
+            consumer: EdgeEndpoint::Stage {
+                node_id: placements[stage_index as usize + 1].node_id,
+                stage_index: stage_index + 1,
+            },
+            object_spec: activation_spec,
+            ring_spec: input.activation_ring,
+        });
+    }
+
+    edges.push(EdgePlan {
+        run_id: input.run_id,
+        edge_id: EdgeId(7000 + u64::from(input.stage_count)),
+        kind: EdgeKind::TokenOut,
+        producer: EdgeEndpoint::Stage {
+            node_id: placements[input.stage_count as usize - 1].node_id,
+            stage_index: input.stage_count - 1,
+        },
+        consumer: EdgeEndpoint::Orchestrator {
+            node_id: input.orchestrator_node_id,
+        },
+        object_spec: token_spec,
+        ring_spec: input.token_ring,
+    });
+
+    let mut stages = Vec::with_capacity(input.stage_count as usize);
+    for placement in &placements {
+        let stage_index = placement.stage_index;
+        let (start, end) = layer_range(input.model.num_layers, input.stage_count, stage_index);
+        stages.push(StagePlan {
+            run_id: input.run_id,
+            stage_index,
+            stage_count: input.stage_count,
+            node_id: placement.node_id,
+            layer_start: start,
+            layer_end_exclusive: end,
+            inbound_edge: EdgeId(7000 + u64::from(stage_index)),
+            outbound_edge: EdgeId(7001 + u64::from(stage_index)),
+        });
+    }
+
+    Ok(RunPlan {
+        run_id: input.run_id,
+        stages,
+        edges,
+    })
+}
+
+pub fn derive_stage_provision(
+    plan: &RunPlan,
+    stage_index: u32,
+) -> Result<ProvisionStage, ProjectionRejection> {
+    let stage = plan
+        .stages
+        .iter()
+        .find(|stage| stage.stage_index == stage_index)
+        .ok_or(ProjectionRejection::UnknownStage)?;
+    let inbound = plan
+        .edges
+        .iter()
+        .find(|edge| edge.edge_id == stage.inbound_edge)
+        .ok_or(ProjectionRejection::MissingEdge)?;
+    let outbound = plan
+        .edges
+        .iter()
+        .find(|edge| edge.edge_id == stage.outbound_edge)
+        .ok_or(ProjectionRejection::MissingEdge)?;
+    Ok(ProvisionStage {
+        run_id: plan.run_id,
+        node_id: stage.node_id,
+        stage_index,
+        stage_count: stage.stage_count,
+        layer_start: stage.layer_start,
+        layer_end_exclusive: stage.layer_end_exclusive,
+        inbound: InboundEdgeProvision {
+            edge_id: inbound.edge_id,
+            kind: inbound.kind,
+            object_spec: inbound.object_spec,
+            ring_spec: inbound.ring_spec,
+        },
+        outbound: OutboundEdgeProvision {
+            edge_id: outbound.edge_id,
+            kind: outbound.kind,
+            consumer_node_id: endpoint_node_id(&outbound.consumer),
+            object_spec: outbound.object_spec,
+            ring_spec: outbound.ring_spec,
+        },
+    })
+}
+
+fn validate_global_input(input: &PlannerInput) -> Result<(), PlanRejection> {
+    if input.stage_count == 0 {
+        return Err(reject(PlanRejectionKind::InvalidStageCount));
+    }
+    if input.model.num_layers < input.stage_count {
+        return Err(reject(PlanRejectionKind::ModelStageLayoutMismatch));
+    }
+    if input.model.max_seq_len == 0 || input.model.dtype_width_bytes == 0 {
+        return Err(reject(PlanRejectionKind::InvalidObjectSpec));
+    }
+    if input.model.hidden_dim == 0 {
+        return Err(reject(PlanRejectionKind::UnsupportedShapeOrLayout));
+    }
+    if !valid_ring(input.activation_ring) || !valid_ring(input.token_ring) {
+        return Err(reject(PlanRejectionKind::InvalidRingSpec));
+    }
+    Ok(())
+}
+
+fn validated_placements(input: &PlannerInput) -> Result<Vec<StagePlacement>, PlanRejection> {
+    let (stages, forced_edges) = match &input.placement {
+        PlacementInput::FixedLinear(stages) => (stages.as_slice(), &[][..]),
+        PlacementInput::FixedLinearWithEdgeOverride {
+            stages,
+            forced_activation_edges,
+        } => (stages.as_slice(), forced_activation_edges.as_slice()),
+    };
+
+    if forced_edges
+        .iter()
+        .any(|(producer, consumer)| *consumer != producer.saturating_add(1))
+    {
+        return Err(reject(PlanRejectionKind::EdgeEndpointMismatch));
+    }
+
+    let candidate_nodes = input
+        .candidate_pool
+        .iter()
+        .copied()
+        .collect::<std::collections::BTreeSet<_>>();
+    let mut by_stage = std::collections::BTreeMap::new();
+    for placement in stages {
+        if !candidate_nodes.contains(&placement.node_id) {
+            return Err(reject(PlanRejectionKind::UnknownNode));
+        }
+        if by_stage.insert(placement.stage_index, *placement).is_some() {
+            return Err(reject(PlanRejectionKind::DuplicateStageAssignment));
+        }
+    }
+
+    let mut dense = Vec::with_capacity(input.stage_count as usize);
+    for stage_index in 0..input.stage_count {
+        let placement = by_stage
+            .remove(&stage_index)
+            .ok_or_else(|| reject(PlanRejectionKind::MissingStage))?;
+        dense.push(placement);
+    }
+    Ok(dense)
+}
+
+fn layer_range(num_layers: u32, stage_count: u32, stage_index: u32) -> (u32, u32) {
+    let start = (u64::from(num_layers) * u64::from(stage_index) / u64::from(stage_count)) as u32;
+    let end = (u64::from(num_layers) * u64::from(stage_index + 1) / u64::from(stage_count)) as u32;
+    (start, end)
+}
+
+fn endpoint_node_id(endpoint: &EdgeEndpoint) -> NodeId {
+    match endpoint {
+        EdgeEndpoint::Orchestrator { node_id } | EdgeEndpoint::Stage { node_id, .. } => *node_id,
+    }
+}
+
+fn valid_ring(spec: RingSpec) -> bool {
+    spec.data_capacity > 0 && spec.alignment > 0 && spec.alignment.is_power_of_two()
+}
+
+fn reject(kind: PlanRejectionKind) -> PlanRejection {
+    PlanRejection { kind }
+}
diff --git a/crates/mvp-system/src/shared_ring_helper_abi.rs b/crates/mvp-system/src/shared_ring_helper_abi.rs
new file mode 100644
index 0000000..8ac33b4
--- /dev/null
+++ b/crates/mvp-system/src/shared_ring_helper_abi.rs
@@ -0,0 +1,293 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RingId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct EndpointId(pub String);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ArenaBase(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ProcessLocalPointer(pub u64);
+
+impl ProcessLocalPointer {
+    pub fn from_base_plus_offset(base: ArenaBase, offset: u64) -> Self {
+        Self(base.0 + offset)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingConfig {
+    pub node_id: NodeId,
+    pub ring_id: RingId,
+    pub capacity: u64,
+    pub producer: EndpointId,
+    pub consumer: EndpointId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RingIdentity {
+    pub ring_id: RingId,
+    pub capacity: u64,
+    pub producer_count: u32,
+    pub consumer_count: u32,
+    generation: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct CursorSnapshot {
+    pub commit: u64,
+    pub consume: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WakeHint {
+    RingReadable { ring_id: RingId },
+    RingWritable { ring_id: RingId },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ReserveError {
+    InsufficientSpace,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ReadError {
+    BeyondCommittedBytes,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Reservation {
+    start: u64,
+    len: u64,
+    generation: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct StaleWake {
+    ring_id: RingId,
+    generation: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct WakeDelivery {
+    pub was_accepted: bool,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct SchedulerState {
+    pub readable_rings: std::collections::BTreeSet<RingId>,
+    pub writable_rings: std::collections::BTreeSet<RingId>,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct RingLayout {
+    pub data_offset: u64,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ProcessLocalView {
+    pub layout: RingLayout,
+    pub data_pointer: ProcessLocalPointer,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PythonOperation {
+    ReserveViaHelper { ring_id: RingId },
+    CommitViaHelper { ring_id: RingId },
+    ReadableViaHelper { ring_id: RingId },
+    ConsumeViaHelper { ring_id: RingId },
+    MapPointerViaHelper { ring_id: RingId },
+    DirectAtomicAccess { ring_id: RingId },
+    DirectWrapArithmetic { ring_id: RingId },
+}
+
+#[cfg(test)]
+pub struct RingHelperHarness {
+    identity: RingIdentity,
+    buffer: Vec<u8>,
+    commit: u64,
+    consume: u64,
+    retired: bool,
+    wake_hints: Vec<WakeHint>,
+    wake_log: Vec<WakeDelivery>,
+    scheduler_state: SchedulerState,
+}
+
+#[cfg(test)]
+impl RingHelperHarness {
+    pub fn create(config: RingConfig) -> Self {
+        Self::with_generation(config.ring_id, config.capacity, 1)
+    }
+
+    pub fn create_replacement(ring_id: RingId) -> Self {
+        Self::with_generation(ring_id, 8, 2)
+    }
+
+    fn with_generation(ring_id: RingId, capacity: u64, generation: u64) -> Self {
+        Self {
+            identity: RingIdentity {
+                ring_id,
+                capacity,
+                producer_count: 1,
+                consumer_count: 1,
+                generation,
+            },
+            buffer: vec![0; capacity as usize],
+            commit: 0,
+            consume: 0,
+            retired: false,
+            wake_hints: Vec::new(),
+            wake_log: Vec::new(),
+            scheduler_state: SchedulerState {
+                readable_rings: std::collections::BTreeSet::new(),
+                writable_rings: std::collections::BTreeSet::new(),
+            },
+        }
+    }
+
+    pub fn identity(&self) -> RingIdentity {
+        self.identity.clone()
+    }
+
+    pub fn retire_and_capture_stale_wake(&mut self) -> StaleWake {
+        self.retired = true;
+        StaleWake {
+            ring_id: self.identity.ring_id,
+            generation: self.identity.generation,
+        }
+    }
+
+    pub fn deliver_wake(&mut self, wake: StaleWake) {
+        self.wake_log.push(WakeDelivery {
+            was_accepted: wake.ring_id == self.identity.ring_id
+                && wake.generation == self.identity.generation
+                && !self.retired,
+        });
+    }
+
+    pub fn wake_log(&self) -> &[WakeDelivery] {
+        &self.wake_log
+    }
+
+    pub fn producer_reserve(&self, len: u64) -> Result<Reservation, ReserveError> {
+        let used = self.commit.saturating_sub(self.consume);
+        if len <= self.identity.capacity.saturating_sub(used) {
+            Ok(Reservation {
+                start: self.commit,
+                len,
+                generation: self.identity.generation,
+            })
+        } else {
+            Err(ReserveError::InsufficientSpace)
+        }
+    }
+
+    pub fn producer_write(&mut self, reservation: &Reservation, bytes: &[u8]) {
+        assert_eq!(reservation.generation, self.identity.generation);
+        assert_eq!(reservation.len as usize, bytes.len());
+        for (i, byte) in bytes.iter().copied().enumerate() {
+            let idx = (reservation.start + i as u64) % self.identity.capacity;
+            self.buffer[idx as usize] = byte;
+        }
+    }
+
+    pub fn producer_commit(&mut self, reservation: Reservation) {
+        assert_eq!(reservation.start, self.commit);
+        self.commit = self.commit.saturating_add(reservation.len);
+        self.wake_hints.push(WakeHint::RingReadable {
+            ring_id: self.identity.ring_id,
+        });
+        self.scheduler_state
+            .readable_rings
+            .insert(self.identity.ring_id);
+    }
+
+    pub fn consumer_readable(&self) -> u64 {
+        self.commit.saturating_sub(self.consume)
+    }
+
+    pub fn consumer_try_read(&self, len: u64) -> Result<Vec<u8>, ReadError> {
+        if len > self.consumer_readable() {
+            return Err(ReadError::BeyondCommittedBytes);
+        }
+        Ok(self.consumer_read(len))
+    }
+
+    pub fn consumer_read(&self, len: u64) -> Vec<u8> {
+        assert!(len <= self.consumer_readable());
+        (0..len)
+            .map(|i| self.buffer[((self.consume + i) % self.identity.capacity) as usize])
+            .collect()
+    }
+
+    pub fn consumer_consume(&mut self, len: u64) {
+        assert!(len <= self.consumer_readable());
+        self.consume = self.consume.saturating_add(len);
+        self.wake_hints.push(WakeHint::RingWritable {
+            ring_id: self.identity.ring_id,
+        });
+        self.scheduler_state
+            .writable_rings
+            .insert(self.identity.ring_id);
+    }
+
+    pub fn cursor_snapshot(&self) -> CursorSnapshot {
+        CursorSnapshot {
+            commit: self.commit,
+            consume: self.consume,
+        }
+    }
+
+    pub fn wake_hints(&self) -> &[WakeHint] {
+        &self.wake_hints
+    }
+
+    pub fn coalesce_duplicate_wakes(&mut self) {
+        for wake in &self.wake_hints {
+            match wake {
+                WakeHint::RingReadable { ring_id } => {
+                    self.scheduler_state.readable_rings.insert(*ring_id);
+                }
+                WakeHint::RingWritable { ring_id } => {
+                    self.scheduler_state.writable_rings.insert(*ring_id);
+                }
+            }
+        }
+    }
+
+    pub fn scheduler_state(&self) -> &SchedulerState {
+        &self.scheduler_state
+    }
+
+    pub fn map_process_local_view(&self, base: ArenaBase) -> ProcessLocalView {
+        let layout = RingLayout { data_offset: 128 };
+        ProcessLocalView {
+            layout,
+            data_pointer: ProcessLocalPointer::from_base_plus_offset(base, layout.data_offset),
+        }
+    }
+
+    pub fn python_visible_operations(&self) -> Vec<PythonOperation> {
+        vec![
+            PythonOperation::ReserveViaHelper {
+                ring_id: self.identity.ring_id,
+            },
+            PythonOperation::CommitViaHelper {
+                ring_id: self.identity.ring_id,
+            },
+            PythonOperation::ReadableViaHelper {
+                ring_id: self.identity.ring_id,
+            },
+            PythonOperation::ConsumeViaHelper {
+                ring_id: self.identity.ring_id,
+            },
+            PythonOperation::MapPointerViaHelper {
+                ring_id: self.identity.ring_id,
+            },
+        ]
+    }
+}
diff --git a/crates/mvp-system/src/stage_controller.rs b/crates/mvp-system/src/stage_controller.rs
new file mode 100644
index 0000000..b68494b
--- /dev/null
+++ b/crates/mvp-system/src/stage_controller.rs
@@ -0,0 +1,399 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct StepId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct DeviceHandle {
+    pub generation: u64,
+    pub id: u64,
+}
+
+impl DeviceHandle {
+    pub fn new_current(id: u64) -> Self {
+        Self { generation: 1, id }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct LayerRange {
+    pub start: u32,
+    pub end_exclusive: u32,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WeightSource {
+    TestArtifact(String),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum EdgeDirection {
+    Inbound,
+    Outbound,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct EdgeProvision {
+    pub edge_id: EdgeId,
+    pub direction: EdgeDirection,
+}
+
+impl EdgeProvision {
+    pub fn inbound(edge_id: EdgeId) -> Self {
+        Self {
+            edge_id,
+            direction: EdgeDirection::Inbound,
+        }
+    }
+
+    pub fn outbound(edge_id: EdgeId) -> Self {
+        Self {
+            edge_id,
+            direction: EdgeDirection::Outbound,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ProvisionStage {
+    pub run_id: RunId,
+    pub authorized_orchestrator: NodeId,
+    pub node_id: NodeId,
+    pub stage_index: u32,
+    pub stage_count: u32,
+    pub layer_range: LayerRange,
+    pub inbound: EdgeProvision,
+    pub outbound: EdgeProvision,
+    pub weight_source: WeightSource,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum StageEvent {
+    ProvisionStage {
+        from: NodeId,
+        provision: ProvisionStage,
+    },
+    WorkerReady,
+    WeightsReady,
+    InboundEdgeReady {
+        edge_id: EdgeId,
+    },
+    OutboundEdgeReady {
+        edge_id: EdgeId,
+    },
+    ObjectLoaded {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+        handle: DeviceHandle,
+    },
+    StepCompleted {
+        step_id: StepId,
+    },
+    WorkerCrashed,
+    StopRun {
+        run_id: RunId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StageFaultReason {
+    UnauthorizedProvision,
+    SequenceViolation,
+    WorkerCrashed,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum StageLifecycleEvent {
+    StageReady {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    StepAccepted {
+        run_id: RunId,
+        stage_index: u32,
+        sequence: u64,
+    },
+    StageFault {
+        run_id: RunId,
+        stage_index: u32,
+        reason: StageFaultReason,
+    },
+    StageStopped {
+        run_id: RunId,
+        stage_index: u32,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct StepInput {
+    pub edge_id: EdgeId,
+    pub object_id: ObjectId,
+    pub sequence: u64,
+    pub handle: DeviceHandle,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct OutputBinding {
+    pub edge_id: EdgeId,
+    pub sequence: u64,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ExecuteStep {
+    pub step_id: StepId,
+    pub input: StepInput,
+    pub outputs: Vec<OutputBinding>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum StageCommand {
+    EstablishInboundEdge {
+        edge_id: EdgeId,
+    },
+    EstablishOutboundEdge {
+        edge_id: EdgeId,
+    },
+    ConfigureWorkerRole {
+        run_id: RunId,
+        stage_index: u32,
+        layer_range: LayerRange,
+    },
+    LoadWeights {
+        source: WeightSource,
+        range: LayerRange,
+    },
+    RewireEdge {
+        edge_id: EdgeId,
+    },
+    ExecuteStep(ExecuteStep),
+    ReleaseInputHandle {
+        object_id: ObjectId,
+        handle: DeviceHandle,
+    },
+    StopLocalEdges {
+        run_id: RunId,
+    },
+    ReleaseRunDeviceObjects {
+        run_id: RunId,
+    },
+}
+
+#[cfg(test)]
+pub struct StageControllerHarness {
+    local_node_id: NodeId,
+    provision: Option<ProvisionStage>,
+    worker_ready: bool,
+    weights_ready: bool,
+    inbound_ready: bool,
+    outbound_ready: bool,
+    stage_ready_emitted: bool,
+    busy: bool,
+    expected_sequence: u64,
+    active_input: Option<StepInput>,
+    commands: Vec<StageCommand>,
+    events: Vec<StageLifecycleEvent>,
+    faulted: bool,
+    stopped: bool,
+}
+
+#[cfg(test)]
+impl StageControllerHarness {
+    pub fn new(local_node_id: NodeId) -> Self {
+        Self {
+            local_node_id,
+            provision: None,
+            worker_ready: false,
+            weights_ready: false,
+            inbound_ready: false,
+            outbound_ready: false,
+            stage_ready_emitted: false,
+            busy: false,
+            expected_sequence: 0,
+            active_input: None,
+            commands: Vec::new(),
+            events: Vec::new(),
+            faulted: false,
+            stopped: false,
+        }
+    }
+
+    pub fn observe(&mut self, event: StageEvent) {
+        match event {
+            StageEvent::ProvisionStage { from, provision } => self.provision(from, provision),
+            StageEvent::WorkerReady => self.worker_ready = true,
+            StageEvent::WeightsReady => self.weights_ready = true,
+            StageEvent::InboundEdgeReady { edge_id } => {
+                if self
+                    .provision
+                    .as_ref()
+                    .is_some_and(|p| p.inbound.edge_id == edge_id)
+                {
+                    self.inbound_ready = true;
+                }
+            }
+            StageEvent::OutboundEdgeReady { edge_id } => {
+                if self
+                    .provision
+                    .as_ref()
+                    .is_some_and(|p| p.outbound.edge_id == edge_id)
+                {
+                    self.outbound_ready = true;
+                }
+            }
+            StageEvent::ObjectLoaded {
+                edge_id,
+                object_id,
+                sequence,
+                handle,
+            } => self.object_loaded(edge_id, object_id, sequence, handle),
+            StageEvent::StepCompleted { .. } => self.step_completed(),
+            StageEvent::WorkerCrashed => self.fault(StageFaultReason::WorkerCrashed),
+            StageEvent::StopRun { run_id } => self.stop(run_id),
+        }
+        self.maybe_stage_ready();
+    }
+
+    pub fn commands(&self) -> &[StageCommand] {
+        &self.commands
+    }
+
+    pub fn events(&self) -> &[StageLifecycleEvent] {
+        &self.events
+    }
+
+    fn provision(&mut self, from: NodeId, provision: ProvisionStage) {
+        if from != provision.authorized_orchestrator || provision.node_id != self.local_node_id {
+            self.provision = Some(provision.clone());
+            self.fault(StageFaultReason::UnauthorizedProvision);
+            return;
+        }
+        self.commands.push(StageCommand::EstablishInboundEdge {
+            edge_id: provision.inbound.edge_id,
+        });
+        self.commands.push(StageCommand::EstablishOutboundEdge {
+            edge_id: provision.outbound.edge_id,
+        });
+        self.commands.push(StageCommand::ConfigureWorkerRole {
+            run_id: provision.run_id,
+            stage_index: provision.stage_index,
+            layer_range: provision.layer_range,
+        });
+        self.commands.push(StageCommand::LoadWeights {
+            source: provision.weight_source.clone(),
+            range: provision.layer_range,
+        });
+        self.provision = Some(provision);
+    }
+
+    fn maybe_stage_ready(&mut self) {
+        if self.stage_ready_emitted || self.faulted || self.stopped {
+            return;
+        }
+        if self.worker_ready && self.weights_ready && self.inbound_ready && self.outbound_ready {
+            if let Some(provision) = &self.provision {
+                self.stage_ready_emitted = true;
+                self.events.push(StageLifecycleEvent::StageReady {
+                    run_id: provision.run_id,
+                    stage_index: provision.stage_index,
+                });
+            }
+        }
+    }
+
+    fn object_loaded(
+        &mut self,
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+        handle: DeviceHandle,
+    ) {
+        if self.faulted || self.stopped || !self.stage_ready_emitted || self.busy {
+            return;
+        }
+        let Some(provision) = &self.provision else {
+            return;
+        };
+        if edge_id != provision.inbound.edge_id {
+            return;
+        }
+        if sequence != self.expected_sequence {
+            self.fault(StageFaultReason::SequenceViolation);
+            return;
+        }
+        let input = StepInput {
+            edge_id,
+            object_id,
+            sequence,
+            handle,
+        };
+        let step = ExecuteStep {
+            step_id: StepId(sequence),
+            input: input.clone(),
+            outputs: vec![OutputBinding {
+                edge_id: provision.outbound.edge_id,
+                sequence,
+            }],
+        };
+        self.busy = true;
+        self.active_input = Some(input);
+        self.commands.push(StageCommand::ExecuteStep(step));
+        self.events.push(StageLifecycleEvent::StepAccepted {
+            run_id: provision.run_id,
+            stage_index: provision.stage_index,
+            sequence,
+        });
+    }
+
+    fn step_completed(&mut self) {
+        if self.faulted || self.stopped || !self.busy {
+            return;
+        }
+        if let Some(input) = self.active_input.take() {
+            self.commands.push(StageCommand::ReleaseInputHandle {
+                object_id: input.object_id,
+                handle: input.handle,
+            });
+            self.expected_sequence = input.sequence + 1;
+        }
+        self.busy = false;
+    }
+
+    fn fault(&mut self, reason: StageFaultReason) {
+        if self.faulted || self.stopped {
+            return;
+        }
+        self.faulted = true;
+        let (run_id, stage_index) = self
+            .provision
+            .as_ref()
+            .map(|p| (p.run_id, p.stage_index))
+            .unwrap_or((RunId(0), 0));
+        self.events.push(StageLifecycleEvent::StageFault {
+            run_id,
+            stage_index,
+            reason,
+        });
+    }
+
+    fn stop(&mut self, run_id: RunId) {
+        if self.stopped {
+            return;
+        }
+        self.stopped = true;
+        self.commands.push(StageCommand::StopLocalEdges { run_id });
+        self.commands
+            .push(StageCommand::ReleaseRunDeviceObjects { run_id });
+        let stage_index = self.provision.as_ref().map_or(0, |p| p.stage_index);
+        self.events.push(StageLifecycleEvent::StageStopped {
+            run_id,
+            stage_index,
+        });
+    }
+}
diff --git a/tests/mvp_system/arena_manager_guarantees.rs b/crates/mvp-system/src/tests/arena_manager_guarantees.rs
similarity index 97%
rename from tests/mvp_system/arena_manager_guarantees.rs
rename to crates/mvp-system/src/tests/arena_manager_guarantees.rs
index 1fbfb73..0bb9c77 100644
--- a/tests/mvp_system/arena_manager_guarantees.rs
+++ b/crates/mvp-system/src/tests/arena_manager_guarantees.rs
@@ -74,7 +74,10 @@ fn arena_boot_creates_stable_offset_only_layout_domain() {
     // Layout facts are arena offsets and stay under the reservation ceiling.
     assert!(lease.layout.start_offset < arena_config().reservation_ceiling);
     assert!(lease.layout.end_offset <= arena_config().reservation_ceiling);
-    assert!(matches!(lease.layout.pointer, arena::LayoutPointer::NoProcessPointer));
+    assert!(matches!(
+        lease.layout.pointer,
+        arena::LayoutPointer::NoProcessPointer
+    ));
 
