diff --git a/.changeset/fn-8945-lineage-approval-invalidation.md b/.changeset/fn-8945-lineage-approval-invalidation.md
new file mode 100644
index 0000000000..0068c0d867
--- /dev/null
+++ b/.changeset/fn-8945-lineage-approval-invalidation.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Keep approved plans accurate when parent task lineage is removed.
+category: fix
+dev: Parent delete and archive now invalidate approved lineage evidence atomically.
diff --git a/docs/architecture.md b/docs/architecture.md
index 62be8c05cf..de7f829daa 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -2385,6 +2385,12 @@ An accepted `PROMPT.md` is preserved as an immutable, project-scoped spec-lock.
 
 Each authoritative prompt write reaches `PROMPT.md` before its task-row approval invalidation, then serializes evidence capture and reconciliation under the planning lifecycle lock. Current-plan evidence structurally binds the live task dependency set plus mission, slice, and parent-task lineage IDs as well as the prompt sections, so a dependency or lineage mutation appends comparable evidence even when `PROMPT.md` bytes are unchanged. Manual approval and a successful workflow-graph Plan Review create/reuse the lock before publishing acceptance evidence consumed by scheduling. If evidence persistence is interrupted after the file/row write, the inactive task remains safely unreleased; startup or event reconciliation re-reads `PROMPT.md`, appends the missing comparable revision, and reports drift. Re-approval reuses identical content or appends a lock with a prior-version diff; a clean later lock after an earlier retained divergence reports `diverged-relocked-approved` rather than losing that history. Drift reports compare the latest lock with current evidence and execution file paths, producing only machine-observable `scope-creep`, `silent-expansion`, or `plan-deviation` findings. Added File Scope boundaries, dependencies, lineage, durable steps, and acceptance criteria are silent expansion; reordered steps and changed Mission hashes are plan deviation. Reports are retained independently of live task rows, so archive, cleanup, and unarchive retain operator history.
 
+Parent delete/archive with `removeLineageReferences:true` uses the same contract. It enters the invalidation boundary based on that flag even when its pre-read set is empty: the empty fast path skips prompt reads, probing, and locks but still revalidates inside the transaction, so a raced-in child aborts and retries once under its planning lock. One archive-lane value is resolved per operation and threaded through candidate reads and revalidation; delete retains resolved project archive lanes while archive retains its legacy `archived` lane semantics.
+
+Each attempt orders candidates → prompt map → structural transport probe → child locks → (archive workspace reservation → transaction → outcome → reconciliation). The transaction clears each affected child's parent binding and approved fingerprint, then resolves evidence from the pre-read prompt before committing. Evidence conflicts are classified by the matching `source_hash` row at any version (never only the latest row), and a reused row is accepted only after its canonical lineage is verified not to name the removed parent; an unresolvable or untruthful append raises `LineageEvidenceAppendError` and rolls the deletion/archive back. The only evidence-less commit is a child without a readable `PROMPT.md`; append-only history remains, so its report fences pre-existing, possibly stale evidence but cannot claim approved alignment after the fingerprint clear. The archive path pre-resolves prompts because filesystem reads never occur in its transaction.
+
+A session-scoped multi-key advisory lock covers every affected child, acquired in sorted order and nested under the parent task lock. Its callback publishes post-commit drift reconciliation before releasing those locks; lock acquisition failure occurs before archive workspace reservation, while an in-body failure releases its prepared reservation. Candidate revalidation is one retry only, then raises `LineageInvalidationCandidateRaceError`; no-clear gate rejection or lost delete claim publishes nothing. Structural pooler-only deployments may degrade serialization only after a pre-flight probe, but lock contention never degrades into an unlocked clear. Both channels reconcile through lock-free `reconcileSpecDriftWhilePlanningLocked`; report publication is the sole best-effort part. The transaction's resolved evidence version can differ from the report's `evaluateSpecDrift`-fenced latest evidence version; cleared approval, rather than evidence history removal, makes the report truthful.
+
 The evaluator fences the latest lock version, current-plan evidence version/hash, approval fingerprint, and execution fingerprint before insertion. A stale candidate is re-evaluated from a fresh snapshot; project-engine task create, update, and move events enqueue a coalesced fresh comparison, while failed report persistence schedules a retry and shutdown cancels queued work and timers. Read APIs derive `activeLock` from the live fingerprint and current-plan hash, and return a current report only when its lock/current-plan/approval identities match the latest snapshots; older reports remain history rather than falsely showing `on-plan` after a dependency or lineage invalidation. Reports and run-audit events store hashes, IDs, and fixed outcomes only, never prompt or Mission prose. Drift is neither an admission nor quality/completion decision and does not move or fail work.
 
