feat: actor direct control via runtime admin

Add a RuntimeAdmin control plane for out-of-band inspection and mutation of live actors, bypassing their normal message handlers.

- src/admin.rs: add RuntimeAdmin + Admin<T> reply handle, the AdminCommand enum (ListActors, InspectActor, GetActorState, ReplaceActorState, StopActor, SuspendActor, ResumeActor), typed result types (ActorSummary/ActorStatus/ActorStateSnapshot/ListActorsResponse), and AdminError (ActorNotFound/AddressMismatch/TypeMismatch/Timeout)
- src/actor.rs: expose type-erased accessors on AnyActor — metadata() returning ActorTypeMetadata plus as_any()/as_any_mut() for downcasting — and Actor::inner()/replace_inner() so admin can snapshot or swap concrete actor state
- src/runtime.rs: wire a per-worker admin channel (admin_txs), expose Runtime::admin(), and implement the RuntimeAdmin ops that resolve an address to its owning worker, send the command, notify that worker, and return an Admin<T> handle; Admin::recv_ticking drives ticks and collects the reply
- src/worker.rs: add an admin_rx receiver and a drain_admin tick phase run before actor handlers, plus ActorPool helpers (actor_summary, get_actor_erased[_mut], suspend/resume/stop_actor_admin) that apply commands on the worker thread; fold admin_rx into the fast-idle has_work/tick_once checks
- tests/runtime_admin.rs: add 608 lines of end-to-end coverage for list/inspect/get/replace/stop/suspend/resume and the type-mismatch and not-found error paths

Signed-off-by: Zachery Aaron Shores-Chmielewski <zacheryasc@gmail.com>

src/actor.rs

@@ -443,6 +443,22 @@ impl<A: ActorInterface> Actor<A> {
     pub fn new(inner: A) -> Self {
         Self { inner }
     }
+
+    pub(crate) fn inner(&self) -> &A {
+        &self.inner
+    }
+
+    pub(crate) fn replace_inner(&mut self, inner: A) {
+        self.inner = inner;
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ActorTypeMetadata {
+    pub actor_type_id: TypeId,
+    pub actor_type_name: &'static str,
+    pub message_type_id: TypeId,
+    pub message_type_name: &'static str,
 }
 
 /// Trait for type-erased actors — single-message handler.
@@ -456,6 +472,12 @@ pub trait AnyActor: Send {
 
     /// Called on graceful stop, before removal. See [`ActorInterface::on_stop`].
     fn on_stop(&mut self, _ctx: &Ctx) {}
+
+    fn metadata(&self) -> ActorTypeMetadata;
+
+    fn as_any(&self) -> &dyn Any;
+
+    fn as_any_mut(&mut self) -> &mut dyn Any;
 }
 
 impl<A> AnyActor for Actor<A>
@@ -493,6 +515,23 @@ where
     fn on_stop(&mut self, ctx: &Ctx) {
         self.inner.on_stop(ctx);
     }
+
+    fn metadata(&self) -> ActorTypeMetadata {
+        ActorTypeMetadata {
+            actor_type_id: TypeId::of::<A>(),
+            actor_type_name: std::any::type_name::<A>(),
+            message_type_id: TypeId::of::<A::Incoming>(),
+            message_type_name: std::any::type_name::<A::Incoming>(),
+        }
+    }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn as_any_mut(&mut self) -> &mut dyn Any {
+        self
+    }
 }
 
 /// Unique token identifying a monitor subscription.

src/admin.rs

@@ -0,0 +1,163 @@
+use crate::actor::{ActorAddress, ActorInterface, ActorTypeMetadata, AnyActor, Message};
+use crate::runtime::{Inbox, Runtime};
+use parking_lot::Mutex;
+use std::any::Any;
+use std::sync::Arc;
+use std::sync::atomic::AtomicUsize;
+
+pub type AdminResult<T> = Result<T, AdminError>;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum AdminError {
+    ActorNotFound {
+        actor: ActorAddress,
+    },
+    AddressMismatch {
+        requested: ActorAddress,
+        snapshot: ActorAddress,
+    },
+    TypeMismatch {
+        expected_actor_type: &'static str,
+        expected_message_type: &'static str,
+        actual_actor_type: &'static str,
+        actual_message_type: &'static str,
+    },
+    Timeout,
+}
+
+pub struct RuntimeAdmin<'a> {
+    pub(crate) runtime: &'a Runtime,
+}
+
+pub struct Admin<T: Message> {
+    pub(crate) inbox: Inbox<AdminResult<T>>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct OperationResult {
+    pub applied: bool,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ActorStatus {
+    pub started: bool,
+    pub suspended: bool,
+    pub stopping: bool,
+    pub poisoned: bool,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ActorSummary {
+    pub address: ActorAddress,
+    pub actor_type: &'static str,
+    pub message_type: &'static str,
+    pub worker_id: usize,
+    pub parent: Option<ActorAddress>,
+    pub mailbox_depth: usize,
+    pub status: ActorStatus,
+    pub last_message_type: Option<&'static str>,
+    pub messages_handled: u64,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ListActorsResponse {
+    pub actors: Vec<ActorSummary>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct InspectActorResponse {
+    pub summary: ActorSummary,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ActorStateSnapshot<A> {
+    pub actor: ActorAddress,
+    pub actor_type: &'static str,
+    pub message_type: &'static str,
+    pub actor_instance: A,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct GetActorStateResponse<A> {
+    pub state: ActorStateSnapshot<A>,
+}
+
+impl<A: ActorInterface> ActorStateSnapshot<A> {
+    pub fn new(actor: ActorAddress, actor_instance: A) -> Self {
+        Self {
+            actor,
+            actor_type: std::any::type_name::<A>(),
+            message_type: std::any::type_name::<A::Incoming>(),
+            actor_instance,
+        }
+    }
+}
+
+impl<T: Message> Admin<T> {
+    pub(crate) fn new(inbox: Inbox<AdminResult<T>>) -> Self {
+        Self { inbox }
+    }
+
+    pub fn try_recv(&self) -> Option<AdminResult<T>> {
+        self.inbox.try_recv()
+    }
+
+    pub fn recv_ticking(&self, rt: &Runtime, max_ticks: usize) -> AdminResult<T> {
+        for _ in 0..max_ticks {
+            rt.tick();
+            if let Some(resp) = self.inbox.try_recv() {
+                return resp;
+            }
+        }
+        Err(AdminError::Timeout)
+    }
+
+    pub fn reply_addr(&self) -> &ActorAddress {
+        self.inbox.addr()
+    }
+}
+
+pub(crate) type AdminBoxedReply = Box<dyn Any + Send>;
+
+pub(crate) enum AdminCommand {
+    ListActors {
+        acc: Arc<ListActorsAccumulator>,
+    },
+    InspectActor {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+    },
+    GetActorState {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+        get: Box<
+            dyn FnOnce(ActorAddress, &dyn AnyActor, ActorTypeMetadata) -> AdminBoxedReply + Send,
+        >,
+        not_found: Box<dyn FnOnce(ActorAddress) -> AdminBoxedReply + Send>,
+    },
+    ReplaceActorState {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+        replace: Box<
+            dyn FnOnce(&mut dyn AnyActor, ActorTypeMetadata) -> AdminResult<OperationResult> + Send,
+        >,
+    },
+    StopActor {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+    },
+    SuspendActor {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+    },
+    ResumeActor {
+        actor: ActorAddress,
+        reply_to: ActorAddress,
+    },
+}
+
+pub(crate) struct ListActorsAccumulator {
+    pub(crate) remaining: AtomicUsize,
+    pub(crate) summaries: Mutex<Vec<ActorSummary>>,
+    pub(crate) reply_to: ActorAddress,
+}

