Claude runtime review

lib/runtime/src/op/completion.rs

@@ -26,8 +26,11 @@ impl<T: Send + 'static> CompletionState<T> {
             return;
         }
 
+        // Queue as a macrotask: I/O completion events belong to the macrotask
+        // queue, consistent with the JavaScript event-loop model where I/O
+        // callbacks are macrotasks and the microtask queue is thread-local only.
         let state = Arc::clone(self);
-        if !self.owner.queue_microtask(move || {
+        if !self.owner.queue_task(move || {
             state.wake_queued.store(false, Ordering::Release);
             if let Some(waker) = state.waker.lock().unwrap().take() {
                 waker.wake();
@@ -138,10 +141,25 @@ impl<T> Drop for CompletionFuture<T> {
         let _ = self.state.result.lock().unwrap().take();
         let _ = self.state.waker.lock().unwrap().take();
 
-        if !self.state.finished.load(Ordering::Acquire)
-            && let Some(cancel) = self.state.cancel.lock().unwrap().take()
-        {
+        if self.state.finished.load(Ordering::Acquire) {
+            return;
+        }
+
+        if let Some(cancel) = self.state.cancel.lock().unwrap().take() {
+            // Delegate to the cancel callback (e.g. submit an io_uring cancel).
+            // The actual I/O completion will eventually call handle.finish(),
+            // which decrements pending_ops.
             cancel();
+        } else {
+            // No cancel callback was registered — this happens when submit_operation
+            // failed before set_cancel could be called, leaving no path through
+            // which finish() would run. Decrement pending_ops directly so the
+            // runtime does not stall indefinitely waiting for an operation that
+            // will never complete. The swap is atomic: if finish() races to set
+            // finished first, the swap returns true and we skip the decrement.
+            if !self.state.finished.swap(true, Ordering::AcqRel) {
+                self.state.owner.finish_async_operation();
+            }
         }
     }
 }