 ## Durable intake executor ownership
diff --git a/packages/core/src/__tests__/postgres/lineage-approval-invalidation.pg.test.ts b/packages/core/src/__tests__/postgres/lineage-approval-invalidation.pg.test.ts
new file mode 100644
index 0000000000..25e0b5cd64
--- /dev/null
+++ b/packages/core/src/__tests__/postgres/lineage-approval-invalidation.pg.test.ts
@@ -0,0 +1,379 @@
+/*
+FNXC:SpecLockLineageInvalidation 2026-08-10-14:47:
+Parent removal changes a child's canonical lineage binding. The regression covers both lifecycle
+surfaces so neither may retain an active approval or report approved alignment after clearing it.
+`evaluateSpecDrift` fences reports to the latest current-plan evidence; source hashes include the
+canonical plan bindings, and listCurrentPlanEvidence is the row-enumeration API for this harness.
+
+FNXC:SpecLockLineageInvalidation 2026-08-10-15:37:
+Evidence-conflict coverage must exercise both legal idempotence shapes: a matching hash may be
+latest or historical, so classification must query that hash rather than inspect the latest row.
+A deliberately malformed matching snapshot also proves that hash identity never substitutes for
+verifying the stored lineage before committing a parent removal.
+*/
+import { afterAll, afterEach, beforeAll, beforeEach, expect, it, vi } from "vitest";
+import { rm, writeFile } from "node:fs/promises";
+import { join } from "node:path";
+import {
+  createSharedPgTaskStoreTestHarness,
+  pgDescribe,
+  type SharedPgTaskStoreHarness,
+} from "../../__test-utils__/pg-test-harness.js";
+import { storeLog, type TaskStore } from "../../store.js";
+import { PlanningLifecycleLockTransportError } from "../../postgres/advisory-locks.js";
+import { LineageEvidenceAppendError, type LineageInvalidationTestEvent } from "../../task-store/lineage-approval-invalidation.js";
+import { createCurrentPlanEvidence } from "../../planner/spec-lock.js";
+
+const SPEC_LOCK_PROMPT = `# Task
+
+## Mission
+
+Keep lineage scope observable.
+
+## File Scope
+
+- packages/core/src/task-store/async/async-lifecycle.ts
+
+## Steps
+
+1. Preserve evidence
+
+## Completion Criteria
+
+- [ ] Evidence is retained
+
+## Do NOT
+
+- Hide lineage changes
+
+## Dependencies
+
+- None
+`;
+
+pgDescribe("lineage approval invalidation", () => {
+  const h: SharedPgTaskStoreHarness = createSharedPgTaskStoreTestHarness({ prefix: "fusion_lineage_approval" });
+  let store: TaskStore;
+
+  beforeAll(h.beforeAll);
+  afterAll(h.afterAll);
+  beforeEach(async () => {
+    await h.beforeEach();
+    store = h.store();
+  });
+  afterEach(h.afterEach);
+
+  async function createApprovedLineagePair() {
+    const parent = await store.createTask({ description: "parent scope" });
+    const child = await store.createTask({
+      description: "approved child scope",
+      source: { sourceType: "api", sourceParentTaskId: parent.id },
+    });
+    await writeFile(join(store.taskDir(child.id), "PROMPT.md"), SPEC_LOCK_PROMPT);
+    const lock = await store.lockCurrentPlan(child.id, "approved-lineage-scope", SPEC_LOCK_PROMPT);
+    await store.updateTask(child.id, { approvedPlanFingerprint: "approved-lineage-scope" });
+    return { parent, child, lock };
+  }
+
+  it("invalidates approval and publishes a divergent report when parent lineage is removed by delete or archive", async () => {
+    for (const operation of ["delete", "archive"] as const) {
+      const { parent, child, lock } = await createApprovedLineagePair();
+    expect(lock.plan.sections.lineage.canonical).toContain(`parent-task:${parent.id}`);
+    expect(await store.getActiveSpecLock(child.id)).toBeDefined();
+
+    if (operation === "delete") {
+      await store.deleteTask(parent.id, { removeLineageReferences: true });
+    } else {
+      await store.archiveTask(parent.id, { cleanup: false, removeLineageReferences: true });
+    }
+
+    const [updated, activeLock, latestLock, evidence, report] = await Promise.all([
+      store.getTask(child.id),
+      store.getActiveSpecLock(child.id),
+      store.getLatestSpecLock(child.id),
+      store.getLatestCurrentPlanEvidence(child.id),
+      store.getLatestSpecDriftReport(child.id),
+    ]);
+    expect(updated?.sourceParentTaskId).toBeUndefined();
+    expect(updated?.approvedPlanFingerprint).toBeUndefined();
+    expect(activeLock).toBeUndefined();
+    expect(latestLock?.version).toBe(lock.version);
+    expect(evidence?.version).toBeGreaterThan(lock.currentPlanVersion);
+    expect(evidence?.plan.sections.lineage.canonical).not.toContain(`parent-task:${parent.id}`);
+    expect(report).toEqual(expect.objectContaining({
+      alignment: "diverged-needs-review",
+      currentPlanVersion: evidence?.version,
+    }));
+    expect(report?.approvedPlanFingerprint).toBeUndefined();
+    expect(report?.alignment).not.toBe("on-plan");
+    }
+  });
+
+  it("warns when a missing prompt is the sanctioned evidence-unavailable input", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const events: LineageInvalidationTestEvent[] = [];
+    const warn = vi.spyOn(storeLog, "warn").mockImplementation(() => undefined);
+    (store as unknown as { __lineageInvalidationForTest?: { onEvent: (event: LineageInvalidationTestEvent) => void } }).__lineageInvalidationForTest = {
+      onEvent: (event) => events.push(event),
+    };
+    await rm(join(store.taskDir(child.id), "PROMPT.md"));
+
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+
+    expect((await store.getTask(child.id))?.approvedPlanFingerprint).toBeUndefined();
+    expect(events.find((event) => event.kind === "outcome")).toMatchObject({
+      kind: "outcome", outcome: { evidenceUnavailableChildIds: [child.id], evidenceInsertAttempts: 0 },
+    });
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining(child.id));
+    warn.mockRestore();
+  });
+
+  async function appendPostClearEvidence(childId: string, version: number, prompt = SPEC_LOCK_PROMPT) {
+    const evidence = createCurrentPlanEvidence({
+      version,
+      sourceRevision: Date.now(),
+      capturedAt: new Date().toISOString(),
+      prompt,
+    });
+    return await store.appendCurrentPlanEvidence(childId, evidence);
+  }
+
+  it("reuses a verified latest matching source-hash evidence row without duplicating it", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const events: LineageInvalidationTestEvent[] = [];
+    const existing = await store.listCurrentPlanEvidence(child.id);
+    const matching = await appendPostClearEvidence(child.id, existing.at(-1)!.version + 1);
+    const before = await store.listCurrentPlanEvidence(child.id);
+    expect(matching.plan.sections.lineage.canonical).not.toContain(`parent-task:${parent.id}`);
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      onEvent: (event: LineageInvalidationTestEvent) => events.push(event),
+    };
+
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+
+    expect(await store.listCurrentPlanEvidence(child.id)).toEqual(before);
+    expect(events.find((event) => event.kind === "outcome")).toMatchObject({
+      kind: "outcome", outcome: { evidenceVersionByChild: new Map([[child.id, matching.version]]), evidenceInsertAttempts: 1 },
+    });
+  });
+
+  it("resolves a verified stale matching hash instead of comparing only the latest evidence", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const events: LineageInvalidationTestEvent[] = [];
+    const original = await store.listCurrentPlanEvidence(child.id);
+    const matching = await appendPostClearEvidence(child.id, original.at(-1)!.version + 1);
+    const newer = await appendPostClearEvidence(child.id, matching.version + 1, `${SPEC_LOCK_PROMPT}\n\n## Later revision\nDifferent evidence.`);
+    const before = await store.listCurrentPlanEvidence(child.id);
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      onEvent: (event: LineageInvalidationTestEvent) => events.push(event),
+    };
+
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+
+    expect(await store.listCurrentPlanEvidence(child.id)).toEqual(before);
+    const outcome = events.find((event) => event.kind === "outcome");
+    expect(outcome).toMatchObject({
+      kind: "outcome", outcome: { evidenceVersionByChild: new Map([[child.id, matching.version]]), evidenceInsertAttempts: 1 },
+    });
+    const report = await store.getLatestSpecDriftReport(child.id);
+    // The report fences to the latest row; the durable idempotence row may be older.
+    expect(report?.currentPlanVersion).toBe(newer.version);
+    expect(report?.alignment).toBe("diverged-needs-review");
+  });
+
+  it("rolls back an untruthful matching-hash row instead of accepting it by hash alone", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const existing = await store.listCurrentPlanEvidence(child.id);
+    const postClearPrompt = `${SPEC_LOCK_PROMPT}\n\n## Truthfulness fixture\nUnique source identity.`;
+    await writeFile(join(store.taskDir(child.id), "PROMPT.md"), postClearPrompt);
+    const truthful = createCurrentPlanEvidence({
+      version: existing.at(-1)!.version + 1,
+      sourceRevision: Date.now(),
+      capturedAt: new Date().toISOString(),
+      prompt: postClearPrompt,
+    });
+    const untruthful = {
+      ...truthful,
+      plan: {
+        ...truthful.plan,
+        sections: {
+          ...truthful.plan.sections,
+          lineage: { canonical: `parent-task:${parent.id}` },
+        },
+      },
+    };
+    await store.appendCurrentPlanEvidence(child.id, untruthful);
+    const before = await store.listCurrentPlanEvidence(child.id);
+
+    await expect(store.deleteTask(parent.id, { removeLineageReferences: true }))
+      .rejects.toMatchObject({ name: "LineageEvidenceAppendError", reason: "matched-row-not-truthful" } satisfies Partial<LineageEvidenceAppendError>);
+    expect((await store.getTask(parent.id))?.deletedAt).toBeUndefined();
+    expect((await store.getTask(child.id))?.sourceParentTaskId).toBe(parent.id);
+    expect((await store.getTask(child.id))?.approvedPlanFingerprint).toBe("approved-lineage-scope");
+    expect(await store.listCurrentPlanEvidence(child.id)).toEqual(before);
+  });
+
+  it("retries a forced evidence version collision and rolls back an unresolvable evidence append", async () => {
+    const collisionVersion = 99;
+    const events: LineageInvalidationTestEvent[] = [];
+    const { parent, child } = await createApprovedLineagePair();
+    // A disk-only prompt revision supplies a post-clear hash absent from approval-time evidence.
+    await writeFile(join(store.taskDir(child.id), "PROMPT.md"), `${SPEC_LOCK_PROMPT}\n\n## Collision target\nFresh lineage evidence.`);
+    await store.appendCurrentPlanEvidence(child.id, createCurrentPlanEvidence({
+      version: collisionVersion,
+      sourceRevision: Date.now(),
+      capturedAt: new Date().toISOString(),
+      prompt: `${SPEC_LOCK_PROMPT}\n\n## Collision fixture\nDifferent source hash.`,
+    }));
+    const beforeRetry = await store.listCurrentPlanEvidence(child.id);
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      evidenceTargetVersionForTest: (_childId: string, computed: number, attempt: number) => attempt === 0 ? collisionVersion : computed,
+      onEvent: (event: LineageInvalidationTestEvent) => events.push(event),
+    };
+
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+
+    const afterRetry = await store.listCurrentPlanEvidence(child.id);
+    expect(afterRetry).toHaveLength(beforeRetry.length + 1);
+    expect(afterRetry.at(-1)?.version).toBeGreaterThan(collisionVersion);
+    expect(events.find((event) => event.kind === "outcome")).toMatchObject({
+      kind: "outcome", outcome: { evidenceInsertAttempts: 2 },
+    });
+
+    const abortPair = await createApprovedLineagePair();
+    await writeFile(join(store.taskDir(abortPair.child.id), "PROMPT.md"), `${SPEC_LOCK_PROMPT}\n\n## Abort target\nFresh lineage evidence.`);
+    await store.appendCurrentPlanEvidence(abortPair.child.id, createCurrentPlanEvidence({
+      version: collisionVersion,
+      sourceRevision: Date.now(),
+      capturedAt: new Date().toISOString(),
+      prompt: `${SPEC_LOCK_PROMPT}\n\n## Permanent collision fixture\nDifferent source hash.`,
+    }));
+    const beforeAbort = await store.listCurrentPlanEvidence(abortPair.child.id);
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      evidenceTargetVersionForTest: () => collisionVersion,
+    };
+
+    await expect(store.archiveTask(abortPair.parent.id, { cleanup: false, removeLineageReferences: true }))
+      .rejects.toMatchObject({ name: "LineageEvidenceAppendError", reason: "no-durable-version" } satisfies Partial<LineageEvidenceAppendError>);
+    expect((await store.getTask(abortPair.parent.id))?.deletedAt).toBeUndefined();
+    expect((await store.getTask(abortPair.child.id))?.sourceParentTaskId).toBe(abortPair.parent.id);
+    expect((await store.getTask(abortPair.child.id))?.approvedPlanFingerprint).toBe("approved-lineage-scope");
+    expect(await store.listCurrentPlanEvidence(abortPair.child.id)).toEqual(beforeAbort);
+  });
+
+  it("retries a raced-in delete child and publishes before releasing all child locks", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const events: LineageInvalidationTestEvent[] = [];
+    let secondChildId: string | undefined;
+    (store as unknown as {
+      __lineageInvalidationForTest?: {
+        availability: () => { available: true };
+        withLocks: <T>(ids: readonly string[], callback: () => Promise<T>) => Promise<T>;
+        onEvent: (event: LineageInvalidationTestEvent) => void;
+      };
+      __beforeDeleteClaimForTest?: () => Promise<void>;
+    }).__lineageInvalidationForTest = {
+      availability: () => ({ available: true }),
+      async withLocks(_ids, callback) {
+        return await callback();
+      },
+      onEvent: (event) => events.push(event),
+    };
+    (store as unknown as { __beforeDeleteClaimForTest?: () => Promise<void> }).__beforeDeleteClaimForTest = async () => {
+      const second = await store.createTask({
+        description: "raced-in approved child",
+        source: { sourceType: "api", sourceParentTaskId: parent.id },
+      });
+      secondChildId = second.id;
+      await writeFile(join(store.taskDir(second.id), "PROMPT.md"), SPEC_LOCK_PROMPT);
+      await store.lockCurrentPlan(second.id, "raced-in-lineage-scope", SPEC_LOCK_PROMPT);
+      await store.updateTask(second.id, { approvedPlanFingerprint: "raced-in-lineage-scope" });
+    };
+
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+
+    expect(secondChildId).toBeDefined();
+    for (const id of [child.id, secondChildId!]) {
+      expect((await store.getTask(id))?.sourceParentTaskId).toBeUndefined();
+      expect((await store.getTask(id))?.approvedPlanFingerprint).toBeUndefined();
+      expect(await store.getActiveSpecLock(id)).toBeUndefined();
+    }
+    const acquisitions = events.filter((event) => event.kind === "acquire");
+    expect(acquisitions).toHaveLength(2);
+    expect(acquisitions[1]?.childIds).toEqual([child.id, secondChildId].sort());
+    const reconciles = events.filter((event) => event.kind === "reconcile");
+    expect(reconciles.map((event) => event.kind === "reconcile" ? event.childId : undefined).sort())
+      .toEqual([child.id, secondChildId].sort());
+  });
+
+  it("retries an archive child discovered inside its transaction and publishes before releasing its lock", async () => {
+    const parent = await store.createTask({ description: "archive lineage parent" });
+    const events: LineageInvalidationTestEvent[] = [];
+    let childId: string | undefined;
+    let injected = false;
+    (store as unknown as {
+      __lineageInvalidationForTest?: { onEvent: (event: LineageInvalidationTestEvent) => void };
+      __beforeArchiveLineageGateForTest?: () => Promise<void>;
+    }).__lineageInvalidationForTest = { onEvent: (event) => events.push(event) };
+    (store as unknown as { __beforeArchiveLineageGateForTest?: () => Promise<void> }).__beforeArchiveLineageGateForTest = async () => {
+      if (injected) return;
+      injected = true;
+      const child = await store.createTask({
+        description: "archive raced-in approved child",
+        source: { sourceType: "api", sourceParentTaskId: parent.id },
+      });
+      childId = child.id;
+      await writeFile(join(store.taskDir(child.id), "PROMPT.md"), SPEC_LOCK_PROMPT);
+      await store.lockCurrentPlan(child.id, "archive-raced-lineage-scope", SPEC_LOCK_PROMPT);
+      await store.updateTask(child.id, { approvedPlanFingerprint: "archive-raced-lineage-scope" });
+    };
+
+    await store.archiveTask(parent.id, { cleanup: false, removeLineageReferences: true });
+
+    expect(childId).toBeDefined();
+    const child = await store.getTask(childId!);
+    expect(child?.sourceParentTaskId).toBeUndefined();
+    expect(child?.approvedPlanFingerprint).toBeUndefined();
+    expect(await store.getActiveSpecLock(childId!)).toBeUndefined();
+    const outcomes = events.filter((event) => event.kind === "outcome");
+    expect(outcomes).toHaveLength(2);
+    expect(outcomes[0]).toMatchObject({ kind: "outcome", outcome: { candidateIds: [], clearedChildIds: [], evidenceInsertAttempts: 0 } });
+    expect(outcomes[1]).toMatchObject({ kind: "outcome", outcome: { candidateIds: [childId], clearedChildIds: [childId] } });
+    const acquire = events.findIndex((event) => event.kind === "acquire" && event.childIds.includes(childId!));
+    const reconcile = events.findIndex((event) => event.kind === "reconcile" && event.childId === childId);
+    const release = events.findIndex((event) => event.kind === "release" && event.childIds.includes(childId!));
+    expect(acquire).toBeGreaterThan(-1);
+    expect(reconcile).toBeGreaterThan(acquire);
+    expect(release).toBeGreaterThan(reconcile);
+  });
+
+  it("records lifecycle outcomes and uses structural degradation but never turns a lock acquisition failure into an unlocked delete", async () => {
+    const { parent, child } = await createApprovedLineagePair();
+    const degradedEvents: LineageInvalidationTestEvent[] = [];
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      availability: () => ({ available: false, reason: "direct-session-unavailable" }),
+      onEvent: (event: LineageInvalidationTestEvent) => degradedEvents.push(event),
+    };
+    await store.deleteTask(parent.id, { removeLineageReferences: true });
+    expect((await store.getTask(child.id))?.approvedPlanFingerprint).toBeUndefined();
+    expect(degradedEvents.some((event) => event.kind === "run" && event.degraded)).toBe(true);
+    expect(degradedEvents.some((event) => event.kind === "acquire")).toBe(false);
+    expect(degradedEvents.some((event) => event.kind === "reconcile" && event.childId === child.id)).toBe(true);
+
+    await h.beforeEach();
+    store = h.store();
+    const pair = await createApprovedLineagePair();
+    let ranBody = false;
+    (store as unknown as { __lineageInvalidationForTest?: unknown }).__lineageInvalidationForTest = {
+      availability: () => ({ available: true }),
+      withLocks: async () => { throw new PlanningLifecycleLockTransportError("contended"); },
+      onEvent: (event: LineageInvalidationTestEvent) => { if (event.kind === "run") ranBody = true; },
+    };
+    await expect(store.deleteTask(pair.parent.id, { removeLineageReferences: true }))
+      .rejects.toBeInstanceOf(PlanningLifecycleLockTransportError);
+    expect(ranBody).toBe(false);
+    expect((await store.getTask(pair.parent.id))?.deletedAt).toBeUndefined();
+    expect((await store.getTask(pair.child.id))?.sourceParentTaskId).toBe(pair.parent.id);
+    expect((await store.getTask(pair.child.id))?.approvedPlanFingerprint).toBe("approved-lineage-scope");
+  });
+});
diff --git a/packages/core/src/__tests__/postgres/planning-lifecycle-advisory-lock.pg.test.ts b/packages/core/src/__tests__/postgres/planning-lifecycle-advisory-lock.pg.test.ts
index a463b69772..bd9e29fce1 100644
--- a/packages/core/src/__tests__/postgres/planning-lifecycle-advisory-lock.pg.test.ts
+++ b/packages/core/src/__tests__/postgres/planning-lifecycle-advisory-lock.pg.test.ts
@@ -7,7 +7,9 @@ import {
 } from "../../__test-utils__/pg-test-harness.js";
 import {
   PlanningLifecycleLockTransportError,
+  planningLifecycleLockTransportAvailability,
   withPlanningLifecycleAdvisoryLock,
+  withPlanningLifecycleAdvisoryLocks,
 } from "../../postgres/advisory-locks.js";
 import { resolveBackendWithOptions } from "../../postgres/backend-resolver.js";
 
