fix(server): queue Copilot follow-ups without killing background agents

apps/server/src/orchestration-v2/Adapters/AcpRegistryAdapterV2.test.ts

@@ -1007,6 +1007,42 @@ describe("AcpRegistryAdapterV2", () => {
     }).pipe(Effect.provide(layerTest), Effect.scoped),
   );
 
+  // regression: #26695 cancelling a Copilot prompt kills its background agents
+  it.effect("never steers Copilot by cancelling its prompt", () =>
+    Effect.gen(function* () {
+      const steering = Effect.fn("steering")(function* (config: Record<string, unknown>) {
+        const instanceId = ProviderInstanceId.make("acp-registry-steering");
+        const adapter = yield* makeAcpRegistryAdapterV2({
+          selfInvocation: yield* resolveSelfInvocation(),
+          instanceId,
+          settings: yield* decodeAcpRegistryAdapterSettings(config),
+          environment: {},
+        }).pipe(Effect.provide(layerInjectedRuntimeCatalog));
+        const { turns } = yield* adapter.getCapabilities();
+        return {
+          supportsInterrupt: turns.supportsInterrupt,
+          supportsActiveSteering: turns.supportsActiveSteering,
+          supportsSteeringByInterruptRestart: turns.supportsSteeringByInterruptRestart,
+        };
+      });
+      const copilot = {
+        supportsInterrupt: true,
+        supportsActiveSteering: false,
+        supportsSteeringByInterruptRestart: false,
+      };
+
+      assert.deepEqual(yield* steering({ agentId: "github-copilot-cli" }), copilot);
+      assert.deepEqual(
+        yield* steering({ source: "local", commandPath: "C:\\tools\\copilot.cmd" }),
+        copilot,
+      );
+      assert.deepEqual(yield* steering({ agentId: "gemini" }), {
+        ...copilot,
+        supportsSteeringByInterruptRestart: true,
+      });
+    }).pipe(Effect.provide(layerTest), Effect.scoped),
+  );
+
   it.effect("settles Claude's accepted foreground reply while retaining child output", () =>
     Effect.gen(function* () {
       const gate = makeProviderReplayGate(["accepted", "child-output", "wake"]);

apps/server/src/orchestration-v2/CommandPolicy.test.ts

@@ -164,6 +164,53 @@ it.each([
   );
 });
 
+// regression: #26695 an interrupt-restart steer cancels Copilot's background agents
+it("queues a steer for a provider that cannot steer either way", () => {
+  const projection = dispatchProjection(
+    capabilities((current) => ({
+      ...current,
+      turns: {
+        ...current.turns,
+        supportsActiveSteering: false,
+        supportsSteeringByInterruptRestart: false,
+        supportsQueuedMessages: true,
+      },
+    })),
+  );
+  for (const deliveryIntent of ["auto", "steer"] as const) {
+    assert.deepEqual(
+      CommandPolicy.resolveMessageDispatchIntent(
+        projection,
+        { type: "start_immediately" },
+        deliveryIntent,
+      ),
+      { type: "queue_after_active" },
+    );
+  }
+  assert.deepEqual(
+    CommandPolicy.resolveMessageDispatchIntent(projection, {
+      type: "steer_active",
+      targetRunId: activeRunId,
+    }),
+    { type: "queue_after_active" },
+  );
+  assert.deepEqual(
+    CommandPolicy.resolveMessageDispatchIntent(
+      projection,
+      { type: "start_immediately" },
+      "restart",
+    ),
+    { type: "restart_active", targetRunId: activeRunId },
+  );
+  assert.deepEqual(
+    CommandPolicy.resolveMessageDispatchIntent(projection, {
+      type: "steer_active",
+      targetRunId: RunId.make("command-policy-missing-run"),
+    }),
+    { type: "steer_active", targetRunId: RunId.make("command-policy-missing-run") },
+  );
+});
+
 it.each(["/compact", " /LOGOUT "])("queues a steer sent while %s runs", (text) => {
   const projection = dispatchProjection(baseCapabilities);
   const maintenance = {

apps/server/src/orchestration-v2/CommandPolicy.ts

@@ -99,25 +99,55 @@ export function resolveMessageDispatchIntent(
   // Compaction and sign-out cannot accept steers; queue follow-ups.
   const target = projection.runs.find((run) => run.id === mode.targetRunId);
   const targetMessage = projection.messages.find((message) => message.id === target?.userMessageId);
-  return targetMessage !== undefined && isNativeMaintenanceCommand(targetMessage)
+  if (targetMessage !== undefined && isNativeMaintenanceCommand(targetMessage)) {
+    return { type: "queue_after_active" };
+  }
+  // A provider that can neither steer nor restart its turn takes the message after the turn.
+  const turns =
+    target === undefined || !isActiveRun(target)
+      ? undefined
+      : providerTurnCapabilities(projection, target);
+  return turns !== undefined &&
+    !turns.supportsActiveSteering &&
+    !(turns.supportsInterrupt && turns.supportsSteeringByInterruptRestart) &&
+    turns.supportsQueuedMessages
     ? { type: "queue_after_active" }
     : mode;
 }
 
