fleetd #345: test timeout cancellation race

fleetd/src/main/java/dev/ltms/fleet/msg/MessageService.java

@@ -871,6 +871,10 @@ public final class MessageService {
                     boolean wasDelivered = delivery.completion().isDone()
                             && !delivery.completion().isCompletedExceptionally();
                     if (!wasDelivered) {
+                        if (timeoutCancellationRaceHookForTest != null) {
+                            // Test-only (fleetd #345): see the field's own javadoc.
+                            timeoutCancellationRaceHookForTest.run();
+                        }
                         // The target monitor makes cancellation atomic with onStatus picking this
                         // Pending up. If pickup won, report TIMED_OUT_WORKING because the text landed.
                         wasDelivered = injector.cancel(delivery) == Injector.Cancellation.DELIVERED;
@@ -1370,6 +1374,24 @@ public final class MessageService {
         this.afterFinishAsyncTaskCompleteHookForTest = hook;
     }
 
+    /**
+     * Null in production; test seam for fleetd #345 — invoked in {@link #send}'s timeout path after
+     * {@link Injector.Delivery#completion()} reports incomplete and before {@link Injector#cancel}
+     * takes the target monitor. A test installs this to make {@code onStatus} pick the exact queued
+     * delivery up in that window, so {@code cancel} returns {@link Injector.Cancellation#DELIVERED}.
+     * This deterministically covers the caller's need to use that result rather than relying on a
+     * timing-sensitive real race.
+     */
+    private volatile Runnable timeoutCancellationRaceHookForTest;
+
+    /**
+     * Test-only (fleetd #345): install {@link #timeoutCancellationRaceHookForTest}. Package-private
+     * so the test, in the same package, can reach it without widening any production API.
+     */
+    void setTimeoutCancellationRaceHookForTest(Runnable hook) {
+        this.timeoutCancellationRaceHookForTest = hook;
+    }
+
     /**
      * Null in production; test seam for fleetd #329 (F3) — invoked from {@link #reply} right after
      * the single local read of {@code orphan.turnId} passes its null-check and before that (now-local)

fleetd/src/test/java/dev/ltms/fleet/msg/MessageServiceTest.java

@@ -410,6 +410,29 @@ class MessageServiceTest {
                 "a delivered send whose worker never replies times out as still working");
     }
 
+    /**
+     * fleetd #345. This forces the injector to pick up the exact pending delivery after {@code send}
+     * first observes its completion as incomplete, but before {@code cancel} takes the target monitor.
+     * The timeout must use {@link Injector.Cancellation#DELIVERED} from {@code cancel} and report
+     * {@link MessageService.Outcome#TIMED_OUT_WORKING}, because the text landed.
+     *
+     * <p>What this does not prove: that this precise interleaving happens by itself under production
+     * timing. The test forces it through a test-only hook; it proves the timeout caller handles the
+     * injector result when the interleaving occurs.
+     */
+    @Test
+    void sendTimeoutUsesCancellationDeliveredWhenPickupWinsTheRace() {
+        messages.setTimeoutCancellationRaceHookForTest(() -> injector.onStatus(T, AgentStatus.IDLE));
+        try {
+            MessageService.Reply reply = messages.send(T, "race delivery", 50);
+
+            assertEquals(MessageService.Outcome.TIMED_OUT_WORKING, reply.outcome(),
+                    "cancel reporting DELIVERED means the worker received the timed-out message");
+        } finally {
+            messages.setTimeoutCancellationRaceHookForTest(null);
+        }
+    }
+
     @Test
     void answerTimesOutWhenTheResumedWorkerNeverReplies() throws Exception {
         CompletableFuture<MessageService.Reply> send = sendAsync();