fix: notify on significant transitions, preserve stuck state on probe failure

Two bugs fixed:

1. Transitions with non-info priority (e.g. merge.completed,
   review.approved, session.errored) now call notifyHuman() directly
   when no reaction config handles notification. Before, these
   transitions updated state silently with no human notification.

2. When agent.detectActivity() throws, sessions in stuck/needs_input
   state now preserve that state instead of being coerced to "working"
   by the fallback at the bottom of determineStatus().

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/__tests__/lifecycle-manager.test.ts

@@ -13,6 +13,7 @@ import type {
   Runtime,
   Agent,
   SCM,
+  Notifier,
   ActivityState,
   PRInfo,
 } from "../types.js";
@@ -253,6 +254,56 @@ describe("check (single session)", () => {
     expect(lm.getStates().get("app-1")).toBe("needs_input");
   });
 
+  it("preserves stuck state when detectActivity throws", async () => {
+    vi.mocked(mockAgent.detectActivity).mockRejectedValue(new Error("probe failed"));
+
+    const session = makeSession({ status: "stuck" });
+    vi.mocked(mockSessionManager.get).mockResolvedValue(session);
+
+    writeMetadata(dataDir, "app-1", {
+      worktree: "/tmp",
+      branch: "main",
+      status: "stuck",
+      project: "my-app",
+    });
+
+    const lm = createLifecycleManager({
+      config,
+      registry: mockRegistry,
+      sessionManager: mockSessionManager,
+    });
+
+    await lm.check("app-1");
+
+    // Should preserve "stuck" — NOT coerce to "working"
+    expect(lm.getStates().get("app-1")).toBe("stuck");
+  });
+
+  it("preserves needs_input state when detectActivity throws", async () => {
+    vi.mocked(mockAgent.detectActivity).mockRejectedValue(new Error("probe failed"));
+
+    const session = makeSession({ status: "needs_input" });
+    vi.mocked(mockSessionManager.get).mockResolvedValue(session);
+
+    writeMetadata(dataDir, "app-1", {
+      worktree: "/tmp",
+      branch: "main",
+      status: "needs_input",
+      project: "my-app",
+    });
+
+    const lm = createLifecycleManager({
+      config,
+      registry: mockRegistry,
+      sessionManager: mockSessionManager,
+    });
+
+    await lm.check("app-1");
+
+    // Should preserve "needs_input" — NOT coerce to "working"
+    expect(lm.getStates().get("app-1")).toBe("needs_input");
+  });
+
   it("detects PR states from SCM", async () => {
     const mockSCM: SCM = {
       name: "mock-scm",
@@ -550,6 +601,64 @@ describe("reactions", () => {
 
     expect(mockSessionManager.send).not.toHaveBeenCalled();
   });
+  it("notifies humans on significant transitions without reaction config", async () => {
+    const mockNotifier: Notifier = {
+      name: "mock-notifier",
+      notify: vi.fn().mockResolvedValue(undefined),
+    };
+
+    const mockSCM: SCM = {
+      name: "mock-scm",
+      detectPR: vi.fn(),
+      getPRState: vi.fn().mockResolvedValue("merged"),
+      mergePR: vi.fn(),
+      closePR: vi.fn(),
+      getCIChecks: vi.fn(),
+      getCISummary: vi.fn(),
+      getReviews: vi.fn(),
+      getReviewDecision: vi.fn(),
+      getPendingComments: vi.fn(),
+      getAutomatedComments: vi.fn(),
+      getMergeability: vi.fn(),
+    };
+
+    const registryWithNotifier: PluginRegistry = {
+      ...mockRegistry,
+      get: vi.fn().mockImplementation((slot: string, name: string) => {
+        if (slot === "runtime") return mockRuntime;
+        if (slot === "agent") return mockAgent;
+        if (slot === "scm") return mockSCM;
+        if (slot === "notifier" && name === "desktop") return mockNotifier;
+        return null;
+      }),
+    };
+
+    // merge.completed has "action" priority but NO reaction key mapping,
+    // so it must reach notifyHuman directly
+    const session = makeSession({ status: "approved", pr: makePR() });
+    vi.mocked(mockSessionManager.get).mockResolvedValue(session);
+
+    writeMetadata(dataDir, "app-1", {
+      worktree: "/tmp",
+      branch: "main",
+      status: "approved",
+      project: "my-app",
+    });
+
+    const lm = createLifecycleManager({
+      config,
+      registry: registryWithNotifier,
+      sessionManager: mockSessionManager,
+    });
+
+    await lm.check("app-1");
+
+    expect(lm.getStates().get("app-1")).toBe("merged");
+    expect(mockNotifier.notify).toHaveBeenCalled();
+    expect(mockNotifier.notify).toHaveBeenCalledWith(
+      expect.objectContaining({ type: "merge.completed" }),
+    );
+  });
 });
 
 describe("getStates", () => {

packages/core/src/lifecycle-manager.ts

@@ -192,10 +192,18 @@ export function createLifecycleManager(deps: LifecycleManagerDeps): LifecycleMan
 
     // 2. Check agent activity
     if (agent) {
-      const activity = await agent.detectActivity(session).catch(() => session.activity);
+      try {
+        const activity = await agent.detectActivity(session);
         if (activity === "exited") return "killed";
         if (activity === "blocked") return "stuck";
         if (activity === "waiting_input") return "needs_input";
+      } catch {
+        // On probe failure, preserve current stuck/needs_input state rather
+        // than letting the fallback at the bottom coerce them to "working"
+        if (session.status === "stuck" || session.status === "needs_input") {
+          return session.status;
+        }
+      }
     }
 
     // 3. Check PR state if PR exists
@@ -412,10 +420,12 @@ export function createLifecycleManager(deps: LifecycleManagerDeps): LifecycleMan
         }
       }
 
-      // Check if there's a reaction for this transition
+      // Handle transition: notify humans and/or trigger reactions
       const eventType = statusToEventType(oldStatus, newStatus);
       if (eventType) {
+        let reactionHandledNotify = false;
         const reactionKey = eventToReactionKey(eventType);
+
         if (reactionKey) {
           // Merge project-specific overrides with global defaults
           const project = config.projects[session.projectId];
@@ -434,10 +444,28 @@ export function createLifecycleManager(deps: LifecycleManagerDeps): LifecycleMan
                 reactionKey,
                 reactionConfig as ReactionConfig,
               );
+              // "notify" and "auto-merge" reactions already call notifyHuman
+              if (reactionConfig.action === "notify" || reactionConfig.action === "auto-merge") {
+                reactionHandledNotify = true;
               }
             }
           }
         }
+
+        // For significant transitions not already notified by a reaction, notify humans
+        if (!reactionHandledNotify) {
+          const priority = inferPriority(eventType);
+          if (priority !== "info") {
+            const event = createEvent(eventType, {
+              sessionId: session.id,
+              projectId: session.projectId,
+              message: `${session.id}: ${oldStatus} → ${newStatus}`,
+              data: { oldStatus, newStatus },
+            });
+            await notifyHuman(event, priority);
+          }
+        }
+      }
     } else {
       // No transition but track current state
       states.set(session.id, newStatus);