feat(FN-4990): complete Step 2 — recompute currentStep after lost work reset

Fusion-Task-Id: FN-4990
Fusion-Task-Lineage: 167a6011-d246-45bd-ad7a-1f2fe8b99323

packages/engine/src/__tests__/executor-reset-steps-if-work-lost.test.ts

@@ -0,0 +1,62 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import "./executor-test-helpers.js";
+import { TaskExecutor } from "../executor.js";
+import type { Task } from "@fusion/core";
+import { createMockStore, mockedExecSync, resetExecutorMocks } from "./executor-test-helpers.js";
+
+describe("TaskExecutor.resetStepsIfWorkLost", () => {
+  beforeEach(() => {
+    resetExecutorMocks();
+  });
+
+  it("resets completed steps and recomputes currentStep when branch has no unique commits", async () => {
+    const store = createMockStore();
+    const task: Task = {
+      id: "FN-4990",
+      title: "Reset steps",
+      description: "desc",
+      column: "in-progress",
+      dependencies: [],
+      steps: [
+        { name: "Step 1", status: "done" },
+        { name: "Step 2", status: "done" },
+        { name: "Step 3", status: "done" },
+        { name: "Step 4", status: "pending" },
+        { name: "Step 5", status: "pending" },
+      ],
+      currentStep: 3,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+      branch: "fusion/fn-4990",
+    };
+
+    store.getTask.mockImplementation(async () => task);
+    store.updateStep.mockImplementation(async (_taskId: string, stepIndex: number, status: Task["steps"][number]["status"]) => {
+      task.steps[stepIndex].status = status;
+      return task;
+    });
+    store.updateTask.mockImplementation(async (_taskId: string, updates: Partial<Task>) => {
+      Object.assign(task, updates);
+      return task;
+    });
+
+    mockedExecSync.mockImplementation((cmd: string) => {
+      if (cmd.includes("git merge-base")) return "abc123\n";
+      if (cmd.includes("git rev-parse")) return "abc123\n";
+      return "";
+    });
+
+    const executor = new TaskExecutor(store as any, "/tmp/test");
+    await (executor as any).resetStepsIfWorkLost(task);
+
+    expect(task.steps[0].status).toBe("pending");
+    expect(task.steps[1].status).toBe("pending");
+    expect(task.steps[2].status).toBe("pending");
+    expect(task.currentStep).toBe(0);
+    expect(store.logEntry).toHaveBeenCalledWith(
+      task.id,
+      expect.stringContaining("currentStep"),
+    );
+  });
+});

packages/engine/src/executor.ts

@@ -9417,6 +9417,23 @@ Backward compat fallback: if JSON is unavailable, you may still begin output wit
           }
         }
 
+        const refreshedTask = await this.store.getTask(task.id);
+        const prevCurrentStep = refreshedTask.currentStep;
+        if (refreshedTask.steps.length > 0) {
+          const firstPendingStep = refreshedTask.steps.findIndex((s) => s.status === "pending");
+          const newCurrentStep = firstPendingStep >= 0 ? firstPendingStep : 0;
+          if (newCurrentStep !== prevCurrentStep) {
+            await this.store.updateTask(task.id, { currentStep: newCurrentStep });
+            executorLog.log(
+              `${task.id}: reset currentStep to ${newCurrentStep} after lost-work reset (was ${prevCurrentStep})`,
+            );
+            await this.store.logEntry(
+              task.id,
+              `Reset currentStep to ${newCurrentStep} after lost-work step reset (was ${prevCurrentStep})`,
+            );
+          }
+        }
+
         await this.store.logEntry(
           task.id,
           `Reset ${completedSteps.length} step(s) to pending — branch had no commits (uncommitted work lost with worktree)`,