@@ -69,6 +71,62 @@ pgDescribe("planning lifecycle advisory lock", () => {
     expect(order).toEqual(["first-enter", "first-exit", "second-enter"]);
   });
 
+  it("shares key space with a single-key holder across a sorted multi-key session", async () => {
+    let releaseMulti!: () => void;
+    const multiCanFinish = new Promise<void>((resolve) => { releaseMulti = resolve; });
+    let multiEntered!: () => void;
+    const multiIsHolding = new Promise<void>((resolve) => { multiEntered = resolve; });
+    const multi = withPlanningLifecycleAdvisoryLocks({
+      projectId: "project-a",
+      taskIds: ["FN-2", "FN-1", "FN-2"],
+      directSessionUrl: h.testUrl(),
+      provenance: "migration-override",
+      runtimeUrl: h.testUrl(),
+      migrationUrl: h.testUrl(),
+      timeoutMs: 1_000,
+    }, async () => {
+      multiEntered();
+      await multiCanFinish;
+    });
+    await multiIsHolding;
+
+    let singleAttempted!: () => void;
+    const singleDispatched = new Promise<void>((resolve) => { singleAttempted = resolve; });
+    const single = lock("project-a", "FN-1", async () => {}, 1_000, singleAttempted);
+    await singleDispatched;
+    releaseMulti();
+    await Promise.all([multi, single]);
+  });
+
+  it("releases every multi-key lock when its callback fails", async () => {
+    await expect(withPlanningLifecycleAdvisoryLocks({
+      projectId: "project-a",
+      taskIds: ["FN-1", "FN-2"],
+      directSessionUrl: h.testUrl(),
+      provenance: "migration-override",
+      runtimeUrl: h.testUrl(),
+      migrationUrl: h.testUrl(),
+    }, async () => { throw new Error("callback failed"); })).rejects.toThrow("callback failed");
+
+    await Promise.all([
+      lock("project-a", "FN-1", async () => {}),
+      lock("project-a", "FN-2", async () => {}),
+    ]);
+  });
+
+  it("shares the structural availability predicate used by acquisition", () => {
+    expect(planningLifecycleLockTransportAvailability({
+      directSessionUrl: null,
+      provenance: null,
+    })).toEqual({ available: false, reason: "direct-session-unavailable" });
+    expect(planningLifecycleLockTransportAvailability({
+      directSessionUrl: h.testUrl(),
+      provenance: "migration-override",
+      runtimeUrl: h.testUrl(),
+      migrationUrl: h.testUrl(),
+    })).toEqual({ available: true });
+  });
+
   it("does not contend across project or task keys", async () => {
     let releaseFirst!: () => void;
     const firstCanFinish = new Promise<void>((resolve) => { releaseFirst = resolve; });
diff --git a/packages/core/src/__tests__/postgres/runtime-lifecycle-async.test.ts b/packages/core/src/__tests__/postgres/runtime-lifecycle-async.test.ts
index d7030d1d75..bdaaade61c 100644
--- a/packages/core/src/__tests__/postgres/runtime-lifecycle-async.test.ts
+++ b/packages/core/src/__tests__/postgres/runtime-lifecycle-async.test.ts
@@ -269,6 +269,7 @@ pgDescribe("runtime-lifecycle-async: deleteTask lineage gate (PostgreSQL)", () =
         createdAt: new Date().toISOString(),
         updatedAt: new Date().toISOString(),
         sourceParentTaskId: "FN-PARENT2",
+        approvedPlanFingerprint: "approved-lineage-scope",
         status: null,
       } as never,
       { lineageId: "test" },
@@ -284,5 +285,8 @@ pgDescribe("runtime-lifecycle-async: deleteTask lineage gate (PostgreSQL)", () =
       .where(eq(schema.project.tasks.id, "FN-PARENT2"));
     expect(rows.length).toBe(1);
     expect(rows[0].deletedAt).not.toBeNull();
+    const child = await h.store.getTask("FN-CHILD2");
+    expect(child.sourceParentTaskId).toBeUndefined();
+    expect(child.approvedPlanFingerprint).toBeUndefined();
   });
 });
diff --git a/packages/core/src/__tests__/postgres/taskstore-lifecycle.test.ts b/packages/core/src/__tests__/postgres/taskstore-lifecycle.test.ts
index 67a900b164..1b09288f45 100644
--- a/packages/core/src/__tests__/postgres/taskstore-lifecycle.test.ts
+++ b/packages/core/src/__tests__/postgres/taskstore-lifecycle.test.ts
@@ -219,7 +219,8 @@ pgDescribe("U13 taskstore-lifecycle (PostgreSQL)", () => {
       const childIds = await findLiveLineageChildren(tx, "KB-PARENT");
       expect(childIds).toEqual(["KB-CHILD"]);
       const cleared = await removeLineageReferences(tx, "KB-PARENT", childIds, nowIso);
-      expect(cleared).toBe(1);
+      expect(cleared.clearedChildIds).toEqual(["KB-CHILD"]);
+      expect(cleared.evidenceUnavailableChildIds).toEqual(["KB-CHILD"]);
     });
 
