FN-151: make task reset always complete

Make reset a reliable description-only fresh start by fencing active planning work and cleaning discarded execution state. - Add reset lifecycle disposal for planning sessions, locks, artifacts, and reset worktrees. - Preserve operator-provided descriptions while clearing stale execution and planning projections. - Expose reset routes and add core, dashboard, and engine regression coverage. Files changed: .changeset/fn-151-task-reset-always-completes.md | 7 + docs/architecture.md | 3 + docs/dashboard-guide.md | 6 +- .../postgres/task-reset-publication.pg.test.ts | 71 +++++++++- .../core/src/__tests__/task-move-disposer.test.ts | 38 ++++++ packages/core/src/index.gate.ts | 2 + packages/core/src/index.ts | 2 + packages/core/src/task-store/reset-lifecycle.ts | 38 +++++- packages/core/src/tasks/task-move-disposer.ts | 36 +++++- .../src/__tests__/task-reset-lifecycle.test.ts | 110 +++++++++++++++- .../src/routes/register-task-workflow-routes.ts | 29 +++-- .../src/__tests__/agent-document-tools.test.ts | 49 +++++++ .../src/__tests__/reset-worktree-removal.test.ts | 77 +++++++++++ .../__tests__/triage-reset-planning-fence.test.ts | 118 +++++++++++++++++ packages/engine/src/agent-tools.ts | 60 +++++++-- packages/engine/src/agents/planning-liveness.ts | 19 +++ packages/engine/src/index.ts | 4 + packages/engine/src/plan-artifact-writeback.ts | 27 +++- packages/engine/src/planning-reset-fence.ts | 26 +++ packages/engine/src/triage.ts | 143 +++++++++++++++++++-- packages/engine/src/worktree/remove-reset-worktree.ts | 65 ++++++++++ 21 files changed, 882 insertions(+), 48 deletions(-) Fusion-Task-Id: FN-151 Fusion-Task-Lineage: 1c25d58e-2d23-4340-a489-51f3e2d8a7f4 Co-authored-by: Fusion <noreply@runfusion.ai>
2026-08-22 18:32:16 +00:00
parent a786c45bb9
commit c1818ea819
21 changed files with 882 additions and 48 deletions
--- a/.changeset/fn-151-task-reset-always-completes.md
+++ b/.changeset/fn-151-task-reset-always-completes.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Make task reset safely fence active planning sessions.
+category: fix
+dev: Reset adds planner reset disposers, releases held symbol locks, and clears discarded-run projections while retaining operator input.
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -32,6 +32,9 @@ The dashboard completes an ordinary approval through the public `@fusion/engine`

 The conservative stranded-shape recovery claims only a complete non-seed prompt after planner staleness grace, with no live/finalizing session, approval park, handoff, graph continuation/work item evidence, or any persisted workflow-run step instance; those step instances are graph-owned evidence even before a result or continuation exists. Automatic unplanned release refusals atomically claim a project/task episode and append one durable task-log diagnostic; changed prompt, dependency, status, fingerprint, or Plan Review node state starts a new episode. Direct-session validation compares PostgreSQL server identity as well as database name, preventing a same-named database on another cluster from becoming the lifecycle lock namespace.

+<!-- FNXC:TaskReset 2026-08-22-18:15: Reset holds this non-reentrant lock while it cancels planner ownership and clears discarded output, so planner publications re-check their attempt generation inside the authoritative lock-held mutation. The reset disposer only aborts/disposes and unregisters its own planning paths; it never waits for a finalizer that needs this lock. -->
+A task Reset is therefore a planner-inclusive but lock-free cancellation fence. A surviving self-owned worktree registration is reconciled only after normal live-owner and idle checks, while live or foreign holders remain conflicts rather than force-removal candidates.
+
 ## 1) Overview

 Fusion is an AI-orchestrated task board. It takes tasks through a structured lifecycle (`planning → todo → in-progress → in-review → done → archived`) and automates planning, execution, review, merge, and operational recovery.
--- a/docs/dashboard-guide.md
+++ b/docs/dashboard-guide.md
@@ -74,9 +74,11 @@ Both actions are irreversible; there is no undo after confirming. The dialog clo

 <!-- FNXC:TaskResetDocs 2026-08-19-06:45: Task Reset is a destructive fresh-planning boundary. The guide must explain the cancellation fence, filesystem cleanup, retained history, atomic intake publication, and retry behavior for incomplete cleanup. -->

-**Reset** is destructive and has no undo. After confirmation, Fusion fences active task work, removes only the task-owned standard worktree and the current `.fusion/tasks/<task-id>/PROMPT.md` plan, then atomically returns the same task to its workflow's **Planning/intake** column with pending steps and `needs-replan`. The task ID, title, description, dependencies, workflow selection, attachments, documents, logs/audit history, and branch history remain intact.
+**Reset** is destructive and has no undo. After confirmation, Fusion fences executor and planner work without waiting for a planner that needs the reset-held planning lock. It removes only the task-owned standard worktree and current `.fusion/tasks/<task-id>/PROMPT.md` plan, then atomically returns the same task to its workflow's **Planning/intake** column with pending steps and `needs-replan`.

-Reset does not support workspace tasks or external/operator-owned, foreign, unsafe, or project-root worktrees. If cancellation, worktree removal, plan removal, runtime finalization, or durable publication fails, Fusion reports incomplete cleanup and does not claim success or expose the task to Planning; retry **Reset** after the reported problem is resolved. A plan-removal failure may leave the worktree already removed, but the stored task lifecycle state remains unchanged until a retry completes. Once the atomic publication commits, a task-file mirror problem is repaired separately and does not turn the successful reset into a false failure.
+A stale self-owned session registration is reconciled only under the ordinary liveness and idle gates, then removal is retried once. A live planner, executor claim, or foreign holder is reported as an actionable conflict; Reset never forces deletion over live work. Workspace tasks and external/operator-owned, foreign, unsafe, or project-root worktrees remain unsupported.
+
+Reset retains the task ID, title, description, dependencies, workflow selection, comments, attachments, attachment-backed artifacts, operator-authored documents and their revisions, spec-lock history, commit associations, logs, and audit history. It clears agent-only documents and run-produced planning, verification, merge, and artifact projections; held symbol locks are released as history. If cancellation, cleanup, or publication fails, Fusion reports incomplete cleanup and does not expose the task to Planning. Once publication commits, a task-file mirror problem is repaired separately and does not turn the successful reset into a false failure.

 ## Keyboard shortcuts

--- a/packages/core/src/tests/postgres/task-reset-publication.pg.test.ts
+++ b/packages/core/src/tests/postgres/task-reset-publication.pg.test.ts
@@ -1,4 +1,6 @@
 import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { eq } from "drizzle-orm";
+import * as schema from "../../postgres/schema/index.js";
 import { __setResetPublicationFailureForTesting } from "../../task-store/reset-lifecycle.js";
 import {
  pgDescribe,
@@ -27,10 +29,10 @@ pgDescribe("TaskStore reset publication", () => {
      status: "failed",
      worktree: "/tmp/owned-worktree",
      branch: "fusion/fn-reset",
+      branchWriteOrigin: "engine",
      checkedOutBy: "agent-reset",
      workflowIrPin: "pin-before-reset",
      workflowStepResults: [{ workflowStepId: "plan-review", status: "failed" }],
-      reviewState: { status: "changes-requested" },
      awaitingApprovalReason: "plan-review-replan-cap",
    } as never);
    const continuation = await store.upsertWorkflowWorkItem({
@@ -68,7 +70,7 @@ pgDescribe("TaskStore reset publication", () => {
    expect(reset.branch).toBeUndefined();
    expect(reset.checkedOutBy).toBeUndefined();
    expect(reset.workflowIrPin).toBeUndefined();
-    expect(reset.workflowStepResults).toEqual([]);
+    expect(reset.workflowStepResults ?? []).toEqual([]);
    expect(reset.reviewState).toBeUndefined();
    expect(reset.awaitingApprovalReason).toBeUndefined();
    expect(await store.listWorkflowWorkItemsForTask(task.id, { kinds: ["task"] })).toEqual([
@@ -77,9 +79,60 @@ pgDescribe("TaskStore reset publication", () => {
    expect(await store.hasWorkflowRunStepInstancesForTask(task.id)).toBe(false);
  });

