diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2dd4091892..df5ca355bea 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ Docs: https://docs.openclaw.ai
 - WhatsApp/reactions: add `reactionLevel` guidance for agent reactions. Thanks @mcaxtr.
 - Feishu/comments: add a dedicated Drive comment-event flow with comment-thread context resolution, in-thread replies, and `feishu_drive` comment actions for document collaboration workflows. (#58497) thanks @wittam-01.
 - Tasks/TaskFlow: restore the core TaskFlow substrate with managed-vs-mirrored sync modes, durable flow state/revision tracking, and `openclaw flows` inspection/recovery primitives so background orchestration can persist and be operated separately from plugin authoring layers. (#58930) Thanks @mbelinky.
+- Tasks/TaskFlow: add managed child task spawning plus sticky cancel intent, so external orchestrators can stop scheduling immediately and let parent TaskFlows settle to `cancelled` once active child tasks finish. (#59610) Thanks @mbelinky.
 
 ### Fixes
 
diff --git a/src/commands/doctor-workspace-status.ts b/src/commands/doctor-workspace-status.ts
index 3a7a14949bd..eb5f440c964 100644
--- a/src/commands/doctor-workspace-status.ts
+++ b/src/commands/doctor-workspace-status.ts
@@ -19,7 +19,7 @@ function noteFlowRecoveryHints() {
       flow.waitJson === undefined
     ) {
       findings.push(
-        `${flow.flowId}: running managed flow has no linked tasks or wait state; inspect or cancel it manually.`,
+        `${flow.flowId}: running managed TaskFlow has no linked tasks or wait state; inspect or cancel it manually.`,
       );
     }
     if (
@@ -28,7 +28,7 @@ function noteFlowRecoveryHints() {
       !tasks.some((task) => task.taskId === flow.blockedTaskId)
     ) {
       findings.push(
-        `${flow.flowId}: blocked flow points at missing task ${flow.blockedTaskId}; inspect before retrying.`,
+        `${flow.flowId}: blocked TaskFlow points at missing task ${flow.blockedTaskId}; inspect before retrying.`,
       );
     }
     return findings;
diff --git a/src/tasks/runtime-internal.ts b/src/tasks/runtime-internal.ts
index 53566c7232b..8a9f41d7764 100644
--- a/src/tasks/runtime-internal.ts
+++ b/src/tasks/runtime-internal.ts
@@ -23,6 +23,7 @@ export {
   recordTaskProgressByRunId,
   resolveTaskForLookupToken,
   resetTaskRegistryForTests,
+  isParentFlowLinkError,
   setTaskCleanupAfterById,
   setTaskProgressById,
   setTaskRunDeliveryStatusByRunId,
diff --git a/src/tasks/task-executor.test.ts b/src/tasks/task-executor.test.ts
index 86cf925a123..e9db6feb840 100644
--- a/src/tasks/task-executor.test.ts
+++ b/src/tasks/task-executor.test.ts
@@ -16,6 +16,8 @@ import {
   failTaskRunByRunId,
   recordTaskRunProgressByRunId,
   retryBlockedFlowAsQueuedTaskRun,
+  runTaskInFlow,
+  runTaskInFlowForOwner,
   setDetachedTaskDeliveryStatusByRunId,
   startTaskRunByRunId,
 } from "./task-executor.js";
@@ -289,7 +291,7 @@ describe("task-executor", () => {
     });
   });
 
-  it("cancels active tasks linked to a managed flow", async () => {
+  it("cancels active tasks linked to a managed TaskFlow", async () => {
     await withTaskExecutorStateDir(async () => {
       hoisted.cancelSessionMock.mockResolvedValue(undefined);
 
@@ -330,6 +332,139 @@ describe("task-executor", () => {
     });
   });
 