     // After: gate passes (no live children).
diff --git a/packages/core/src/postgres/advisory-locks.ts b/packages/core/src/postgres/advisory-locks.ts
index 6909943706..0de4658213 100644
--- a/packages/core/src/postgres/advisory-locks.ts
+++ b/packages/core/src/postgres/advisory-locks.ts
@@ -30,9 +30,40 @@ export class PlanningLifecycleLockTransportError extends Error {
   }
 }
 
-const DEFAULT_PLANNING_LIFECYCLE_LOCK_TIMEOUT_MS = 5_000;
+export const DEFAULT_PLANNING_LIFECYCLE_LOCK_TIMEOUT_MS = 5_000;
 
 type DedicatedPostgresClient = ReturnType<typeof postgres>;
+type PlanningLifecycleLockInput = {
+  projectId: string;
+  taskId: string;
+  directSessionUrl: string | null;
+  provenance: "embedded-lifecycle" | "migration-override" | "runtime-direct" | null;
+  runtimeUrl?: string | null;
+  migrationUrl?: string | null;
+  timeoutMs?: number;
+  onLockAcquisitionAttempt?: () => void;
+};
+
+/** Side-effect-free structural check shared by the lineage degrade path and lock acquisition. */
+export function planningLifecycleLockTransportAvailability(input: Pick<PlanningLifecycleLockInput, "directSessionUrl" | "provenance" | "runtimeUrl" | "migrationUrl">): { available: true } | { available: false; reason: string } {
+  const directUrl = input.directSessionUrl;
+  if (!directUrl || !input.provenance || looksLikePoolerUrl(directUrl)) return { available: false, reason: "direct-session-unavailable" };
+  let directDatabase: string;
+  try { directDatabase = decodeURIComponent(new URL(directUrl).pathname.replace(/^\//, "")); } catch { return { available: false, reason: "direct-session-invalid" }; }
+  if (!directDatabase) return { available: false, reason: "direct-session-database-missing" };
+  const descriptorEndpoint = input.provenance === "embedded-lifecycle" || input.provenance === "runtime-direct" ? input.runtimeUrl : input.migrationUrl;
+  if (!descriptorEndpoint || descriptorEndpoint !== directUrl) return { available: false, reason: "backend-descriptor-mismatch" };
+  const operationalUrl = input.runtimeUrl ?? input.migrationUrl;
+  if (operationalUrl) {
+    try {
+      const operationalDatabase = decodeURIComponent(new URL(operationalUrl).pathname.replace(/^\//, ""));
+      if (!operationalDatabase || operationalDatabase !== directDatabase) return { available: false, reason: "backend-database-mismatch" };
+    } catch { return { available: false, reason: "backend-endpoint-invalid" }; }
+  }
+  return { available: true };
+}
+
+const planningLifecycleLockKey = (projectId: string, taskId: string): string => `fusion:planning-lifecycle:${projectId}:${taskId}`;
 type PostgresBackendIdentity = {
   database: string;
   host: string | null;
@@ -85,53 +116,17 @@ async function runBoundedTransportPhase<T>(
  * lock and unlock and silently defeat session advisory locking.
  */
 export async function withPlanningLifecycleAdvisoryLock<T>(
-  input: {
-    projectId: string;
-    taskId: string;
-    directSessionUrl: string | null;
-    provenance: "embedded-lifecycle" | "migration-override" | "runtime-direct" | null;
-    runtimeUrl?: string | null;
-    migrationUrl?: string | null;
-    /** Bounds dedicated-session setup and lock acquisition, not callback work. */
-    timeoutMs?: number;
-    /** @internal Test seam fired when the driver dispatches the lock query. */
-    onLockAcquisitionAttempt?: () => void;
-  },
+  input: PlanningLifecycleLockInput,
   callback: () => Promise<T>,
 ): Promise<T> {
-  const directUrl = input.directSessionUrl;
-  const timeoutMs = Math.max(1, input.timeoutMs ?? DEFAULT_PLANNING_LIFECYCLE_LOCK_TIMEOUT_MS);
-  if (!directUrl || !input.provenance || looksLikePoolerUrl(directUrl)) {
-    throw new PlanningLifecycleLockTransportError("Planning lifecycle lock requires a direct PostgreSQL session endpoint; set DATABASE_MIGRATION_URL to a direct, non-pooled connection");
-  }
-
-  let directDatabase: string;
-  try {
-    directDatabase = decodeURIComponent(new URL(directUrl).pathname.replace(/^\//, ""));
-  } catch {
-    throw new PlanningLifecycleLockTransportError("Planning lifecycle lock has an invalid direct PostgreSQL session endpoint");
-  }
-  if (!directDatabase) {
-    throw new PlanningLifecycleLockTransportError("Planning lifecycle lock direct endpoint must select a database");
-  }
-  const descriptorEndpoint = input.provenance === "embedded-lifecycle" || input.provenance === "runtime-direct"
-    ? input.runtimeUrl
-    : input.migrationUrl;
-  if (!descriptorEndpoint || descriptorEndpoint !== directUrl) {
-    throw new PlanningLifecycleLockTransportError("Planning lifecycle lock endpoint does not match the resolved backend descriptor");
+  const availability = planningLifecycleLockTransportAvailability(input);
+  if (!availability.available) {
+    throw new PlanningLifecycleLockTransportError(`Planning lifecycle lock transport unavailable: ${availability.reason}`);
   }
+  const directUrl = input.directSessionUrl!;
+  const directDatabase = decodeURIComponent(new URL(directUrl).pathname.replace(/^\//, ""));
   const operationalUrl = input.runtimeUrl ?? input.migrationUrl;
-  if (operationalUrl) {
-    try {
-      const operationalDatabase = decodeURIComponent(new URL(operationalUrl).pathname.replace(/^\//, ""));
-      if (!operationalDatabase || operationalDatabase !== directDatabase) {
-        throw new PlanningLifecycleLockTransportError("Planning lifecycle lock endpoint selects a different database than the resolved backend");
-      }
-    } catch (error) {
-      if (error instanceof PlanningLifecycleLockTransportError) throw error;
-      throw new PlanningLifecycleLockTransportError("Resolved backend has an invalid PostgreSQL endpoint");
-    }
-  }
+  const timeoutMs = Math.max(1, input.timeoutMs ?? DEFAULT_PLANNING_LIFECYCLE_LOCK_TIMEOUT_MS);
 