     // Boot failure is typed and emits no usable arena.
     let failed = arena::ArenaManagerHarness::boot(arena::ArenaConfig {
@@ -232,9 +235,12 @@ fn release_requires_quiescence_and_reuse_happens_only_after_release() {
         proof: arena::QuiescenceProof::verified(),
     });
     harness.request(arena::ArenaRequest::LeaseRing(lease_request(3, 1024, 64)));
-    assert!(harness.events().iter().any(|event| {
-        matches!(event, arena::ArenaEvent::RingLeased { .. })
-    }));
+    assert!(
+        harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, arena::ArenaEvent::RingLeased { .. }) })
+    );
 }
 
 // This proves shutdown rejects new leases, preserves live lease records, and
diff --git a/tests/mvp_system/device_bridge_guarantees.rs b/crates/mvp-system/src/tests/device_bridge_guarantees.rs
similarity index 83%
rename from tests/mvp_system/device_bridge_guarantees.rs
rename to crates/mvp-system/src/tests/device_bridge_guarantees.rs
index d8c6f21..aa167ed 100644
--- a/tests/mvp_system/device_bridge_guarantees.rs
+++ b/crates/mvp-system/src/tests/device_bridge_guarantees.rs
@@ -77,11 +77,17 @@ fn allocation_creates_current_generation_handle_or_typed_failure() {
 fn host_to_device_copies_exact_range_and_defers_release_until_safe() {
     // Allocate a device object and request an asynchronous copy.
     let (mut harness, handle) = allocated_bridge();
-    let copy = harness.host_to_device(
-        device::HostRange { offset: 4, len: 8 },
-        device::DeviceRange { handle, offset: 0, len: 8 },
-        device::CopyMode::Async,
-    ).expect("copy request must be accepted");
+    let copy = harness
+        .host_to_device(
+            device::HostRange { offset: 4, len: 8 },
+            device::DeviceRange {
+                handle,
+                offset: 0,
+                len: 8,
+            },
+            device::CopyMode::Async,
+        )
+        .expect("copy request must be accepted");
 
     // The backend sees the exact ranges.
     assert!(harness.backend_calls().iter().any(|call| {
@@ -89,7 +95,11 @@ fn host_to_device_copies_exact_range_and_defers_release_until_safe() {
             call,
             device::BackendCall::HostToDevice {
                 host: device::HostRange { offset: 4, len: 8 },
-                device: device::DeviceRange { offset: 0, len: 8, .. },
+                device: device::DeviceRange {
+                    offset: 0,
+                    len: 8,
+                    ..
+                },
                 ..
             }
         )
@@ -110,18 +120,28 @@ fn host_to_device_copies_exact_range_and_defers_release_until_safe() {
 fn device_to_host_copies_exact_range_and_defers_host_validity_until_safe() {
     // Allocate a device object and request an asynchronous device-to-host copy.
     let (mut harness, handle) = allocated_bridge();
-    let copy = harness.device_to_host(
-        device::DeviceRange { handle, offset: 0, len: 8 },
-        device::HostRange { offset: 12, len: 8 },
-        device::CopyMode::Async,
-    ).expect("copy request must be accepted");
+    let copy = harness
+        .device_to_host(
+            device::DeviceRange {
+                handle,
+                offset: 0,
+                len: 8,
+            },
+            device::HostRange { offset: 12, len: 8 },
+            device::CopyMode::Async,
+        )
+        .expect("copy request must be accepted");
 
     // The backend sees the exact ranges.
     assert!(harness.backend_calls().iter().any(|call| {
         matches!(
             call,
             device::BackendCall::DeviceToHost {
-                device: device::DeviceRange { offset: 0, len: 8, .. },
+                device: device::DeviceRange {
+                    offset: 0,
+                    len: 8,
+                    ..
+                },
                 host: device::HostRange { offset: 12, len: 8 },
                 ..
             }
@@ -176,11 +196,17 @@ fn lifetime_blocks_free_until_dependencies_clear_and_rejects_old_generation() {
         handle,
         step_id: device::StepId(77),
     });
-    let copy = harness.host_to_device(
-        device::HostRange { offset: 0, len: 8 },
-        device::DeviceRange { handle, offset: 0, len: 8 },
-        device::CopyMode::Async,
-    ).expect("copy request must be accepted");
+    let copy = harness
+        .host_to_device(
+            device::HostRange { offset: 0, len: 8 },
+            device::DeviceRange {
+                handle,
+                offset: 0,
+                len: 8,
+            },
+            device::CopyMode::Async,
+        )
+        .expect("copy request must be accepted");
 
     // Free is blocked while compute/copy depends on the allocation.
     assert_eq!(
@@ -195,9 +221,11 @@ fn lifetime_blocks_free_until_dependencies_clear_and_rejects_old_generation() {
     });
     harness.observe(device::DeviceEvent::CopyCompleted { copy });
     assert_eq!(harness.free_device(handle), Ok(()));
-    assert!(harness.backend_calls().iter().any(|call| {
-        matches!(call, device::BackendCall::Free { freed } if *freed == handle)
-    }));
+    assert!(
+        harness.backend_calls().iter().any(|call| {
+            matches!(call, device::BackendCall::Free { freed } if *freed == handle)
+        })
+    );
 