+function isActiveRun(run: OrchestrationV2Run): boolean {
+  return (
+    run.status === "preparing" ||
+    run.status === "starting" ||
+    run.status === "running" ||
+    run.status === "waiting"
+  );
+}
+
+function providerTurnCapabilities(
+  projection: OrchestrationV2ThreadProjection,
+  run: OrchestrationV2Run,
+) {
+  const providerThread = projection.providerThreads.find(
+    (candidate) => candidate.id === run.providerThreadId,
+  );
+  const providerSession =
+    providerThread?.providerSessionId == null
+      ? undefined
+      : projection.providerSessions.find(
+          (candidate) => candidate.id === providerThread.providerSessionId,
+        );
+  return providerSession?.capabilities.turns;
+}
+
 function resolveDeliveryIntent(
   projection: OrchestrationV2ThreadProjection,
   requestedMode: MessageDispatchMode,
   deliveryIntent?: "auto" | "steer" | "restart",
 ): MessageDispatchMode {
   if (deliveryIntent === undefined) return requestedMode;
 
-  const activeRun = projection.runs.findLast(
-    (run) =>
-      run.status === "preparing" ||
-      run.status === "starting" ||
-      run.status === "running" ||
-      run.status === "waiting",
-  );
+  const activeRun = projection.runs.findLast(isActiveRun);
   if (activeRun === undefined) return { type: "start_immediately" };
   if (deliveryIntent === "steer") {
     return { type: "steer_active", targetRunId: activeRun.id };
@@ -137,16 +167,7 @@ function resolveDeliveryIntent(
     return { type: "queue_after_active" };
   }
 
-  const providerThread = projection.providerThreads.find(
-    (candidate) => candidate.id === activeRun.providerThreadId,
-  );
-  const providerSession =
-    providerThread?.providerSessionId == null
-      ? undefined
-      : projection.providerSessions.find(
-          (candidate) => candidate.id === providerThread.providerSessionId,
-        );
-  const capabilities = providerSession?.capabilities.turns;
+  const capabilities = providerTurnCapabilities(projection, activeRun);
   if (capabilities?.supportsActiveSteering === true) {
     return { type: "steer_active", targetRunId: activeRun.id };
   }

apps/server/src/orchestration-v2/SteeringCompletion.integration.test.ts

@@ -447,16 +447,18 @@ const composerSelection = {
 const nextTurnSelectionHarness = Effect.fn("nextTurnSelectionHarness")(function* (
   name: string,
   canRestart = false,
+  canSteer = true,
 ) {
   const cwd = yield* checkpointWorkspace(name);
   const events = yield* Queue.unbounded<ProviderAdapter.ProviderAdapterV2Event>();
   const started: ProviderAdapter.ProviderAdapterV2TurnInput[] = [];
   const steered: string[] = [];
+  const interrupted: ProviderTurnId[] = [];
   const capabilities = {
     ...CodexProviderCapabilitiesV2,
     turns: {
       ...CodexProviderCapabilitiesV2.turns,
-      supportsActiveSteering: true,
+      supportsActiveSteering: canSteer,
       supportsSteeringByInterruptRestart: canRestart,
     },
   };
@@ -533,7 +535,10 @@ const nextTurnSelectionHarness = Effect.fn("nextTurnSelectionHarness")(function*
             Effect.sync(() => {
               steered.push(turn.message.text);
             }),
-          interruptTurn: () => Effect.void,
+          interruptTurn: ({ providerTurnId }) =>
+            Effect.sync(() => {
+              interrupted.push(providerTurnId);
+            }),
           respondToRuntimeRequest: () => Effect.void,
           readThreadSnapshot: () => Effect.die("unused"),
           rollbackThread: () => Effect.die("unused"),
@@ -588,7 +593,7 @@ const nextTurnSelectionHarness = Effect.fn("nextTurnSelectionHarness")(function*
     yield* Fiber.join(running);
     return threadId;
   });
-  return { cwd, events, started, steered, layer, startFirstTurn };
+  return { cwd, events, started, steered, interrupted, layer, startFirstTurn };
 });
 
 it.effect("sends a selected held message once and preserves the remaining queue order", () =>
@@ -938,6 +943,82 @@ it.effect("starts a steer that missed the turn on the saved next-turn selection"
   ),
 );
 