   const client = postgres(directUrl, {
     max: 1,
@@ -144,7 +139,7 @@ export async function withPlanningLifecycleAdvisoryLock<T>(
         }
       : undefined,
   });
-  const key = `fusion:planning-lifecycle:${input.projectId}:${input.taskId}`;
+  const key = planningLifecycleLockKey(input.projectId, input.taskId);
   let acquired = false;
   try {
     /*
@@ -231,3 +226,82 @@ export async function withPlanningLifecycleAdvisoryLock<T>(
     }
   }
 }
+
+/**
+ * FNXC:SpecLockLineageInvalidation 2026-08-10-14:33:
+ * Parent removal can affect many children, but no child may be cleared outside its planning lock.
+ * Advisory locks are session-scoped, so this acquires every sorted task key on one dedicated session
+ * instead of trading correctness for a fan-out cap or opening one connection per child.
+ */
+export async function withPlanningLifecycleAdvisoryLocks<T>(
+  input: Omit<PlanningLifecycleLockInput, "taskId"> & { taskIds: readonly string[] },
+  callback: () => Promise<T>,
+): Promise<T> {
+  const taskIds = [...new Set(input.taskIds)].sort();
+  if (taskIds.length === 0) return callback();
+  const availability = planningLifecycleLockTransportAvailability(input);
+  if (!availability.available) throw new PlanningLifecycleLockTransportError(`Planning lifecycle lock transport unavailable: ${availability.reason}`);
+  const directUrl = input.directSessionUrl!;
+  const timeoutMs = Math.max(1, input.timeoutMs ?? DEFAULT_PLANNING_LIFECYCLE_LOCK_TIMEOUT_MS);
+  const directDatabase = decodeURIComponent(new URL(directUrl).pathname.replace(/^\//, ""));
+  const operationalUrl = input.runtimeUrl ?? input.migrationUrl;
+  const client = postgres(directUrl, {
+    max: 1, connect_timeout: Math.max(1, Math.ceil(timeoutMs / 1_000)), prepare: false, onnotice: () => {},
+    debug: input.onLockAcquisitionAttempt ? (_connection, query) => { if (query.includes("pg_advisory_lock(")) input.onLockAcquisitionAttempt?.(); } : undefined,
+  });
+  const keys = taskIds.map((taskId) => planningLifecycleLockKey(input.projectId, taskId));
+  const acquired: string[] = [];
+  try {
+    const identity = await runBoundedTransportPhase(client, timeoutMs, `Planning lifecycle lock session setup timed out after ${timeoutMs}ms`, "Planning lifecycle lock could not establish its dedicated session", async () => {
+      const rows = await readPostgresBackendIdentity(client);
+      await client`SELECT set_config('lock_timeout', ${`${timeoutMs}ms`}, false)`;
+      return rows;
+    });
+    if (identity[0]?.database !== directDatabase) throw new PlanningLifecycleLockTransportError("Planning lifecycle lock session selected an unexpected database");
+
+    /*
+    FNXC:SpecLockLineageInvalidation 2026-08-10-14:47:
+    The multi-key session must prove the same resolved backend identity as the single-key lock.
+    Matching advisory key strings on a different PostgreSQL server would serialize nothing.
+    */
+    if (operationalUrl && operationalUrl !== directUrl) {
+      const operationalClient = postgres(operationalUrl, {
+        max: 1,
+        connect_timeout: Math.max(1, Math.ceil(timeoutMs / 1_000)),
+        prepare: false,
+        onnotice: () => {},
+      });
+      try {
+        const operationalIdentity = await runBoundedTransportPhase(
+          operationalClient,
+          timeoutMs,
+          `Planning lifecycle lock backend identity check timed out after ${timeoutMs}ms`,
+          "Planning lifecycle lock could not verify the resolved backend server identity",
+          () => readPostgresBackendIdentity(operationalClient),
+        );
+        const expected = operationalIdentity[0];
+        const actual = identity[0];
+        if (!expected || !actual
+          || expected.database !== actual.database
+          || expected.host !== actual.host
+          || expected.port !== actual.port
+          || (expected.cluster && actual.cluster && expected.cluster !== actual.cluster)) {
+          throw new PlanningLifecycleLockTransportError("Planning lifecycle lock endpoint targets a different PostgreSQL server than the resolved backend");
+        }
+      } catch (error) {
+        if (error instanceof PlanningLifecycleLockTransportError) throw error;
+        throw new PlanningLifecycleLockTransportError("Planning lifecycle lock could not verify the resolved backend server identity");
+      } finally {
+        await operationalClient.end({ timeout: 5 }).catch(() => undefined);
+      }
+    }
+    for (const key of keys) {
+      await runBoundedTransportPhase(client, timeoutMs, `Planning lifecycle lock acquisition timed out after ${timeoutMs}ms`, "Planning lifecycle lock acquisition failed", () => client`SELECT pg_advisory_lock(hashtext(${key}))`);
+      acquired.push(key);
+    }
+    return await callback();
+  } finally {
+    for (const key of acquired.reverse()) await runBoundedTransportPhase(client, timeoutMs, `Planning lifecycle lock cleanup timed out after ${timeoutMs}ms`, "Planning lifecycle lock cleanup failed", () => client`SELECT pg_advisory_unlock(hashtext(${key}))`).catch(() => undefined);
+    await client.end({ timeout: 5 }).catch(() => undefined);
+  }
+}
diff --git a/packages/core/src/store.ts b/packages/core/src/store.ts
index e2699cb813..0d5cf6a46d 100644
--- a/packages/core/src/store.ts
+++ b/packages/core/src/store.ts
@@ -78,7 +78,7 @@ import { GlobalSettingsStore } from "./config/global-settings.js";
 import { Database } from "./db/db.js";
 import { ArchiveDatabase } from "./db/archive-db.js";
 import { projectScopeFor, type AsyncDataLayer, type DbTransaction } from "./postgres/data-layer.js";
-import { withPlanningLifecycleAdvisoryLock } from "./postgres/advisory-locks.js";
+import { planningLifecycleLockTransportAvailability, withPlanningLifecycleAdvisoryLock, withPlanningLifecycleAdvisoryLocks } from "./postgres/advisory-locks.js";
 import { MissionStore } from "./missions/mission-store.js";
 import { AsyncMissionStore } from "./async-stores/async-mission-store.js";
 import { AsyncIdeationStore } from "./async-stores/async-ideation-store.js";
@@ -891,6 +891,30 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       if (planningLifecycleLocks.get(key) === current) planningLifecycleLocks.delete(key);
     }
   }
+  /** Acquire all child planning keys in deterministic order without a fan-out connection cost. */
+  public async withPlanningLifecycleLocks<T>(ids: readonly string[], fn: () => Promise<T>): Promise<T> {
+    const sorted = [...new Set(ids)].sort();
+    if (sorted.length === 0) return fn();
+    const backend = this.asyncLayer?.backend;
+    if (this.asyncLayer && backend) {
+      return withPlanningLifecycleAdvisoryLocks({
+        projectId: this.asyncLayer.projectId ?? this.rootDir,
+        taskIds: sorted,
+        directSessionUrl: backend.directSessionUrl ?? null,
+        provenance: backend.directSessionProvenance ?? null,
+        runtimeUrl: backend.runtimeUrl,
+        migrationUrl: backend.migrationUrl,
+      }, fn);
+    }
+    const acquire = async (index: number): Promise<T> => index === sorted.length ? fn() : this.withPlanningLifecycleLock(sorted[index]!, () => acquire(index + 1));
+    return acquire(0);
+  }
+  public planningLifecycleLockTransportAvailability(): { available: true } | { available: false; reason: string } {
+    const backend = this.asyncLayer?.backend;
+    if (!this.asyncLayer || !backend) return { available: true };
+    return planningLifecycleLockTransportAvailability({ directSessionUrl: backend.directSessionUrl ?? null, provenance: backend.directSessionProvenance ?? null, runtimeUrl: backend.runtimeUrl, migrationUrl: backend.migrationUrl });
+  }
+
   public getTaskIdFromDir(dir: string): string {
     return getTaskIdFromDirImpl(this, dir);
   }
diff --git a/packages/core/src/task-store/archive-lifecycle-2.ts b/packages/core/src/task-store/archive-lifecycle-2.ts
index b06610c019..22bfccadde 100644
--- a/packages/core/src/task-store/archive-lifecycle-2.ts
+++ b/packages/core/src/task-store/archive-lifecycle-2.ts
@@ -26,7 +26,8 @@ import {sanitizeFileScopeInPromptContent} from "../task-store/file-scope.js";
 import {__setTaskActivityLogLimitsForTesting} from "../task-store/comments.js";
 import {softDeleteTaskRowInTransaction, readTaskRow as readTaskRowAsync, readTaskRowInTransaction} from "../task-store/async/async-persistence.js";
 import {appendTaskLifecycleEventInTransaction} from "../task-store/lifecycle-outbox.js";
-import {findLiveLineageChildren as findLiveLineageChildrenAsync, projectPartition, removeLineageReferences} from "../task-store/async/async-lifecycle.js";
+import {findLiveLineageChildren as findLiveLineageChildrenAsync, projectPartition, removeLineageReferences, type LineageRemovalOutcome} from "../task-store/async/async-lifecycle.js";
+import { classifyLineageInvalidationOutcomeError, lineageEvidenceTargetVersionForTest, recordLineageInvalidationOutcome, reconcileClearedLineageChildren, resolveAndAssertLineageCandidatesUnchanged, runLineageInvalidation } from "../task-store/lineage-approval-invalidation.js";
 import { resolveProjectColumnsForRoles } from "../project-lane-vocabulary.js";
 import {archiveParentTaskWithLineageGate, findArchivedTaskEntry, deleteArchivedTaskEntry, restoreTaskFromArchive} from "../task-store/async/async-archive-lineage.js";
 import {getArchivedRowCount, listArchivedTaskEntriesPage} from "../async-stores/async-archive-db.js";
@@ -190,7 +191,11 @@ async function deleteTaskBackendWithClaimResultImpl(store: TaskStore, id: string
     await (store as unknown as { __beforeDeleteClaimForTest?: (taskId: string) => void | Promise<void> }).__beforeDeleteClaimForTest?.(id);
 