src/lib.rs

@@ -1,4 +1,5 @@
 pub mod actor;
+pub mod admin;
 pub mod extension;
 pub mod process_observer;
 pub mod worker;

src/runtime.rs

@@ -1,15 +1,19 @@
 use crate::Instant;
-use std::any::Any;
+use std::any::{Any, TypeId};
 use std::cell::RefCell;
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Arc, OnceLock};
 use std::thread::Thread;
 #[cfg(not(target_arch = "wasm32"))]
 use std::thread::{self, JoinHandle};
 
 use crate::actor::{
-    Actor, ActorAddress, ActorInterface, AnyActor, Environment, ExitValue, Message, ResumeSignal,
-    SpawnRequest, StopSignal, StopWithSignal, SystemInfo,
+    Actor, ActorAddress, ActorInterface, ActorTypeMetadata, AnyActor, Environment, ExitValue,
+    Message, ResumeSignal, SpawnRequest, StopSignal, StopWithSignal, SystemInfo,
+};
+use crate::admin::{
+    ActorStateSnapshot, Admin, AdminCommand, AdminError, AdminResult, GetActorStateResponse,
+    InspectActorResponse, ListActorsAccumulator, ListActorsResponse, OperationResult, RuntimeAdmin,
 };
 use crate::channel::{Receiver, Sender};
 // Re-export config types so existing code using `runtime::RuntimeConfig` still works
@@ -106,6 +110,7 @@ pub struct Runtime {
     extension: Option<Arc<dyn RuntimeExtension>>,
     transfer_txs: Vec<Sender<Envelope>>,
     spawn_txs: Vec<Sender<SpawnRequest>>,
+    admin_txs: Vec<Sender<AdminCommand>>,
     placement: Placement,
     is_running: AtomicBool,
     worker_stats: Vec<Arc<WorkerStats>>,
@@ -221,6 +226,7 @@ impl Runtime {
 
         let mut transfer_txs = Vec::with_capacity(num_workers);
         let mut spawn_txs = Vec::with_capacity(num_workers);
+        let mut admin_txs = Vec::with_capacity(num_workers);
         let mut worker_stats = Vec::with_capacity(num_workers);
         let mut workers = Vec::with_capacity(num_workers);
 
@@ -233,9 +239,19 @@ impl Runtime {
             let spawn_tx = spawn_rx.new_sender();
             spawn_txs.push(spawn_tx);
 
+            let admin_rx = Receiver::<AdminCommand>::new(config.channel_buffer_size);
+            let admin_tx = admin_rx.new_sender();
+            admin_txs.push(admin_tx);
+
             let stats = Arc::new(WorkerStats::new());
             worker_stats.push(stats.clone());
-            workers.push(Worker::new(WorkerId(i), transfer_rx, spawn_rx, stats));
+            workers.push(Worker::new(
+                WorkerId(i),
+                transfer_rx,
+                spawn_rx,
+                admin_rx,
+                stats,
+            ));
         }
 
         let placement = Placement::new(num_workers, worker_stats.clone());
@@ -250,6 +266,7 @@ impl Runtime {
             extension: None,
             transfer_txs,
             spawn_txs,
+            admin_txs,
             placement,
             is_running: AtomicBool::new(false),
             worker_stats,
@@ -342,6 +359,10 @@ impl Runtime {
         self.extension.as_deref()
     }
 
+    pub fn admin(&self) -> RuntimeAdmin<'_> {
+        RuntimeAdmin { runtime: self }
+    }
+
     /// Send a request and get a handle for the response.
     ///
     /// Creates a temporary inbox, calls `msg_builder` with the inbox's address
@@ -590,6 +611,218 @@ impl Runtime {
     }
 }
 