     // Restart invalidates prior handles.
     harness.observe(device::DeviceEvent::WorkerRestarted {
@@ -219,7 +247,11 @@ fn backend_copy_and_view_failures_are_typed() {
     let copy_failure = harness
         .host_to_device(
             device::HostRange { offset: 0, len: 8 },
-            device::DeviceRange { handle, offset: 0, len: 8 },
+            device::DeviceRange {
+                handle,
+                offset: 0,
+                len: 8,
+            },
             device::CopyMode::Sync,
         )
         .expect_err("copy failure must surface");
diff --git a/tests/mvp_system/driver_pumps_guarantees.rs b/crates/mvp-system/src/tests/driver_pumps_guarantees.rs
similarity index 84%
rename from tests/mvp_system/driver_pumps_guarantees.rs
rename to crates/mvp-system/src/tests/driver_pumps_guarantees.rs
index e31f106..780ff6e 100644
--- a/tests/mvp_system/driver_pumps_guarantees.rs
+++ b/crates/mvp-system/src/tests/driver_pumps_guarantees.rs
@@ -77,13 +77,22 @@ fn driver_owns_endpoint_connection_demux_and_pump_tasks() {
 
     // Pump tasks are driver-owned.
     assert!(harness.commands().iter().any(|command| {
-        matches!(command, driver::DriverCommand::SpawnSendPump { edge_id: driver::EdgeId(7001), .. })
+        matches!(
+            command,
+            driver::DriverCommand::SpawnSendPump {
+                edge_id: driver::EdgeId(7001),
+                ..
+            }
+        )
     }));
 
     // Actor commands must not expose stream polling.
-    assert!(!harness.actor_messages().iter().any(|message| {
-        matches!(message, driver::ActorMessage::PollStreamFuture { .. })
-    }));
+    assert!(
+        !harness
+            .actor_messages()
+            .iter()
+            .any(|message| { matches!(message, driver::ActorMessage::PollStreamFuture { .. }) })
+    );
 }
 
 // This proves each edge uses one persistent uni-stream, writes an edge-id
@@ -131,15 +140,24 @@ fn recv_rendezvous_starts_pump_only_after_spec_and_stream_exist() {
     // Spec first, stream second.
     let mut spec_first = new_driver();
     spec_first.observe(driver::DriverEvent::EstablishRecv(recv_spec()));
-    assert!(!spec_first.commands().iter().any(|command| {
-        matches!(command, driver::DriverCommand::SpawnRecvPump { .. })
-    }));
+    assert!(
+        !spec_first
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, driver::DriverCommand::SpawnRecvPump { .. }) })
+    );
     spec_first.observe(driver::DriverEvent::IncomingUniStream {
         edge_id: driver::EdgeId(7001),
         stream_id: driver::StreamId(1),
     });
     assert!(spec_first.commands().iter().any(|command| {
-        matches!(command, driver::DriverCommand::SpawnRecvPump { edge_id: driver::EdgeId(7001), .. })
+        matches!(
+            command,
+            driver::DriverCommand::SpawnRecvPump {
+                edge_id: driver::EdgeId(7001),
+                ..
+            }
+        )
     }));
 
     // Stream first, spec second.
@@ -172,12 +190,20 @@ fn recv_pump_copies_bytes_without_parsing_and_respects_backpressure() {
         edge_id: driver::EdgeId(7001),
         bytes: driver::fake_object_header_bytes(),
     });
-    assert!(!harness.events().iter().any(|event| {
-        matches!(event, driver::DriverEventOut::ObjectHeaderParsed { .. })
-    }));
+    assert!(
+        !harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, driver::DriverEventOut::ObjectHeaderParsed { .. }) })
+    );
     assert!(harness.ring_commit(driver::EdgeId(7001)) > 0);
     assert!(harness.wake_hints().iter().any(|wake| {
-        matches!(wake, driver::WakeHint::RingReadable { edge_id: driver::EdgeId(7001) })
+        matches!(
+            wake,
+            driver::WakeHint::RingReadable {
+                edge_id: driver::EdgeId(7001)
+            }
+        )
     }));
 
     // With no ring space, the pump stops reading and waits for RingWritable.
@@ -217,7 +243,12 @@ fn send_pump_advances_consume_only_after_write_acceptance() {
     });
     assert_eq!(harness.ring_consume(driver::EdgeId(7001)), 7);
     assert!(harness.wake_hints().iter().any(|wake| {
-        matches!(wake, driver::WakeHint::RingWritable { edge_id: driver::EdgeId(7001) })
+        matches!(
+            wake,
+            driver::WakeHint::RingWritable {
+                edge_id: driver::EdgeId(7001)
+            }
+        )
     }));
 }
 
@@ -236,7 +267,13 @@ fn driver_faults_and_stop_emit_stream_fault_or_pump_stopped() {
         edge_id: driver::EdgeId(7001),
     });
     assert!(recv.events().iter().any(|event| {
-        matches!(event, driver::DriverEventOut::StreamFault { edge_id: driver::EdgeId(7001), .. })
+        matches!(
+            event,
+            driver::DriverEventOut::StreamFault {
+                edge_id: driver::EdgeId(7001),
+                ..
+            }
+        )
     }));
 
     // Write error faults the send edge.
@@ -246,7 +283,13 @@ fn driver_faults_and_stop_emit_stream_fault_or_pump_stopped() {
         edge_id: driver::EdgeId(7001),
     });
     assert!(send.events().iter().any(|event| {
-        matches!(event, driver::DriverEventOut::StreamFault { edge_id: driver::EdgeId(7001), .. })
+        matches!(
+            event,
+            driver::DriverEventOut::StreamFault {
+                edge_id: driver::EdgeId(7001),
+                ..
+            }
+        )
     }));
 
     // StopEdge stops the corresponding pump.
@@ -254,6 +297,12 @@ fn driver_faults_and_stop_emit_stream_fault_or_pump_stopped() {
         edge_id: driver::EdgeId(7001),
     });
     assert!(send.events().iter().any(|event| {
-        matches!(event, driver::DriverEventOut::PumpStopped { edge_id: driver::EdgeId(7001), .. })
+        matches!(
+            event,
+            driver::DriverEventOut::PumpStopped {
+                edge_id: driver::EdgeId(7001),
+                ..
+            }
+        )
     }));
 }
diff --git a/tests/mvp_system/edge_establisher_guarantees.rs b/crates/mvp-system/src/tests/edge_establisher_guarantees.rs
similarity index 85%
rename from tests/mvp_system/edge_establisher_guarantees.rs
rename to crates/mvp-system/src/tests/edge_establisher_guarantees.rs
index 7c896fe..93eeb1a 100644
--- a/tests/mvp_system/edge_establisher_guarantees.rs
+++ b/crates/mvp-system/src/tests/edge_establisher_guarantees.rs
@@ -89,7 +89,10 @@ fn provisioning_creates_local_edge_records_without_remote_actor_addresses() {
     assert!(rx.local_record(edge::EdgeId(7001)).is_some());
 
     // Data-flow provisioning must not require remote actor addresses.
-    for record in [tx.local_record(edge::EdgeId(7001)).unwrap(), rx.local_record(edge::EdgeId(7001)).unwrap()] {
+    for record in [
+        tx.local_record(edge::EdgeId(7001)).unwrap(),
+        rx.local_record(edge::EdgeId(7001)).unwrap(),
+    ] {
         assert!(record.remote_actor_address.is_none());
     }
 }
@@ -109,9 +112,12 @@ fn lease_flow_matches_records_and_suppresses_stale_or_cancelled_leases() {
     });
 
     // Mismatched lease must not install worker or pump state.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::InstallWorkerRing { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::InstallWorkerRing { .. }) })
+    );
 
     // A matching rejection faults the record.
     harness.observe(edge::EdgeEvent::RingLeaseRejected {
@@ -164,9 +170,12 @@ fn worker_ring_install_precedes_driver_establishment_and_uses_provision_specs()
     });
 
     // Before ring installation, no driver command may be issued.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::EstablishSend { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::EstablishSend { .. }) })
+    );
 
     // Matching ring installation advances establishment.
     harness.observe(edge::EdgeEvent::RingInstalled {
@@ -188,7 +197,13 @@ fn worker_ring_install_precedes_driver_establishment_and_uses_provision_specs()
 
     // Now the driver may be established.
     assert!(harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::EstablishSend { edge_id: edge::EdgeId(7001), .. })
+        matches!(
+            command,
+            edge::EdgeCommand::EstablishSend {
+                edge_id: edge::EdgeId(7001),
+                ..
+            }
+        )
     }));
 }
 
@@ -212,9 +227,11 @@ fn driver_ready_marks_local_edge_actor_ready() {
     }));
 
     // The edge is not ready until DriverEdgeReady arrives.
-    assert!(!tx.events().iter().any(|event| {
-        matches!(event, edge::EdgeLifecycleEvent::EdgeReady { .. })
-    }));
+    assert!(
+        !tx.events()
+            .iter()
+            .any(|event| { matches!(event, edge::EdgeLifecycleEvent::EdgeReady { .. }) })
+    );
     tx.observe(edge::EdgeEvent::DriverEdgeReady {
         edge_id: edge::EdgeId(7001),
     });
@@ -230,9 +247,11 @@ fn driver_ready_marks_local_edge_actor_ready() {
 
     // After readiness, stream and pump behavior belongs to the driver; the
     // establisher should not emit hot-path byte commands.
-    assert!(!tx.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::CopyHotPathBytes { .. })
-    }));
+    assert!(
+        !tx.commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::CopyHotPathBytes { .. }) })
+    );
 }
 
 // This proves StopEdge cancels queued leases, stops pumps, uninstalls worker
@@ -251,20 +270,32 @@ fn stop_edge_tears_down_local_state_and_terminal_stopped_ignores_late_events() {
     });
 
     // Stop commands must cover queued lease, pump, and worker ring cleanup.
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::CancelQueuedLease { .. })
-    }));
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::StopPump { .. })
-    }));
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::UninstallWorkerRing { .. })
-    }));
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::CancelQueuedLease { .. }) })
+    );
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::StopPump { .. }) })
+    );
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::UninstallWorkerRing { .. }) })
+    );
 
     // Arena release is withheld until quiescence proof arrives.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, edge::EdgeCommand::ReleaseArenaLease { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, edge::EdgeCommand::ReleaseArenaLease { .. }) })
+    );
     harness.observe(edge::EdgeEvent::QuiescenceProven {
         ring_id: edge::RingId(8001),
     });
diff --git a/tests/mvp_system/gpu_worker_ctl_guarantees.rs b/crates/mvp-system/src/tests/gpu_worker_ctl_guarantees.rs
similarity index 64%
rename from tests/mvp_system/gpu_worker_ctl_guarantees.rs
rename to crates/mvp-system/src/tests/gpu_worker_ctl_guarantees.rs
index 8a7f425..d4daefa 100644
--- a/tests/mvp_system/gpu_worker_ctl_guarantees.rs
+++ b/crates/mvp-system/src/tests/gpu_worker_ctl_guarantees.rs
@@ -70,24 +70,35 @@ fn worker_lifecycle_runs_start_initialize_ready_and_fault_paths() {
     // Start the worker process.
     let mut harness = new_controller();
     harness.observe(ctl::WorkerCtlEvent::StartWorker);
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, ctl::WorkerCtlCommand::SpawnProcessActor { .. })
-    }));
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, ctl::WorkerCtlCommand::SpawnProcessActor { .. }) })
+    );
 
     // Process start triggers InitializeWorker.
     harness.observe(ctl::WorkerCtlEvent::ProcessStarted {
         pid: ctl::ProcessId(1234),
     });
-    assert!(harness.serialized_worker_commands().iter().any(|command| {
-        matches!(command, ctl::WorkerCommand::InitializeWorker { .. })
-    }));
+    assert!(
+        harness
+            .serialized_worker_commands()
+            .iter()
+            .any(|command| { matches!(command, ctl::WorkerCommand::InitializeWorker { .. }) })
+    );
 
     // WorkerReady emits a running lifecycle event.
     harness.observe(ctl::WorkerCtlEvent::WorkerReady {
         generation: ctl::WorkerGeneration(1),
     });
     assert!(harness.events().iter().any(|event| {
-        matches!(event, ctl::WorkerCtlOut::WorkerRunning { generation: ctl::WorkerGeneration(1) })
+        matches!(
+            event,
+            ctl::WorkerCtlOut::WorkerRunning {
+                generation: ctl::WorkerGeneration(1)
+            }
+        )
     }));
 
     // Initialization timeout in a fresh controller is terminal failure.
@@ -95,7 +106,13 @@ fn worker_lifecycle_runs_start_initialize_ready_and_fault_paths() {
     timed_out.observe(ctl::WorkerCtlEvent::StartWorker);
     timed_out.advance_time_ms(1_001);
     assert!(timed_out.events().iter().any(|event| {
-        matches!(event, ctl::WorkerCtlOut::WorkerFailed { reason: ctl::WorkerFailure::InitializationTimeout, .. })
+        matches!(
+            event,
+            ctl::WorkerCtlOut::WorkerFailed {
+                reason: ctl::WorkerFailure::InitializationTimeout,
+                ..
+            }
+        )
     }));
 }
 
@@ -112,7 +129,10 @@ fn command_routing_requires_running_current_generation_and_is_payload_free() {
     }
 
     // All valid commands are serialized to the worker.
-    assert_eq!(harness.serialized_worker_commands().len(), current_generation_commands().len() + 1);
+    assert_eq!(
+        harness.serialized_worker_commands().len(),
+        current_generation_commands().len() + 1
+    );
 
     // Serialized commands must not contain payload bytes.
     for command in harness.serialized_worker_commands() {
@@ -136,13 +156,21 @@ fn command_routing_requires_running_current_generation_and_is_payload_free() {
     harness.observe(ctl::WorkerCtlEvent::WorkerReady {
         generation: ctl::WorkerGeneration(2),
     });
-    harness.observe(ctl::WorkerCtlEvent::ActorCommand(ctl::ActorCommand::ExecuteStep {
-        generation: ctl::WorkerGeneration(1),
-        step_id: ctl::StepId(9002),
-        input: ctl::DeviceHandle::new(ctl::WorkerGeneration(1), 42),
-    }));
+    harness.observe(ctl::WorkerCtlEvent::ActorCommand(
+        ctl::ActorCommand::ExecuteStep {
+            generation: ctl::WorkerGeneration(1),
+            step_id: ctl::StepId(9002),
+            input: ctl::DeviceHandle::new(ctl::WorkerGeneration(1), 42),
+        },
+    ));
     assert!(harness.events().iter().any(|event| {
-        matches!(event, ctl::WorkerCtlOut::CommandRejected { reason: ctl::CommandRejection::OldGenerationHandle, .. })
+        matches!(
+            event,
+            ctl::WorkerCtlOut::CommandRejected {
+                reason: ctl::CommandRejection::OldGenerationHandle,
+                ..
+            }
+        )
     }));
 }
 
@@ -154,31 +182,66 @@ fn parsed_worker_events_route_to_their_control_owners() {
     let mut harness = running_controller();
 
     // Deliver each worker event family through stdout parsing.
-    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(ctl::WorkerEvent::RingInstalled {
-        ring_id: ctl::RingId(8001),
-    }));
-    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(ctl::WorkerEvent::ObjectLoaded {
-        object_id: ctl::ObjectId(9000),
-        sequence: 0,
-    }));
-    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(ctl::WorkerEvent::ObjectProduced {
-        object_id: ctl::ObjectId(9001),
-        sequence: 0,
-    }));
-    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(ctl::WorkerEvent::StepCompleted {
-        step_id: ctl::StepId(77),
-    }));
-    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(ctl::WorkerEvent::RingReadable {
-        ring_id: ctl::RingId(8001),
-    }));
+    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(
+        ctl::WorkerEvent::RingInstalled {
+            ring_id: ctl::RingId(8001),
+        },
+    ));
+    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(
+        ctl::WorkerEvent::ObjectLoaded {
+            object_id: ctl::ObjectId(9000),
+            sequence: 0,
+        },
+    ));
+    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(
+        ctl::WorkerEvent::ObjectProduced {
+            object_id: ctl::ObjectId(9001),
+            sequence: 0,
+        },
+    ));
+    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(
+        ctl::WorkerEvent::StepCompleted {
+            step_id: ctl::StepId(77),
+        },
+    ));
+    harness.observe(ctl::WorkerCtlEvent::StdoutEvent(
+        ctl::WorkerEvent::RingReadable {
+            ring_id: ctl::RingId(8001),
+        },
+    ));
 
