test(FN-4601): add retry race reliability interaction coverage

Fusion-Task-Id: FN-4601
Fusion-Task-Lineage: 136888a7-aee7-4eda-a165-16448a98e626

packages/engine/src/__tests__/reliability-interactions/executor-no-task-done-vs-worktree-reclaim.test.ts

@@ -0,0 +1,131 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import "../executor-test-helpers.js";
+import { TaskExecutor } from "../../executor.js";
+import { mockedCreateFnAgent, createMockStore, resetExecutorMocks } from "../executor-test-helpers.js";
+
+function makeTask(overrides: Record<string, unknown> = {}) {
+  return {
+    id: "FN-4601",
+    title: "Test",
+    description: "Test task",
+    column: "in-progress",
+    dependencies: [],
+    steps: [{ name: "Preflight", status: "in-progress" }],
+    currentStep: 0,
+    taskDoneRetryCount: 0,
+    worktree: "/tmp/test/.worktrees/fn-4601",
+    branch: "fusion/fn-4601",
+    log: [],
+    prompt: "# test\n## Steps\n### Step 0: Preflight\n- [ ] check",
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+    ...overrides,
+  } as any;
+}
+
+function makeSession() {
+  return {
+    prompt: vi.fn().mockResolvedValue(undefined),
+    dispose: vi.fn(),
+    subscribe: vi.fn(),
+    on: vi.fn(),
+    sessionManager: { getLeafId: vi.fn().mockReturnValue("leaf-1") },
+    state: {},
+  };
+}
+
+describe("reliability interactions: executor no-fn_task_done vs worktree reclaim", () => {
+  beforeEach(() => {
+    resetExecutorMocks();
+  });
+
+  it("pre-retry liveness recheck aborts retry and requeues", async () => {
+    const store = createMockStore();
+    const state = makeTask();
+    let getTaskCalls = 0;
+    store.getTask.mockImplementation(async () => {
+      getTaskCalls++;
+      if (getTaskCalls >= 2) {
+        state.worktree = null;
+        state.branch = null;
+      }
+      return { ...state };
+    });
+
+    mockedCreateFnAgent.mockResolvedValue({ session: makeSession() } as any);
+
+    const executor = new TaskExecutor(store as any, "/tmp/test");
+    await executor.execute(state);
+
+    expect(mockedCreateFnAgent).toHaveBeenCalledTimes(1);
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4601", "todo", { preserveProgress: true });
+    expect(store.logEntry).toHaveBeenCalledWith(
+      "FN-4601",
+      expect.stringContaining("worktree/branch reclaimed during no-fn_task_done retry"),
+      undefined,
+      expect.any(Object),
+    );
+    expect(store.updateTask).toHaveBeenCalledWith("FN-4601", expect.objectContaining({ taskDoneRetryCount: 1 }));
+  });
+
+  it("missing-worktree session-start error during retry clears metadata and requeues", async () => {
+    const store = createMockStore();
+    const state = makeTask();
+    store.getTask.mockImplementation(async () => ({ ...state }));
+
+    mockedCreateFnAgent
+      .mockResolvedValueOnce({ session: makeSession() } as any)
+      .mockRejectedValueOnce(new Error("Refusing to start coding agent in missing worktree: /tmp/test/.worktrees/fn-4601"));
+
+    const executor = new TaskExecutor(store as any, "/tmp/test");
+    await executor.execute(state);
+
+    expect(store.updateTask).toHaveBeenCalledWith("FN-4601", {
+      sessionFile: null,
+      worktree: null,
+      branch: null,
+      baseCommitSha: null,
+    });
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4601", "todo", { preserveProgress: true });
+    expect(store.updateTask).toHaveBeenCalledWith("FN-4601", expect.objectContaining({ taskDoneRetryCount: 1 }));
+    expect(store.moveTask).not.toHaveBeenCalledWith("FN-4601", "in-review");
+  });
+
+  it("non-recoverable retry error still follows failure path", async () => {
+    const store = createMockStore();
+    const state = makeTask();
+    store.getTask.mockImplementation(async () => ({ ...state }));
+
+    mockedCreateFnAgent
+      .mockResolvedValueOnce({ session: makeSession() } as any)
+      .mockRejectedValueOnce(new Error("boom"));
+
+    const executor = new TaskExecutor(store as any, "/tmp/test");
+    await executor.execute(state);
+
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4601", "in-review");
+    expect(store.updateTask).not.toHaveBeenCalledWith("FN-4601", expect.objectContaining({ baseCommitSha: null, worktree: null, branch: null }));
+  });
+
+  it("exhausted requeue budget keeps reclaim path in in-review", async () => {
+    const store = createMockStore();
+    const state = makeTask({ taskDoneRetryCount: 3 });
+    let getTaskCalls = 0;
+    store.getTask.mockImplementation(async () => {
+      getTaskCalls++;
+      if (getTaskCalls >= 2) {
+        state.worktree = null;
+        state.branch = null;
+      }
+      return { ...state };
+    });
+
+    mockedCreateFnAgent.mockResolvedValue({ session: makeSession() } as any);
+
+    const executor = new TaskExecutor(store as any, "/tmp/test");
+    await executor.execute(state);
+
+    expect(store.moveTask).toHaveBeenCalledWith("FN-4601", "in-review");
+    expect(store.moveTask).not.toHaveBeenCalledWith("FN-4601", "todo", { preserveProgress: true });
+  });
+});