+  it("clears run projections while retaining operator documents, attachments, and released symbol-lock history", async () => {
+    const { store, task } = await seedPopulatedResetState();
+    const originalTitle = task.title;
+    const originalDescription = task.description;
+    const now = new Date().toISOString();
+    await store.upsertTaskDocument(task.id, { key: "agent-only", content: "discard", author: "agent" });
+    await store.upsertTaskDocument(task.id, { key: "operator", content: "keep", author: "user" });
+    await store.upsertTaskDocument(task.id, { key: "operator", content: "agent update", author: "agent" });
+    await store.updateTask(task.id, { declaredSymbols: ["src/reset.ts#freshStart"] });
+    await store.acquireSymbolLocks(["src/reset.ts#freshStart"], { ownerTaskId: task.id }, 60_000);
+    const db = h.layer().db;
+    await db.insert(schema.project.artifacts).values([
+      { id: `${task.id}-run`, type: "document", title: "run", authorId: "agent", taskId: task.id, createdAt: now, updatedAt: now },
+      { id: `${task.id}-attachment`, type: "image", title: "attachment", authorId: "user", taskId: task.id, metadata: { source: "attachment" }, createdAt: now, updatedAt: now },
+    ]);
+    await db.insert(schema.project.currentPlanEvidence).values({ taskId: task.id, version: 1, sourceRevision: 1, sourceHash: `${task.id}-plan`, capturedAt: now, snapshot: {} });
+    await db.insert(schema.project.specDriftReports).values({ taskId: task.id, reportHash: `${task.id}-drift`, executionHash: "execution", report: {}, createdAt: now });
+    await db.insert(schema.project.taskVerificationRequests).values({ taskId: task.id, requestId: `${task.id}-verify`, status: "pending", profile: "default", command: "true", scope: "package", requestedBy: "agent", requestedAt: now });
+    await db.insert(schema.project.unplannedExecutionBlocks).values({ taskId: task.id, episode: "episode", createdAt: now });
+    await db.insert(schema.project.completionHandoffMarkers).values({ taskId: task.id, acceptedAt: now, source: "test" });
+    await db.insert(schema.project.mergeQueue).values({ taskId: task.id, enqueuedAt: now });
+    await db.insert(schema.project.mergeRequests).values({ taskId: task.id, state: "pending", createdAt: now, updatedAt: now });
+
+    const reset = await store.resetTaskPublication(task.id, "todo");
+
+    expect(reset.title).toBe(originalTitle);
+    expect(reset.description).toBe(originalDescription);
+    expect(reset.declaredSymbols ?? []).toEqual([]);
+    expect((await db.select().from(schema.project.taskDocuments).where(eq(schema.project.taskDocuments.taskId, task.id))).map((row) => row.key)).toEqual(["operator"]);
+    expect((await db.select().from(schema.project.taskDocumentRevisions).where(eq(schema.project.taskDocumentRevisions.taskId, task.id))).map((row) => row.key)).toEqual(["operator"]);
+    expect(await db.select().from(schema.project.artifacts).where(eq(schema.project.artifacts.taskId, task.id))).toEqual([expect.objectContaining({ id: `${task.id}-attachment` })]);
+    await expect(db.select().from(schema.project.currentPlanEvidence).where(eq(schema.project.currentPlanEvidence.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.specDriftReports).where(eq(schema.project.specDriftReports.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.taskVerificationRequests).where(eq(schema.project.taskVerificationRequests.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.unplannedExecutionBlocks).where(eq(schema.project.unplannedExecutionBlocks.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.completionHandoffMarkers).where(eq(schema.project.completionHandoffMarkers.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.mergeQueue).where(eq(schema.project.mergeQueue.taskId, task.id))).resolves.toEqual([]);
+    await expect(db.select().from(schema.project.mergeRequests).where(eq(schema.project.mergeRequests.taskId, task.id))).resolves.toEqual([]);
+    expect(await db.select().from(schema.project.symbolLocks).where(eq(schema.project.symbolLocks.ownerTaskId, task.id))).toEqual([expect.objectContaining({ status: "released" })]);
+  });
+
  it("rolls back every publication participant after workflow mutation failure", async () => {
    const { store, task, continuation } = await seedPopulatedResetState();
+    const now = new Date().toISOString();
+    await store.upsertTaskDocument(task.id, { key: "agent-only", content: "must survive rollback", author: "agent" });
+    await h.layer().db.insert(schema.project.artifacts).values({ id: `${task.id}-rollback-artifact`, type: "document", title: "rollback", authorId: "agent", taskId: task.id, createdAt: now, updatedAt: now });
+    const [beforeFailure] = await h.layer().db.select({
+      column: schema.project.tasks.column,
+      status: schema.project.tasks.status,
+      worktree: schema.project.tasks.worktree,
+    }).from(schema.project.tasks).where(eq(schema.project.tasks.id, task.id));
+    let injected = false;
    const release = __setResetPublicationFailureForTesting(() => {
+      injected = true;
      throw new Error("injected reset publication failure");
    });
    try {
@@ -88,12 +141,16 @@ pgDescribe("TaskStore reset publication", () => {
      release();
    }

-    const durable = await store.getTask(task.id);
-    expect(durable?.column).toBe("in-progress");
-    expect(durable?.status).toBe("failed");
-    expect(durable?.worktree).toBe("/tmp/owned-worktree");
-    expect(durable?.workflowStepResults).toHaveLength(1);
+    expect(injected).toBe(true);
+    const [durable] = await h.layer().db.select({
+      column: schema.project.tasks.column,
+      status: schema.project.tasks.status,
+      worktree: schema.project.tasks.worktree,
+    }).from(schema.project.tasks).where(eq(schema.project.tasks.id, task.id));
+    expect(durable).toEqual(beforeFailure);
    expect((await store.listWorkflowWorkItemsForTask(task.id, { kinds: ["task"] })).find((item) => item.id === continuation.id)?.state).toBe("running");
    expect(await store.hasWorkflowRunStepInstancesForTask(task.id)).toBe(true);
+    expect(await h.layer().db.select().from(schema.project.taskDocuments).where(eq(schema.project.taskDocuments.taskId, task.id))).toEqual([expect.objectContaining({ key: "agent-only" })]);
+    expect(await h.layer().db.select().from(schema.project.artifacts).where(eq(schema.project.artifacts.taskId, task.id))).toEqual([expect.objectContaining({ id: `${task.id}-rollback-artifact` })]);
  });
 });
--- a/packages/core/src/tests/task-move-disposer.test.ts
+++ b/packages/core/src/tests/task-move-disposer.test.ts
@@ -4,7 +4,9 @@ import {
  __setTaskMoveDisposalTimeoutForTesting,
  disposeTaskBeforeMove,
  disposeTaskBeforeReset,
+  getTaskResetDisposer,
  registerTaskMoveDisposer,
+  registerTaskResetDisposer,
 } from "../tasks/task-move-disposer.js";

 describe("task move disposer", () => {
@@ -162,6 +164,42 @@ describe("task move disposer", () => {
    expect(resetReady).toBe(true);
  });

+  it("starts move and reset owners concurrently before awaiting either", async () => {
+    const store = {} as never;
+    let releaseMove!: () => void;
+    let releaseReset!: () => void;
+    const move = vi.fn(() => new Promise<void>((resolve) => { releaseMove = resolve; }));
+    const reset = vi.fn(() => new Promise<void>((resolve) => { releaseReset = resolve; }));
+    registerTaskMoveDisposer(store, move);
+    registerTaskResetDisposer(store, reset);
+    const pending = disposeTaskBeforeReset(store, { id: "FN-BOTH" } as never);
+    await Promise.resolve();
+    expect(move).toHaveBeenCalledOnce();
+    expect(reset).toHaveBeenCalledOnce();
+    releaseMove();
+    releaseReset();
+    await expect(pending).resolves.toBeUndefined();
+  });
+
+  it("supports store-scoped reset disposers and independent unregistration", async () => {
+    const first = {} as never;
+    const second = {} as never;
+    const disposer = vi.fn().mockResolvedValue(undefined);
+    const unregister = registerTaskResetDisposer(first, disposer);
+    await disposeTaskBeforeReset(second, { id: "FN-OTHER" } as never);
+    expect(disposer).not.toHaveBeenCalled();
+    await disposeTaskBeforeReset(first, { id: "FN-FIRST" } as never);
+    expect(disposer).toHaveBeenCalledOnce();
+    unregister();
+    expect(getTaskResetDisposer(first)).toBeUndefined();
+  });
+
+  it("propagates reset-only disposer rejection", async () => {
+    const store = {} as never;
+    registerTaskResetDisposer(store, vi.fn().mockRejectedValue(new Error("planner still active")));
+    await expect(disposeTaskBeforeReset(store, { id: "FN-RESET-ONLY" } as never)).rejects.toThrow("planner still active");
+  });
+
  it("is a no-op when reset has no registered runtime owners", async () => {
    await expect(disposeTaskBeforeReset({} as never, { id: "FN-RESET-NO-OWNER" } as never)).resolves.toBeUndefined();
  });
--- a/packages/core/src/index.gate.ts
+++ b/packages/core/src/index.gate.ts
@@ -643,7 +643,9 @@ export {
  disposeTaskBeforeMove,
  disposeTaskBeforeReset,
  getTaskMoveDisposer,
+  getTaskResetDisposer,
  registerTaskMoveDisposer,
+  registerTaskResetDisposer,
  type TaskMoveDisposer,
  type TaskResetDisposer,
  type TaskMoveDisposalInput,
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -773,7 +773,9 @@ export {
  disposeTaskBeforeMove,
  disposeTaskBeforeReset,
  getTaskMoveDisposer,
+  getTaskResetDisposer,
  registerTaskMoveDisposer,
+  registerTaskResetDisposer,
  type TaskMoveDisposer,
  type TaskResetDisposer,
  type TaskMoveDisposalInput,
--- a/packages/core/src/task-store/reset-lifecycle.ts
+++ b/packages/core/src/task-store/reset-lifecycle.ts
@@ -1,4 +1,4 @@
-import { and, eq, inArray } from "drizzle-orm";
+import { and, eq, inArray, sql } from "drizzle-orm";
 import type { ColumnId, Task, TaskStep } from "../types.js";
 import * as schema from "../postgres/schema/index.js";
 import { projectScopeFor } from "../postgres/data-layer.js";
@@ -7,6 +7,7 @@ import { withTaskWorkflowSerialization } from "./async/async-workflow-workitems.
 import { readTaskRowInTransaction, upsertTaskRowInTransaction } from "./async/async-persistence.js";
 import type { TaskStore } from "../store.js";
 import { createLogger } from "../process/logger.js";
+import { resolveTaskSymbolsForTask } from "../tasks/task-symbol-resolution.js";

 const resetLog = createLogger("task-store-reset-lifecycle");
 const ACTIVE_TASK_CONTINUATION_STATES = ["runnable", "running", "held", "retrying"] as const;
@@ -138,6 +139,14 @@ export async function resetTaskPublicationImpl(
    throw new Error("Atomic task reset publication requires the PostgreSQL backend");
  }
  const projectId = layer.projectId;
+  const beforeReset = await store.getTask(taskId);
+  if (!beforeReset) throw new Error(`Task ${taskId} not found`);
+  const symbols = resolveTaskSymbolsForTask(beforeReset);
+  /*
+  FNXC:TaskReset 2026-08-22-04:45:
+  Symbol release is intentionally before publication: it owns a separate transaction, while publication clears declaredSymbols. Releasing preserves audit history instead of leaking held rows until expiry.
+  */
+  if (store.backendMode && symbols.resolvable) await store.releaseSymbolLocks(symbols.symbols, taskId);
  let published!: Task;