     // Soft-delete + lineage clear + mission unlink + audit in one transaction (atomicity).
-    const deletion = await layer.transactionImmediate(async (tx) => {
+    const executeDelete = async (context?: { candidateIds: string[]; promptByChildId: ReadonlyMap<string, string>; locksHeld: boolean; attempt: number }) => {
+    let deletion: DeleteTaskClaimResult & { lineageOutcome: LineageRemovalOutcome };
+    try {
+      deletion = await layer.transactionImmediate(async (tx) => {
+      if (context) await resolveAndAssertLineageCandidatesUnchanged(tx, id, layer.projectId, lineageArchivedLanes, context.candidateIds);
       /*
       FNXC:LifecycleOutbox 2026-08-01-10:33:
       The pre-transaction deletedAt read is a cross-process TOCTOU window. A conditional
@@ -201,12 +206,12 @@ async function deleteTaskBackendWithClaimResultImpl(store: TaskStore, id: string
       if (claimed === false) {
         const reloaded = await readTaskRowInTransaction(tx, id, { includeDeleted: true }, projectId);
         if (!reloaded) throw new TaskNotFoundError(id);
-        return { claimed: false, task: store.rowToTask(store.pgRowToTaskRow(reloaded)) };
-      }
-      // Clear lineage references on live children so the parent can be deleted.
-      if (lineageChildIds.length > 0) {
-        await removeLineageReferences(tx, id, lineageChildIds, deletedAt, layer.projectId);
+        return { claimed: false, task: store.rowToTask(store.pgRowToTaskRow(reloaded)), lineageOutcome: { clearedChildIds: [] as string[], evidenceVersionByChild: new Map<string, number>(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 } };
       }
+      // Clear lineage references and approval only after locked candidates were revalidated.
+      const lineageOutcome = context
+        ? await removeLineageReferences(tx, id, context.candidateIds, deletedAt, layer.projectId, context.promptByChildId, lineageEvidenceTargetVersionForTest(store))
+        : { clearedChildIds: [], evidenceVersionByChild: new Map<string, number>(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 };
       /*
       FNXC:MissionStore 2026-07-17-17:40:
       Clear any mission feature→task link IN THIS TRANSACTION so it commits (or rolls
@@ -281,8 +286,32 @@ async function deleteTaskBackendWithClaimResultImpl(store: TaskStore, id: string
       // callers so neither receives the pre-claim live snapshot after a successful delete.
       const reloaded = await readTaskRowInTransaction(tx, id, { includeDeleted: true }, projectId);
       if (!reloaded) throw new TaskNotFoundError(id);
-      return { claimed: true, task: store.rowToTask(store.pgRowToTaskRow(reloaded)) };
+      return { claimed: true, task: store.rowToTask(store.pgRowToTaskRow(reloaded)), lineageOutcome };
     });
+    } catch (error) {
+      if (context) recordLineageInvalidationOutcome(store, {
+        attempt: context.attempt, locksHeld: context.locksHeld, degraded: !context.locksHeld,
+        candidateIds: context.candidateIds, clearedChildIds: [], evidenceVersionByChild: new Map(),
+        evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0,
+        error: classifyLineageInvalidationOutcomeError(error),
+      });
+      throw error;
+    }
+      if (context) {
+        recordLineageInvalidationOutcome(store, {
+          attempt: context.attempt, locksHeld: context.locksHeld, degraded: !context.locksHeld,
+          candidateIds: context.candidateIds, clearedChildIds: deletion.lineageOutcome.clearedChildIds,
+          evidenceVersionByChild: deletion.lineageOutcome.evidenceVersionByChild,
+          evidenceUnavailableChildIds: deletion.lineageOutcome.evidenceUnavailableChildIds,
+          evidenceInsertAttempts: deletion.lineageOutcome.evidenceInsertAttempts,
+        });
+        await reconcileClearedLineageChildren(store, deletion.lineageOutcome.clearedChildIds, { locksHeld: context.locksHeld });
+      }
+      return deletion;
+    };
+    const deletion = options?.removeLineageReferences
+      ? await runLineageInvalidation(store, id, { archivedColumns: lineageArchivedLanes, initialCandidateIds: lineageChildIds }, executeDelete)
+      : await executeDelete();
 
     if (!deletion.claimed) return deletion;
 
@@ -396,31 +425,61 @@ export async function archiveTaskBackendImpl(store: TaskStore, id: string, optio
     const entry = await store.taskToArchiveEntry(task, archivedAt);
 
     /*
-    FNXC:WorkflowLifecycle 2026-07-16-15:30:
-    Backend archive persists cold storage before its cleanup phase. Hold the
-    per-repository reservations across that transaction so another process sees
-    the path as unavailable until the awaited workspace disposer has removed it.
+    FNXC:SpecLockLineageInvalidation 2026-08-10-14:33:
+    Archive keeps its legacy archived-lane semantics (undefined -> "archived") but threads that
+    one value through pre-read and gate. The workspace reservation is created inside the locked body.
     */
-    const preparedWorkspace = cleanup ? await prepareArchivedWorkspaceWorktrees(store, task) : undefined;
-    let result;
-    try {
-      // Lineage gate + archive in one transaction.
-      result = await archiveParentTaskWithLineageGate(layer, id, entry, {
-        removeLineageReferences: removeLineageRefs,
-        now: archivedAt,
-        beforeArchive: async (tx) => {
-          const linkedFeature = await getMissionFeatureByTaskId(tx, id);
-          if (linkedFeature) {
-            await recordGeneratedFixOperatorStop(tx, linkedFeature, "task-archive");
-            await unlinkMissionFeatureFromTaskId(tx, linkedFeature.id);
-          }
-        },
-      });
-    } catch (error) {
-      if (preparedWorkspace) await releasePreparedWorkspaceArchiveDisposal(preparedWorkspace);
-      throw error;
-    }
-
+    const archiveLineageArchivedLanes: ReadonlySet<string> | undefined = undefined;
+    const archiveRun = async (context?: { candidateIds: string[]; promptByChildId: ReadonlyMap<string, string>; locksHeld: boolean; attempt: number }) => {
+      const preparedWorkspace = cleanup ? await prepareArchivedWorkspaceWorktrees(store, task) : undefined;
+      try {
+        const result = await archiveParentTaskWithLineageGate(layer, id, entry, {
+          removeLineageReferences: removeLineageRefs,
+          now: archivedAt,
+          archivedColumns: archiveLineageArchivedLanes,
+          ...(context ? {
+            revalidateAgainst: context.candidateIds,
+            promptByChildId: context.promptByChildId,
+            evidenceTargetVersionForTest: lineageEvidenceTargetVersionForTest(store),
+            beforeLineageGate: (store as unknown as { __beforeArchiveLineageGateForTest?: () => void | Promise<void> }).__beforeArchiveLineageGateForTest,
+          } : {}),
+          beforeArchive: async (tx) => {
+            const linkedFeature = await getMissionFeatureByTaskId(tx, id);
+            if (linkedFeature) {
+              await recordGeneratedFixOperatorStop(tx, linkedFeature, "task-archive");
+              await unlinkMissionFeatureFromTaskId(tx, linkedFeature.id);
+            }
+          },
+        });
+        // Reconcile only rows the guarded UPDATE actually cleared; candidates can reparent away.
+        if (context) {
+          const lineageOutcome = result.archived
+            ? result.lineageOutcome ?? { clearedChildIds: [], evidenceVersionByChild: new Map<string, number>(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 }
+            : { clearedChildIds: [], evidenceVersionByChild: new Map<string, number>(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 };
+          recordLineageInvalidationOutcome(store, {
+            attempt: context.attempt, locksHeld: context.locksHeld, degraded: !context.locksHeld,
+            candidateIds: context.candidateIds, ...lineageOutcome,
+            ...(result.archived ? {} : { error: "gate-rejected" as const }),
+          });
+          if (result.archived) await reconcileClearedLineageChildren(store, lineageOutcome.clearedChildIds, { locksHeld: context.locksHeld });
+        }
+        return { result, preparedWorkspace };
+      } catch (error) {
+        if (context) recordLineageInvalidationOutcome(store, {
+          attempt: context.attempt, locksHeld: context.locksHeld, degraded: !context.locksHeld,
+          candidateIds: context.candidateIds, clearedChildIds: [], evidenceVersionByChild: new Map(),
+          evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0,
+          error: classifyLineageInvalidationOutcomeError(error),
+        });
+        if (preparedWorkspace) await releasePreparedWorkspaceArchiveDisposal(preparedWorkspace);
+        throw error;
+      }
+    };
+    const archiveExecution = removeLineageRefs
+      ? await runLineageInvalidation(store, id, { archivedColumns: archiveLineageArchivedLanes }, archiveRun)
+      : await archiveRun();
+    const result = archiveExecution.result;
+    const preparedWorkspace = archiveExecution.preparedWorkspace;
     if (!result.archived) {
       if (preparedWorkspace) await releasePreparedWorkspaceArchiveDisposal(preparedWorkspace);
       throw new TaskHasLineageChildrenError(id, result.liveChildIds);
diff --git a/packages/core/src/task-store/async/async-archive-lineage.ts b/packages/core/src/task-store/async/async-archive-lineage.ts
index 9aaf4210f8..9eff02fbf8 100644
--- a/packages/core/src/task-store/async/async-archive-lineage.ts
+++ b/packages/core/src/task-store/async/async-archive-lineage.ts
@@ -32,7 +32,8 @@ import { and, desc, eq, inArray, sql } from "drizzle-orm";
 import * as schema from "../../postgres/schema/index.js";
 import type { AsyncDataLayer, DbTransaction } from "../../postgres/data-layer.js";
 import { ACTIVE_TASK_FILTER } from "./async-persistence.js";
-import { findLiveLineageChildren, projectPartition, removeLineageReferences } from "./async-lifecycle.js";
+import { findLiveLineageChildren, projectPartition, removeLineageReferences, type LineageRemovalOutcome } from "./async-lifecycle.js";
+import { assertLineageCandidatesUnchanged } from "../lineage-approval-invalidation.js";
 import {
   softDeleteTaskRowInTransaction,
   readTaskRowInTransaction,
@@ -236,21 +237,25 @@ export async function archiveParentTaskWithLineageGate(
   layer: AsyncDataLayer,
   taskId: string,
   entry: ArchivedTaskEntry,
-  options: { removeLineageReferences?: boolean; now?: string; beforeArchive?: (tx: DbTransaction) => Promise<void> } = {},
-): Promise<{ archived: true } | { archived: false; liveChildIds: string[] }> {
+  options: { removeLineageReferences?: boolean; now?: string; beforeArchive?: (tx: DbTransaction) => Promise<void>; beforeLineageGate?: () => void | Promise<void>; archivedColumns?: ReadonlySet<string>; revalidateAgainst?: readonly string[]; promptByChildId?: ReadonlyMap<string, string>; evidenceTargetVersionForTest?: (childId: string, computed: number, attempt: number) => number } = {},
+
+): Promise<{ archived: true; lineageOutcome?: LineageRemovalOutcome } | { archived: false; liveChildIds: string[] }> {
   const now = options.now ?? new Date().toISOString();
 
   return layer.transactionImmediate(async (tx) => {
+    // Test-only barrier is before this operation's single in-transaction lineage read.
+    await options.beforeLineageGate?.();
     // 1. Lineage gate — check for live children inside the transaction.
-    const liveChildIds = await findLiveLineageChildren(tx, taskId, layer.projectId);
+    const liveChildIds = await findLiveLineageChildren(tx, taskId, layer.projectId, options.archivedColumns);
     if (liveChildIds.length > 0 && !options.removeLineageReferences) {
       return { archived: false as const, liveChildIds };
     }
 