     // Routing is proven by destination commands/events, not private dispatch
     // tables.
-    assert!(harness.routed().iter().any(|route| matches!(route, ctl::RoutedEvent::ToEdgeEstablisher(_))));
-    assert!(harness.routed().iter().any(|route| matches!(route, ctl::RoutedEvent::ToRxOrRole(_))));
-    assert!(harness.routed().iter().any(|route| matches!(route, ctl::RoutedEvent::ToTxOrRole(_))));
-    assert!(harness.routed().iter().any(|route| matches!(route, ctl::RoutedEvent::ToStageController(_))));
-    assert!(harness.routed().iter().any(|route| matches!(route, ctl::RoutedEvent::ToDriverOrWorkerSide(_))));
+    assert!(
+        harness
+            .routed()
+            .iter()
+            .any(|route| matches!(route, ctl::RoutedEvent::ToEdgeEstablisher(_)))
+    );
+    assert!(
+        harness
+            .routed()
+            .iter()
+            .any(|route| matches!(route, ctl::RoutedEvent::ToRxOrRole(_)))
+    );
+    assert!(
+        harness
+            .routed()
+            .iter()
+            .any(|route| matches!(route, ctl::RoutedEvent::ToTxOrRole(_)))
+    );
+    assert!(
+        harness
+            .routed()
+            .iter()
+            .any(|route| matches!(route, ctl::RoutedEvent::ToStageController(_)))
+    );
+    assert!(
+        harness
+            .routed()
+            .iter()
+            .any(|route| matches!(route, ctl::RoutedEvent::ToDriverOrWorkerSide(_)))
+    );
 }
 
 // This proves worker crash invalidates old handles, roles, rings, in-flight
@@ -188,15 +251,19 @@ fn parsed_worker_events_route_to_their_control_owners() {
 fn crash_invalidates_generation_state_and_fans_out_faults() {
     // Install one ring and start one step in generation 1.
     let mut harness = running_controller();
-    harness.observe(ctl::WorkerCtlEvent::ActorCommand(ctl::ActorCommand::InstallRing {
-        generation: ctl::WorkerGeneration(1),
-        ring_id: ctl::RingId(8001),
-    }));
-    harness.observe(ctl::WorkerCtlEvent::ActorCommand(ctl::ActorCommand::ExecuteStep {
-        generation: ctl::WorkerGeneration(1),
-        step_id: ctl::StepId(9001),
-        input: ctl::DeviceHandle::new(ctl::WorkerGeneration(1), 42),
-    }));
+    harness.observe(ctl::WorkerCtlEvent::ActorCommand(
+        ctl::ActorCommand::InstallRing {
+            generation: ctl::WorkerGeneration(1),
+            ring_id: ctl::RingId(8001),
+        },
+    ));
+    harness.observe(ctl::WorkerCtlEvent::ActorCommand(
+        ctl::ActorCommand::ExecuteStep {
+            generation: ctl::WorkerGeneration(1),
+            step_id: ctl::StepId(9001),
+            input: ctl::DeviceHandle::new(ctl::WorkerGeneration(1), 42),
+        },
+    ));
 
     // Crash the worker process.
     harness.observe(ctl::WorkerCtlEvent::ProcessExited {
@@ -205,10 +272,22 @@ fn crash_invalidates_generation_state_and_fans_out_faults() {
 
     // Installed rings fault and affected pumps are stopped.
     assert!(harness.events().iter().any(|event| {
-        matches!(event, ctl::WorkerCtlOut::RingFaulted { ring_id: ctl::RingId(8001), .. })
+        matches!(
+            event,
+            ctl::WorkerCtlOut::RingFaulted {
+                ring_id: ctl::RingId(8001),
+                ..
+            }
+        )
     }));
     assert!(harness.commands().iter().any(|command| {
-        matches!(command, ctl::WorkerCtlCommand::StopDriverPump { ring_id: ctl::RingId(8001), .. })
+        matches!(
+            command,
+            ctl::WorkerCtlCommand::StopDriverPump {
+                ring_id: ctl::RingId(8001),
+                ..
+            }
+        )
     }));
 
     // Restart increments worker generation.
@@ -229,16 +308,21 @@ fn crash_invalidates_generation_state_and_fans_out_faults() {
 fn graceful_shutdown_sends_worker_shutdown_and_reaches_terminal_stopped() {
     // Start from a running worker with an installed ring.
     let mut harness = running_controller();
-    harness.observe(ctl::WorkerCtlEvent::ActorCommand(ctl::ActorCommand::InstallRing {
-        generation: ctl::WorkerGeneration(1),
-        ring_id: ctl::RingId(8001),
-    }));
+    harness.observe(ctl::WorkerCtlEvent::ActorCommand(
+        ctl::ActorCommand::InstallRing {
+            generation: ctl::WorkerGeneration(1),
+            ring_id: ctl::RingId(8001),
+        },
+    ));
 
     // Request graceful shutdown.
     harness.observe(ctl::WorkerCtlEvent::ShutdownRequested);
-    assert!(harness.serialized_worker_commands().iter().any(|command| {
-        matches!(command, ctl::WorkerCommand::ShutdownWorker { .. })
-    }));
+    assert!(
+        harness
+            .serialized_worker_commands()
+            .iter()
+            .any(|command| { matches!(command, ctl::WorkerCommand::ShutdownWorker { .. }) })
+    );
 
     // WorkerStopped must precede terminal stopped.
     harness.observe(ctl::WorkerCtlEvent::WorkerStopped {
@@ -261,6 +345,12 @@ fn graceful_shutdown_sends_worker_shutdown_and_reaches_terminal_stopped() {
 
     // Rings are marked quiesced on graceful stop.
     assert!(harness.events().iter().any(|event| {
-        matches!(event, ctl::WorkerCtlOut::RingQuiesced { ring_id: ctl::RingId(8001), .. })
+        matches!(
+            event,
+            ctl::WorkerCtlOut::RingQuiesced {
+                ring_id: ctl::RingId(8001),
+                ..
+            }
+        )
     }));
 }
diff --git a/tests/mvp_system/gpu_worker_egress_producer_guarantees.rs b/crates/mvp-system/src/tests/gpu_worker_egress_producer_guarantees.rs
similarity index 79%
rename from tests/mvp_system/gpu_worker_egress_producer_guarantees.rs
rename to crates/mvp-system/src/tests/gpu_worker_egress_producer_guarantees.rs
index 3014c45..a60246e 100644
--- a/tests/mvp_system/gpu_worker_egress_producer_guarantees.rs
+++ b/crates/mvp-system/src/tests/gpu_worker_egress_producer_guarantees.rs
@@ -109,7 +109,12 @@ fn header_is_written_and_committed_before_payload() {
     // Payload bytes are not committed before the payload copy is valid.
     assert_eq!(harness.committed_payload_bytes(egress::RingId(8002)), 0);
     assert!(harness.wake_hints().iter().any(|wake| {
-        matches!(wake, egress::WakeHint::RingReadable { ring_id: egress::RingId(8002) })
+        matches!(
+            wake,
+            egress::WakeHint::RingReadable {
+                ring_id: egress::RingId(8002)
+            }
+        )
     }));
 }
 
@@ -156,29 +161,37 @@ fn payload_copy_is_exact_extent_and_respects_backpressure() {
 fn object_produced_precedes_step_completed_after_all_outputs() {
     // Execute a step with two outputs.
     let mut harness = installed_producer();
-    harness.observe(egress::WorkerEgressEvent::InstallRing(egress::InstallRing {
-        ring_id: egress::RingId(8003),
-        edge_id: egress::EdgeId(7003),
-        port_id: egress::PortId("out2".into()),
-        ..egress_ring()
-    }));
+    harness.observe(egress::WorkerEgressEvent::InstallRing(
+        egress::InstallRing {
+            ring_id: egress::RingId(8003),
+            edge_id: egress::EdgeId(7003),
+            port_id: egress::PortId("out2".into()),
+            ..egress_ring()
+        },
+    ));
     harness.observe(egress::WorkerEgressEvent::ExecuteStep {
         step_id: egress::StepId(77),
-        outputs: vec![output_binding(0, 8), egress::OutputBinding {
-            ring_id: egress::RingId(8003),
-            object_id: egress::ObjectId(9100),
-            sequence: 0,
-            extent: 8,
-            flags: egress::ObjectFlags::default(),
-            device_source: egress::DeviceHandle::new(egress::WorkerGeneration(1), 55),
-        }],
+        outputs: vec![
+            output_binding(0, 8),
+            egress::OutputBinding {
+                ring_id: egress::RingId(8003),
+                object_id: egress::ObjectId(9100),
+                sequence: 0,
+                extent: 8,
+                flags: egress::ObjectFlags::default(),
+                device_source: egress::DeviceHandle::new(egress::WorkerGeneration(1), 55),
+            },
+        ],
     });
 
     // Produce only the first output and prove StepCompleted is still absent.
     harness.complete_output(egress::ObjectId(9000));
-    assert!(!harness.events().iter().any(|event| {
-        matches!(event, egress::WorkerEgressOut::StepCompleted { .. })
-    }));
+    assert!(
+        !harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, egress::WorkerEgressOut::StepCompleted { .. }) })
+    );
 
     // Produce the second output and complete role state update.
     harness.complete_output(egress::ObjectId(9100));
@@ -190,17 +203,41 @@ fn object_produced_precedes_step_completed_after_all_outputs() {
     let first_object_pos = harness
         .events()
         .iter()
-        .position(|event| matches!(event, egress::WorkerEgressOut::ObjectProduced { object_id: egress::ObjectId(9000), .. }))
+        .position(|event| {
+            matches!(
+                event,
+                egress::WorkerEgressOut::ObjectProduced {
+                    object_id: egress::ObjectId(9000),
+                    ..
+                }
+            )
+        })
         .expect("first object produced");
     let second_object_pos = harness
         .events()
         .iter()
-        .position(|event| matches!(event, egress::WorkerEgressOut::ObjectProduced { object_id: egress::ObjectId(9100), .. }))
+        .position(|event| {
+            matches!(
+                event,
+                egress::WorkerEgressOut::ObjectProduced {
+                    object_id: egress::ObjectId(9100),
+                    ..
+                }
+            )
+        })
         .expect("second object produced");
     let completed_pos = harness
         .events()
         .iter()
-        .position(|event| matches!(event, egress::WorkerEgressOut::StepCompleted { step_id: egress::StepId(77), .. }))
+        .position(|event| {
+            matches!(
+                event,
+                egress::WorkerEgressOut::StepCompleted {
+                    step_id: egress::StepId(77),
+                    ..
+                }
+            )
+        })
         .expect("step completed");
     assert!(first_object_pos < completed_pos);
     assert!(second_object_pos < completed_pos);
@@ -220,7 +257,13 @@ fn egress_faults_are_visible_and_suppress_success_events() {
         }],
     });
     assert!(invalid_ring.events().iter().any(|event| {
-        matches!(event, egress::WorkerEgressOut::StepFailed { reason: egress::StepFailureReason::InvalidOutputRing, .. })
+        matches!(
+            event,
+            egress::WorkerEgressOut::StepFailed {
+                reason: egress::StepFailureReason::InvalidOutputRing,
+                ..
+            }
+        )
     }));
 
     // Extent violation fails the step.
@@ -230,7 +273,13 @@ fn egress_faults_are_visible_and_suppress_success_events() {
         outputs: vec![output_binding(0, 32)],
     });
     assert!(bad_extent.events().iter().any(|event| {
-        matches!(event, egress::WorkerEgressOut::StepFailed { reason: egress::StepFailureReason::OutputExtentViolation, .. })
+        matches!(
+            event,
+            egress::WorkerEgressOut::StepFailed {
+                reason: egress::StepFailureReason::OutputExtentViolation,
+                ..
+            }
+        )
     }));
 
     // Copy failure faults the ring or fails the step, but must not emit
@@ -247,7 +296,10 @@ fn egress_faults_are_visible_and_suppress_success_events() {
         matches!(event, egress::WorkerEgressOut::StepFailed { .. })
             || matches!(event, egress::WorkerEgressOut::RingFault { .. })
     }));
-    assert!(!copy_failed.events().iter().any(|event| {
-        matches!(event, egress::WorkerEgressOut::ObjectProduced { .. })
-    }));
+    assert!(
+        !copy_failed
+            .events()
+            .iter()
+            .any(|event| { matches!(event, egress::WorkerEgressOut::ObjectProduced { .. }) })
+    );
 }
diff --git a/tests/mvp_system/gpu_worker_ingress_parser_guarantees.rs b/crates/mvp-system/src/tests/gpu_worker_ingress_parser_guarantees.rs
similarity index 97%
rename from tests/mvp_system/gpu_worker_ingress_parser_guarantees.rs
rename to crates/mvp-system/src/tests/gpu_worker_ingress_parser_guarantees.rs
index 2bf536e..6f815d8 100644
--- a/tests/mvp_system/gpu_worker_ingress_parser_guarantees.rs
+++ b/crates/mvp-system/src/tests/gpu_worker_ingress_parser_guarantees.rs
@@ -163,10 +163,7 @@ fn payload_loading_is_exact_extent_and_release_after_copy_completion() {
         object_id: ingress::ObjectId(9000),
         byte_count: 8,
     });
-    assert_eq!(
-        harness.device_copy_log().last().unwrap().byte_count,
-        8
-    );
+    assert_eq!(harness.device_copy_log().last().unwrap().byte_count, 8);
     assert!(harness.consume_cursor(ingress::RingId(8001)) > before_copy_complete);
 
     // EOF mid-object faults the object.
@@ -208,9 +205,12 @@ fn object_loaded_requires_complete_valid_object_and_current_handle() {
 
     // No ObjectLoaded may appear before device copy completion and handle
     // creation.
-    assert!(!harness.events().iter().any(|event| {
-        matches!(event, ingress::WorkerIngressOut::ObjectLoaded { .. })
-    }));
+    assert!(
+        !harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, ingress::WorkerIngressOut::ObjectLoaded { .. }) })
+    );
 
     // Complete device work.
     harness.observe(ingress::WorkerIngressEvent::DeviceCopyCompleted {
diff --git a/tests/mvp_system/gpu_worker_process_adapter_guarantees.rs b/crates/mvp-system/src/tests/gpu_worker_process_adapter_guarantees.rs
similarity index 85%
rename from tests/mvp_system/gpu_worker_process_adapter_guarantees.rs
rename to crates/mvp-system/src/tests/gpu_worker_process_adapter_guarantees.rs
index 5a58305..cdf499e 100644
--- a/tests/mvp_system/gpu_worker_process_adapter_guarantees.rs
+++ b/crates/mvp-system/src/tests/gpu_worker_process_adapter_guarantees.rs
@@ -84,9 +84,12 @@ fn control_stream_is_line_framed_json_without_payload_bytes() {
 
     // Stderr alone is diagnostic and does not define lifecycle state.
     harness.receive_stderr_line("loading tinygrad backend");
-    assert!(!harness.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::WorkerFatal { .. })
-    }));
+    assert!(
+        !harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, adapter::AdapterEvent::WorkerFatal { .. }) })
+    );
 }
 