  await layer.transactionImmediate(async (tx) => {
@@ -161,6 +170,33 @@ export async function resetTaskPublicationImpl(
          .where(and(scope, inArray(schema.project.workflowWorkItems.id, active.map((row) => row.id))));
      }
      await resetPublicationFailureForTesting?.();
+      const documentScope = projectScopeFor(schema.project.taskDocuments.projectId, projectId);
+      const revisionScope = projectScopeFor(schema.project.taskDocumentRevisions.projectId, projectId);
+      const documents = await tx.select({ key: schema.project.taskDocuments.key, author: schema.project.taskDocuments.author })
+        .from(schema.project.taskDocuments).where(and(documentScope, eq(schema.project.taskDocuments.taskId, taskId)));
+      const revisions = await tx.select({ key: schema.project.taskDocumentRevisions.key, author: schema.project.taskDocumentRevisions.author })
+        .from(schema.project.taskDocumentRevisions).where(and(revisionScope, eq(schema.project.taskDocumentRevisions.taskId, taskId)));
+      /*
+      FNXC:TaskReset 2026-08-22-04:45:
+      Reset retains user-authored documents and their complete revision history. Agent-only documents and run projections are discarded, while attachments, spec-locks, commit associations, and audit history remain operator history.
+      */
+      const userTouchedKeys = new Set([...documents, ...revisions].filter((row) => row.author === "user").map((row) => row.key));
+      const removableKeys = documents.filter((row) => !userTouchedKeys.has(row.key)).map((row) => row.key);
+      if (removableKeys.length) {
+        await tx.delete(schema.project.taskDocumentRevisions).where(and(revisionScope, eq(schema.project.taskDocumentRevisions.taskId, taskId), inArray(schema.project.taskDocumentRevisions.key, removableKeys)));
+        await tx.delete(schema.project.taskDocuments).where(and(documentScope, eq(schema.project.taskDocuments.taskId, taskId), inArray(schema.project.taskDocuments.key, removableKeys)));
+      }
+      await tx.delete(schema.project.currentPlanEvidence).where(and(projectScopeFor(schema.project.currentPlanEvidence.projectId, projectId), eq(schema.project.currentPlanEvidence.taskId, taskId)));
+      await tx.delete(schema.project.specDriftReports).where(and(projectScopeFor(schema.project.specDriftReports.projectId, projectId), eq(schema.project.specDriftReports.taskId, taskId)));
+      await tx.delete(schema.project.taskVerificationRequests).where(and(projectScopeFor(schema.project.taskVerificationRequests.projectId, projectId), eq(schema.project.taskVerificationRequests.taskId, taskId)));
+      await tx.delete(schema.project.unplannedExecutionBlocks).where(and(projectScopeFor(schema.project.unplannedExecutionBlocks.projectId, projectId), eq(schema.project.unplannedExecutionBlocks.taskId, taskId)));
+      await tx.delete(schema.project.completionHandoffMarkers).where(and(projectScopeFor(schema.project.completionHandoffMarkers.projectId, projectId), eq(schema.project.completionHandoffMarkers.taskId, taskId)));
+      await tx.delete(schema.project.mergeQueue).where(and(projectScopeFor(schema.project.mergeQueue.projectId, projectId), eq(schema.project.mergeQueue.taskId, taskId)));
+      await tx.delete(schema.project.mergeRequests).where(and(projectScopeFor(schema.project.mergeRequests.projectId, projectId), eq(schema.project.mergeRequests.taskId, taskId)));
+      await tx.delete(schema.project.artifacts).where(and(
+        projectScopeFor(schema.project.artifacts.projectId, projectId), eq(schema.project.artifacts.taskId, taskId),
+        sql`coalesce(${schema.project.artifacts.metadata}->>'source', '') <> 'attachment'`,
+      ));
      await tx.delete(schema.project.workflowRunStepInstances).where(and(
        projectScopeFor(schema.project.workflowRunStepInstances.projectId, projectId),
        eq(schema.project.workflowRunStepInstances.taskId, taskId),
--- a/packages/core/src/tasks/task-move-disposer.ts
+++ b/packages/core/src/tasks/task-move-disposer.ts
@@ -20,6 +20,11 @@ export interface TaskMoveDisposalInput {
 * owned by another store. A set preserves every live owner during overlap.
 */
 const disposers = new WeakMap<TaskStore, Set<TaskMoveDisposer>>();
+/*
+FNXC:TaskReset 2026-08-22-04:32:
+Reset fences planner owners in addition to move owners because a reset discards task state while an ordinary move does not. Reset disposers run under the caller's held, non-reentrant planning-lifecycle lock, so they must never wait on work that needs that lock.
+*/
+const resetDisposers = new WeakMap<TaskStore, Set<TaskResetDisposer>>();
 const TASK_MOVE_DISPOSAL_TIMEOUT_MS = 30_000;
 let taskMoveDisposalTimeoutMs = TASK_MOVE_DISPOSAL_TIMEOUT_MS;

@@ -48,6 +53,25 @@ export function getTaskMoveDisposer(store: TaskStore): TaskMoveDisposer | undefi
  };
 }

+export function registerTaskResetDisposer(store: TaskStore, disposer: TaskResetDisposer): () => void {
+  const registered = resetDisposers.get(store) ?? new Set<TaskResetDisposer>();
+  registered.add(disposer);
+  resetDisposers.set(store, registered);
+  return () => {
+    const current = resetDisposers.get(store);
+    current?.delete(disposer);
+    if (current?.size === 0) resetDisposers.delete(store);
+  };
+}
+
+export function getTaskResetDisposer(store: TaskStore): TaskResetDisposer | undefined {
+  const registered = resetDisposers.get(store);
+  if (!registered?.size) return undefined;
+  return async (task) => {
+    await Promise.all([...registered].map((disposer) => disposer(task)));
+  };
+}
+
 /**
 * FNXC:WorkflowLifecycle 2026-07-18-14:32:
 * A user move from active execution back to Todo is a hard cancel. Await every
@@ -133,13 +157,19 @@ FNXC:TaskReset 2026-08-19-06:30:
 Reset is a destructive fresh-planning boundary, so it fences every registered runtime owner regardless of the task's current column before filesystem cleanup begins. The timeout is fail-closed: worktree and plan deletion never starts while an executor, agent, CLI, or planner still holds the task.
 */
 export async function disposeTaskBeforeReset(store: TaskStore, task: Task): Promise<void> {
-  const disposer = getTaskMoveDisposer(store);
-  if (!disposer) return;
+  const moveDisposer = getTaskMoveDisposer(store);
+  const resetDisposer = getTaskResetDisposer(store);
+  if (!moveDisposer && !resetDisposer) return;

+  // Start both domains before awaiting either so cancellation cannot serialize owners.
+  const disposal = Promise.all([
+    moveDisposer?.(task),
+    resetDisposer?.(task),
+  ]);
  let timeout: ReturnType<typeof setTimeout> | undefined;
  try {
    await Promise.race([
-      disposer(task),
+      disposal,
      new Promise<void>((_resolve, reject) => {
        timeout = setTimeout(() => {
          reject(new Error(`Timed out stopping active work for ${task.id} before resetting the task`));
--- a/packages/dashboard/src/tests/task-reset-lifecycle.test.ts
+++ b/packages/dashboard/src/tests/task-reset-lifecycle.test.ts
@@ -5,8 +5,8 @@ import { mkdir, mkdtemp, readFile, stat, writeFile } from "node:fs/promises";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
 import type { Task, TaskStore } from "@fusion/core";
-import { registerTaskMoveDisposer } from "@fusion/core";
-import { getRegisteredWorktreeBranches } from "@fusion/engine";
+import { registerTaskMoveDisposer, registerTaskResetDisposer } from "@fusion/core";
+import { activeSessionRegistry, getRegisteredWorktreeBranches, registerPlanningLivenessProbe } from "@fusion/engine";
 import { createApiRoutes } from "../routes.js";
 import { request as performRequest } from "../test-request.js";

@@ -19,6 +19,14 @@ vi.mock("@fusion/engine", async () => {
      await rm(input.worktreePath, { recursive: true, force: true });
      return { removed: true, classification: "removed" };
    }),
+    removeTaskResetWorktree: vi.fn(async (input: Parameters<typeof actual.removeTaskResetWorktree>[0]) => await actual.removeTaskResetWorktree({
+      ...input,
+      remove: async ({ worktreePath }) => {
+        const { rm } = await import("node:fs/promises");
+        await rm(worktreePath, { recursive: true, force: true });
+        return { removed: true, classification: "removed" };
+      },
+    })),
    pruneWorktreeAdminEntries: vi.fn().mockResolvedValue(undefined),
    getRegisteredWorktreeBranches: vi.fn().mockResolvedValue([]),
  };
@@ -133,6 +141,104 @@ describe("POST /tasks/:id/reset", () => {
    }
  });