+impl RuntimeAdmin<'_> {
+    fn new_admin<T: Message>(&self) -> Result<(Admin<T>, ActorAddress), Error> {
+        let inbox = self.runtime.new_inbox::<AdminResult<T>>()?;
+        let reply_to = *inbox.addr();
+        Ok((Admin::new(inbox), reply_to))
+    }
+
+    fn ready<T: Message>(&self, result: AdminResult<T>) -> Result<Admin<T>, Error> {
+        let (admin, reply_to) = self.new_admin::<T>()?;
+        let _ = self
+            .runtime
+            .inbox_registry
+            .try_deliver(reply_to, Box::new(result));
+        Ok(admin)
+    }
+
+    pub fn list_actors(&self) -> Result<Admin<ListActorsResponse>, Error> {
+        let (admin, reply_to) = self.new_admin::<ListActorsResponse>()?;
+        let acc = Arc::new(ListActorsAccumulator {
+            remaining: AtomicUsize::new(self.runtime.admin_txs.len()),
+            summaries: parking_lot::Mutex::new(Vec::new()),
+            reply_to,
+        });
+
+        for (idx, tx) in self.runtime.admin_txs.iter().enumerate() {
+            tx.send(AdminCommand::ListActors { acc: acc.clone() });
+            notify_worker(&self.runtime.worker_threads, idx);
+        }
+
+        Ok(admin)
+    }
+
+    pub fn inspect_actor(&self, actor: ActorAddress) -> Result<Admin<InspectActorResponse>, Error> {
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self.ready::<InspectActorResponse>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<InspectActorResponse>()?;
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::InspectActor { actor, reply_to });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+
+    pub fn get_actor_state<A>(
+        &self,
+        actor: ActorAddress,
+    ) -> Result<Admin<GetActorStateResponse<A>>, Error>
+    where
+        A: ActorInterface + Clone + Sync,
+    {
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self
+                .ready::<GetActorStateResponse<A>>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<GetActorStateResponse<A>>()?;
+
+        let get = Box::new(
+            |actor: ActorAddress,
+             erased: &dyn AnyActor,
+             metadata: ActorTypeMetadata|
+             -> Box<dyn Any + Send> {
+                let expected_actor_type = std::any::type_name::<A>();
+                let expected_message_type = std::any::type_name::<A::Incoming>();
+                if metadata.actor_type_id != TypeId::of::<A>()
+                    || metadata.message_type_id != TypeId::of::<A::Incoming>()
+                {
+                    return Box::new(Err::<GetActorStateResponse<A>, AdminError>(
+                        AdminError::TypeMismatch {
+                            expected_actor_type,
+                            expected_message_type,
+                            actual_actor_type: metadata.actor_type_name,
+                            actual_message_type: metadata.message_type_name,
+                        },
+                    ));
+                }
+
+                let Some(typed) = erased.as_any().downcast_ref::<Actor<A>>() else {
+                    return Box::new(Err::<GetActorStateResponse<A>, AdminError>(
+                        AdminError::TypeMismatch {
+                            expected_actor_type,
+                            expected_message_type,
+                            actual_actor_type: metadata.actor_type_name,
+                            actual_message_type: metadata.message_type_name,
+                        },
+                    ));
+                };
+
+                Box::new(Ok::<GetActorStateResponse<A>, AdminError>(
+                    GetActorStateResponse {
+                        state: ActorStateSnapshot {
+                            actor,
+                            actor_type: metadata.actor_type_name,
+                            message_type: metadata.message_type_name,
+                            actor_instance: typed.inner().clone(),
+                        },
+                    },
+                ))
+            },
+        );
+        let not_found = Box::new(|actor| {
+            Box::new(Err::<GetActorStateResponse<A>, AdminError>(
+                AdminError::ActorNotFound { actor },
+            )) as Box<dyn Any + Send>
+        });
+
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::GetActorState {
+            actor,
+            reply_to,
+            get,
+            not_found,
+        });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+
+    pub fn replace_actor_state<A>(
+        &self,
+        actor: ActorAddress,
+        state: ActorStateSnapshot<A>,
+    ) -> Result<Admin<OperationResult>, Error>
+    where
+        A: ActorInterface,
+    {
+        if state.actor != actor {
+            return self.ready::<OperationResult>(Err(AdminError::AddressMismatch {
+                requested: actor,
+                snapshot: state.actor,
+            }));
+        }
+
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self.ready::<OperationResult>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<OperationResult>()?;
+
+        let actor_instance = state.actor_instance;
+        let replace = Box::new(
+            move |erased: &mut dyn AnyActor,
+                  metadata: ActorTypeMetadata|
+                  -> AdminResult<OperationResult> {
+                let expected_actor_type = std::any::type_name::<A>();
+                let expected_message_type = std::any::type_name::<A::Incoming>();
+                if metadata.actor_type_id != TypeId::of::<A>()
+                    || metadata.message_type_id != TypeId::of::<A::Incoming>()
+                {
+                    return Err(AdminError::TypeMismatch {
+                        expected_actor_type,
+                        expected_message_type,
+                        actual_actor_type: metadata.actor_type_name,
+                        actual_message_type: metadata.message_type_name,
+                    });
+                }
+
+                let Some(typed) = erased.as_any_mut().downcast_mut::<Actor<A>>() else {
+                    return Err(AdminError::TypeMismatch {
+                        expected_actor_type,
+                        expected_message_type,
+                        actual_actor_type: metadata.actor_type_name,
+                        actual_message_type: metadata.message_type_name,
+                    });
+                };
+
+                typed.replace_inner(actor_instance);
+                Ok(OperationResult { applied: true })
+            },
+        );
+
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::ReplaceActorState {
+            actor,
+            reply_to,
+            replace,
+        });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+
+    pub fn stop_actor(&self, actor: ActorAddress) -> Result<Admin<OperationResult>, Error> {
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self.ready::<OperationResult>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<OperationResult>()?;
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::StopActor { actor, reply_to });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+
+    pub fn suspend_actor(&self, actor: ActorAddress) -> Result<Admin<OperationResult>, Error> {
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self.ready::<OperationResult>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<OperationResult>()?;
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::SuspendActor { actor, reply_to });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+
+    pub fn resume_actor(&self, actor: ActorAddress) -> Result<Admin<OperationResult>, Error> {
+        let Some(wid) = self.runtime.address_map.lookup(&actor) else {
+            return self.ready::<OperationResult>(Err(AdminError::ActorNotFound { actor }));
+        };
+        let (admin, reply_to) = self.new_admin::<OperationResult>()?;
+        let worker_idx = wid.as_usize();
+        self.runtime.admin_txs[worker_idx].send(AdminCommand::ResumeActor { actor, reply_to });
+        notify_worker(&self.runtime.worker_threads, worker_idx);
+        Ok(admin)
+    }
+}
+
 /// Wake a parked worker thread so it can process new work.
 /// No-op if the thread handle hasn't been registered yet (single-threaded tick mode).
 #[inline]