 // This proves worker initialization reads arena environment, waits for
@@ -130,16 +133,24 @@ fn initialization_order_is_env_initialize_map_helper_backend_ready() {
     // Successful initialization emits WorkerReady.
     harness.receive_stdout_line(r#"{"type":"WorkerReady","generation":1}"#);
     assert!(harness.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::WorkerReady { generation: adapter::WorkerGeneration(1) })
+        matches!(
+            event,
+            adapter::AdapterEvent::WorkerReady {
+                generation: adapter::WorkerGeneration(1)
+            }
+        )
     }));
 
     // Initialization failure emits WorkerFatal if possible and exits non-zero.
     let mut failed = new_adapter();
     failed.start_worker_process();
     failed.inject_initialization_failure(adapter::InitializationFailure::BackendUnavailable);
-    assert!(failed.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::WorkerFatal { .. })
-    }));
+    assert!(
+        failed
+            .events()
+            .iter()
+            .any(|event| { matches!(event, adapter::AdapterEvent::WorkerFatal { .. }) })
+    );
     assert_ne!(failed.exit_status(), Some(adapter::ExitStatus::Code(0)));
 }
 
@@ -151,14 +162,26 @@ fn parsing_and_abi_errors_fault_the_worker_process() {
     let mut invalid_json = new_adapter();
     invalid_json.receive_stdout_line("{not-json");
     assert!(invalid_json.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::ProcessFault { reason: adapter::ProcessFaultReason::InvalidJson, .. })
+        matches!(
+            event,
+            adapter::AdapterEvent::ProcessFault {
+                reason: adapter::ProcessFaultReason::InvalidJson,
+                ..
+            }
+        )
     }));
 
     // Unknown event shape faults the adapter.
     let mut unknown = new_adapter();
     unknown.receive_stdout_line(r#"{"type":"NotAWorkerEvent"}"#);
     assert!(unknown.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::ProcessFault { reason: adapter::ProcessFaultReason::UnknownEventShape, .. })
+        matches!(
+            event,
+            adapter::AdapterEvent::ProcessFault {
+                reason: adapter::ProcessFaultReason::UnknownEventShape,
+                ..
+            }
+        )
     }));
 
     // Unsupported helper ABI emits WorkerFatal.
@@ -167,7 +190,13 @@ fn parsing_and_abi_errors_fault_the_worker_process() {
         helper_abi_version: adapter::HelperAbiVersion(999),
     });
     assert!(abi.events().iter().any(|event| {
-        matches!(event, adapter::AdapterEvent::WorkerFatal { reason: adapter::WorkerFatalReason::UnsupportedHelperAbi, .. })
+        matches!(
+            event,
+            adapter::AdapterEvent::WorkerFatal {
+                reason: adapter::WorkerFatalReason::UnsupportedHelperAbi,
+                ..
+            }
+        )
     }));
 }
 
@@ -186,14 +215,20 @@ fn command_discipline_rejects_payload_bearing_control_messages() {
     // Payload bytes in a control command are rejected at the adapter boundary.
     harness.send_raw_json_command(r#"{"type":"ExecuteStep","step_id":1,"payload":[1,2,3]}"#);
     assert!(harness.command_rejections().iter().any(|rejection| {
-        matches!(rejection.reason, adapter::CommandRejectionReason::PayloadBytesForbidden)
+        matches!(
+            rejection.reason,
+            adapter::CommandRejectionReason::PayloadBytesForbidden
+        )
     }));
 
     // Wake hints reload cursors; they do not carry byte ranges or credits.
     harness.send_command(adapter::WorkerCommand::RingReadable {
         ring_id: adapter::RingId(8001),
     });
-    let wake_line = harness.stdin_lines().last().expect("wake command must be written");
+    let wake_line = harness
+        .stdin_lines()
+        .last()
+        .expect("wake command must be written");
     let parsed = adapter::JsonLine::parse(wake_line).expect("wake line must parse");
     assert_no_payload_bytes(&parsed);
     assert!(!parsed.contains_key("range") && !parsed.contains_key("credits"));
diff --git a/tests/mvp_system/membership_pool_readiness_guarantees.rs b/crates/mvp-system/src/tests/membership_pool_readiness_guarantees.rs
similarity index 87%
rename from tests/mvp_system/membership_pool_readiness_guarantees.rs
rename to crates/mvp-system/src/tests/membership_pool_readiness_guarantees.rs
index fe268a5..ea20897 100644
--- a/tests/mvp_system/membership_pool_readiness_guarantees.rs
+++ b/crates/mvp-system/src/tests/membership_pool_readiness_guarantees.rs
@@ -34,10 +34,7 @@ fn readiness_config() -> membership::ReadinessConfig {
 // This helper provides every required public fact for one node. Tests use it to
 // build complete and deliberately incomplete pool views without observing any
 // private readiness bookkeeping.
-fn report_node_ready(
-    gate: &mut membership::ReadinessGateHarness,
-    node_id: membership::NodeId,
-) {
+fn report_node_ready(gate: &mut membership::ReadinessGateHarness, node_id: membership::NodeId) {
     gate.observe(membership::Observation::NodeKnown { node_id });
     gate.observe(membership::Observation::SwimLive { node_id });
     gate.observe(membership::Observation::NodeAvailable { node_id });
@@ -88,8 +85,14 @@ fn pool_ready_requires_complete_stable_candidate_pool() {
         .expect("complete stable pool must emit PoolReady");
 
     // Compare as sets so ordering is not part of the behavioral contract.
-    let observed = ready.iter().copied().collect::<std::collections::BTreeSet<_>>();
-    let expected = pool.iter().copied().collect::<std::collections::BTreeSet<_>>();
+    let observed = ready
+        .iter()
+        .copied()
+        .collect::<std::collections::BTreeSet<_>>();
+    let expected = pool
+        .iter()
+        .copied()
+        .collect::<std::collections::BTreeSet<_>>();
     assert_eq!(observed, expected);
 }
 
@@ -142,9 +145,11 @@ fn planning_starts_only_after_pool_ready_and_stops_if_readiness_is_lost() {
     gate.request_run_planning(membership::RunRequest::new(membership::RunId(7)));
 
     // With no PoolReady event, there must be no planning command.
-    assert!(!gate.commands().iter().any(|command| {
-        matches!(command, membership::ReadinessCommand::StartPlanning { .. })
-    }));
+    assert!(
+        !gate.commands().iter().any(|command| {
+            matches!(command, membership::ReadinessCommand::StartPlanning { .. })
+        })
+    );
 
     // Satisfy readiness, then immediately lose a required node before plan
     // commit. The policy may wait or abort, but it must not commit placement.
@@ -155,9 +160,11 @@ fn planning_starts_only_after_pool_ready_and_stops_if_readiness_is_lost() {
     gate.observe(membership::Observation::SwimLost { node_id: pool[1] });
 
     // No plan commitment command may be emitted from an unstable pool view.
-    assert!(!gate.commands().iter().any(|command| {
-        matches!(command, membership::ReadinessCommand::CommitRunPlan { .. })
-    }));
+    assert!(
+        !gate.commands().iter().any(|command| {
+            matches!(command, membership::ReadinessCommand::CommitRunPlan { .. })
+        })
+    );
 }
 
 // This proves membership loss after provisioning is a run fault, not active
@@ -180,16 +187,20 @@ fn required_node_loss_after_provisioning_faults_without_replacement() {
     gate.observe(membership::Observation::SwimLost { node_id: pool[1] });
 
     // The run must fault with a membership reason.
-    assert!(gate.events().contains(&membership::ReadinessEvent::RunFaulted {
-        run_id: membership::RunId(7),
-        reason: membership::RunFaultReason::RequiredNodeLost {
-            node_id: pool[1],
-        },
-    }));
+    assert!(
+        gate.events()
+            .contains(&membership::ReadinessEvent::RunFaulted {
+                run_id: membership::RunId(7),
+                reason: membership::RunFaultReason::RequiredNodeLost { node_id: pool[1] },
+            })
+    );
 
     // Re-placement would violate the committed-plan authority boundary.
     assert!(!gate.commands().iter().any(|command| {
-        matches!(command, membership::ReadinessCommand::RecomputePlacement { .. })
+        matches!(
+            command,
+            membership::ReadinessCommand::RecomputePlacement { .. }
+        )
     }));
 }
 
@@ -212,7 +223,9 @@ fn swim_observations_do_not_create_graph_assignments() {
             | membership::ReadinessCommand::StartPlanning { .. }
             | membership::ReadinessCommand::WaitForStability { .. }
             | membership::ReadinessCommand::AbortPendingRun { .. } => {}
-            membership::ReadinessCommand::AssignStage { .. }
+            membership::ReadinessCommand::CommitRunPlan { .. }
+            | membership::ReadinessCommand::RecomputePlacement { .. }
+            | membership::ReadinessCommand::AssignStage { .. }
             | membership::ReadinessCommand::AssignEdge { .. }
             | membership::ReadinessCommand::AssignLayerRange { .. }
             | membership::ReadinessCommand::AssignObjectSpec { .. } => {
diff --git a/crates/mvp-system/src/tests/mod.rs b/crates/mvp-system/src/tests/mod.rs
new file mode 100644
index 0000000..3f8c1c8
--- /dev/null
+++ b/crates/mvp-system/src/tests/mod.rs
@@ -0,0 +1,18 @@
+mod arena_manager_guarantees;
+mod device_bridge_guarantees;
+mod edge_establisher_guarantees;
+mod gpu_worker_ctl_guarantees;
+mod gpu_worker_egress_producer_guarantees;
+mod gpu_worker_ingress_parser_guarantees;
+mod gpu_worker_process_adapter_guarantees;
+mod membership_pool_readiness_guarantees;
+mod node_boot_lifecycle_guarantees;
+mod observability_surface_guarantees;
+mod orchestrator_run_fsm_guarantees;
+mod orchestrator_token_endpoint_guarantees;
+mod resource_inventory_guarantees;
+mod run_plan_guarantees;
+mod shared_ring_helper_abi_guarantees;
+mod stage_controller_guarantees;
+mod tx_rx_edge_actor_guarantees;
+mod weight_lifecycle_guarantees;
diff --git a/tests/mvp_system/node_boot_lifecycle_guarantees.rs b/crates/mvp-system/src/tests/node_boot_lifecycle_guarantees.rs
similarity index 90%
rename from tests/mvp_system/node_boot_lifecycle_guarantees.rs
rename to crates/mvp-system/src/tests/node_boot_lifecycle_guarantees.rs
index f045752..e463db7 100644
--- a/tests/mvp_system/node_boot_lifecycle_guarantees.rs
+++ b/crates/mvp-system/src/tests/node_boot_lifecycle_guarantees.rs
@@ -75,9 +75,13 @@ fn node_available_waits_for_all_required_readiness_facts() {
     let final_fact = facts.pop().expect("fixture has a final fact");
     for fact in facts {
         harness.observe(fact);
-        assert!(!harness.events().contains(&boot::LifecycleEvent::NodeAvailable {
-            node_id: boot::NodeId(10),
-        }));
+        assert!(
+            !harness
+                .events()
+                .contains(&boot::LifecycleEvent::NodeAvailable {
+                    node_id: boot::NodeId(10),
+                })
+        );
     }
 
     // Once the final required fact arrives, availability becomes observable.
@@ -160,15 +164,22 @@ fn boot_resource_failure_faults_without_node_availability() {
 
         // The emitted fault must carry the stable reason enum for operators and
         // tests; logs are not part of the contract.
-        assert!(harness.events().contains(&boot::LifecycleEvent::NodeFaulted {
-            node_id: boot::NodeId(10),
-            kind: expected_kind,
-        }));
+        assert!(
+            harness
+                .events()
+                .contains(&boot::LifecycleEvent::NodeFaulted {
+                    node_id: boot::NodeId(10),
+                    kind: expected_kind,
+                })
+        );
 
         // A faulted boot attempt must not also become available.
-        assert!(!harness.events().iter().any(|event| {
-            matches!(event, boot::LifecycleEvent::NodeAvailable { .. })
-        }));
+        assert!(
+            !harness
+                .events()
+                .iter()
+                .any(|event| { matches!(event, boot::LifecycleEvent::NodeAvailable { .. }) })
+        );
 
         // The orchestrator-facing eligibility check must agree with the
         // lifecycle transcript.
@@ -193,7 +204,10 @@ fn boot_never_self_assigns_run_topology() {
             boot::BootCommand::AdvertiseLifecycle { .. }
             | boot::BootCommand::JoinMembership { .. }
             | boot::BootCommand::OpenProvisioningInbox { .. } => {}
-            boot::BootCommand::AssignStage { .. }
+            boot::BootCommand::LoadWeights { .. }
+            | boot::BootCommand::ConfigureRole { .. }
+            | boot::BootCommand::EstablishEdge { .. }
+            | boot::BootCommand::AssignStage { .. }
             | boot::BootCommand::AssignLayerRange { .. }
             | boot::BootCommand::AssignEdge { .. }
             | boot::BootCommand::AssignObjectSpec { .. } => {
diff --git a/tests/mvp_system/observability_surface_guarantees.rs b/crates/mvp-system/src/tests/observability_surface_guarantees.rs
similarity index 92%
rename from tests/mvp_system/observability_surface_guarantees.rs
rename to crates/mvp-system/src/tests/observability_surface_guarantees.rs
index cf0c27f..25e8a73 100644
--- a/tests/mvp_system/observability_surface_guarantees.rs
+++ b/crates/mvp-system/src/tests/observability_surface_guarantees.rs
@@ -54,7 +54,10 @@ fn fault_trace() -> Vec<obs::Event> {
             obs::FaultReason::WorkerCrashed,
             obs::Component::StageController,
         )
-        .run_faulted(obs::FaultReason::WorkerCrashed, obs::Component::StageController)
+        .run_faulted(
+            obs::FaultReason::WorkerCrashed,
+            obs::Component::StageController,
+        )
         .stop_run_sent(obs::StageIndex(0))
         .stage_stopped(obs::StageIndex(0))
         .run_torn_down()
@@ -94,13 +97,19 @@ fn assert_required_identity(event: &obs::Event) {
             sequence,
             ..
         } => {
-            assert!([obs::ObjectId(9000), obs::ObjectId(9001), obs::ObjectId(9002)].contains(object_id));
+            assert!(
+                [
+                    obs::ObjectId(9000),
+                    obs::ObjectId(9001),
+                    obs::ObjectId(9002)
+                ]
+                .contains(object_id)
+            );
             assert_eq!(*sequence, obs::Sequence(0));
         }
         obs::Event::StepScoped { step_id, .. } => assert_eq!(*step_id, obs::StepId(77)),
         obs::Event::WorkerScoped {
-            worker_generation,
-            ..
+            worker_generation, ..
         } => assert_eq!(*worker_generation, obs::WorkerGeneration(1)),
     }
 }
@@ -166,7 +175,10 @@ fn lifecycle_events_cover_successful_run_milestones() {
         obs::EventKind::RunTornDown,
     ];
     for kind in required {
-        assert!(observed.contains(&kind), "missing lifecycle event: {kind:?}");
+        assert!(
+            observed.contains(&kind),
+            "missing lifecycle event: {kind:?}"
+        );
     }
 }
 