+  it("resets a planning-owned worktree after the planner reset fence releases it", async () => {
+    const root = await mkdtemp(join(tmpdir(), "fusion-reset-route-planning-"));
+    const worktree = join(root, ".worktrees", "fn-400");
+    const taskDir = join(root, ".fusion", "tasks", "FN-400");
+    await mkdir(worktree, { recursive: true });
+    await mkdir(taskDir, { recursive: true });
+    await writeFile(join(taskDir, "PROMPT.md"), "# Discarded plan\n");
+    const task = taskFixture(worktree);
+    vi.mocked(getRegisteredWorktreeBranches).mockResolvedValue([{ branch: task.branch!, worktreePath: worktree }]);
+    activeSessionRegistry.registerPath(worktree, { taskId: task.id, kind: "planning", ownerKey: `planning:${task.id}` });
+    const publication = vi.fn().mockResolvedValue({ ...task, column: "triage", status: "needs-replan", worktree: undefined, branch: undefined });
+    const store = createStore(root, task, [], publication);
+    const unregister = registerTaskResetDisposer(store, async () => activeSessionRegistry.unregisterPath(worktree));
+    try {
+      const res = await performRequest(createApp(store), "POST", "/api/tasks/FN-400/reset", JSON.stringify({ confirm: true }), { "content-type": "application/json" });
+      expect(res.status).toBe(200);
+      expect(publication).toHaveBeenCalledOnce();
+      expect(activeSessionRegistry.lookupByPath(worktree)).toBeNull();
+      await expect(readFile(join(taskDir, "PROMPT.md"), "utf8")).rejects.toMatchObject({ code: "ENOENT" });
+      await expect(stat(worktree)).rejects.toMatchObject({ code: "ENOENT" });
+      expect(JSON.stringify(res.body)).not.toContain("cannot remove active-session worktree");
+    } finally {
+      unregister();
+      activeSessionRegistry.unregisterPath(worktree);
+    }
+  });
+
+  it("reconciles an aged orphaned planning registration when no disposer owns it", async () => {
+    const root = await mkdtemp(join(tmpdir(), "fusion-reset-route-stale-planning-"));
+    const worktree = join(root, ".worktrees", "fn-400");
+    await mkdir(worktree, { recursive: true });
+    await mkdir(join(root, ".fusion", "tasks", "FN-400"), { recursive: true });
+    await writeFile(join(root, ".fusion", "tasks", "FN-400", "PROMPT.md"), "# Discarded plan\n");
+    const task = taskFixture(worktree);
+    vi.mocked(getRegisteredWorktreeBranches).mockResolvedValue([{ branch: task.branch!, worktreePath: worktree }]);
+    activeSessionRegistry.registerPath(worktree, { taskId: task.id, kind: "planning", ownerKey: `planning:${task.id}` });
+    (activeSessionRegistry.lookupByPath(worktree) as { registeredAt: number }).registeredAt = 0;
+    const publication = vi.fn().mockResolvedValue({ ...task, column: "triage", status: "needs-replan", worktree: undefined, branch: undefined });
+    const store = createStore(root, task, [], publication);
+    try {
+      const res = await performRequest(createApp(store), "POST", "/api/tasks/FN-400/reset", JSON.stringify({ confirm: true }), { "content-type": "application/json" });
+      expect(res.status).toBe(200);
+      expect(activeSessionRegistry.lookupByPath(worktree)).toBeNull();
+      expect(publication).toHaveBeenCalledOnce();
+    } finally {
+      activeSessionRegistry.unregisterPath(worktree);
+    }
+  });
+
+  it("reports a live planner as an actionable conflict without deleting its plan", async () => {
+    const root = await mkdtemp(join(tmpdir(), "fusion-reset-route-live-planning-"));
+    const worktree = join(root, ".worktrees", "fn-400");
+    const promptPath = join(root, ".fusion", "tasks", "FN-400", "PROMPT.md");
+    await mkdir(worktree, { recursive: true });
+    await mkdir(join(root, ".fusion", "tasks", "FN-400"), { recursive: true });
+    await writeFile(promptPath, "# Keep plan\n");
+    const task = taskFixture(worktree);
+    vi.mocked(getRegisteredWorktreeBranches).mockResolvedValue([{ branch: task.branch!, worktreePath: worktree }]);
+    activeSessionRegistry.registerPath(worktree, { taskId: task.id, kind: "planning", ownerKey: `planning:${task.id}` });
+    (activeSessionRegistry.lookupByPath(worktree) as { registeredAt: number }).registeredAt = 0;
+    const unregisterProbe = registerPlanningLivenessProbe((id) => id === task.id);
+    const publication = vi.fn();
+    const store = createStore(root, task, [], publication);
+    try {
+      const res = await performRequest(createApp(store), "POST", "/api/tasks/FN-400/reset", JSON.stringify({ confirm: true }), { "content-type": "application/json" });
+      expect(res.status).toBe(409);
+      expect(res.body.error).toMatch(/active task FN-400 \(planning\).*stop or finish/i);
+      expect(publication).not.toHaveBeenCalled();
+      await expect(readFile(promptPath, "utf8")).resolves.toBe("# Keep plan\n");
+    } finally {
+      unregisterProbe();
+      activeSessionRegistry.unregisterPath(worktree);
+    }
+  });
+
+  it("reports a foreign session holder as an actionable conflict", async () => {
+    const root = await mkdtemp(join(tmpdir(), "fusion-reset-route-foreign-session-"));
+    const worktree = join(root, ".worktrees", "fn-400");
+    const promptPath = join(root, ".fusion", "tasks", "FN-400", "PROMPT.md");
+    await mkdir(worktree, { recursive: true });
+    await mkdir(join(root, ".fusion", "tasks", "FN-400"), { recursive: true });
+    await writeFile(promptPath, "# Keep plan\n");
+    const task = taskFixture(worktree);
+    vi.mocked(getRegisteredWorktreeBranches).mockResolvedValue([{ branch: task.branch!, worktreePath: worktree }]);
+    activeSessionRegistry.registerPath(worktree, { taskId: "FN-OTHER", kind: "planning", ownerKey: "planning:FN-OTHER" });
+    const publication = vi.fn();
+    const store = createStore(root, task, [], publication);
+    try {
+      const res = await performRequest(createApp(store), "POST", "/api/tasks/FN-400/reset", JSON.stringify({ confirm: true }), { "content-type": "application/json" });
+      expect(res.status).toBe(409);
+      expect(res.body.error).toMatch(/active task FN-OTHER \(planning\).*stop or finish/i);
+      expect(publication).not.toHaveBeenCalled();
+      await expect(readFile(promptPath, "utf8")).resolves.toBe("# Keep plan\n");
+    } finally {
+      activeSessionRegistry.unregisterPath(worktree);
+    }
+  });
+
  it("keeps durable state non-replannable when prompt removal fails after worktree cleanup", async () => {
    const root = await mkdtemp(join(tmpdir(), "fusion-reset-route-failure-"));
    const worktree = join(root, ".worktrees", "fn-400");
--- a/packages/dashboard/src/routes/register-task-workflow-routes.ts
+++ b/packages/dashboard/src/routes/register-task-workflow-routes.ts
@@ -114,8 +114,9 @@ import {
  // FN-8004 follow-up: shared with SelfHealingManager.recoverStaleMergingStatus so the manual
  // Retry gate and the automatic sweep agree on when a merge-active stamp is orphaned.
  isStaleMergeActiveStatus,
-  removeWorktree,
-  RemovalReason,
+  removeTaskResetWorktree,
+  ResetWorktreeForeignSessionError,
+  ActiveSessionWorktreeRemovalError,
  getRegisteredWorktreeBranches,
  pruneWorktreeAdminEntries,
  isInsideConfiguredWorktreesDir,
@@ -3815,14 +3816,22 @@ export function registerTaskWorkflowRoutes(ctx: ApiRoutesContext, deps: TaskWork

          if (worktreePath) {
            if (existsSync(worktreePath)) {
-              const removal = await removeWorktree({
-                worktreePath,
-                rootDir,
-                settings,
-                reason: RemovalReason.TaskReset,
-                taskId: req.params.id,
-                expectedOwnerTaskId: req.params.id,
-              });
+              /*
+              FNXC:TaskReset 2026-08-22-04:32:
+              Reset has fenced planner and executor owners while holding the planning lock. The helper only reconciles proven-stale self-owned registrations under the normal staleness gates; it never forces a live session.
+              */
+              let removal;
+              try {
+                removal = await removeTaskResetWorktree({ worktreePath, rootDir, settings, taskId: req.params.id });
+              } catch (error) {
+                if (error instanceof ResetWorktreeForeignSessionError || error instanceof ActiveSessionWorktreeRemovalError) {
+                  const message = error instanceof ResetWorktreeForeignSessionError
+                    ? `Reset is blocked by active task ${error.details.holderTaskId} (${error.details.holderKind}); stop or finish it before retrying Reset`
+                    : `Reset is blocked by active task ${error.details.taskId} (${error.details.kind}); stop or finish it before retrying Reset`;
+                  throw conflict(message);
+                }
+                throw error;
+              }
              if (!removal.removed && existsSync(worktreePath)) {
                throw conflict(`Reset incomplete; worktree removal failed for ${req.params.id}`);
              }
--- a/packages/engine/src/tests/agent-document-tools.test.ts
+++ b/packages/engine/src/tests/agent-document-tools.test.ts
@@ -207,6 +207,55 @@ describe("task_prompt_write tool", () => {
    expect(getText(result)).toBe(`Updated PROMPT.md for ${TASK_ID}.`);
  });