src/worker.rs

@@ -11,6 +11,10 @@ use crate::actor::{
     ActorAddress, AnyActor, ContextInner, Ctx, Environment, ExitValue, ResumeSignal, SpawnRequest,
     StopReason, StopSignal, StopWithSignal, SystemInfo,
 };
+use crate::admin::{
+    ActorStatus, ActorSummary, AdminCommand, AdminError, AdminResult, InspectActorResponse,
+    ListActorsResponse, OperationResult,
+};
 use crate::channel::Receiver;
 use crate::delivery::{AddrBuildHasher, AddrMap, Envelope, TickContext, WorkerId};
 use crate::stats::{ActorSnapshot, TickTiming, WorkerStats};
@@ -69,6 +73,7 @@ pub(crate) struct Worker {
     pub(crate) pool: ActorPool,
     transfer_rx: Receiver<Envelope>,
     spawn_rx: Receiver<SpawnRequest>,
+    admin_rx: Receiver<AdminCommand>,
     stats: Arc<WorkerStats>,
     /// Reusable scratch buffer for building per-actor snapshots.
     snapshot_buf: Vec<ActorSnapshot>,
@@ -84,6 +89,7 @@ impl Worker {
         id: WorkerId,
         transfer_rx: Receiver<Envelope>,
         spawn_rx: Receiver<SpawnRequest>,
+        admin_rx: Receiver<AdminCommand>,
         stats: Arc<WorkerStats>,
     ) -> Self {
         Self {
@@ -91,6 +97,7 @@ impl Worker {
             pool: ActorPool::new(),
             transfer_rx,
             spawn_rx,
+            admin_rx,
             stats,
             snapshot_buf: Vec::new(),
             worker_ext: None,
@@ -132,6 +139,88 @@ impl Worker {
         did_work
     }
 
+    fn drain_admin(&mut self, tc: &TickContext) -> bool {
+        let mut did_work = false;
+        while let Some(cmd) = self.admin_rx.try_recv() {
+            did_work = true;
+            self.apply_admin_command(tc, cmd);
+        }
+        did_work
+    }
+
+    fn send_admin_reply<T: crate::actor::Message>(
+        tc: &TickContext,
+        reply_to: ActorAddress,
+        result: AdminResult<T>,
+    ) {
+        let _ = tc.inbox_registry.try_deliver(reply_to, Box::new(result));
+    }
+
+    fn apply_admin_command(&mut self, tc: &TickContext, cmd: AdminCommand) {
+        match cmd {
+            AdminCommand::ListActors { acc } => {
+                let mut local = Vec::new();
+                self.pool.actor_summaries_into(self.id, &mut local);
+                {
+                    let mut summaries = acc.summaries.lock();
+                    summaries.extend(local);
+                }
+                if acc.remaining.fetch_sub(1, Ordering::AcqRel) == 1 {
+                    let actors = {
+                        let mut summaries = acc.summaries.lock();
+                        std::mem::take(&mut *summaries)
+                    };
+                    Self::send_admin_reply(tc, acc.reply_to, Ok(ListActorsResponse { actors }));
+                }
+            }
+            AdminCommand::InspectActor { actor, reply_to } => {
+                let result = self
+                    .pool
+                    .actor_summary(self.id, actor)
+                    .map(|summary| InspectActorResponse { summary });
+                Self::send_admin_reply(tc, reply_to, result);
+            }
+            AdminCommand::GetActorState {
+                actor,
+                reply_to,
+                get,
+                not_found,
+            } => {
+                let boxed = match self.pool.get_actor_erased(actor) {
+                    Some(erased) => get(actor, erased, erased.metadata()),
+                    None => not_found(actor),
+                };
+                let _ = tc.inbox_registry.try_deliver(reply_to, boxed);
+            }
+            AdminCommand::ReplaceActorState {
+                actor,
+                reply_to,
+                replace,
+            } => {
+                let result = match self.pool.get_actor_erased_mut(actor) {
+                    Some(erased) => {
+                        let metadata = erased.metadata();
+                        replace(erased, metadata)
+                    }
+                    None => Err(AdminError::ActorNotFound { actor }),
+                };
+                Self::send_admin_reply(tc, reply_to, result);
+            }
+            AdminCommand::StopActor { actor, reply_to } => {
+                let result = self.pool.stop_actor_admin(actor, &self.stats);
+                Self::send_admin_reply(tc, reply_to, result);
+            }
+            AdminCommand::SuspendActor { actor, reply_to } => {
+                let result = self.pool.suspend_actor_admin(actor);
+                Self::send_admin_reply(tc, reply_to, result);
+            }
+            AdminCommand::ResumeActor { actor, reply_to } => {
+                let result = self.pool.resume_actor_admin(actor);
+                Self::send_admin_reply(tc, reply_to, result);
+            }
+        }
+    }
+
     /// Phase 7: clean up dead actors, deliver death notifications, GC extension state.
     fn cleanup_dead_actors(&mut self, tc: &TickContext) -> bool {
         let cleanup_pending: RefCell<Vec<(ActorAddress, Box<dyn Any + Send>)>> =
@@ -197,6 +286,7 @@ impl Worker {
         if !self.has_backlog
             && self.spawn_rx.is_empty()
             && self.transfer_rx.is_empty()
+            && self.admin_rx.is_empty()
             && !self
                 .worker_ext
                 .as_ref()
@@ -221,7 +311,10 @@ impl Worker {
         }
         let t2 = Instant::now();
 