@@ -242,7 +254,10 @@ fn event_ordering_reflects_component_contracts_and_one_terminal_outcome() {
     let terminal_count = events
         .iter()
         .filter(|event| {
-            matches!(event.kind(), obs::EventKind::RunCompleted | obs::EventKind::RunFaulted)
+            matches!(
+                event.kind(),
+                obs::EventKind::RunCompleted | obs::EventKind::RunFaulted
+            )
         })
         .count();
     assert_eq!(terminal_count, 1);
@@ -253,8 +268,10 @@ fn event_ordering_reflects_component_contracts_and_one_terminal_outcome() {
 #[test]
 fn event_contract_survives_transport_storage_and_batching_policy() {
     // Build the same logical events under two batching policies.
-    let unbatched = obs::EventSubscriberHarness::collect(successful_run_trace(), obs::Batching::None);
-    let batched = obs::EventSubscriberHarness::collect(successful_run_trace(), obs::Batching::Fixed(8));
+    let unbatched =
+        obs::EventSubscriberHarness::collect(successful_run_trace(), obs::Batching::None);
+    let batched =
+        obs::EventSubscriberHarness::collect(successful_run_trace(), obs::Batching::Fixed(8));
 
     // Flattened public event facts must match as an ordered stream.
     let unbatched_kinds = unbatched
diff --git a/tests/mvp_system/orchestrator_run_fsm_guarantees.rs b/crates/mvp-system/src/tests/orchestrator_run_fsm_guarantees.rs
similarity index 93%
rename from tests/mvp_system/orchestrator_run_fsm_guarantees.rs
rename to crates/mvp-system/src/tests/orchestrator_run_fsm_guarantees.rs
index 750aa2e..9a5fedb 100644
--- a/tests/mvp_system/orchestrator_run_fsm_guarantees.rs
+++ b/crates/mvp-system/src/tests/orchestrator_run_fsm_guarantees.rs
@@ -77,9 +77,12 @@ fn planning_and_provisioning_start_only_after_pool_ready() {
     harness.observe(fsm::RunEvent::PlanAvailable(plan.clone()));
 
     // Without PoolReady, provisioning must not begin.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, fsm::RunCommand::ProvisionStage { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, fsm::RunCommand::ProvisionStage { .. }) })
+    );
 
     // Once PoolReady is observed, the committed plan may be provisioned.
     harness.observe(fsm::RunEvent::PoolReady {
@@ -103,7 +106,10 @@ fn planning_and_provisioning_start_only_after_pool_ready() {
     assert_eq!(provisioned, expected);
 
     // Provisioning must not mention nodes outside the committed plan.
-    let plan_nodes = plan.stage_nodes().into_iter().collect::<std::collections::BTreeSet<_>>();
+    let plan_nodes = plan
+        .stage_nodes()
+        .into_iter()
+        .collect::<std::collections::BTreeSet<_>>();
     for command in harness.commands() {
         if let fsm::RunCommand::ProvisionStage { provision } = command {
             assert!(plan_nodes.contains(&provision.node_id));
@@ -143,9 +149,12 @@ fn readiness_barrier_controls_prompt_injection() {
     });
     harness.observe(fsm::RunEvent::TokenInEndpointReady);
     harness.observe(fsm::RunEvent::TokenOutEndpointReady);
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, fsm::RunCommand::InjectPrompt { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, fsm::RunCommand::InjectPrompt { .. }) })
+    );
 
     // Complete the remaining stage readiness facts.
     for event in stage_ready_events(&plan).into_iter().skip(1) {
@@ -198,9 +207,12 @@ fn execution_injects_next_sequence_only_after_consuming_previous_token() {
     }
 
     // No separate broadcast start command may exist alongside prompt injection.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, fsm::RunCommand::BroadcastStart { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, fsm::RunCommand::BroadcastStart { .. }) })
+    );
 
     // Sequence 0 must be injected first.
     assert_eq!(harness.injected_sequences(), vec![0]);
@@ -341,9 +353,12 @@ fn terminal_outcome_is_single_and_requires_teardown() {
         .map(|stage| stage.stage_index)
         .collect::<std::collections::BTreeSet<_>>();
     assert_eq!(stopped_stages, expected_stages);
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, fsm::RunCommand::TearDownTokenEndpoints { .. })
-    }));
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, fsm::RunCommand::TearDownTokenEndpoints { .. }) })
+    );
 }
 
 // This proves run_torn_down is emitted exactly once and only after teardown
@@ -369,9 +384,12 @@ fn run_torn_down_is_emitted_once_after_teardown_terminal_state() {
         run_id: fsm::RunId(7),
         stage_index: 0,
     });
-    assert!(!harness.events().iter().any(|event| {
-        matches!(event, fsm::LifecycleEvent::RunTornDown { .. })
-    }));
+    assert!(
+        !harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, fsm::LifecycleEvent::RunTornDown { .. }) })
+    );
 
     // Finish teardown through remaining stopped events and local endpoint stop.
     harness.observe(fsm::RunEvent::StageStopped {
diff --git a/tests/mvp_system/orchestrator_token_endpoint_guarantees.rs b/crates/mvp-system/src/tests/orchestrator_token_endpoint_guarantees.rs
similarity index 91%
rename from tests/mvp_system/orchestrator_token_endpoint_guarantees.rs
rename to crates/mvp-system/src/tests/orchestrator_token_endpoint_guarantees.rs
index c4b555c..416e34c 100644
--- a/tests/mvp_system/orchestrator_token_endpoint_guarantees.rs
+++ b/crates/mvp-system/src/tests/orchestrator_token_endpoint_guarantees.rs
@@ -18,8 +18,16 @@ fn token_plan() -> token::TokenEndpointPlan {
     token::TokenEndpointPlan {
         run_id: token::RunId(7),
         orchestrator_node_id: token::NodeId(99),
-        token_in_edge: token::EdgePlan::token_in(token::EdgeId(7000), token::NodeId(99), token::NodeId(10)),
-        token_out_edge: token::EdgePlan::token_out(token::EdgeId(7003), token::NodeId(12), token::NodeId(99)),
+        token_in_edge: token::EdgePlan::token_in(
+            token::EdgeId(7000),
+            token::NodeId(99),
+            token::NodeId(10),
+        ),
+        token_out_edge: token::EdgePlan::token_out(
+            token::EdgeId(7003),
+            token::NodeId(12),
+            token::NodeId(99),
+        ),
         token_spec: token::ObjectSpec::test_tokens(),
         max_tokens: 4,
     }
@@ -95,9 +103,12 @@ fn prompt_injection_is_barrier_gated_sequence_zero_token_object() {
     harness.request_prompt_injection(vec![101, 102, 103]);
 
     // No prompt object may be written before the barrier.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, token::EndpointCommand::WriteTokenObject { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, token::EndpointCommand::WriteTokenObject { .. }) })
+    );
 
     // Passing the global barrier permits the first prompt write.
     pass_global_barrier(&mut harness);
@@ -117,9 +128,12 @@ fn prompt_injection_is_barrier_gated_sequence_zero_token_object() {
 
     // Prompt injection is the start signal; there must not be a separate
     // broadcast start command.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, token::EndpointCommand::BroadcastStart { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, token::EndpointCommand::BroadcastStart { .. }) })
+    );
 }
 
 // This proves token-out is consumed in sequence order and sequence k + 1 is
@@ -242,7 +256,10 @@ fn token_endpoint_failures_fault_the_run_or_teardown() {
     malformed.observe(token::EndpointEvent::TeardownFailed {
         edge_id: token::EdgeId(7003),
     });
-    assert!(malformed.events().iter().any(|event| {
-        matches!(event, token::EndpointLifecycleEvent::TeardownFailed { .. })
-    }));
+    assert!(
+        malformed
+            .events()
+            .iter()
+            .any(|event| { matches!(event, token::EndpointLifecycleEvent::TeardownFailed { .. }) })
+    );
 }
diff --git a/tests/mvp_system/resource_inventory_guarantees.rs b/crates/mvp-system/src/tests/resource_inventory_guarantees.rs
similarity index 96%
rename from tests/mvp_system/resource_inventory_guarantees.rs
rename to crates/mvp-system/src/tests/resource_inventory_guarantees.rs
index 72bc72f..7d47ce8 100644
--- a/tests/mvp_system/resource_inventory_guarantees.rs
+++ b/crates/mvp-system/src/tests/resource_inventory_guarantees.rs
@@ -91,7 +91,10 @@ fn inventory_entries_are_known_before_planning_and_not_negotiated_by_nodes() {
         .collect::<std::collections::BTreeSet<_>>();
     assert_eq!(after_nodes, before_nodes);
     assert!(!harness.commands().iter().any(|command| {
-        matches!(command, inventory::InventoryCommand::AcceptPlacementNegotiation { .. })
+        matches!(
+            command,
+            inventory::InventoryCommand::AcceptPlacementNegotiation { .. }
+        )
     }));
 }
 
@@ -224,7 +227,8 @@ fn planning_preserves_candidate_pool_and_emits_no_hidden_nodes() {
 #[test]
 fn provisioned_stages_do_not_reinterpret_inventory() {
     // Commit a plan and provision its stages.
-    let plan = inventory::plan_from_inventory(planning_request()).expect("valid inventory must plan");
+    let plan =
+        inventory::plan_from_inventory(planning_request()).expect("valid inventory must plan");
     let mut harness = inventory::InventoryHarness::new(inventory_entries());
     harness.commit_plan(plan.clone());
     harness.provision_stages();
@@ -238,7 +242,10 @@ fn provisioned_stages_do_not_reinterpret_inventory() {
 
     // No provisioned stage may be asked to reinterpret its assignment.
     assert!(!harness.commands().iter().any(|command| {
-        matches!(command, inventory::InventoryCommand::RewriteStagePlacement { .. })
+        matches!(
+            command,
+            inventory::InventoryCommand::RewriteStagePlacement { .. }
+        )
     }));
 
     // The committed plan remains the only graph-visible placement fact.
diff --git a/tests/mvp_system/run_plan_guarantees.rs b/crates/mvp-system/src/tests/run_plan_guarantees.rs
similarity index 99%
rename from tests/mvp_system/run_plan_guarantees.rs
rename to crates/mvp-system/src/tests/run_plan_guarantees.rs
index 992f7fe..935bb41 100644
--- a/tests/mvp_system/run_plan_guarantees.rs
+++ b/crates/mvp-system/src/tests/run_plan_guarantees.rs
@@ -20,7 +20,7 @@ type EdgeKind = plan::EdgeKind;
 type EdgePlan = plan::EdgePlan;
 type InboundEdgeProvision = plan::InboundEdgeProvision;
 type ModelFacts = plan::ModelFacts;
-type NodeId = plan::NodeId;
+use plan::NodeId;
 type ObjectKind = plan::ObjectKind;
 type OutboundEdgeProvision = plan::OutboundEdgeProvision;
 type PlacementInput = plan::PlacementInput;
@@ -283,7 +283,10 @@ fn edge_graph_is_exactly_the_linear_pipeline() {
         .filter(|edge| edge.kind == EdgeKind::TokenOut)
         .collect::<Vec<_>>();
     assert_eq!(token_out.len(), 1);
-    assert_eq!(edge_stage_index(&token_out[0].producer), Some(stage_count - 1));
+    assert_eq!(
+        edge_stage_index(&token_out[0].producer),
+        Some(stage_count - 1)
+    );
     assert!(matches!(
         token_out[0].consumer,
         EdgeEndpoint::Orchestrator { node_id } if node_id == node(99)
diff --git a/tests/mvp_system/shared_ring_helper_abi_guarantees.rs b/crates/mvp-system/src/tests/shared_ring_helper_abi_guarantees.rs
similarity index 92%
rename from tests/mvp_system/shared_ring_helper_abi_guarantees.rs
rename to crates/mvp-system/src/tests/shared_ring_helper_abi_guarantees.rs
index 01f62b4..5da98f2 100644
--- a/tests/mvp_system/shared_ring_helper_abi_guarantees.rs
+++ b/crates/mvp-system/src/tests/shared_ring_helper_abi_guarantees.rs
@@ -37,8 +37,7 @@ fn drain_committed(helper: &mut ring::RingHelperHarness) -> Vec<u8> {
 // depending on scheduler internals.
 fn assert_wake_is_payload_free(wake: &ring::WakeHint) {
     match wake {
-        ring::WakeHint::RingReadable { ring_id }
-        | ring::WakeHint::RingWritable { ring_id } => {
+        ring::WakeHint::RingReadable { ring_id } | ring::WakeHint::RingWritable { ring_id } => {
             assert_eq!(*ring_id, ring::RingId(7000));
         }
     }
@@ -85,11 +84,16 @@ fn cursors_are_monotonic_and_wrap_by_modulo_capacity() {
     assert_eq!(helper.cursor_snapshot().consume, 6);
 
     // Wrap the physical index while logical cursors keep increasing.
-    let wrapped = helper.producer_reserve(5).expect("space must exist after consume");
+    let wrapped = helper
+        .producer_reserve(5)
+        .expect("space must exist after consume");
     helper.producer_write(&wrapped, b"ghijk");
     helper.producer_commit(wrapped);
     assert_eq!(helper.cursor_snapshot().commit, 11);
-    assert_eq!(helper.cursor_snapshot().commit % helper.identity().capacity, 3);
+    assert_eq!(
+        helper.cursor_snapshot().commit % helper.identity().capacity,
+        3
+    );
     assert_eq!(drain_committed(&mut helper), b"ghijk");
     assert_eq!(helper.cursor_snapshot().consume, 11);
 }
@@ -101,7 +105,9 @@ fn cursors_are_monotonic_and_wrap_by_modulo_capacity() {
 fn producer_respects_free_space_and_publishes_after_writing() {
     // Reserve the full ring and publish it.
     let mut helper = new_ring();
-    let reservation = helper.producer_reserve(8).expect("full ring reservation fits");
+    let reservation = helper
+        .producer_reserve(8)
+        .expect("full ring reservation fits");
     helper.producer_write(&reservation, b"12345678");
     helper.producer_commit(reservation);
 
@@ -170,12 +176,22 @@ fn wake_hints_are_edge_hints_without_hiding_transitions() {
     // The readable transition must be discoverable even if duplicate wakes are
     // coalesced.
     helper.coalesce_duplicate_wakes();
-    assert!(helper.scheduler_state().readable_rings.contains(&ring::RingId(7000)));
+    assert!(
+        helper
+            .scheduler_state()
+            .readable_rings
+            .contains(&ring::RingId(7000))
+    );
 
     // Fill then release space to cause full-to-writable.
     let _ = drain_committed(&mut helper);
     helper.coalesce_duplicate_wakes();
-    assert!(helper.scheduler_state().writable_rings.contains(&ring::RingId(7000)));
+    assert!(
+        helper
+            .scheduler_state()
+            .writable_rings
+            .contains(&ring::RingId(7000))
+    );
 
     // Every wake remains a payload-free hint.
     for wake in helper.wake_hints() {
diff --git a/tests/mvp_system/stage_controller_guarantees.rs b/crates/mvp-system/src/tests/stage_controller_guarantees.rs
similarity index 90%
rename from tests/mvp_system/stage_controller_guarantees.rs
rename to crates/mvp-system/src/tests/stage_controller_guarantees.rs
index 0ce241b..10970ee 100644
--- a/tests/mvp_system/stage_controller_guarantees.rs
+++ b/crates/mvp-system/src/tests/stage_controller_guarantees.rs
@@ -101,9 +101,12 @@ fn provisioning_validates_authority_and_assigned_shape_before_setup() {
 
     // The controller must not emit any command that replaces the provisioned
     // edge ids with a locally chosen edge.
-    assert!(!harness.commands().iter().any(|command| {
-        matches!(command, stage::StageCommand::RewireEdge { .. })
-    }));
+    assert!(
+        !harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, stage::StageCommand::RewireEdge { .. }) })
+    );
 
     // An unauthorized provision attempt must fault before setup can begin.
     let mut unauthorized = new_controller();
@@ -120,9 +123,12 @@ fn provisioning_validates_authority_and_assigned_shape_before_setup() {
             }
         )
     }));
-    assert!(!unauthorized.commands().iter().any(|command| {
-        matches!(command, stage::StageCommand::ConfigureWorkerRole { .. })
-    }));
+    assert!(
+        !unauthorized
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, stage::StageCommand::ConfigureWorkerRole { .. }) })
+    );
 }
 