+  it("refuses a reset-fenced planning write before durable prompt persistence", async () => {
+    const updateTask = vi.fn();
+    const store = { updateTask, getTask: vi.fn().mockResolvedValue({ id: TASK_ID }) } as unknown as TaskStore;
+
+    const result = await runTool(
+      createTaskPromptWriteTool(store, TASK_ID, undefined, () => false),
+      "call-reset-fenced",
+      { content: "# Stale plan" },
+    );
+
+    expect(getText(result)).toContain("was reset before PROMPT.md could be persisted");
+    expect(updateTask).not.toHaveBeenCalled();
+  });
+
+  it("refuses a pre-reset planner write after it queues behind the reset lifecycle lock", async () => {
+    let releaseReset!: () => void;
+    let enteredQueue!: () => void;
+    const resetPublication = new Promise<void>((resolve) => { releaseReset = resolve; });
+    const queuedBehindReset = new Promise<void>((resolve) => { enteredQueue = resolve; });
+    let generationCurrent = true;
+    const updateTask = vi.fn();
+    const store = {
+      getTask: vi.fn().mockResolvedValue({ id: TASK_ID }),
+      updateTask,
+      withPlanningLifecycleLock: vi.fn(async (_id: string, write: () => Promise<void>) => {
+        enteredQueue();
+        await resetPublication;
+        await write();
+      }),
+      withTaskLock: vi.fn(async (_id: string, write: () => Promise<void>) => await write()),
+      updateTaskUnlocked: vi.fn(),
+      isBackendMode: vi.fn(() => false),
+    } as unknown as TaskStore;
+
+    const resultPromise = runTool(
+      createTaskPromptWriteTool(store, TASK_ID, undefined, () => generationCurrent),
+      "call-queued-before-reset",
+      { content: "# Discarded plan" },
+    );
+    await queuedBehindReset;
+    generationCurrent = false;
+    releaseReset();
+
+    const result = await resultPromise;
+    expect(getText(result)).toContain("was reset before PROMPT.md could be persisted");
+    expect(store.updateTaskUnlocked).not.toHaveBeenCalled();
+    expect(updateTask).not.toHaveBeenCalled();
+  });
+
  it("fails closed when the authoritative prompt read-back is missing or different", async () => {
    const updateTask = vi.fn().mockResolvedValue({});
    const getTask = vi.fn().mockResolvedValue({ id: TASK_ID, prompt: "" });
--- a/packages/engine/src/tests/reset-worktree-removal.test.ts
+++ b/packages/engine/src/tests/reset-worktree-removal.test.ts
@@ -0,0 +1,77 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { DEFAULT_SELF_OWNED_MIN_IDLE_MS, activeSessionRegistry, executingTaskLock } from "../agents/active-session-registry.js";
+import { registerPlanningLivenessProbe } from "../agents/planning-liveness.js";
+import { ActiveSessionWorktreeRemovalError } from "../worktree/worktree-backend.js";
+import { removeTaskResetWorktree, ResetWorktreeForeignSessionError } from "../worktree/remove-reset-worktree.js";
+
+const PATH = "/tmp/fn-151-reset-worktree";
+const TASK = "FN-151";
+
+afterEach(() => {
+  activeSessionRegistry.clear();
+  executingTaskLock.release(TASK);
+});
+
+function input(overrides: Partial<Parameters<typeof removeTaskResetWorktree>[0]> = {}) {
+  return {
+    worktreePath: PATH,
+    rootDir: "/tmp",
+    settings: {},
+    taskId: TASK,
+    now: () => Date.now() + DEFAULT_SELF_OWNED_MIN_IDLE_MS + 1,
+    remove: vi.fn().mockResolvedValue({ removed: true, classification: "removed" }),
+    ...overrides,
+  };
+}
+
+describe("removeTaskResetWorktree", () => {
+  it("reconciles an aged dead self-owned planning entry before removal", async () => {
+    activeSessionRegistry.registerPath(PATH, { taskId: TASK, kind: "planning", ownerKey: `planning:${TASK}` });
+    const options = input();
+    await expect(removeTaskResetWorktree(options)).resolves.toMatchObject({ removed: true });
+    expect(activeSessionRegistry.lookupByPath(PATH)).toBeNull();
+    expect(options.remove).toHaveBeenCalledOnce();
+  });
+
+  it("waits once for a recent stale entry and then removes it", async () => {
+    activeSessionRegistry.registerPath(PATH, { taskId: TASK, kind: "planning", ownerKey: `planning:${TASK}` });
+    let now = Date.now();
+    const wait = vi.fn().mockImplementation(async (ms: number) => { now += ms + 1; });
+    const options = input({ now: () => now, wait });
+    await removeTaskResetWorktree(options);
+    expect(wait).toHaveBeenCalledWith(expect.any(Number));
+    expect(wait.mock.calls[0][0]).toBeLessThanOrEqual(DEFAULT_SELF_OWNED_MIN_IDLE_MS);
+    expect(options.remove).toHaveBeenCalledOnce();
+  });
+
+  it("refuses an aged live planning holder without removing it", async () => {
+    activeSessionRegistry.registerPath(PATH, { taskId: TASK, kind: "planning", ownerKey: `planning:${TASK}` });
+    const unregister = registerPlanningLivenessProbe((id) => id === TASK);
+    const options = input();
+    try {
+      await expect(removeTaskResetWorktree(options)).rejects.toBeInstanceOf(ActiveSessionWorktreeRemovalError);
+      expect(activeSessionRegistry.lookupByPath(PATH)?.kind).toBe("planning");
+      expect(options.remove).not.toHaveBeenCalled();
+    } finally { unregister(); }
+  });
+
+  it("refuses a foreign holder without calling removal", async () => {
+    activeSessionRegistry.registerPath(PATH, { taskId: "FN-OTHER", kind: "planning", ownerKey: "planning:FN-OTHER" });
+    const options = input();
+    await expect(removeTaskResetWorktree(options)).rejects.toBeInstanceOf(ResetWorktreeForeignSessionError);
+    expect(options.remove).not.toHaveBeenCalled();
+  });
+
+  it("re-applies liveness gates before its single post-removal race retry", async () => {
+    const remove = vi.fn()
+      .mockImplementationOnce(async () => {
+        activeSessionRegistry.registerPath(PATH, { taskId: TASK, kind: "planning", ownerKey: `planning:${TASK}` });
+        throw new ActiveSessionWorktreeRemovalError({ worktreePath: PATH, taskId: TASK, kind: "planning", ownerKey: `planning:${TASK}`, reason: "task-reset" as never });
+      });
+    const unregister = registerPlanningLivenessProbe((id) => id === TASK);
+    try {
+      await expect(removeTaskResetWorktree(input({ remove }))).rejects.toBeInstanceOf(ActiveSessionWorktreeRemovalError);
+      expect(remove).toHaveBeenCalledOnce();
+    } finally { unregister(); }
+  });
+});
--- a/packages/engine/src/tests/triage-reset-planning-fence.test.ts
+++ b/packages/engine/src/tests/triage-reset-planning-fence.test.ts
@@ -0,0 +1,118 @@
+import { describe, expect, it, vi } from "vitest";
+import { disposeTaskBeforeReset, type Task, type TaskStore } from "@fusion/core";
+import { activeSessionRegistry } from "../agents/active-session-registry.js";
+import { PLANNING_RESET_HOLD_MS, PlanningResetFence } from "../planning-reset-fence.js";
+import { TriageProcessor } from "../triage.js";
+
+/*
+FNXC:TaskReset 2026-08-22-18:10:
+The planner fence is deliberately synchronous: Reset must cancel a planner that may be waiting for
+its non-reentrant lifecycle lock without awaiting that planner's settlement.
+*/
+describe("Triage planning reset fence", () => {
+  it("invalidates a captured attempt and holds new admission until publication clears it", () => {
+    let now = 1_000;
+    const fence = new PlanningResetFence(() => now);
+    const generation = fence.currentGeneration("FN-151");
+
+    fence.cancelPlanning("FN-151");
+
+    expect(fence.isStale("FN-151", generation)).toBe(true);
+    expect(fence.isResetHoldActive("FN-151")).toBe(true);
+    now += PLANNING_RESET_HOLD_MS + 1;
+    expect(fence.isResetHoldActive("FN-151")).toBe(false);
+    fence.clearHold("FN-151");
+    expect(fence.isResetHoldActive("FN-151")).toBe(false);
+  });
+
+  it("does not republish a recovered worktree artifact queued behind Reset", async () => {
+    const task = {
+      id: "FN-151-QUEUED-ARTIFACT",
+      description: "reset planner",
+      column: "triage",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    } as Task;
+    let releaseReset!: () => void;
+    let enteredQueue!: () => void;
+    const resetPublication = new Promise<void>((resolve) => { releaseReset = resolve; });
+    const entered = new Promise<void>((resolve) => { enteredQueue = resolve; });
+    const updateTaskUnlocked = vi.fn();
+    const store = {
+      on: vi.fn(),
+      off: vi.fn(),
+      withPlanningLifecycleLock: vi.fn(async (_id: string, work: () => Promise<void>) => {
+        enteredQueue();
+        await resetPublication;
+        await work();
+      }),
+      withTaskLock: vi.fn(async (_id: string, work: () => Promise<unknown>) => await work()),
+      updateTaskUnlocked,
+      isBackendMode: vi.fn(() => false),
+    } as unknown as TaskStore;
+    const processor = new TriageProcessor(store, "/tmp/fn-151-root");
+    const generation = (processor as unknown as { resetFence: PlanningResetFence }).resetFence.currentGeneration(task.id);
+
+    try {
+      const publish = (processor as unknown as {
+        persistResetFencedPlanningArtifact: (task: Task, generation: number, content: string, mirror: boolean) => Promise<boolean>;
+      }).persistResetFencedPlanningArtifact(task, generation, "# Discarded plan", false);
+      await entered;
+      await disposeTaskBeforeReset(store, task);
+      releaseReset();
+
+      await expect(publish).resolves.toBe(false);
+      expect(updateTaskUnlocked).not.toHaveBeenCalled();
+    } finally {
+      processor.stop();
+    }
+  });
+
+  it("fences a live TriageProcessor session without awaiting its lifecycle-lock finalize", async () => {
+    const task = {
+      id: "FN-151-RESET-FENCE",
+      description: "reset planner",
+      column: "triage",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    } as Task;
+    const worktree = "/tmp/fn-151-reset-fence";
+    const neverSettles = new Promise<never>(() => undefined);
+    const store = {
+      on: vi.fn(),
+      off: vi.fn(),
+      withPlanningLifecycleLock: vi.fn(() => neverSettles),
+    } as unknown as TaskStore;
+    const processor = new TriageProcessor(store, "/tmp/fn-151-root");
+    const abort = vi.fn().mockResolvedValue(undefined);
+    const dispose = vi.fn(() => { throw new Error("synthetic dispose failure"); });
+    (processor as unknown as { activeSessions: Map<string, unknown> }).activeSessions.set(task.id, { abort, dispose });
+    activeSessionRegistry.registerPath(worktree, { taskId: task.id, kind: "planning", ownerKey: `planning:${task.id}` });
+    activeSessionRegistry.registerPath(`${worktree}-executor`, { taskId: task.id, kind: "executor", ownerKey: task.id });
+    activeSessionRegistry.registerPath(`${worktree}-foreign`, { taskId: "FN-OTHER", kind: "planning", ownerKey: "planning:FN-OTHER" });
+
+    try {
+      await expect(disposeTaskBeforeReset(store, task)).resolves.toBeUndefined();
+      expect(abort).toHaveBeenCalledOnce();
+      expect(dispose).toHaveBeenCalledOnce();
+      expect(store.withPlanningLifecycleLock).not.toHaveBeenCalled();
+      expect(activeSessionRegistry.lookupByPath(worktree)).toBeNull();
+      expect(activeSessionRegistry.lookupByPath(`${worktree}-executor`)?.kind).toBe("executor");
+      expect(activeSessionRegistry.lookupByPath(`${worktree}-foreign`)?.taskId).toBe("FN-OTHER");
+      expect((processor as unknown as { activeSessions: Map<string, unknown> }).activeSessions.has(task.id)).toBe(false);
+    } finally {
+      processor.stop();
+      activeSessionRegistry.unregisterPath(worktree);
+      activeSessionRegistry.unregisterPath(`${worktree}-executor`);
+      activeSessionRegistry.unregisterPath(`${worktree}-foreign`);
+    }
+  });
+});
--- a/packages/engine/src/agent-tools.ts
+++ b/packages/engine/src/agent-tools.ts
@@ -2150,7 +2150,12 @@ function parsePlanRepositoryScope(content: string, configured: readonly string[]
  return [...new Set(repositories)].sort();
 }