+  it("runs child tasks under managed TaskFlows", async () => {
+    await withTaskExecutorStateDir(async () => {
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/managed-flow",
+        goal: "Inspect PR batch",
+        requesterOrigin: {
+          channel: "telegram",
+          to: "telegram:123",
+        },
+      });
+
+      const created = runTaskInFlow({
+        flowId: flow.flowId,
+        runtime: "acp",
+        childSessionKey: "agent:codex:acp:child",
+        runId: "run-flow-child",
+        label: "Inspect a PR",
+        task: "Inspect a PR",
+        status: "running",
+        startedAt: 10,
+        lastEventAt: 10,
+      });
+
+      expect(created).toMatchObject({
+        found: true,
+        created: true,
+        task: expect.objectContaining({
+          parentFlowId: flow.flowId,
+          ownerKey: "agent:main:main",
+          status: "running",
+          runId: "run-flow-child",
+        }),
+      });
+      expect(getTaskById(created.task!.taskId)).toMatchObject({
+        parentFlowId: flow.flowId,
+        ownerKey: "agent:main:main",
+        childSessionKey: "agent:codex:acp:child",
+      });
+    });
+  });
+
+  it("refuses to add child tasks once cancellation is requested on a managed TaskFlow", async () => {
+    await withTaskExecutorStateDir(async () => {
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/managed-flow",
+        goal: "Protected flow",
+      });
+
+      const cancelled = await cancelFlowById({
+        cfg: {} as never,
+        flowId: flow.flowId,
+      });
+
+      expect(cancelled).toMatchObject({
+        found: true,
+        cancelled: true,
+      });
+
+      const created = runTaskInFlow({
+        flowId: flow.flowId,
+        runtime: "acp",
+        childSessionKey: "agent:codex:acp:child",
+        runId: "run-flow-after-cancel",
+        task: "Should be denied",
+      });
+
+      expect(created).toMatchObject({
+        found: true,
+        created: false,
+        reason: "Flow cancellation has already been requested.",
+      });
+    });
+  });
+
+  it("sets cancel intent before child tasks settle and finalizes later", async () => {
+    await withTaskExecutorStateDir(async () => {
+      hoisted.cancelSessionMock.mockRejectedValue(new Error("still shutting down"));
+
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/managed-flow",
+        goal: "Long running batch",
+      });
+      const child = runTaskInFlow({
+        flowId: flow.flowId,
+        runtime: "acp",
+        childSessionKey: "agent:codex:acp:child",
+        runId: "run-flow-sticky-cancel",
+        task: "Inspect a PR",
+        status: "running",
+        startedAt: 10,
+        lastEventAt: 10,
+      }).task!;
+
+      const cancelled = await cancelFlowById({
+        cfg: {} as never,
+        flowId: flow.flowId,
+      });
+
+      expect(cancelled).toMatchObject({
+        found: true,
+        cancelled: false,
+        reason: "One or more child tasks are still active.",
+        flow: expect.objectContaining({
+          flowId: flow.flowId,
+          cancelRequestedAt: expect.any(Number),
+          status: "queued",
+        }),
+      });
+
+      failTaskRunByRunId({
+        runId: "run-flow-sticky-cancel",
+        endedAt: 50,
+        lastEventAt: 50,
+        error: "cancel completed later",
+        status: "cancelled",
+      });
+
+      expect(getTaskById(child.taskId)).toMatchObject({
+        taskId: child.taskId,
+        status: "cancelled",
+      });
+      expect(getFlowById(flow.flowId)).toMatchObject({
+        flowId: flow.flowId,
+        cancelRequestedAt: expect.any(Number),
+        status: "cancelled",
+        endedAt: 50,
+      });
+    });
+  });
+
   it("denies cross-owner flow cancellation through the owner-scoped wrapper", async () => {
     await withTaskExecutorStateDir(async () => {
       const flow = createManagedFlow({
@@ -356,6 +491,32 @@ describe("task-executor", () => {
     });
   });
 