 // This proves StageReady is emitted only after worker readiness, weight
@@ -143,9 +149,12 @@ fn stage_ready_waits_for_worker_weights_and_both_edges() {
     let final_event = events.pop().expect("fixture has final setup event");
     for event in events {
         harness.observe(event);
-        assert!(!harness.events().iter().any(|event| {
-            matches!(event, stage::StageLifecycleEvent::StageReady { .. })
-        }));
+        assert!(
+            !harness
+                .events()
+                .iter()
+                .any(|event| { matches!(event, stage::StageLifecycleEvent::StageReady { .. }) })
+        );
     }
 
     // The final prerequisite crosses the barrier.
@@ -220,11 +229,7 @@ fn accepted_inbound_object_creates_one_same_sequence_execute_step() {
 #[test]
 fn duplicate_skipped_and_out_of_order_sequences_fault() {
     // Each invalid trace starts from a freshly readied stage.
-    let invalid_traces = vec![
-        vec![0, 0],
-        vec![0, 2],
-        vec![0, 1, 0],
-    ];
+    let invalid_traces = vec![vec![0, 0], vec![0, 2], vec![0, 1, 0]];
 
     for trace in invalid_traces {
         // Accept the first object and complete its step when needed so the next
@@ -272,7 +277,10 @@ fn step_completed_releases_input_and_admits_next_object() {
 
     // Before worker completion, no compute-complete lifecycle event is allowed.
     assert!(!harness.events().iter().any(|event| {
-        matches!(event, stage::StageLifecycleEvent::StepAccepted { sequence: 1, .. })
+        matches!(
+            event,
+            stage::StageLifecycleEvent::StepAccepted { sequence: 1, .. }
+        )
     }));
 
     // Worker StepCompleted is the public completion signal.
@@ -348,13 +356,21 @@ fn stage_fault_rejects_new_work_until_stopped() {
     harness.observe(stage::StageEvent::StopRun {
         run_id: stage::RunId(7),
     });
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, stage::StageCommand::StopLocalEdges { .. })
-    }));
-    assert!(harness.commands().iter().any(|command| {
-        matches!(command, stage::StageCommand::ReleaseRunDeviceObjects { .. })
-    }));
-    assert!(harness.events().iter().any(|event| {
-        matches!(event, stage::StageLifecycleEvent::StageStopped { .. })
-    }));
+    assert!(
+        harness
+            .commands()
+            .iter()
+            .any(|command| { matches!(command, stage::StageCommand::StopLocalEdges { .. }) })
+    );
+    assert!(
+        harness.commands().iter().any(|command| {
+            matches!(command, stage::StageCommand::ReleaseRunDeviceObjects { .. })
+        })
+    );
+    assert!(
+        harness
+            .events()
+            .iter()
+            .any(|event| { matches!(event, stage::StageLifecycleEvent::StageStopped { .. }) })
+    );
 }
diff --git a/crates/mvp-system/src/tests/tinygrad_device_bridge_backend.py b/crates/mvp-system/src/tests/tinygrad_device_bridge_backend.py
new file mode 100755
index 0000000..aa49777
--- /dev/null
+++ b/crates/mvp-system/src/tests/tinygrad_device_bridge_backend.py
@@ -0,0 +1,305 @@
+#!/usr/bin/env python3
+"""Tinygrad-backed device bridge probe for Rust MVP bridge tests.
+
+Line-delimited JSON control only. Payload bytes live in the arena file whose
+path Rust passes during initialize.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import struct
+import sys
+from dataclasses import dataclass
+from typing import Any
+
+try:
+    from tinygrad import Tensor  # type: ignore
+except Exception as exc:  # pragma: no cover - exercised from Rust process tests
+    print(
+        json.dumps(
+            {
+                "type": "worker_fatal",
+                "reason": "tinygrad_unavailable",
+                "message": str(exc),
+            }
+        ),
+        flush=True,
+    )
+    raise SystemExit(2)
+
+
+@dataclass
+class DeviceObject:
+    dtype: str
+    shape: str
+    extent: int
+    values: list[int]
+    tensor: Any
+
+
+@dataclass
+class PendingCopy:
+    kind: str
+    copy_id: int
+    handle_id: int
+    host_offset: int
+    device_offset: int
+    length: int
+
+
+arena_path: str | None = None
+arena_bytes = 0
+generation = 0
+objects: dict[int, DeviceObject] = {}
+pending_copies: dict[int, PendingCopy] = {}
+fail_next: str | None = None
+
+
+def emit(obj: dict[str, Any]) -> None:
+    print(json.dumps(obj, separators=(",", ":")), flush=True)
+
+
+def backend_error(reason: str) -> None:
+    emit({"type": "backend_error", "reason": reason})
+
+
+def fatal(reason: str, message: str) -> None:
+    emit({"type": "worker_fatal", "reason": reason, "message": message})
+
+
+def require_arena() -> str:
+    if arena_path is None:
+        raise RuntimeError("arena is not initialized")
+    return arena_path
+
+
+def consume_failure(reason: str) -> bool:
+    global fail_next
+    if fail_next == reason:
+        fail_next = None
+        backend_error(reason)
+        return True
+    return False
+
+
+def check_u32_range(offset: int, length: int) -> None:
+    if offset < 0 or length < 0 or offset % 4 != 0 or length % 4 != 0:
+        raise ValueError("u32 ranges must be non-negative and 4-byte aligned")
+
+
+def tensor_from_values(values: list[int]) -> Any:
+    try:
+        return Tensor(values, dtype="uint32").realize()
+    except Exception:
+        return Tensor(values, dtype="int32").realize()
+
+
+def allocate_tensor(dtype: str, extent: int) -> tuple[list[int], Any]:
+    if dtype == "u32":
+        if extent % 4 != 0:
+            raise ValueError("u32 extent must be 4-byte aligned")
+        values = [0] * (extent // 4)
+        return values, tensor_from_values(values)
+    if dtype == "f16":
+        values = [0] * (extent // 2)
+        return values, Tensor(values, dtype="float16").realize()
+    raise ValueError(f"unsupported dtype {dtype!r}")
+
+
+def update_tensor(obj: DeviceObject) -> None:
+    if obj.dtype == "u32":
+        obj.tensor = tensor_from_values(obj.values)
+    elif obj.dtype == "f16":
+        obj.tensor = Tensor(obj.values, dtype="float16").realize()
+    else:
+        raise ValueError(f"unsupported dtype {obj.dtype!r}")
+
+
+def materialized_values(obj: DeviceObject) -> list[int]:
+    return [int(v) for v in obj.tensor.tolist()]
+
+
+def read_arena(offset: int, length: int) -> bytes:
+    path = require_arena()
+    with open(path, "rb", buffering=0) as f:
+        f.seek(offset)
+        data = f.read(length)
+    if len(data) != length:
+        raise EOFError("short arena read")
+    return data
+
+
+def write_arena(offset: int, data: bytes) -> None:
+    path = require_arena()
+    with open(path, "r+b", buffering=0) as f:
+        f.seek(offset)
+        f.write(data)
+        f.flush()
+
+
+def perform_host_to_device(copy: PendingCopy) -> None:
+    obj = objects[copy.handle_id]
+    if obj.dtype != "u32":
+        raise ValueError("payload copy is implemented for u32 test objects only")
+    check_u32_range(copy.device_offset, copy.length)
+    payload = read_arena(copy.host_offset, copy.length)
+    words = list(struct.unpack("<" + "I" * (copy.length // 4), payload))
+    start = copy.device_offset // 4
+    end = start + len(words)
+    if end > len(obj.values):
+        raise ValueError("device range out of bounds")
+    obj.values[start:end] = words
+    update_tensor(obj)
+
+
+def perform_device_to_host(copy: PendingCopy) -> None:
+    obj = objects[copy.handle_id]
+    if obj.dtype != "u32":
+        raise ValueError("payload copy is implemented for u32 test objects only")
+    check_u32_range(copy.device_offset, copy.length)
+    values = materialized_values(obj)
+    start = copy.device_offset // 4
+    end = start + (copy.length // 4)
+    if end > len(values):
+        raise ValueError("device range out of bounds")
+    payload = struct.pack("<" + "I" * (end - start), *values[start:end])
+    write_arena(copy.host_offset, payload)
+
+
+def perform_copy(copy: PendingCopy) -> None:
+    if copy.kind == "host_to_device":
+        perform_host_to_device(copy)
+    elif copy.kind == "device_to_host":
+        perform_device_to_host(copy)
+    else:
+        raise ValueError(f"unknown copy kind {copy.kind!r}")
+
+
+def handle(req: dict[str, Any]) -> bool:
+    global arena_path, arena_bytes, generation, fail_next
+
+    typ = req.get("type")
+    if typ == "initialize":
+        arena_path = str(req["arena_path"])
+        arena_bytes = int(req["arena_bytes"])
+        generation = int(req["generation"])
+        with open(arena_path, "r+b", buffering=0) as f:
+            f.truncate(arena_bytes)
+        emit({"type": "worker_ready", "generation": generation})
+        return True
+
+    if typ == "alloc":
+        if consume_failure("allocation_failed"):
+            return True
+        handle_id = int(req["handle_id"])
+        dtype = str(req["dtype"])
+        shape = str(req["shape"])
+        extent = int(req["extent"])
+        values, tensor = allocate_tensor(dtype, extent)
+        objects[handle_id] = DeviceObject(dtype=dtype, shape=shape, extent=extent, values=values, tensor=tensor)
+        emit({"type": "allocated", "handle_id": handle_id})
+        return True
+
+    if typ in ("host_to_device", "device_to_host"):
+        if consume_failure("copy_failed"):
+            return True
+        copy = PendingCopy(
+            kind=typ,
+            copy_id=int(req["copy_id"]),
+            handle_id=int(req["handle_id"]),
+            host_offset=int(req["host_offset"]),
+            device_offset=int(req["device_offset"]),
+            length=int(req["len"]),
+        )
+        if copy.handle_id not in objects:
+            backend_error("copy_failed")
+            return True
+        if bool(req.get("defer", False)):
+            pending_copies[copy.copy_id] = copy
+            emit({"type": "copy_started", "copy_id": copy.copy_id})
+        else:
+            perform_copy(copy)
+            emit({"type": "copy_completed", "copy_id": copy.copy_id})
+        return True
+
+    if typ == "complete_copy":
+        copy_id = int(req["copy_id"])
+        copy = pending_copies.pop(copy_id, None)
+        if copy is None:
+            backend_error("copy_failed")
+            return True
+        perform_copy(copy)
+        emit({"type": "copy_completed", "copy_id": copy_id})
+        return True
+
+    if typ == "wrap_for_tinygrad":
+        if consume_failure("invalid_view"):
+            return True
+        handle_id = int(req["handle_id"])
+        obj = objects.get(handle_id)
+        if obj is None:
+            backend_error("invalid_view")
+            return True
+        dtype = str(req["dtype"])
+        shape = str(req["shape"])
+        if obj.dtype != dtype or obj.shape != shape:
+            backend_error("invalid_view")
+            return True
+        # Force materialization at view time so success depends on live tensor state.
+        _ = obj.tensor.tolist()
+        emit({"type": "view", "handle_id": handle_id, "dtype": dtype, "shape": shape})
+        return True
+
+    if typ == "free":
+        handle_id = int(req["handle_id"])
+        if handle_id not in objects:
+            backend_error("invalid_view")
+            return True
+        del objects[handle_id]
+        emit({"type": "freed", "handle_id": handle_id})
+        return True
+
+    if typ == "restart":
+        generation = int(req["generation"])
+        objects.clear()
+        pending_copies.clear()
+        fail_next = None
+        emit({"type": "worker_ready", "generation": generation})
+        return True
+
+    if typ == "fail_next":
+        fail_next = str(req["failure"])
+        emit({"type": "ok"})
+        return True
+
+    if typ == "shutdown":
+        emit({"type": "worker_stopped"})
+        return False
+
+    fatal("protocol_error", f"unknown command type {typ!r}")
+    return False
+
+
+def main() -> int:
+    for line in sys.stdin:
+        line = line.strip()
+        if not line:
+            continue
+        try:
+            req = json.loads(line)
+            if not isinstance(req, dict):
+                raise ValueError("request must be an object")
+            if not handle(req):
+                return 0
+        except SystemExit:
+            raise
+        except Exception as exc:
+            fatal("backend_exception", str(exc))
+            return 2
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/tests/mvp_system/tx_rx_edge_actor_guarantees.rs b/crates/mvp-system/src/tests/tx_rx_edge_actor_guarantees.rs
similarity index 90%
rename from tests/mvp_system/tx_rx_edge_actor_guarantees.rs
rename to crates/mvp-system/src/tests/tx_rx_edge_actor_guarantees.rs
index d64733b..9993658 100644
--- a/tests/mvp_system/tx_rx_edge_actor_guarantees.rs
+++ b/crates/mvp-system/src/tests/tx_rx_edge_actor_guarantees.rs
@@ -82,8 +82,16 @@ fn edge_actor_messages_are_lifecycle_identity_and_handle_only() {
     }
 
     // Both actors remain tied to exactly one edge id.
-    assert!(tx.messages().iter().all(|message| message.edge_id() == edge_id()));
-    assert!(rx.messages().iter().all(|message| message.edge_id() == edge_id()));
+    assert!(
+        tx.messages()
+            .iter()
+            .all(|message| message.edge_id() == edge_id())
+    );
+    assert!(
+        rx.messages()
+            .iter()
+            .all(|message| message.edge_id() == edge_id())
+    );
 }
 
 // This proves Tx starts in provisioning, becomes ready only after EdgeReady,
@@ -98,9 +106,11 @@ fn tx_lifecycle_gates_production_and_faults_on_stream_or_object_failure() {
         object_id: edge_actor::ObjectId(9000),
         sequence: 0,
     });
-    assert!(!tx.messages().iter().any(|message| {
-        matches!(message, edge_actor::ActorMessage::ObjectIdentity { .. })
-    }));
+    assert!(
+        !tx.messages()
+            .iter()
+            .any(|message| { matches!(message, edge_actor::ActorMessage::ObjectIdentity { .. }) })
+    );
 
     // EdgeReady admits production.
     tx.observe(edge_actor::TxEvent::EdgeReady { edge_id: edge_id() });
@@ -154,9 +164,11 @@ fn rx_lifecycle_gates_loaded_objects_and_faults_on_stream_or_object_failure() {
         sequence: 0,
         handle: edge_actor::OpaqueHandle::new(42),
     });
-    assert!(!rx.messages().iter().any(|message| {
-        matches!(message, edge_actor::ActorMessage::OpaqueHandle { .. })
-    }));
+    assert!(
+        !rx.messages()
+            .iter()
+            .any(|message| { matches!(message, edge_actor::ActorMessage::OpaqueHandle { .. }) })
+    );
 
     // EdgeReady admits ObjectLoaded exposure.
     rx.observe(edge_actor::RxEvent::EdgeReady { edge_id: edge_id() });
@@ -223,12 +235,16 @@ fn stop_and_mismatched_edge_events_do_not_create_run_work() {
         sequence: 0,
         handle: edge_actor::OpaqueHandle::new(42),
     });
-    assert!(!tx.messages().iter().any(|message| {
-        matches!(message, edge_actor::ActorMessage::ObjectIdentity { .. })
-    }));
-    assert!(!rx.messages().iter().any(|message| {
-        matches!(message, edge_actor::ActorMessage::OpaqueHandle { .. })
-    }));
+    assert!(
+        !tx.messages()
+            .iter()
+            .any(|message| { matches!(message, edge_actor::ActorMessage::ObjectIdentity { .. }) })
+    );
+    assert!(
+        !rx.messages()
+            .iter()
+            .any(|message| { matches!(message, edge_actor::ActorMessage::OpaqueHandle { .. }) })
+    );
 