-export function createTaskPromptWriteTool(store: TaskStore, taskId: string, runContext?: RunMutationContext): ToolDefinition {
+export function createTaskPromptWriteTool(
+  store: TaskStore,
+  taskId: string,
+  runContext?: RunMutationContext,
+  canPersist?: () => boolean,
+): ToolDefinition {
  return {
    name: "fn_task_prompt_write",
    label: "Write PROMPT.md",
@@ -2202,10 +2207,45 @@ export function createTaskPromptWriteTool(store: TaskStore, taskId: string, runC
              extensions: current?.repositoryScope?.extensions,
            }
          : undefined;
-        await store.updateTask(taskId, {
+        /*
+        FNXC:TaskReset 2026-08-22-04:49:
+        A triage attempt captured before Reset can outlive the route's non-reentrant planning lock.
+        Check its generation immediately before the authoritative write so a stale planner cannot
+        recreate PROMPT.md after Reset publishes the description-only state.
+        */
+        if (canPersist && !canPersist()) {
+          throw new Error(`Planning for ${taskId} was reset before PROMPT.md could be persisted`);
+        }
+        const promptUpdate = {
          prompt: params.content,
          ...(repositoryScope ? { repositoryScope } : {}),
-        }, runContext);
+        };
+        if (canPersist) {
+          /*
+          FNXC:TaskReset 2026-08-22-18:07:
+          Reset serializes its publication with the non-reentrant planning lifecycle lock. A
+          generation check before `updateTask` is insufficient because that writer can queue behind
+          Reset and recreate PROMPT.md after reset commits. Check and write under the same lock,
+          using the lock-held TaskStore variants so this tool never re-enters the advisory lock.
+          */
+          await store.withPlanningLifecycleLock(taskId, async () => {
+            if (!canPersist()) {
+              throw new Error(`Planning for ${taskId} was reset before PROMPT.md could be persisted`);
+            }
+            const updated = await store.withTaskLock(taskId, () => store.updateTaskUnlocked(taskId, promptUpdate, runContext));
+            if (store.isBackendMode()) {
+              await store.reconcileSpecDriftWhilePlanningLocked(updated).catch((error: unknown) => {
+                log.warn(`[spec-lock] deferred drift reconciliation for ${updated.id}: ${error instanceof Error ? error.message : String(error)}`);
+              });
+            }
+            /* FNXC:TaskReset 2026-08-22-18:15: Reset clears agent-authored plan documents under this lifecycle lock. */
+            await mirrorPlanToProjectDb(store, taskId, params.content, {
+              author: runContext?.agentId ?? "agent",
+            });
+          });
+        } else {
+          await store.updateTask(taskId, promptUpdate, runContext);
+        }
        /*
        FNXC:PlanArtifactPersistence 2026-08-22-03:37:
        FN-094 repointed this fail-closed check at updateTask's task-row return value after adding
@@ -2225,13 +2265,15 @@ export function createTaskPromptWriteTool(store: TaskStore, taskId: string, runC
        /*
        FNXC:PlanArtifactPersistence 2026-07-26-03:55:
        `updateTask({ prompt })` writes the project-root PROMPT.md and task.json, but `project.tasks` has
-        no `prompt` column — the spec would live only as a file in the project checkout. Mirror it into the
-        `plan` task document so the plan is durable in the project database too. Best-effort: a mirror
-        failure must not fail a write whose authoritative persistence was just verified above.
+        no `prompt` column — the spec would live only as a file in the project checkout. Reset-fenced
+        planners mirror it inside the serialized prompt publication above, preventing Reset from clearing
+        the document and then observing a stale mirror recreated after its transaction commits.
        */
-        await mirrorPlanToProjectDb(store, taskId, params.content, {
-          author: runContext?.agentId ?? "agent",
-        });
+        if (!canPersist) {
+          await mirrorPlanToProjectDb(store, taskId, params.content, {
+            author: runContext?.agentId ?? "agent",
+          });
+        }
        return {
          content: [{ type: "text" as const, text: `Updated PROMPT.md for ${taskId}.` }],
          details: {},
--- a/packages/engine/src/agents/planning-liveness.ts
+++ b/packages/engine/src/agents/planning-liveness.ts
@@ -0,0 +1,19 @@
+export type PlanningLivenessProbe = (taskId: string) => boolean;
+const probes = new Set<PlanningLivenessProbe>();
+/*
+FNXC:TaskReset 2026-08-22-04:32:
+Planning probes are process-wide and multi-project safe. Any true or throwing probe refuses removal: ambiguity must preserve a possibly live planner; no probe means no in-process planner exists.
+*/
+export const planningLivenessRegistry = {
+  registerPlanningLivenessProbe(probe: PlanningLivenessProbe): () => void {
+    probes.add(probe);
+    return () => probes.delete(probe);
+  },
+  isPlanningLive(taskId: string): boolean {
+    for (const probe of probes) { try { if (probe(taskId)) return true; } catch { return true; } }
+    return false;
+  },
+  hasRegisteredProbe(): boolean { return probes.size > 0; },
+};
+export const registerPlanningLivenessProbe = planningLivenessRegistry.registerPlanningLivenessProbe.bind(planningLivenessRegistry);
+export const isPlanningLive = planningLivenessRegistry.isPlanningLive.bind(planningLivenessRegistry);
--- a/packages/engine/src/index.ts
+++ b/packages/engine/src/index.ts
@@ -1,4 +1,8 @@
 export { AgentLogger, type AgentLoggerOptions, summarizeToolArgs } from "./agents/agent-logger.js";
+export { PlanningResetFence, PLANNING_RESET_HOLD_MS } from "./planning-reset-fence.js";
+export { removeTaskResetWorktree, ResetWorktreeForeignSessionError } from "./worktree/remove-reset-worktree.js";
+export { ActiveSessionWorktreeRemovalError } from "./worktree/worktree-backend.js";
+export { planningLivenessRegistry, registerPlanningLivenessProbe, isPlanningLive } from "./agents/planning-liveness.js";
 export {
  classifyReportHealth,
  type ReportHealthBucket,
--- a/packages/engine/src/plan-artifact-writeback.ts
+++ b/packages/engine/src/plan-artifact-writeback.ts
@@ -43,6 +43,13 @@ export interface ReconcileWorktreePlanArtifactOptions {
  /** cwd the planning session ran in. Equal to `rootDir` when planning did not get a worktree. */
  planningCwd: string;
  logger?: PlanWritebackLogger;
+  /**
+   * Optional caller-owned authoritative writer. Triage uses this to serialize a recovered
+   * worktree artifact with its reset-generation fence before it can recreate PROMPT.md.
+   */
+  writeAuthoritativePrompt?: (content: string) => Promise<boolean>;
+  /** Optional caller-owned plan-document writer subject to the same publication fence. */
+  mirrorAuthoritativePlan?: (content: string, author?: string) => Promise<boolean>;
 }

 export type PlanWritebackOutcome =
@@ -57,7 +64,9 @@ export type PlanWritebackOutcome =
  /** Worktree copy was copied back into the project `.fusion/` folder. */
  | "recovered"
  /** A worktree copy existed but persisting it failed; the root copy is untouched. */
-  | "recovery-failed";
+  | "recovery-failed"
+  /** A reset fenced this planning attempt before its worktree copy could be published. */
+  | "recovery-fenced";

 export interface ReconcileWorktreePlanArtifactResult {
  outcome: PlanWritebackOutcome;
@@ -109,7 +118,10 @@ export async function reconcileWorktreePlanArtifact(

