feat(runtime): expose resident driver boundaries

Expose exact Actor instance identity and manifest mailbox capacity so Host supervisors can distinguish idempotent starts from fault recovery and preserve revision-specific limits.

Expose resident stream chunk and endpoint-policy validation to drivers, and mark terminal streams closing before dispatching their final callback.

Cover Actor identity reuse and replacement in the Runtime integration suite.

crates/wasmeld-runtime/src/resident_host.rs

@@ -515,6 +515,15 @@ impl ResidentSession {
         self.actor.key()
     }
 
+    /// Returns the largest stream chunk that a driver may deliver.
+    ///
+    /// A stream driver should size its read buffer to this value or a smaller
+    /// protocol-specific limit. The Runtime applies the same limit to both
+    /// incoming `stream-data` events and Component `write-stream` effects.
+    pub fn max_stream_chunk_bytes(&self) -> usize {
+        self.actor.resident_stream_chunk_limit()
+    }
+
     /// Registers a configured listener or datagram endpoint after policy checks.
     ///
     /// Registration does not bind an operating-system socket. The driver binds
@@ -664,6 +673,7 @@ impl ResidentSession {
         reason: StreamCloseReason,
     ) -> Result<Vec<ResidentOperation>, ResidentHostError> {
         self.ensure_kind(stream_id, ResidentResourceKind::Stream, "stream")?;
+        *self.stream_state_mut(stream_id)? = StreamState::Closing;
         let result = self.dispatch(ResidentEvent::StreamClosed { stream_id, reason });
         self.resources.remove(&stream_id);
         result
@@ -1056,7 +1066,13 @@ impl ResidentSession {
 }
 
 impl ResidentPolicy {
-    fn validate_endpoint(&self, endpoint: &ResidentEndpoint) -> Result<(), ResidentHostError> {
+    /// Validates one endpoint without registering or binding it.
+    ///
+    /// Management layers can call this while loading static configuration so
+    /// an address outside policy fails before any Actor is started. Drivers
+    /// must still register the endpoint immediately before bind because policy
+    /// is also a runtime ownership boundary.
+    pub fn validate_endpoint(&self, endpoint: &ResidentEndpoint) -> Result<(), ResidentHostError> {
         match endpoint {
             ResidentEndpoint::Tcp { bind, .. } if !self.tcp_listen.allows(*bind) => {
                 Err(ResidentHostError::EndpointDenied(format!(

crates/wasmeld-runtime/src/runtime.rs

@@ -615,10 +615,33 @@ impl ActorHandle {
         self.execution
     }
 
+    /// Returns whether two handles address the exact same Actor instance.
+    ///
+    /// Service keys are revision identities and therefore survive an Actor
+    /// fault/restart. Host resource supervisors use this stronger check to
+    /// retain themselves for an idempotent start but replace stale resources
+    /// when the Runtime created a fresh Store for the same revision.
+    pub fn is_same_instance(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.status, &other.status)
+    }
+
+    /// Returns the immutable mailbox capacity configured for this Actor.
+    ///
+    /// Host supervisors use the same bound for their external event queue so a
+    /// restored revision retains the limits stored in its own manifest instead
+    /// of inheriting newer process defaults.
+    pub fn mailbox_capacity(&self) -> usize {
+        self.limits.mailbox_capacity
+    }
+
     pub(crate) fn resident_resource_limit(&self) -> usize {
         self.limits.resident.max_resources
     }
 
+    pub(crate) fn resident_stream_chunk_limit(&self) -> usize {
+        self.limits.resident.max_stream_chunk_bytes
+    }
+
     /// Sends an invocation and waits up to the remaining service deadline.
     ///
     /// Cloned handles compete for the same bounded mailbox. A Wasm trap is

crates/wasmeld-runtime/tests/runtime_components.rs

@@ -96,12 +96,16 @@ fn faulted_actor_can_be_started_again() {
     let runtime = Runtime::new(RuntimeConfig::default()).expect("runtime should start");
     let (key, actor) = start_component(&runtime, "fault", "fault_component.wasm");
 
+    let already_running = runtime.start(&key, Vec::new()).unwrap();
+    assert!(actor.is_same_instance(&already_running));
+
     assert!(matches!(
         actor.invoke(b"fault".to_vec()),
         Err(RuntimeError::ActorFault { .. })
     ));
 
     let restarted = runtime.start(&key, Vec::new()).unwrap();
+    assert!(!actor.is_same_instance(&restarted));
     assert_eq!(restarted.invoke(b"ready".to_vec()).unwrap(), b"ready");
 
     runtime.stop(&key).unwrap();