     // A mismatched edge id must reject or fault, not create work on this actor.
     let mut mismatched = new_tx();
diff --git a/tests/mvp_system/weight_lifecycle_guarantees.rs b/crates/mvp-system/src/tests/weight_lifecycle_guarantees.rs
similarity index 97%
rename from tests/mvp_system/weight_lifecycle_guarantees.rs
rename to crates/mvp-system/src/tests/weight_lifecycle_guarantees.rs
index b5b40b2..3e1d226 100644
--- a/tests/mvp_system/weight_lifecycle_guarantees.rs
+++ b/crates/mvp-system/src/tests/weight_lifecycle_guarantees.rs
@@ -169,9 +169,11 @@ fn weights_ready_requires_all_weight_facts_and_precedes_stage_ready() {
     let final_event = events.pop().expect("fixture has final weight event");
     for event in events {
         harness.observe(event);
-        assert!(!harness.events().iter().any(|event| {
-            matches!(event, weights::WeightLifecycleEvent::WeightsReady { .. })
-        }));
+        assert!(
+            !harness.events().iter().any(|event| {
+                matches!(event, weights::WeightLifecycleEvent::WeightsReady { .. })
+            })
+        );
     }
 
     // The final weight prerequisite emits WeightsReady.
diff --git a/crates/mvp-system/src/tx_rx_edge_actor.rs b/crates/mvp-system/src/tx_rx_edge_actor.rs
new file mode 100644
index 0000000..5c43902
--- /dev/null
+++ b/crates/mvp-system/src/tx_rx_edge_actor.rs
@@ -0,0 +1,324 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct EdgeId(pub u64);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct PortId(pub String);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ObjectId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct OpaqueHandle(pub u64);
+
+impl OpaqueHandle {
+    pub fn new(id: u64) -> Self {
+        Self(id)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct TxConfig {
+    pub edge_id: EdgeId,
+    pub role_port: PortId,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RxConfig {
+    pub edge_id: EdgeId,
+    pub role_port: PortId,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ActorFaultReason {
+    MismatchedEdgeId,
+    StreamFault,
+    ObjectFault,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ActorMessage {
+    Lifecycle {
+        edge_id: EdgeId,
+        ready: bool,
+    },
+    ObjectIdentity {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+    },
+    OpaqueHandle {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+        handle: OpaqueHandle,
+    },
+    CoarseFault {
+        edge_id: EdgeId,
+        reason: ActorFaultReason,
+    },
+    PayloadBytes {
+        edge_id: EdgeId,
+        bytes: Vec<u8>,
+    },
+    HostPointer {
+        edge_id: EdgeId,
+        address: usize,
+    },
+    ByteRange {
+        edge_id: EdgeId,
+        start: u64,
+        len: u64,
+    },
+    CreditCount {
+        edge_id: EdgeId,
+        credits: u64,
+    },
+}
+
+impl ActorMessage {
+    pub fn edge_id(&self) -> EdgeId {
+        match self {
+            ActorMessage::Lifecycle { edge_id, .. }
+            | ActorMessage::ObjectIdentity { edge_id, .. }
+            | ActorMessage::OpaqueHandle { edge_id, .. }
+            | ActorMessage::CoarseFault { edge_id, .. }
+            | ActorMessage::PayloadBytes { edge_id, .. }
+            | ActorMessage::HostPointer { edge_id, .. }
+            | ActorMessage::ByteRange { edge_id, .. }
+            | ActorMessage::CreditCount { edge_id, .. } => *edge_id,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum TxEvent {
+    EdgeReady {
+        edge_id: EdgeId,
+    },
+    ObjectProduced {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+    },
+    StreamFault {
+        edge_id: EdgeId,
+    },
+    ObjectFailed {
+        edge_id: EdgeId,
+    },
+    StopEdge {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum RxEvent {
+    EdgeReady {
+        edge_id: EdgeId,
+    },
+    ObjectLoaded {
+        edge_id: EdgeId,
+        object_id: ObjectId,
+        sequence: u64,
+        handle: OpaqueHandle,
+    },
+    StreamFault {
+        edge_id: EdgeId,
+    },
+    ObjectFailed {
+        edge_id: EdgeId,
+    },
+    StopEdge {
+        edge_id: EdgeId,
+    },
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum ActorState {
+    Provisioning,
+    Ready,
+    Faulted,
+    Stopped,
+}
+
+#[cfg(test)]
+pub struct TxActorHarness {
+    config: TxConfig,
+    state: ActorState,
+    messages: Vec<ActorMessage>,
+}
+
+#[cfg(test)]
+impl TxActorHarness {
+    pub fn new(config: TxConfig) -> Self {
+        Self {
+            config,
+            state: ActorState::Provisioning,
+            messages: Vec::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: TxEvent) {
+        match event {
+            TxEvent::EdgeReady { edge_id } => {
+                if !self.check_edge(edge_id) {
+                    return;
+                }
+                if self.state == ActorState::Provisioning {
+                    self.state = ActorState::Ready;
+                    self.messages.push(ActorMessage::Lifecycle {
+                        edge_id,
+                        ready: true,
+                    });
+                }
+            }
+            TxEvent::ObjectProduced {
+                edge_id,
+                object_id,
+                sequence,
+            } => {
+                if self.state == ActorState::Ready && self.check_edge(edge_id) {
+                    self.messages.push(ActorMessage::ObjectIdentity {
+                        edge_id,
+                        object_id,
+                        sequence,
+                    });
+                }
+            }
+            TxEvent::StreamFault { edge_id } => {
+                self.fault_if_edge(edge_id, ActorFaultReason::StreamFault)
+            }
+            TxEvent::ObjectFailed { edge_id } => {
+                self.fault_if_edge(edge_id, ActorFaultReason::ObjectFault)
+            }
+            TxEvent::StopEdge { edge_id } => {
+                if edge_id == self.config.edge_id {
+                    self.state = ActorState::Stopped;
+                } else {
+                    self.mismatched();
+                }
+            }
+        }
+    }
+
+    pub fn messages(&self) -> &[ActorMessage] {
+        &self.messages
+    }
+
+    fn check_edge(&mut self, edge_id: EdgeId) -> bool {
+        if edge_id == self.config.edge_id {
+            true
+        } else {
+            self.mismatched();
+            false
+        }
+    }
+
+    fn fault_if_edge(&mut self, edge_id: EdgeId, reason: ActorFaultReason) {
+        if self.check_edge(edge_id) && self.state != ActorState::Stopped {
+            self.state = ActorState::Faulted;
+            self.messages
+                .push(ActorMessage::CoarseFault { edge_id, reason });
+        }
+    }
+
+    fn mismatched(&mut self) {
+        self.state = ActorState::Faulted;
+        self.messages.push(ActorMessage::CoarseFault {
+            edge_id: self.config.edge_id,
+            reason: ActorFaultReason::MismatchedEdgeId,
+        });
+    }
+}
+
+#[cfg(test)]
+pub struct RxActorHarness {
+    config: RxConfig,
+    state: ActorState,
+    messages: Vec<ActorMessage>,
+}
+
+#[cfg(test)]
+impl RxActorHarness {
+    pub fn new(config: RxConfig) -> Self {
+        Self {
+            config,
+            state: ActorState::Provisioning,
+            messages: Vec::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: RxEvent) {
+        match event {
+            RxEvent::EdgeReady { edge_id } => {
+                if !self.check_edge(edge_id) {
+                    return;
+                }
+                if self.state == ActorState::Provisioning {
+                    self.state = ActorState::Ready;
+                    self.messages.push(ActorMessage::Lifecycle {
+                        edge_id,
+                        ready: true,
+                    });
+                }
+            }
+            RxEvent::ObjectLoaded {
+                edge_id,
+                object_id,
+                sequence,
+                handle,
+            } => {
+                if self.state == ActorState::Ready && self.check_edge(edge_id) {
+                    self.messages.push(ActorMessage::OpaqueHandle {
+                        edge_id,
+                        object_id,
+                        sequence,
+                        handle,
+                    });
+                }
+            }
+            RxEvent::StreamFault { edge_id } => {
+                self.fault_if_edge(edge_id, ActorFaultReason::StreamFault)
+            }
+            RxEvent::ObjectFailed { edge_id } => {
+                self.fault_if_edge(edge_id, ActorFaultReason::ObjectFault)
+            }
+            RxEvent::StopEdge { edge_id } => {
+                if edge_id == self.config.edge_id {
+                    self.state = ActorState::Stopped;
+                } else {
+                    self.mismatched();
+                }
+            }
+        }
+    }
+
+    pub fn messages(&self) -> &[ActorMessage] {
+        &self.messages
+    }
+
+    fn check_edge(&mut self, edge_id: EdgeId) -> bool {
+        if edge_id == self.config.edge_id {
+            true
+        } else {
+            self.mismatched();
+            false
+        }
+    }
+
+    fn fault_if_edge(&mut self, edge_id: EdgeId, reason: ActorFaultReason) {
+        if self.check_edge(edge_id) && self.state != ActorState::Stopped {
+            self.state = ActorState::Faulted;
+            self.messages
+                .push(ActorMessage::CoarseFault { edge_id, reason });
+        }
+    }
+
+    fn mismatched(&mut self) {
+        self.state = ActorState::Faulted;
+        self.messages.push(ActorMessage::CoarseFault {
+            edge_id: self.config.edge_id,
+            reason: ActorFaultReason::MismatchedEdgeId,
+        });
+    }
+}
diff --git a/crates/mvp-system/src/weight_lifecycle.rs b/crates/mvp-system/src/weight_lifecycle.rs
new file mode 100644
index 0000000..56649b5
--- /dev/null
+++ b/crates/mvp-system/src/weight_lifecycle.rs
@@ -0,0 +1,203 @@
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RunId(pub u64);
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct NodeId(pub u64);
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct LayerRange {
+    pub start: u32,
+    pub end_exclusive: u32,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WeightSource {
+    WholeGguf { uri: String },
+    ShardSet { uris: Vec<String> },
+    CachedArtifact { cache_key: String },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct WeightAssignment {
+    pub run_id: RunId,
+    pub stage_index: u32,
+    pub plan_layer_range: LayerRange,
+    pub assigned_layer_range: LayerRange,
+    pub source: WeightSource,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ArtifactBytes {
+    Local,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WeightEvent {
+    Provisioned(WeightAssignment),
+    ArtifactAvailable { bytes: ArtifactBytes },
+    LayerRangeValidated,
+    WorkerRangeBound,
+    OtherStagePrerequisitesReady,
+    DownloadFailed,
+    ParseFailed,
+    DeviceAllocationFailed,
+    BindingFailed,
+    InvalidLayerRange,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum StageFaultReason {
+    WeightDownloadFailed,
+    WeightParseFailed,
+    DeviceAllocationFailed,
+    WeightBindingFailed,
+    InvalidLayerRange,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WeightLifecycleEvent {
+    WeightsReady {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    StageReady {
+        run_id: RunId,
+        stage_index: u32,
+    },
+    StageFault {
+        run_id: RunId,
+        stage_index: u32,
+        reason: StageFaultReason,
+    },
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum WeightCommand {
+    LoadOrBindRange {
+        source: WeightSource,
+        range: LayerRange,
+    },
+    AdvertiseLoadedLayerRange {
+        range: LayerRange,
+    },
+}
+
+#[cfg(test)]
+pub struct WeightLifecycleHarness {
+    _node_id: NodeId,
+    assignment: Option<WeightAssignment>,
+    artifact: bool,
+    validated: bool,
+    bound: bool,
+    other_stage_prereqs: bool,
+    weights_ready: bool,
+    faulted: bool,
+    commands: Vec<WeightCommand>,
+    events: Vec<WeightLifecycleEvent>,
+}
+
+#[cfg(test)]
+impl WeightLifecycleHarness {
+    pub fn new(node_id: NodeId) -> Self {
+        Self {
+            _node_id: node_id,
+            assignment: None,
+            artifact: false,
+            validated: false,
+            bound: false,
+            other_stage_prereqs: false,
+            weights_ready: false,
+            faulted: false,
+            commands: Vec::new(),
+            events: Vec::new(),
+        }
+    }
+
+    pub fn observe(&mut self, event: WeightEvent) {
+        match event {
+            WeightEvent::Provisioned(assignment) => {
+                self.commands.push(WeightCommand::LoadOrBindRange {
+                    source: assignment.source.clone(),
+                    range: assignment.assigned_layer_range,
+                });
+                if assignment.assigned_layer_range != assignment.plan_layer_range
+                    || assignment.assigned_layer_range.start
+                        >= assignment.assigned_layer_range.end_exclusive
+                {
+                    self.assignment = Some(assignment);
+                    self.fault(StageFaultReason::InvalidLayerRange);
+                } else {
+                    self.assignment = Some(assignment);
+                }
+            }
+            WeightEvent::ArtifactAvailable { .. } => self.artifact = true,
+            WeightEvent::LayerRangeValidated => self.validated = true,
+            WeightEvent::WorkerRangeBound => self.bound = true,
+            WeightEvent::OtherStagePrerequisitesReady => self.other_stage_prereqs = true,
+            WeightEvent::DownloadFailed => self.fault(StageFaultReason::WeightDownloadFailed),
+            WeightEvent::ParseFailed => self.fault(StageFaultReason::WeightParseFailed),
+            WeightEvent::DeviceAllocationFailed => {
+                self.fault(StageFaultReason::DeviceAllocationFailed)
+            }
+            WeightEvent::BindingFailed => self.fault(StageFaultReason::WeightBindingFailed),
+            WeightEvent::InvalidLayerRange => self.fault(StageFaultReason::InvalidLayerRange),
+        }
+        self.maybe_weights_ready();
+        self.maybe_stage_ready();
+    }
+
+    pub fn commands(&self) -> &[WeightCommand] {
+        &self.commands
+    }
+
+    pub fn events(&self) -> &[WeightLifecycleEvent] {
+        &self.events
+    }
+
+    fn maybe_weights_ready(&mut self) {
+        if self.faulted || self.weights_ready || self.assignment.is_none() {
+            return;
+        }
+        if self.artifact && self.validated && self.bound {
+            self.weights_ready = true;
+            let assignment = self.assignment.as_ref().unwrap();
+            self.events.push(WeightLifecycleEvent::WeightsReady {
+                run_id: assignment.run_id,
+                stage_index: assignment.stage_index,
+            });
+        }
+    }
+
+    fn maybe_stage_ready(&mut self) {
+        if self.faulted || !self.weights_ready || !self.other_stage_prereqs {
+            return;
+        }
+        let assignment = self.assignment.as_ref().unwrap();
+        if !self
+            .events
+            .iter()
+            .any(|event| matches!(event, WeightLifecycleEvent::StageReady { .. }))
+        {
+            self.events.push(WeightLifecycleEvent::StageReady {
+                run_id: assignment.run_id,
+                stage_index: assignment.stage_index,
+            });
+        }
+    }
+
+    fn fault(&mut self, reason: StageFaultReason) {
+        if self.faulted {
+            return;
+        }
+        self.faulted = true;
+        let (run_id, stage_index) = self
+            .assignment
+            .as_ref()
+            .map(|assignment| (assignment.run_id, assignment.stage_index))
+            .unwrap_or((RunId(0), 0));
+        self.events.push(WeightLifecycleEvent::StageFault {
+            run_id,
+            stage_index,
+            reason,
+        });
+    }
+}