  try {
    // The single validated persistence path: File Scope validation + root PROMPT.md write + task.json sync.
-    await store.updateTask(taskId, { prompt: worktreeContent });
+    const persisted = options.writeAuthoritativePrompt
+      ? await options.writeAuthoritativePrompt(worktreeContent)
+      : (await store.updateTask(taskId, { prompt: worktreeContent }), true);
+    if (!persisted) return { outcome: "recovery-fenced", content: rootContent ?? undefined };
    logger?.log?.(
      `${taskId}: recovered a worktree-local PROMPT.md into the project .fusion folder (${planningCwd})`,
    );
@@ -171,11 +183,14 @@ export async function persistPlanArtifact(
  options: ReconcileWorktreePlanArtifactOptions & { author?: string },
 ): Promise<ReconcileWorktreePlanArtifactResult & { mirrored: boolean }> {
  const result = await reconcileWorktreePlanArtifact(options);
+  if (result.outcome === "recovery-fenced") return { ...result, mirrored: false };
  const mirrored = result.content
-    ? await mirrorPlanToProjectDb(options.store, options.taskId, result.content, {
-      author: options.author,
-      logger: options.logger,
-    })
+    ? options.mirrorAuthoritativePlan
+      ? await options.mirrorAuthoritativePlan(result.content, options.author)
+      : await mirrorPlanToProjectDb(options.store, options.taskId, result.content, {
+        author: options.author,
+        logger: options.logger,
+      })
    : false;
  return { ...result, mirrored };
 }
--- a/packages/engine/src/planning-reset-fence.ts
+++ b/packages/engine/src/planning-reset-fence.ts
@@ -0,0 +1,26 @@
+export const PLANNING_RESET_HOLD_MS = 30_000;
+
+/**
+ * FNXC:TaskReset 2026-08-22-04:32:
+ * A reset invalidates planner attempts by generation so an aborted session cannot recreate a worktree or prompt after reset publication.
+ */
+export class PlanningResetFence {
+  private readonly generations = new Map<string, number>();
+  private readonly holds = new Map<string, number>();
+  constructor(private readonly now: () => number = Date.now) {}
+  currentGeneration(taskId: string): number { return this.generations.get(taskId) ?? 0; }
+  cancelPlanning(taskId: string): number {
+    const generation = this.currentGeneration(taskId) + 1;
+    this.generations.set(taskId, generation);
+    this.holds.set(taskId, this.now() + PLANNING_RESET_HOLD_MS);
+    return generation;
+  }
+  isStale(taskId: string, capturedGeneration: number): boolean { return this.currentGeneration(taskId) !== capturedGeneration; }
+  isResetHoldActive(taskId: string, now = this.now()): boolean {
+    const expiresAt = this.holds.get(taskId);
+    if (!expiresAt) return false;
+    if (expiresAt <= now) { this.holds.delete(taskId); return false; }
+    return true;
+  }
+  clearHold(taskId: string): void { this.holds.delete(taskId); }
+}
--- a/packages/engine/src/triage.ts
+++ b/packages/engine/src/triage.ts
@@ -187,6 +187,8 @@ import { AgentLogger } from "./agents/agent-logger.js";
 import { attachAgentUsageTelemetry, emitAgentSessionStart } from "./agents/agent-usage-telemetry.js";
 import { emitApprovalMail } from "./agents/approval-mail.js";
 import { acquireActiveSessionPath, activeSessionRegistry } from "./agents/active-session-registry.js";
+import { PlanningResetFence } from "./planning-reset-fence.js";
+import { registerPlanningLivenessProbe } from "./agents/planning-liveness.js";
 import {
  resolveAgentInstructions,
  resolveAgentInstructionsWithRatings,
@@ -457,6 +459,11 @@ export class TriageProcessor {
  private lastPlanThrottleSignature: string | null = null;
  /** Active agent sessions per task, used to terminate on pause. */
  private activeSessions = new Map<string, { dispose: () => void }>();
+  private readonly resetFence = new PlanningResetFence();
+  /** Captured attempt generations let a delayed finalizer reject a reset-fenced planner. */
+  private readonly activePlanningGenerations = new Map<string, number>();
+  private unregisterPlanningLiveness?: () => void;
+  private unregisterResetDisposer?: () => void;
  /**
   * Reviewer subagent sessions per task. The spec reviewer (`reviewer.ts`)
   * creates its own AgentSession that isn't part of `activeSessions`, so
@@ -615,12 +622,58 @@ export class TriageProcessor {
    };
  }

+  /**
+   * FNXC:TaskReset 2026-08-22-18:15:
+   * Worktree-artifact recovery and duplicate-marker recovery are planner publications, not raw
+   * filesystem cleanup. Reset holds this non-reentrant lifecycle lock while clearing its output,
+   * so each write rechecks the captured generation inside the authoritative serialized mutation;
+   * a pre-lock check alone can queue behind Reset and republish discarded planning output.
+   */
+  private async persistResetFencedPlanningArtifact(
+    task: Task,
+    planningGeneration: number,
+    content: string,
+    mirrorPlan: boolean,
+  ): Promise<boolean> {
+    let persisted = false;
+    await this.store.withPlanningLifecycleLock(task.id, async () => {
+      if (this.resetFence.isStale(task.id, planningGeneration)) return;
+      const updated = await this.store.withTaskLock(task.id, () => this.store.updateTaskUnlocked(task.id, { prompt: content }));
+      if (this.store.isBackendMode()) {
+        await this.store.reconcileSpecDriftWhilePlanningLocked(updated).catch((error: unknown) => {
+          planLog.warn(`[spec-lock] deferred drift reconciliation for ${updated.id}: ${error instanceof Error ? error.message : String(error)}`);
+        });
+      }
+      if (mirrorPlan) {
+        await mirrorPlanToProjectDb(this.store, task.id, content, {
+          author: "triage",
+          logger: { log: (message: string) => planLog.log(message), warn: (message: string) => planLog.warn(message) },
+        });
+      }
+      persisted = true;
+    });
+    return persisted;
+  }
+
  constructor(
    private store: TaskStore,
    private rootDir: string,
    private options: TriageProcessorOptions = {},
  ) {
    this.workflowAgentCapacity = new WorkflowAgentCapacity(this.options.agentStore);
+    this.unregisterPlanningLiveness = registerPlanningLivenessProbe((taskId) => this.getPlanningTaskIds().has(taskId));
+    this.unregisterResetDisposer = fusionCore.registerTaskResetDisposer(this.store, async (task) => {
+      /*
+      FNXC:TaskReset 2026-08-22-04:32:
+      The route already holds the non-reentrant planning lock, so this disposer is synchronous/lock-free: waiting for finalize would deadlock reset against the planner being cancelled.
+      */
+      this.resetFence.cancelPlanning(task.id);
+      this.abortAndDisposePlanningSessionForTask(task.id, "task reset");
+      for (const path of activeSessionRegistry.pathsForTask(task.id)) {
+        const record = activeSessionRegistry.lookupByPath(path);
+        if (record?.ownerKey === `planning:${task.id}`) activeSessionRegistry.unregisterPath(path);
+      }
+    });
    this.unregisterAdmissionProvider = projectAdmissionCoordinator.registerProvider(`specify:${this.rootDir}`, {
      projectId: this.rootDir,
      refresh: async () => {
@@ -761,6 +814,8 @@ export class TriageProcessor {
    */
    this.taskColumnWakeHandler = (task: Task, meta?: { lanes?: TaskMoveLanes }) => {
      if (!task?.id) return;
+      // Reset publication emits this durable state after its held lock commits, so a fresh planner is not delayed by the conservative reset TTL.
+      if (task.status === "needs-replan") this.resetFence.clearHold(task.id);
      const isPlannerWakeColumn = meta?.lanes
        ? task.column === meta.lanes.hold || task.column === meta.lanes.intake
        : LEGACY_PLANNER_WAKE_COLUMNS.has(task.column);
@@ -1044,6 +1099,10 @@ export class TriageProcessor {
    // Tear down any in-flight specify sessions and reviewer subagents so they
    // don't keep streaming LLM tokens / tool calls past engine shutdown.
    this.abortAndDisposeActiveSessions("engine stop");
+    this.unregisterPlanningLiveness?.();
+    this.unregisterPlanningLiveness = undefined;
+    this.unregisterResetDisposer?.();
+    this.unregisterResetDisposer = undefined;
    planLog.log("Processor stopped");
  }

@@ -1056,6 +1115,35 @@ export class TriageProcessor {
   * interrupts any in-flight LLM stream / tool call; dispose() then
   * releases session resources.
   */
+  private abortAndDisposePlanningSessionForTask(taskId: string, reason: string): void {
+    try {
+      this.disposeSubagentsForTask(taskId, reason);
+    } catch (error) {
+      planLog.warn(`${taskId}: failed to dispose planning subagents: ${error instanceof Error ? error.message : String(error)}`);
+    }
+    const session = this.activeSessions.get(taskId);
+    if (!session) return;
+    this.pauseAborted.add(taskId);
+    this.options.stuckTaskDetector?.untrackTask(taskId);
+    const abortable = session as { abort?: () => Promise<void>; dispose: () => void };
+    try {
+      if (typeof abortable.abort === "function") void Promise.resolve(abortable.abort()).catch(() => undefined);
+      this.recordTriageSessionTokenUsageSoon(taskId, session as AgentSession);
+      abortable.dispose();
+    } catch (error) {
+      /*
+      FNXC:TaskReset 2026-08-22-18:10:
+      Reset must finish fencing its own registry records even when an agent session's synchronous
+      disposer is faulty. The route's cleanup remains guarded by ownership and staleness checks;
+      this catch only prevents an already-cancelled planner from turning Reset into a raw failure.
+      */
+      planLog.warn(`${taskId}: failed to dispose planning session: ${error instanceof Error ? error.message : String(error)}`);
+    } finally {
+      // A failed disposer cannot retain an active-session bookkeeping claim past Reset.
+      this.activeSessions.delete(taskId);
+    }
+  }
+
  private abortAndDisposeActiveSessions(reason: string): void {
    for (const taskId of [...this.activeSubagentSessions.keys()]) {
      this.disposeSubagentsForTask(taskId, reason);
@@ -2473,6 +2561,12 @@ export class TriageProcessor {
  }