-        // 2.5. Fire per-worker extension (e.g., timers) → deliver before tick_all
+        // 3. Drain admin queue → inspect or mutate worker-owned slots before handlers
+        did_work |= self.drain_admin(tc);
+
+        // 4. Fire per-worker extension (e.g., timers) → deliver before tick_all
         let ext_msgs: Vec<_> = self
             .worker_ext
             .as_mut()
@@ -232,7 +325,7 @@ impl Worker {
             did_work = true;
         }
 
-        // 3. Tick all actors with WorkerContext
+        // 5. Tick all actors with WorkerContext
         let pending_local: RefCell<Vec<(ActorAddress, Box<dyn Any + Send>)>> =
             RefCell::new(Vec::new());
         let stop_requests: RefCell<Vec<ActorAddress>> = RefCell::new(Vec::new());
@@ -275,12 +368,12 @@ impl Worker {
             );
         }
 
-        // 4. Drain spawn queue again — actors spawned during step 3
+        // 6. Drain spawn queue again — actors spawned during step 5
         //    must be in the pool before pending_local delivery.
         did_work |= self.drain_spawns(tc);
         let t4 = Instant::now();
 
-        // 5. Drain pending_local buffer → deliver to local actors
+        // 7. Drain pending_local buffer → deliver to local actors
         let pending = pending_local.into_inner();
         if !pending.is_empty() {
             did_work = true;
@@ -289,7 +382,7 @@ impl Worker {
             self.pool.deliver(&addr, msg);
         }
 
-        // 5.5. Process worker extension requests from handlers (e.g., timer scheduling)
+        // 7.5. Process worker extension requests from handlers (e.g., timer scheduling)
         if let Some(ext) = &mut self.worker_ext {
             for request in worker_requests.into_inner() {
                 ext.handle_request(request);
@@ -298,7 +391,7 @@ impl Worker {
 
         let t5 = Instant::now();
 
-        // 6. Publish stats (skip entirely when idle to avoid allocation + mutex)
+        // 8. Publish stats (skip entirely when idle to avoid allocation + mutex)
         if did_work {
             self.stats
                 .num_actors
@@ -344,7 +437,7 @@ impl Worker {
             );
         }
 
-        // 7. Clean up poisoned and stopping actors
+        // 9. Clean up poisoned and stopping actors
         did_work |= self.cleanup_dead_actors(tc);
 
         self.has_backlog = did_work;
@@ -545,6 +638,95 @@ impl ActorPool {
         }
     }
 
+    fn get_actor_erased(&self, addr: ActorAddress) -> Option<&dyn AnyActor> {
+        self.actors.get(&addr).map(|slot| slot.actor.as_ref())
+    }
+
+    fn get_actor_erased_mut(
+        &mut self,
+        addr: ActorAddress,
+    ) -> Option<&mut (dyn AnyActor + 'static)> {
+        self.actors.get_mut(&addr).map(|slot| slot.actor.as_mut())
+    }
+
+    fn actor_summary_from_slot(
+        worker_id: WorkerId,
+        address: ActorAddress,
+        slot: &ActorSlot,
+    ) -> ActorSummary {
+        let metadata = slot.actor.metadata();
+        ActorSummary {
+            address,
+            actor_type: metadata.actor_type_name,
+            message_type: metadata.message_type_name,
+            worker_id: worker_id.as_usize(),
+            parent: slot.parent_addr,
+            mailbox_depth: slot.mailbox.len(),
+            status: ActorStatus {
+                started: slot.started,
+                suspended: slot.suspended,
+                stopping: slot.stopping,
+                poisoned: slot.poisoned,
+            },
+            last_message_type: slot.last_msg_type,
+            messages_handled: slot.messages_processed,
+        }
+    }
+
+    fn actor_summary(&self, worker_id: WorkerId, addr: ActorAddress) -> AdminResult<ActorSummary> {
+        self.actors
+            .get(&addr)
+            .map(|slot| Self::actor_summary_from_slot(worker_id, addr, slot))
+            .ok_or(AdminError::ActorNotFound { actor: addr })
+    }
+
+    fn actor_summaries_into(&self, worker_id: WorkerId, out: &mut Vec<ActorSummary>) {
+        out.clear();
+        out.extend(
+            self.actors
+                .iter()
+                .map(|(&addr, slot)| Self::actor_summary_from_slot(worker_id, addr, slot)),
+        );
+    }
+
+    fn suspend_actor_admin(&mut self, addr: ActorAddress) -> AdminResult<OperationResult> {
+        match self.actors.get_mut(&addr) {
+            Some(slot) => {
+                slot.suspended = true;
+                Ok(OperationResult { applied: true })
+            }
+            None => Err(AdminError::ActorNotFound { actor: addr }),
+        }
+    }
+
+    fn resume_actor_admin(&mut self, addr: ActorAddress) -> AdminResult<OperationResult> {
+        match self.actors.get_mut(&addr) {
+            Some(slot) => {
+                slot.suspended = false;
+                Ok(OperationResult { applied: true })
+            }
+            None => Err(AdminError::ActorNotFound { actor: addr }),
+        }
+    }
+
+    fn stop_actor_admin(
+        &mut self,
+        addr: ActorAddress,
+        stats: &WorkerStats,
+    ) -> AdminResult<OperationResult> {
+        match self.actors.get_mut(&addr) {
+            Some(slot) => {
+                if !slot.stopping {
+                    stats.stops.fetch_add(1, Ordering::Relaxed);
+                }
+                slot.stopping = true;
+                slot.mailbox.clear();
+                Ok(OperationResult { applied: true })
+            }
+            None => Err(AdminError::ActorNotFound { actor: addr }),
+        }
+    }
+
     /// Tick all actors in the pool. Returns the number of messages processed.
     ///
     /// Each actor processes up to `budget` messages per tick (0 = unlimited).