-    // 2. Lineage clear (if requested and there are live children).
-    if (liveChildIds.length > 0 && options.removeLineageReferences) {
-      await removeLineageReferences(tx, taskId, liveChildIds, now, layer.projectId);
-    }
+    if (options.removeLineageReferences && options.revalidateAgainst !== undefined) assertLineageCandidatesUnchanged(liveChildIds, options.revalidateAgainst);
+    // 2. Lineage clear only for candidates whose planning locks this attempt holds.
+    const lineageOutcome = options.removeLineageReferences
+      ? await removeLineageReferences(tx, taskId, options.revalidateAgainst ?? liveChildIds, now, layer.projectId, options.promptByChildId, options.evidenceTargetVersionForTest)
+      : { clearedChildIds: [], evidenceVersionByChild: new Map<string, number>(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 };
 
     /*
     FNXC:MissionLineageBudget 2026-07-22-15:00:
@@ -275,7 +280,11 @@ export async function archiveParentTaskWithLineageGate(
     //    breaking atomicity (a later rollback left the soft-delete persisted).
     await softDeleteTaskRowInTransaction(tx, taskId, now, false, layer.projectId);
 
-    return { archived: true as const };
+    // Preserve the public legacy success shape for direct callers; only the serialized boundary
+    // supplies revalidation and needs the actual-clear outcome for post-commit reconciliation.
+    return options.revalidateAgainst === undefined
+      ? { archived: true as const }
+      : { archived: true as const, lineageOutcome };
   });
 }
 
diff --git a/packages/core/src/task-store/async/async-lifecycle.ts b/packages/core/src/task-store/async/async-lifecycle.ts
index c0220ce6f1..1fb63cade4 100644
--- a/packages/core/src/task-store/async/async-lifecycle.ts
+++ b/packages/core/src/task-store/async/async-lifecycle.ts
@@ -27,10 +27,12 @@
  *   integration tests consume. They program against the stable `AsyncDataLayer`
  *   interface (U4), not the underlying driver.
  */
-import { and, eq, ne, sql } from "drizzle-orm";
+import { and, desc, eq, ne, sql } from "drizzle-orm";
 import * as schema from "../../postgres/schema/index.js";
-import type { AsyncDataLayer, DbTransaction } from "../../postgres/data-layer.js";
+import { projectScopeFor, type AsyncDataLayer, type DbTransaction } from "../../postgres/data-layer.js";
 import { ACTIVE_TASK_FILTER } from "./async-persistence.js";
+import { createCurrentPlanEvidence, type CurrentPlanEvidence } from "../../planner/spec-lock.js";
+import { storeLog } from "../../store.js";
 
 /**
  * FNXC:TaskStoreLifecycle 2026-06-24-04:35:
@@ -152,38 +154,71 @@ export async function findLiveLineageChildren(
  * @param nowIso The timestamp to stamp on `updated_at`.
  * @returns The number of child rows actually updated (cleared).
  */
+export class LineageEvidenceAppendError extends Error {
+  constructor(public readonly childId: string, public readonly attempts: number, public readonly reason: "no-durable-version" | "matched-row-not-truthful") {
+    super(`Could not resolve truthful lineage evidence for ${childId}: ${reason}`);
+    this.name = "LineageEvidenceAppendError";
+  }
+}
+
+export type LineageRemovalOutcome = { clearedChildIds: string[]; evidenceVersionByChild: Map<string, number>; evidenceUnavailableChildIds: string[]; evidenceInsertAttempts: number };
+
+/**
+ * FNXC:SpecLockLineageInvalidation 2026-08-10-14:33:
+ * The lineage edge, approval fingerprint, and successor evidence are one transaction: a cleared
+ * parent binding can never retain approval or commit without truthful evidence. Report publication
+ * is deliberately outside this helper because it must evaluate committed state and is retryable.
+ */
 export async function removeLineageReferences(
   tx: DbTransaction,
   parentId: string,
   childIds: readonly string[],
   nowIso: string,
   projectId?: string,
-): Promise<number> {
-  // FNXC:TaskStoreLifecycle 2026-06-24-06:05:
-  // A single bulk UPDATE clears all children that still point at this parent.
-  // The WHERE guards on BOTH id (in the child set) AND source_parent_task_id
-  // (still pointing at this parent), so a child that was reparented elsewhere
-  // is left untouched. Using an IN-list keeps this to one round-trip regardless
-  // of child count. We count affected rows via a RETURNING read so the count is
-  // accurate regardless of how the driver exposes rowCount.
-  if (childIds.length === 0) {
-    return 0;
+  promptByChildId: ReadonlyMap<string, string> = new Map(),
+  evidenceTargetVersionForTest?: (childId: string, computed: number, attempt: number) => number,
+): Promise<LineageRemovalOutcome> {
+  if (childIds.length === 0) return { clearedChildIds: [], evidenceVersionByChild: new Map(), evidenceUnavailableChildIds: [], evidenceInsertAttempts: 0 };
+  const returned = await tx.update(schema.project.tasks).set({ sourceParentTaskId: null, approvedPlanFingerprint: null, awaitingApprovalReason: null, updatedAt: nowIso })
+    .where(and(eq(schema.project.tasks.projectId, projectPartition(projectId)), sql`${schema.project.tasks.id} IN ${childIds}`, eq(schema.project.tasks.sourceParentTaskId, parentId)))
+    .returning({ id: schema.project.tasks.id, dependencies: schema.project.tasks.dependencies, missionId: schema.project.tasks.missionId, sliceId: schema.project.tasks.sliceId });
+  const evidenceVersionByChild = new Map<string, number>();
+  const evidenceUnavailableChildIds: string[] = [];
+  let evidenceInsertAttempts = 0;
+  /*
+  FNXC:SpecLockLineageInvalidation 2026-08-10-14:47:
+  Evidence inserts use the trigger-compatible blank value, while reads preserve an unbound layer's
+  project-agnostic scope instead of filtering for the blank value the trigger rewrites.
+  */
+  const evidenceProjectId = projectId ?? "";
+  for (const child of returned) {
+    const prompt = promptByChildId.get(child.id);
+    if (prompt === undefined) {
+      evidenceUnavailableChildIds.push(child.id);
+      // A missing plan is the sole evidence-less commit: make the repairable input absence visible.
+      storeLog.warn(`[spec-lock] lineage evidence unavailable: missing PROMPT.md for ${child.id}`);
+      continue;
+    }
+    let resolved = false;
+    for (let attempt = 0; attempt < 3 && !resolved; attempt += 1) {
+      const latest = await tx.select({ version: schema.project.currentPlanEvidence.version }).from(schema.project.currentPlanEvidence)
+        .where(and(projectScopeFor(schema.project.currentPlanEvidence.projectId, projectId), eq(schema.project.currentPlanEvidence.taskId, child.id))).orderBy(desc(schema.project.currentPlanEvidence.version)).limit(1);
+      const computed = (latest[0]?.version ?? 0) + 1;
+      const evidence = createCurrentPlanEvidence({ version: evidenceTargetVersionForTest?.(child.id, computed, attempt) ?? computed, sourceRevision: Date.now(), capturedAt: nowIso, prompt, bindings: { dependencies: (child.dependencies as string[] | undefined) ?? [], missionId: child.missionId ?? undefined, sliceId: child.sliceId ?? undefined } });
+      evidenceInsertAttempts += 1;
+      const inserted = await tx.insert(schema.project.currentPlanEvidence).values({ projectId: evidenceProjectId, taskId: child.id, version: evidence.version, sourceRevision: evidence.sourceRevision, sourceHash: evidence.sourceHash, capturedAt: evidence.capturedAt, snapshot: evidence }).onConflictDoNothing().returning({ version: schema.project.currentPlanEvidence.version });
+      if (inserted[0]) { evidenceVersionByChild.set(child.id, inserted[0].version); resolved = true; break; }
+      const matching = await tx.select({ version: schema.project.currentPlanEvidence.version, snapshot: schema.project.currentPlanEvidence.snapshot }).from(schema.project.currentPlanEvidence)
+        .where(and(projectScopeFor(schema.project.currentPlanEvidence.projectId, projectId), eq(schema.project.currentPlanEvidence.taskId, child.id), eq(schema.project.currentPlanEvidence.sourceHash, evidence.sourceHash))).limit(1);
+      if (matching[0]) {
+        const snapshot = matching[0].snapshot as CurrentPlanEvidence;
+        if (snapshot.plan.sections.lineage.canonical.split("\n").includes(`parent-task:${parentId}`)) throw new LineageEvidenceAppendError(child.id, attempt + 1, "matched-row-not-truthful");
+        evidenceVersionByChild.set(child.id, matching[0].version); resolved = true; break;
+      }
+    }
+    if (!resolved) throw new LineageEvidenceAppendError(child.id, 3, "no-durable-version");
   }
-  const returned = await tx
-    .update(schema.project.tasks)
-    .set({
-      sourceParentTaskId: null,
-      updatedAt: nowIso,
-    })
-    .where(
-      and(
-        eq(schema.project.tasks.projectId, projectPartition(projectId)),
-        sql`${schema.project.tasks.id} IN ${childIds}`,
-        eq(schema.project.tasks.sourceParentTaskId, parentId),
-      ),
-    )
-    .returning({ id: schema.project.tasks.id });
-  return returned.length;
+  return { clearedChildIds: returned.map((row) => row.id), evidenceVersionByChild, evidenceUnavailableChildIds, evidenceInsertAttempts };
 }
 
