Preserve extension event ordering

codex-rs/ext/extension-api/src/capabilities/events.rs

@@ -1,13 +1,17 @@
 use codex_protocol::protocol::Event;
+use std::future::Future;
+use std::pin::Pin;
 
-/// Host-provided fire-and-forget sink for extension-generated events.
+pub type ExtensionEventFuture<'a> = Pin<Box<dyn Future<Output = ()> + Send + 'a>>;
+
+/// Host-provided sink for extension-generated events.
 ///
 /// Extensions construct protocol events with the correlation id appropriate for
 /// the callback they are handling, then leave persistence, ordering, transport
 /// fanout, and logging decisions to the host.
 pub trait ExtensionEventSink: Send + Sync {
     /// Queue one protocol event for host-owned delivery.
-    fn emit(&self, event: Event);
+    fn emit<'a>(&'a self, event: Event) -> ExtensionEventFuture<'a>;
 }
 
 /// Event sink used when the host does not expose extension event emission.
@@ -15,5 +19,7 @@ pub trait ExtensionEventSink: Send + Sync {
 pub struct NoopExtensionEventSink;
 
 impl ExtensionEventSink for NoopExtensionEventSink {
-    fn emit(&self, _event: Event) {}
+    fn emit<'a>(&'a self, _event: Event) -> ExtensionEventFuture<'a> {
+        Box::pin(std::future::ready(()))
+    }
 }

codex-rs/ext/extension-api/src/capabilities/mod.rs

@@ -4,6 +4,7 @@ mod response_items;
 
 pub use agent::AgentSpawnFuture;
 pub use agent::AgentSpawner;
+pub use events::ExtensionEventFuture;
 pub use events::ExtensionEventSink;
 pub use events::NoopExtensionEventSink;
 pub use response_items::NoopResponseItemInjector;

codex-rs/ext/extension-api/src/lib.rs

@@ -5,6 +5,7 @@ mod state;
 
 pub use capabilities::AgentSpawnFuture;
 pub use capabilities::AgentSpawner;
+pub use capabilities::ExtensionEventFuture;
 pub use capabilities::ExtensionEventSink;
 pub use capabilities::NoopExtensionEventSink;
 pub use capabilities::NoopResponseItemInjector;