tests/runtime_admin.rs

@@ -0,0 +1,608 @@
+//! Runtime Admin API tests — inventory, typed actor state, lifecycle control, and scheduling.
+
+mod common;
+use common::*;
+
+use std::collections::HashSet;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::time::{Duration, Instant};
+
+use swactor::admin::{ActorStateSnapshot, AdminError, OperationResult};
+use swactor::config::RuntimeConfig;
+
+#[derive(Clone)]
+struct AddAndReport {
+    delta: usize,
+    reply_to: ActorAddress,
+}
+
+#[derive(Clone)]
+struct ReplaceProbe {
+    value: usize,
+    started: Arc<AtomicUsize>,
+    stopped: Arc<AtomicUsize>,
+}
+
+impl ActorInterface for ReplaceProbe {
+    type Incoming = AddAndReport;
+    type Response = Count;
+
+    fn on_start(&mut self, _ctx: &Ctx) {
+        self.started.fetch_add(1, Ordering::SeqCst);
+    }
+
+    fn on_stop(&mut self, _ctx: &Ctx) {
+        self.stopped.fetch_add(1, Ordering::SeqCst);
+    }
+
+    fn handle(&mut self, ctx: &Ctx, msg: AddAndReport) {
+        self.value += msg.delta;
+        let _ = ctx.send(msg.reply_to, Count(self.value));
+    }
+}
+
+struct WrongProbe;
+
+impl ActorInterface for WrongProbe {
+    type Incoming = Ping;
+    type Response = Pong;
+
+    fn handle(&mut self, _ctx: &Ctx, _msg: Ping) {}
+}
+
+struct StopProbe {
+    started: Arc<AtomicUsize>,
+    handled: Arc<AtomicUsize>,
+    stopped: Arc<AtomicUsize>,
+}
+
+impl ActorInterface for StopProbe {
+    type Incoming = Ping;
+    type Response = Pong;
+
+    fn on_start(&mut self, _ctx: &Ctx) {
+        self.started.fetch_add(1, Ordering::SeqCst);
+    }
+
+    fn on_stop(&mut self, _ctx: &Ctx) {
+        self.stopped.fetch_add(1, Ordering::SeqCst);
+    }
+
+    fn handle(&mut self, ctx: &Ctx, msg: Ping) {
+        self.handled.fetch_add(1, Ordering::SeqCst);
+        let _ = ctx.send(msg.reply_to, Pong);
+    }
+}
+
+fn poll_admin<T: swactor::actor::Message>(
+    admin: &swactor::admin::Admin<T>,
+    timeout: Duration,
+) -> Option<swactor::admin::AdminResult<T>> {
+    let start = Instant::now();
+    while start.elapsed() < timeout {
+        if let Some(value) = admin.try_recv() {
+            return Some(value);
+        }
+        std::thread::sleep(Duration::from_millis(5));
+    }
+    None
+}
+
+fn poll_inbox<M: swactor::actor::Message>(inbox: &Inbox<M>, timeout: Duration) -> Option<M> {
+    let start = Instant::now();
+    while start.elapsed() < timeout {
+        if let Some(value) = inbox.try_recv() {
+            return Some(value);
+        }
+        std::thread::sleep(Duration::from_millis(5));
+    }
+    None
+}
+
+fn operation_applied() -> OperationResult {
+    OperationResult { applied: true }
+}
+
+#[test]
+fn ask_recv_ticking_delivers_reply_through_runtime_inbox() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let actor = rt.spawn(SelfAddrActor).unwrap();
+
+    let ask = rt
+        .ask::<WhoAreYou, MyAddr>(actor, |reply_to| WhoAreYou { reply_to })
+        .unwrap();
+
+    assert_eq!(
+        ask.try_recv(),
+        None,
+        "ask reply is not available before ticking"
+    );
+    assert_eq!(
+        ask.recv_ticking(&rt, 5).unwrap(),
+        MyAddr(actor),
+        "recv_ticking drives the runtime inbox reply path"
+    );
+}
+
+#[test]
+fn admin_list_and_inspect_report_actor_slot_metadata() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let ping_pong = rt.spawn(PingPongActor).unwrap();
+    let counter = rt.spawn(CounterActor { count: 0 }).unwrap();
+    rt.tick();
+
+    let count_inbox = rt.new_inbox::<Count>().unwrap();
+    rt.send_to(
+        counter,
+        Increment {
+            reply_to: *count_inbox.addr(),
+        },
+    )
+    .unwrap();
+    rt.send_to(
+        counter,
+        Increment {
+            reply_to: *count_inbox.addr(),
+        },
+    )
+    .unwrap();
+
+    assert_eq!(tick_until_recv(&rt, &count_inbox, 5), Some(Count(1)));
+    assert_eq!(tick_until_recv(&rt, &count_inbox, 5), Some(Count(2)));
+
+    let response = rt
+        .admin()
+        .list_actors()
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+
+    assert_eq!(
+        response
+            .actors
+            .iter()
+            .filter(|summary| summary.address == ping_pong)
+            .count(),
+        1,
+        "ping-pong actor appears exactly once in inventory"
+    );
+    assert_eq!(
+        response
+            .actors
+            .iter()
+            .filter(|summary| summary.address == counter)
+            .count(),
+        1,
+        "counter actor appears exactly once in inventory"
+    );
+
+    let counter_summary = response
+        .actors
+        .iter()
+        .find(|summary| summary.address == counter)
+        .expect("counter summary missing");
+
+    assert_eq!(counter_summary.worker_id, 0);
+    assert_eq!(counter_summary.parent, None);
+    assert_eq!(counter_summary.mailbox_depth, 0);
+    assert!(counter_summary.status.started);
+    assert!(!counter_summary.status.suspended);
+    assert!(!counter_summary.status.stopping);
+    assert!(!counter_summary.status.poisoned);
+    assert_eq!(counter_summary.messages_handled, 2);
+    assert!(counter_summary.actor_type.ends_with("CounterActor"));
+    assert!(counter_summary.message_type.ends_with("Increment"));
+
+    let inspect = rt
+        .admin()
+        .inspect_actor(counter)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(inspect.summary, *counter_summary);
+
+    let missing = ActorAddress::new_random();
+    let missing_result = rt
+        .admin()
+        .inspect_actor(missing)
+        .unwrap()
+        .recv_ticking(&rt, 5);
+    assert!(