  async specifyTask(task: Task): Promise<void> {
+    if (this.resetFence.isResetHoldActive(task.id)) {
+      if (dropPreHeldExecutorSlot(task.id)) this.options.semaphore?.release();
+      return;
+    }
+    const planningGeneration = this.resetFence.currentGeneration(task.id);
+    this.activePlanningGenerations.set(task.id, planningGeneration);
    /*
    FNXC:TriageStuckKill 2026-07-18-21:05:
    Refuse a second planner when finalize/Plan Review is still live even if
@@ -2763,7 +2857,12 @@ export class TriageProcessor {
          ...this.createTriageTools({ parentTaskId: task.id }),
          createTaskDocumentWriteTool(this.store, task.id),
          createTaskDocumentReadTool(this.store, task.id),
-          createTaskPromptWriteTool(this.store, task.id, triageRunContext),
+          createTaskPromptWriteTool(
+            this.store,
+            task.id,
+            triageRunContext,
+            () => !this.resetFence.isStale(task.id, planningGeneration),
+          ),
          createWorkflowListTool(this.store),
          createWorkflowSelectTool(this.store, task.id),
          ...(isResearchToolSurfaceEnabled(settings)
@@ -3017,6 +3116,7 @@ export class TriageProcessor {
          bypasses it. `contended` means a genuinely live foreign holder, so planning falls back to
          the shared checkout rather than running in a worktree someone else owns.
          */
+          if (this.resetFence.isStale(task.id, planningGeneration)) return;
          const acquired = acquireActiveSessionPath(activeSessionRegistry, planningCwd, {
            taskId: task.id,
            kind: "planning",
@@ -3376,6 +3476,13 @@ export class TriageProcessor {
          authoritative into the project database (PROMPT.md has no `tasks` column and is otherwise
          filesystem-only). Both halves are best-effort — validation below still owns the verdict.
          */
+          /*
+          FNXC:TaskReset 2026-08-22-04:49:
+          Reset can commit while a planner session drains. Fence worktree artifact recovery before
+          it writes the project-root PROMPT.md, otherwise a pre-reset generic-file write recreates
+          planning output after the description-only publication.
+          */
+          if (this.resetFence.isStale(task.id, planningGeneration)) return;
          const planPersistence = await persistPlanArtifact({
            store: this.store,
            taskId: task.id,
@@ -3383,7 +3490,20 @@ export class TriageProcessor {
            planningCwd,
            author: "triage",
            logger: { log: (m: string) => planLog.log(m), warn: (m: string) => planLog.warn(m) },
+            writeAuthoritativePrompt: async (content) => await this.persistResetFencedPlanningArtifact(
+              task,
+              planningGeneration,
+              content,
+              false,
+            ),
+            mirrorAuthoritativePlan: async (content) => await this.persistResetFencedPlanningArtifact(
+              task,
+              planningGeneration,
+              content,
+              true,
+            ),
          });
+          if (planPersistence.outcome === "recovery-fenced") return;
          if (planPersistence.outcome === "recovered") {
            await this.store.logEntry(
              task.id,
@@ -3422,13 +3542,16 @@ export class TriageProcessor {
            const recoveredMarker = fusionCore.parseDuplicateMarkerFromSessionText(sessionTextTail);
            if (recoveredMarker) {
              const markerBody = `DUPLICATE: ${recoveredMarker.canonicalId}\n`;
-              const recovered = await writeFile(join(this.rootDir, promptPath), markerBody, "utf-8")
-                .then(() => true)
-                .catch((err: unknown) => {
-                  const msg = err instanceof Error ? err.message : String(err);
-                  planLog.warn(`${task.id}: failed to persist recovered duplicate marker: ${msg}`);
-                  return false;
-                });
+              const recovered = await this.persistResetFencedPlanningArtifact(
+                task,
+                planningGeneration,
+                markerBody,
+                false,
+              ).catch((err: unknown) => {
+                const msg = err instanceof Error ? err.message : String(err);
+                planLog.warn(`${task.id}: failed to persist recovered duplicate marker: ${msg}`);
+                return false;
+              });
              if (recovered) {
                written = markerBody;
                planLog.log(`${task.id}: recovered duplicate verdict ${recoveredMarker.canonicalId} from the planner's reply (no PROMPT.md was written)`);
@@ -3876,6 +3999,7 @@ export class TriageProcessor {
        this.options.onSpecifyError?.(task, err instanceof Error ? err : new Error(errorMessage));
      }
    } finally {
+      this.activePlanningGenerations.delete(task.id);
      // FNXC:ConcurrencyAdmission 2026-08-03-10:00: a coordinator reservation
      // can exist before planner setup reaches takePreHeldExecutorSlot(). Every
      // early setup failure must return that untransferred host slot; after a
@@ -4366,6 +4490,9 @@ export class TriageProcessor {
        after acquiring it so a dependency invalidation committed first fences this
        stale finalizer before it can restore approval or continuation handoff data.
        */
+        // Reset owns this same non-reentrant lock; only after it releases may a finalizer enter, and its captured generation must then be fenced before any durable handoff.
+        const planningGeneration = this.activePlanningGenerations.get(task.id);
+        if (planningGeneration !== undefined && this.resetFence.isStale(task.id, planningGeneration)) return report;
        const reRead = await Promise.resolve(this.store.getTask(task.id)).catch(() => null);
        // Older pure unit-test adapters expose a no-op getTask; production returns
        // a Task or rejects. Preserve that fixture seam without treating a failed
--- a/packages/engine/src/worktree/remove-reset-worktree.ts
+++ b/packages/engine/src/worktree/remove-reset-worktree.ts
@@ -0,0 +1,65 @@
+import type { Settings } from "@fusion/core";
+import { activeSessionRegistry, executingTaskLock, reconcileSelfOwnedActiveSessionForRemoval, DEFAULT_SELF_OWNED_MIN_IDLE_MS, type LiveBindingProbe } from "../agents/active-session-registry.js";
+import { isPlanningLive } from "../agents/planning-liveness.js";
+import { ActiveSessionWorktreeRemovalError, removeWorktree, RemovalReason, type WorktreeRemoveOutcome } from "./worktree-backend.js";
+
+export interface RemoveTaskResetWorktreeInput {
+  worktreePath: string;
+  rootDir: string;
+  settings: Partial<Settings>;
+  taskId: string;
+  audit?: Parameters<typeof removeWorktree>[0]["audit"];
+  liveOwnerProbe?: LiveBindingProbe;
+  remove?: (input: Parameters<typeof removeWorktree>[0]) => Promise<WorktreeRemoveOutcome>;
+  now?: () => number;
+  wait?: (ms: number) => Promise<void>;
+}
+
+export class ResetWorktreeForeignSessionError extends Error {
+  constructor(public readonly details: { worktreePath: string; holderTaskId: string; holderKind: string }) {
+    super(`worktree ${details.worktreePath} is held by ${details.holderTaskId} (${details.holderKind})`);
+  }
+}
+
+/*
+FNXC:TaskReset 2026-08-22-04:45:
+The reset fence proves only registrations it released. A surviving self-owned entry still needs the normal idle and liveness gates: treating it as dead would let Reset remove a live planner worktree.
+*/
+export async function removeTaskResetWorktree(input: RemoveTaskResetWorktreeInput): Promise<WorktreeRemoveOutcome> {
+  const probe = input.liveOwnerProbe ?? ((_path: string, id: string) => executingTaskLock.has(id) || isPlanningLive(id));
+  const processActiveProbe = (id: string) => executingTaskLock.has(id);
+  const reconcile = () => reconcileSelfOwnedActiveSessionForRemoval(
+    activeSessionRegistry, input.worktreePath, input.taskId, probe, { processActiveProbe, now: input.now },
+  );
+  const reconcileForRemoval = async () => {
+    let outcome = reconcile();
+    if (outcome.action === "too-recent-refuses") {
+      const waitMs = Math.max(0, Math.min(DEFAULT_SELF_OWNED_MIN_IDLE_MS, outcome.minIdleMs - outcome.ageMs));
+      await (input.wait ?? ((ms) => new Promise<void>((resolve) => setTimeout(resolve, ms))))(waitMs);
+      outcome = reconcile();
+    }
+    if (outcome.action === "foreign-task") {
+      const record = activeSessionRegistry.lookupByPath(input.worktreePath);
+      throw new ResetWorktreeForeignSessionError({ worktreePath: input.worktreePath, holderTaskId: outcome.ownerTaskId, holderKind: record?.kind ?? "unknown" });
+    }
+    if (outcome.action === "live-binding-refuses" || outcome.action === "process-active-refuses" || outcome.action === "too-recent-refuses") {
+      const record = activeSessionRegistry.lookupByPath(input.worktreePath);
+      throw new ActiveSessionWorktreeRemovalError({ worktreePath: input.worktreePath, taskId: outcome.ownerTaskId, kind: record?.kind ?? "unknown", ownerKey: record?.ownerKey ?? "unknown", reason: RemovalReason.TaskReset });
+    }
+  };
+  await reconcileForRemoval();
+  const remove = input.remove ?? removeWorktree;
+  const options = {
+    worktreePath: input.worktreePath, rootDir: input.rootDir, settings: input.settings, taskId: input.taskId, audit: input.audit,
+    reason: RemovalReason.TaskReset, expectedOwnerTaskId: input.taskId, liveOwnerProbe: probe, processActiveProbe,
+  };
+  try {
+    return await remove(options);
+  } catch (error) {
+    if (!(error instanceof ActiveSessionWorktreeRemovalError) || error.details.taskId !== input.taskId) throw error;
+    // A new holder can appear after the first reconcile. Re-apply every normal gate before
+    // the sole retry; ignoring this result would turn a live or fresh registration into deletion.
+    await reconcileForRemoval();
+    return await remove(options);
+  }
+}