+// regression: #26695 cancelling a Copilot prompt to steer it kills its background agents
+it.effect("queues a steer until the turn ends when the provider cannot steer it", () =>
+  Effect.scoped(
+    Effect.gen(function* () {
+      const { events, started, steered, interrupted, layer, startFirstTurn } =
+        yield* nextTurnSelectionHarness("steering-unsupported", false, false);
+      yield* Effect.gen(function* () {
+        const orchestrator = yield* Orchestrator.OrchestratorV2;
+        const worker = yield* EffectWorker.OrchestrationEffectWorkerV2;
+        const threadId = yield* startFirstTurn;
+        const first = started[0]!;
+        const messageId = MessageId.make("message:steer");
+        yield* orchestrator.dispatch({
+          type: "message.dispatch",
+          commandId: CommandId.make("steer"),
+          threadId,
+          messageId,
+          text: "follow up",
+          attachments: [],
+          modelSelection: runSelection,
+          dispatchMode: { type: "start_immediately" },
+          deliveryIntent: "steer",
+          createdBy: "user",
+          creationSource: "web",
+        });
+        yield* worker.drain();
+
+        const held = yield* orchestrator.getThreadProjection(threadId);
+        assert.deepEqual(steered, []);
+        assert.deepEqual(interrupted, []);
+        assert.equal(started.length, 1);
+        assert.equal(held.runs.find((run) => run.id === first.runId)?.status, "running");
+        const queued = held.runs.find((run) => run.userMessageId === messageId);
+        assert.equal(queued?.status, "queued");
+
+        const settled = yield* orchestrator.streamDomainEvents.pipe(
+          Stream.filter(
+            (event) =>
+              event.type === "run.updated" &&
+              event.payload.id === first.runId &&
+              event.payload.status === "waiting",
+          ),
+          Stream.take(1),
+          Stream.runDrain,
+          Effect.forkScoped,
+        );
+        const turn = held.providerTurns[0]!;
+        yield* Queue.offer(events, {
+          type: "provider_turn.updated",
+          driver,
+          providerTurn: { ...turn, status: "completed", completedAt: yield* DateTime.now },
+        });
+        yield* Queue.offer(events, {
+          type: "turn.terminal",
+          driver,
+          providerThreadId: turn.providerThreadId,
+          providerTurnId: turn.id,
+          runOrdinal: first.runOrdinal,
+          status: "completed",
+          failure: null,
+          threadDisposition: "reusable",
+        });
+        yield* Fiber.join(settled);
+        yield* worker.drain();
+        yield* orchestrator.resumeQueuedRuns;
+        yield* worker.drain();
+
+        assert.deepEqual(interrupted, []);
+        assert.equal(started.length, 2);
+        assert.equal(started[1]?.runId, queued?.id);
+        assert.equal(started[1]?.message.text, "follow up");
+      }).pipe(Effect.provide(layer));
+    }),
+  ),
+);
+
 // Codex flushes held drafts after the final answer; reserve their pre-steer position before turn end.
 it.effect("keeps a held commentary draft before the steer when turn end flushes it", () =>
   Effect.scoped(

packages/provider-acp-registry/src/server/adapter.ts

@@ -210,7 +210,13 @@ export const makeAcpRegistryAdapterV2 = Effect.fn("makeAcpRegistryAdapterV2")(fu
   const copilotRouting = isCopilot ? makeCopilotSubagentRouting() : undefined;
   const flavor: AcpAdapterV2Flavor = {
     driver: ACP_REGISTRY_PROVIDER,
-    capabilities: AcpProviderCapabilitiesV2,
+    // Cancelling a Copilot prompt also kills the background agents it started.
+    capabilities: isCopilot
+      ? {
+          ...AcpProviderCapabilitiesV2,
+          turns: { ...AcpProviderCapabilitiesV2.turns, supportsSteeringByInterruptRestart: false },
+        }
+      : AcpProviderCapabilitiesV2,
     customModels: readCustomModelEntries(options.settings.customModels).map((entry) => entry.slug),
     promptFailure: (cause) => acpRegistryPromptFailure(registryAgentId, cause),
     ...(registryAgentId === "factory-droid"