+        matches!(missing_result, Err(AdminError::ActorNotFound { actor }) if actor == missing),
+        "missing actor is reported through AdminResult"
+    );
+}
+
+#[test]
+fn admin_get_and_replace_actor_state_preserves_slot_metadata() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let started = Arc::new(AtomicUsize::new(0));
+    let stopped = Arc::new(AtomicUsize::new(0));
+    let addr = rt
+        .spawn(ReplaceProbe {
+            value: 1,
+            started: started.clone(),
+            stopped: stopped.clone(),
+        })
+        .unwrap();
+    rt.tick();
+
+    assert_eq!(started.load(Ordering::SeqCst), 1);
+    assert_eq!(stopped.load(Ordering::SeqCst), 0);
+
+    let count_inbox = rt.new_inbox::<Count>().unwrap();
+    rt.send_to(
+        addr,
+        AddAndReport {
+            delta: 1,
+            reply_to: *count_inbox.addr(),
+        },
+    )
+    .unwrap();
+    assert_eq!(tick_until_recv(&rt, &count_inbox, 5), Some(Count(2)));
+
+    let state = rt
+        .admin()
+        .get_actor_state::<ReplaceProbe>(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap()
+        .state;
+    assert_eq!(state.actor, addr);
+    assert!(state.actor_type.ends_with("ReplaceProbe"));
+    assert!(state.message_type.ends_with("AddAndReport"));
+    assert_eq!(state.actor_instance.value, 2);
+
+    let replacement = ActorStateSnapshot::new(
+        addr,
+        ReplaceProbe {
+            value: 100,
+            started: started.clone(),
+            stopped: stopped.clone(),
+        },
+    );
+    let replace_result = rt
+        .admin()
+        .replace_actor_state::<ReplaceProbe>(addr, replacement)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(replace_result, operation_applied());
+    assert_eq!(
+        started.load(Ordering::SeqCst),
+        1,
+        "replacement does not call on_start"
+    );
+    assert_eq!(
+        stopped.load(Ordering::SeqCst),
+        0,
+        "replacement does not call on_stop"
+    );
+
+    rt.send_to(
+        addr,
+        AddAndReport {
+            delta: 1,
+            reply_to: *count_inbox.addr(),
+        },
+    )
+    .unwrap();
+    assert_eq!(tick_until_recv(&rt, &count_inbox, 5), Some(Count(101)));
+
+    let summary = rt
+        .admin()
+        .inspect_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap()
+        .summary;
+    assert_eq!(summary.address, addr);
+    assert_eq!(summary.worker_id, 0);
+    assert_eq!(
+        summary.messages_handled, 2,
+        "state replacement preserves slot-owned message counters"
+    );
+
+    let stop_result = rt
+        .admin()
+        .stop_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(stop_result, operation_applied());
+    rt.tick();
+    assert_eq!(stopped.load(Ordering::SeqCst), 1);
+}
+
+#[test]
+fn admin_replace_rejects_wrong_actor_type_and_wrong_snapshot_address() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let started = Arc::new(AtomicUsize::new(0));
+    let stopped = Arc::new(AtomicUsize::new(0));
+    let addr = rt
+        .spawn(ReplaceProbe {
+            value: 10,
+            started: started.clone(),
+            stopped: stopped.clone(),
+        })
+        .unwrap();
+    rt.tick();
+
+    let wrong_type_snapshot = ActorStateSnapshot::new(addr, WrongProbe);
+    let wrong_type = rt
+        .admin()
+        .replace_actor_state::<WrongProbe>(addr, wrong_type_snapshot)
+        .unwrap()
+        .recv_ticking(&rt, 5);
+    assert!(
+        matches!(wrong_type, Err(AdminError::TypeMismatch { .. })),
+        "wrong concrete actor type is rejected"
+    );
+
+    let wrong_addr = ActorAddress::new_random();
+    let wrong_addr_snapshot = ActorStateSnapshot::new(
+        wrong_addr,
+        ReplaceProbe {
+            value: 50,
+            started: started.clone(),
+            stopped: stopped.clone(),
+        },
+    );
+    let wrong_address = rt
+        .admin()
+        .replace_actor_state::<ReplaceProbe>(addr, wrong_addr_snapshot)
+        .unwrap()
+        .recv_ticking(&rt, 5);
+    assert!(
+        matches!(wrong_address, Err(AdminError::AddressMismatch { requested, snapshot }) if requested == addr && snapshot == wrong_addr),
+        "snapshot address must match the target address"
+    );
+
+    let count_inbox = rt.new_inbox::<Count>().unwrap();
+    rt.send_to(
+        addr,
+        AddAndReport {
+            delta: 1,
+            reply_to: *count_inbox.addr(),
+        },
+    )
+    .unwrap();
+    assert_eq!(
+        tick_until_recv(&rt, &count_inbox, 5),
+        Some(Count(11)),
+        "failed replacements do not mutate the original actor state"
+    );
+}
+
+#[test]
+fn admin_suspend_queues_messages_until_resume() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let counter = Arc::new(AtomicUsize::new(0));
+    let addr = rt
+        .spawn(CountingPingActor {
+            counter: counter.clone(),
+        })
+        .unwrap();
+    rt.tick();
+
+    let suspend_result = rt
+        .admin()
+        .suspend_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(suspend_result, operation_applied());
+
+    let pong_inbox = rt.new_inbox::<Pong>().unwrap();
+    for _ in 0..3 {
+        rt.send_to(
+            addr,
+            Ping {
+                reply_to: *pong_inbox.addr(),
+            },
+        )
+        .unwrap();
+    }
+    tick_n(&rt, 5);
+    assert_eq!(counter.load(Ordering::SeqCst), 0);
+    assert_eq!(pong_inbox.try_recv(), None);
+
+    let suspended = rt
+        .admin()
+        .inspect_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap()
+        .summary;
+    assert!(suspended.status.suspended);
