fix(FN-7996): release Plan Review fallback lease

Unregister the exact workflow-step path after a repository-root fallback so later Plan Review tasks are not blocked by a stale active-session owner.

.changeset/plan-review-root-lease-cleanup.md

@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Prevent Plan Review tasks from blocking each other after a missing-worktree fallback.
+category: fix
+dev: Releases the exact workflow-step session path after repository-root Plan Review fallback.

packages/engine/src/__tests__/reliability-interactions/graph-node-missing-worktree-recovery.test.ts

@@ -3,7 +3,14 @@ import type { TaskDetail } from "@fusion/core";
 import "../executor-test-helpers.js";
 import { PLAN_REVIEW_PROVIDER_FAILURE_HOLD_VALUE } from "../../workflow-graph-executor.js";
 import { TaskExecutor } from "../../executor.js";
-import { createMockStore, mockedExecSync, mockedExistsSync, resetExecutorMocks } from "../executor-test-helpers.js";
+import { activeSessionRegistry } from "../../active-session-registry.js";
+import {
+  createMockStore,
+  mockedCreateFnAgent,
+  mockedExecSync,
+  mockedExistsSync,
+  resetExecutorMocks,
+} from "../executor-test-helpers.js";
 import { MAX_WORKTREE_SESSION_RETRIES } from "../../self-healing.js";
 
 /*
@@ -319,6 +326,59 @@ describe("Plan Review missing-worktree repo-root fallback (FN-7996)", () => {
     );
   });
 
+  it("releases the repo-root session lease after the fallback reviewer completes", async () => {
+    const store = createMockStore();
+    const agentStore = { getAgent: vi.fn().mockResolvedValue(null), createAgent: vi.fn() };
+    const executor = new TaskExecutor(store, "/tmp/test", { agentStore } as any);
+    const output = '{"verdict":"APPROVE","notes":""}';
+    mockedCreateFnAgent.mockImplementation(async () => {
+      const listeners: Array<(event: any) => void> = [];
+      return {
+        session: {
+          state: {},
+          subscribe: (listener: (event: any) => void) => {
+            listeners.push(listener);
+            return vi.fn();
+          },
+          prompt: vi.fn(async () => {
+            for (const listener of listeners) {
+              listener({
+                type: "message_update",
+                assistantMessageEvent: {
+                  type: "text_delta",
+                  contentIndex: 0,
+                  delta: output,
+                  partial: output,
+                },
+              });
+            }
+          }),
+          dispose: vi.fn(),
+        },
+      } as any;
+    });
+
+    const live = makeTask();
+    const step = {
+      id: "graph:plan-review-step",
+      name: "Plan Review",
+      description: "",
+      mode: "prompt",
+      phase: "pre-merge",
+      gateMode: "gate",
+      prompt: "Review the plan.",
+      toolMode: "readonly",
+      enabled: true,
+      createdAt: live.createdAt,
+      updatedAt: live.updatedAt,
+    };
+
+    const result = await (executor as any).executeWorkflowStep(live, step, "/tmp/test", {});
+
+    expect(result.success).toBe(true);
+    expect(activeSessionRegistry.lookupByPath("/tmp/test")).toBeNull();
+  });
+
   it("keeps other read-only nodes on the recorded path so they fail fast into recovery", async () => {
     const store = createMockStore();
     const executor = new TaskExecutor(store, "/tmp/test");

packages/engine/src/executor.ts

@@ -16731,7 +16731,7 @@ You have access to the file system to review changes.${inlineFixBlock}${verdictB
         if (timeoutHandle) clearTimeout(timeoutHandle);
         const activeWorkflowStepSession = this.activeWorkflowStepSessions.get(task.id);
         if (activeWorkflowStepSession === session) {
-          this.deleteActiveWorkflowStepSession(task.id);
+          this.deleteActiveWorkflowStepSession(task.id, worktreePath);
         }
         // Suppress unused-variable warning; `timedOut` documents intent.
         void timedOut;