 /**
diff --git a/packages/core/src/task-store/lineage-approval-invalidation.ts b/packages/core/src/task-store/lineage-approval-invalidation.ts
new file mode 100644
index 0000000000..97619bf4c5
--- /dev/null
+++ b/packages/core/src/task-store/lineage-approval-invalidation.ts
@@ -0,0 +1,168 @@
+import { readFile } from "node:fs/promises";
+import { join } from "node:path";
+import { storeLog, type TaskStore } from "../store.js";
+import type { AsyncDataLayer, DbTransaction } from "../postgres/data-layer.js";
+import { findLiveLineageChildren, LineageEvidenceAppendError } from "./async/async-lifecycle.js";
+
+/** A raced-in child must be locked on a fresh attempt rather than cleared unlocked. */
+class CandidateChanged extends Error {}
+export class LineageInvalidationCandidateRaceError extends Error {
+  constructor(readonly parentId: string) { super(`Lineage children changed while invalidating ${parentId}`); this.name = "LineageInvalidationCandidateRaceError"; }
+}
+export { LineageEvidenceAppendError };
+
+export type LineageInvalidationOutcome = {
+  attempt: number;
+  locksHeld: boolean;
+  degraded: boolean;
+  candidateIds: readonly string[];
+  clearedChildIds: readonly string[];
+  evidenceVersionByChild: ReadonlyMap<string, number>;
+  evidenceUnavailableChildIds: readonly string[];
+  evidenceInsertAttempts: number;
+  error?: "candidate-race-sentinel" | "evidence-append" | "gate-rejected" | "other";
+};
+
+export type LineageInvalidationTestEvent =
+  | { kind: "probe"; attempt: number }
+  | { kind: "acquire"; attempt: number; childIds: readonly string[] }
+  | { kind: "release"; attempt: number; childIds: readonly string[] }
+  | { kind: "run"; attempt: number; candidateIds: readonly string[]; locksHeld: boolean; degraded: boolean }
+  | { kind: "outcome"; outcome: LineageInvalidationOutcome }
+  | { kind: "run-error"; attempt: number; error: unknown }
+  | { kind: "reconcile"; childId: string };
+
+type LineageInvalidationTestSeam = {
+  availability?: () => { available: true } | { available: false; reason: string };
+  withLocks?: <T>(ids: readonly string[], callback: () => Promise<T>) => Promise<T>;
+  reconcile?: (childId: string) => Promise<void>;
+  /** Test-only deterministic target collision injection for transactional evidence coverage. */
+  evidenceTargetVersionForTest?: (childId: string, computed: number, attempt: number) => number;
+  onEvent?: (event: LineageInvalidationTestEvent) => void;
+};
+
+function testSeam(store: TaskStore): LineageInvalidationTestSeam | undefined {
+  return (store as unknown as { __lineageInvalidationForTest?: LineageInvalidationTestSeam }).__lineageInvalidationForTest;
+}
+
+/*
+FNXC:SpecLockLineageInvalidation 2026-08-10-15:35:
+Evidence version collisions cannot be produced by pre-seeding the next version because the
+transaction derives its target from MAX(version). Expose only this inert deterministic seam so the
+retry and rollback terminals are regression-tested without weakening production conflict handling.
+*/
+export function lineageEvidenceTargetVersionForTest(store: TaskStore):
+  | ((childId: string, computed: number, attempt: number) => number)
+  | undefined {
+  return testSeam(store)?.evidenceTargetVersionForTest;
+}
+
+/*
+FNXC:SpecLockLineageInvalidation 2026-08-10-15:15:
+Delete/archive return only their parent result, so the per-attempt child clear, durable-evidence,
+and error facts would otherwise be untestable. Publish this inert test seam after the transaction
+and before reconciliation, preserving the required acquire → outcome → reconcile → release order.
+*/
+export function recordLineageInvalidationOutcome(store: TaskStore, outcome: LineageInvalidationOutcome): void {
+  testSeam(store)?.onEvent?.({ kind: "outcome", outcome });
+}
+
+export function classifyLineageInvalidationOutcomeError(error: unknown): LineageInvalidationOutcome["error"] {
+  if (error instanceof CandidateChanged) return "candidate-race-sentinel";
+  if (error instanceof LineageEvidenceAppendError) return "evidence-append";
+  return "other";
+}
+
+export async function resolveLineageInvalidationCandidates(layer: AsyncDataLayer, parentId: string, archivedColumns: ReadonlySet<string> | undefined): Promise<string[]> {
+  return (await findLiveLineageChildren(layer.db, parentId, layer.projectId, archivedColumns)).sort();
+}
+export async function readLineagePromptMap(store: TaskStore, childIds: readonly string[]): Promise<Map<string, string>> {
+  const prompts = new Map<string, string>();
+  await Promise.all(childIds.map(async (childId) => {
+    try { prompts.set(childId, await readFile(join(store.taskDir(childId), "PROMPT.md"), "utf8")); } catch { /* Missing plans are the explicitly supported evidence-unavailable case. */ }
+  }));
+  return prompts;
+}
+export function assertLineageCandidatesUnchanged(inTransactionChildIds: readonly string[], candidateIds: readonly string[]): void {
+  const candidates = new Set(candidateIds);
+  if (inTransactionChildIds.some((id) => !candidates.has(id))) throw new CandidateChanged();
+}
+export async function resolveAndAssertLineageCandidatesUnchanged(tx: DbTransaction, parentId: string, projectId: string | undefined, archivedColumns: ReadonlySet<string> | undefined, candidateIds: readonly string[]): Promise<string[]> {
+  const live = await findLiveLineageChildren(tx, parentId, projectId, archivedColumns);
+  assertLineageCandidatesUnchanged(live, candidateIds);
+  return live;
+}
+
+/**
+ * FNXC:SpecLockLineageInvalidation 2026-08-10-14:33:
+ * Enter on the remove-lineage flag even with no candidates: archive discovers children in its
+ * transaction, so an empty pre-read still needs revalidation. A structural pooler-only transport
+ * may omit serialization, but a runtime lock failure propagates before the mutation body.
+ */
+export async function runLineageInvalidation<T>(
+  store: TaskStore,
+  parentId: string,
+  input: { archivedColumns: ReadonlySet<string> | undefined; initialCandidateIds?: readonly string[] },
+  run: (context: { candidateIds: string[]; promptByChildId: ReadonlyMap<string, string>; locksHeld: boolean; attempt: number }) => Promise<T>,
+): Promise<T> {
+  const layer = store.asyncLayer!;
+  const seam = testSeam(store);
+  for (let attempt = 0; attempt < 2; attempt += 1) {
+    const candidateIds = (attempt === 0 && input.initialCandidateIds !== undefined ? [...input.initialCandidateIds] : await resolveLineageInvalidationCandidates(layer, parentId, input.archivedColumns)).sort();
+    const invoke = async (locksHeld: boolean, degraded: boolean, promptByChildId: ReadonlyMap<string, string>): Promise<T> => {
+      seam?.onEvent?.({ kind: "run", attempt, candidateIds, locksHeld, degraded });
+      try {
+        return await run({ candidateIds, promptByChildId, locksHeld, attempt });
+      } catch (error) {
+        seam?.onEvent?.({ kind: "run-error", attempt, error });
+        throw error;
+      }
+    };
+    try {
+      if (candidateIds.length === 0) return await invoke(false, false, new Map());
+      const promptByChildId = await readLineagePromptMap(store, candidateIds);
+      seam?.onEvent?.({ kind: "probe", attempt });
+      const availability = seam?.availability?.() ?? store.planningLifecycleLockTransportAvailability();
+      if (!availability.available) {
+        /*
+        FNXC:SpecLockLineageInvalidation 2026-08-10-15:22:
+        A pooler-only deployment deliberately degrades serialization, not durable invalidation.
+        Warn once per operation so operators can distinguish that sanctioned path from a contention
+        failure, which must still reject before the mutation body.
+        */
+        storeLog.warn(`[spec-lock] lineage invalidation for ${parentId} runs without planning lifecycle locks for ${candidateIds.length} child(ren): ${availability.reason}`);
+        return await invoke(false, true, promptByChildId);
+      }
+      seam?.onEvent?.({ kind: "acquire", attempt, childIds: candidateIds });
+      const withLocks = seam?.withLocks ?? ((ids, callback) => store.withPlanningLifecycleLocks(ids, callback));
+      let callbackEntered = false;
+      try {
+        return await withLocks(candidateIds, () => {
+          callbackEntered = true;
+          return invoke(true, false, promptByChildId);
+        });
+      } finally {
+        // Acquisition failures run no body and therefore own no observable callback lock window.
+        if (callbackEntered) seam?.onEvent?.({ kind: "release", attempt, childIds: candidateIds });
+      }
+    } catch (error) {
+      if (!(error instanceof CandidateChanged)) throw error;
+      if (attempt === 1) throw new LineageInvalidationCandidateRaceError(parentId);
+    }
+  }
+  throw new LineageInvalidationCandidateRaceError(parentId);
+}
+
+/** Publish after commit but before the multi-key callback releases child planning locks. */
+export async function reconcileClearedLineageChildren(store: TaskStore, childIds: readonly string[], _context: { locksHeld: boolean }): Promise<void> {
+  const seam = testSeam(store);
+  for (const childId of [...new Set(childIds)].sort()) {
+    seam?.onEvent?.({ kind: "reconcile", childId });
+    await (seam?.reconcile?.(childId)
+      ?? store.reconcileSpecDriftWhilePlanningLocked({ id: childId, approvedPlanFingerprint: undefined, modifiedFiles: [] }))
+      .catch((error: unknown) => {
+        // Report publication is retryable telemetry, but an operator still needs the failed child id.
+        storeLog.warn(`[spec-lock] deferred lineage drift reconciliation for ${childId}: ${error instanceof Error ? error.message : String(error)}`);
+      });
+  }
+}