+    assert_eq!(suspended.mailbox_depth, 3);
+
+    let resume_result = rt
+        .admin()
+        .resume_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(resume_result, operation_applied());
+    for _ in 0..3 {
+        assert_eq!(tick_until_recv(&rt, &pong_inbox, 5), Some(Pong));
+    }
+    assert_eq!(counter.load(Ordering::SeqCst), 3);
+
+    let resumed = rt
+        .admin()
+        .inspect_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap()
+        .summary;
+    assert!(!resumed.status.suspended);
+    assert_eq!(resumed.mailbox_depth, 0);
+    assert_eq!(resumed.messages_handled, 3);
+}
+
+#[test]
+fn admin_stop_clears_pending_mailbox_without_calling_handle() {
+    let rt = std_runtime(RuntimeConfig::default());
+    let started = Arc::new(AtomicUsize::new(0));
+    let handled = Arc::new(AtomicUsize::new(0));
+    let stopped = Arc::new(AtomicUsize::new(0));
+    let addr = rt
+        .spawn(StopProbe {
+            started: started.clone(),
+            handled: handled.clone(),
+            stopped: stopped.clone(),
+        })
+        .unwrap();
+    rt.tick();
+    assert_eq!(started.load(Ordering::SeqCst), 1);
+
+    let pong_inbox = rt.new_inbox::<Pong>().unwrap();
+    for _ in 0..5 {
+        rt.send_to(
+            addr,
+            Ping {
+                reply_to: *pong_inbox.addr(),
+            },
+        )
+        .unwrap();
+    }
+
+    let stop_result = rt
+        .admin()
+        .stop_actor(addr)
+        .unwrap()
+        .recv_ticking(&rt, 5)
+        .unwrap();
+    assert_eq!(stop_result, operation_applied());
+    rt.tick();
+
+    assert_eq!(handled.load(Ordering::SeqCst), 0);
+    assert_eq!(stopped.load(Ordering::SeqCst), 1);
+    assert_eq!(pong_inbox.try_recv(), None);
+    assert!(
+        rt.send_to(
+            addr,
+            Ping {
+                reply_to: *pong_inbox.addr(),
+            },
+        )
+        .is_err(),
+        "admin-stopped actor is removed from normal send routing"
+    );
+
+    let inspect = rt.admin().inspect_actor(addr).unwrap().recv_ticking(&rt, 5);
+    assert!(
+        matches!(inspect, Err(AdminError::ActorNotFound { actor }) if actor == addr),
+        "admin-stopped actor is no longer inspectable"
+    );
+}
+
+#[test]
+fn threaded_admin_suspend_resume_wakes_parked_worker() {
+    let rt = std_runtime(RuntimeConfig {
+        num_threads: 2,
+        ..Default::default()
+    });
+    let counter = Arc::new(AtomicUsize::new(0));
+    let addr = rt
+        .spawn(CountingPingActor {
+            counter: counter.clone(),
+        })
+        .unwrap();
+    let pong_inbox = rt.new_inbox::<Pong>().unwrap();
+
+    let handle = rt.run().unwrap();
+    std::thread::sleep(Duration::from_millis(50));
+
+    let suspended = handle.runtime.admin().suspend_actor(addr).unwrap();
+    let suspended = poll_admin(&suspended, Duration::from_secs(1));
+
+    handle
+        .runtime
+        .send_to(
+            addr,
+            Ping {
+                reply_to: *pong_inbox.addr(),
+            },
+        )
+        .unwrap();
+    let pong_while_suspended = poll_inbox(&pong_inbox, Duration::from_millis(100));
+    let count_while_suspended = counter.load(Ordering::SeqCst);
+
+    let resumed = handle.runtime.admin().resume_actor(addr).unwrap();
+    let resumed = poll_admin(&resumed, Duration::from_secs(1));
+    let pong_after_resume = poll_inbox(&pong_inbox, Duration::from_secs(1));
+    let final_count = counter.load(Ordering::SeqCst);
+
+    handle.shutdown();
+    handle.join();
+
+    assert_eq!(suspended, Some(Ok(operation_applied())));
+    assert_eq!(pong_while_suspended, None);
+    assert_eq!(count_while_suspended, 0);
+    assert_eq!(resumed, Some(Ok(operation_applied())));
+    assert_eq!(pong_after_resume, Some(Pong));
+    assert_eq!(final_count, 1);
+}
+
+#[test]
+fn admin_list_actors_aggregates_all_workers() {
+    let rt = std_runtime(RuntimeConfig {
+        num_threads: 4,
+        max_actors: 100,
+        ..Default::default()
+    });
+    let mut addrs = Vec::new();
+    for _ in 0..16 {
+        addrs.push(rt.spawn(CounterActor { count: 0 }).unwrap());
+    }
+
+    let handle = rt.run().unwrap();
+    let start = Instant::now();
+    let mut response = None;
+    while start.elapsed() < Duration::from_secs(1) {
+        let admin = handle.runtime.admin().list_actors().unwrap();
+        if let Some(Ok(list)) = poll_admin(&admin, Duration::from_millis(100)) {
+            if list.actors.len() == addrs.len() {
+                response = Some(list);
+                break;
+            }
+        }
+        std::thread::sleep(Duration::from_millis(5));
+    }
+
+    handle.shutdown();
+    handle.join();
+
+    let response = response.expect("admin list did not observe all spawned actors within timeout");
+    let expected: HashSet<_> = addrs.iter().copied().collect();
+    let actual: HashSet<_> = response
+        .actors
+        .iter()
+        .map(|summary| summary.address)
+        .collect();
+    assert_eq!(actual, expected);
+    for addr in &addrs {
+        assert_eq!(
+            response
+                .actors
+                .iter()
+                .filter(|summary| summary.address == *addr)
+                .count(),
+            1,
+            "actor {addr} appears exactly once in aggregated list"
+        );
+    }
+
+    let worker_ids: HashSet<_> = response
+        .actors
+        .iter()
+        .map(|summary| summary.worker_id)
+        .collect();
+    assert!(
+        worker_ids.len() >= 2,
+        "aggregation should include actors from at least two workers, got {worker_ids:?}"
+    );
+}