+  it("denies cross-owner managed TaskFlow child spawning through the owner-scoped wrapper", async () => {
+    await withTaskExecutorStateDir(async () => {
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/managed-flow",
+        goal: "Protected flow",
+      });
+
+      const created = runTaskInFlowForOwner({
+        flowId: flow.flowId,
+        callerOwnerKey: "agent:main:other",
+        runtime: "acp",
+        childSessionKey: "agent:codex:acp:child",
+        runId: "run-flow-cross-owner",
+        task: "Should be denied",
+      });
+
+      expect(created).toMatchObject({
+        found: false,
+        created: false,
+        reason: "Flow not found.",
+      });
+      expect(findLatestTaskForFlowId(flow.flowId)).toBeUndefined();
+    });
+  });
+
   it("cancels active ACP child tasks", async () => {
     await withTaskExecutorStateDir(async () => {
       hoisted.cancelSessionMock.mockResolvedValue(undefined);
diff --git a/src/tasks/task-executor.ts b/src/tasks/task-executor.ts
index 4c7503c7e75..f959a6495f0 100644
--- a/src/tasks/task-executor.ts
+++ b/src/tasks/task-executor.ts
@@ -6,12 +6,14 @@ import {
   createFlowForTask,
   deleteFlowRecordById,
   getFlowById,
+  requestFlowCancel,
   updateFlowRecordByIdExpectedRevision,
 } from "./flow-runtime-internal.js";
 import {
   cancelTaskById,
   createTaskRecord,
   findLatestTaskForFlowId,
+  isParentFlowLinkError,
   linkTaskToFlowById,
   listTasksForFlowId,
   markTaskLostById,
@@ -293,7 +295,7 @@ function resolveRetryableBlockedFlowTask(flowId: string): {
       flowFound: true,
       retryable: false,
       latestTask,
-      reason: "Latest flow task is not blocked.",
+      reason: "Latest TaskFlow task is not blocked.",
     };
   }
   return {
@@ -376,6 +378,14 @@ type CancelFlowResult = {
   tasks?: TaskRecord[];
 };
 
+type RunTaskInFlowResult = {
+  found: boolean;
+  created: boolean;
+  reason?: string;
+  flow?: FlowRecord;
+  task?: TaskRecord;
+};
+
 function isActiveTaskStatus(status: TaskStatus): boolean {
   return status === "queued" || status === "running";
 }
@@ -386,6 +396,237 @@ function isTerminalFlowStatus(status: FlowRecord["status"]): boolean {
   );
 }
 
+function markFlowCancelRequested(flow: FlowRecord): FlowRecord | FlowUpdateFailure {
+  if (flow.cancelRequestedAt != null) {
+    return flow;
+  }
+  const result = requestFlowCancel({
+    flowId: flow.flowId,
+    expectedRevision: flow.revision,
+  });
+  if (result.applied) {
+    return result.flow;
+  }
+  return {
+    reason:
+      result.reason === "revision_conflict"
+        ? "Flow changed while cancellation was in progress."
+        : "Flow not found.",
+    flow: result.current ?? getFlowById(flow.flowId),
+  };
+}
+
+type FlowUpdateFailure = {
+  reason: string;
+  flow?: FlowRecord;
+};
+
+function cancelManagedFlowAfterChildrenSettle(
+  flow: FlowRecord,
+  endedAt: number,
+): FlowRecord | FlowUpdateFailure {
+  const result = updateFlowRecordByIdExpectedRevision({
+    flowId: flow.flowId,
+    expectedRevision: flow.revision,
+    patch: {
+      status: "cancelled",
+      blockedTaskId: null,
+      blockedSummary: null,
+      waitJson: null,
+      endedAt,
+      updatedAt: endedAt,
+    },
+  });
+  if (result.applied) {
+    return result.flow;
+  }
+  return {
+    reason:
+      result.reason === "revision_conflict"
+        ? "Flow changed while cancellation was in progress."
+        : "Flow not found.",
+    flow: result.current ?? getFlowById(flow.flowId),
+  };
+}
+
+function mapRunTaskInFlowCreateError(params: {
+  error: unknown;
+  flowId: string;
+}): RunTaskInFlowResult {
+  const flow = getFlowById(params.flowId);
+  if (isParentFlowLinkError(params.error)) {
+    if (params.error.code === "cancel_requested") {
+      return {
+        found: true,
+        created: false,
+        reason: "Flow cancellation has already been requested.",
+        ...(flow ? { flow } : {}),
+      };
+    }
+    if (params.error.code === "terminal") {
+      const terminalStatus = flow?.status ?? params.error.details?.status ?? "terminal";
+      return {
+        found: true,
+        created: false,
+        reason: `Flow is already ${terminalStatus}.`,
+        ...(flow ? { flow } : {}),
+      };
+    }
+    if (params.error.code === "parent_flow_not_found") {
+      return {
+        found: false,
+        created: false,
+        reason: "Flow not found.",
+      };
+    }
+  }
+  throw params.error;
+}
+
+export function runTaskInFlow(params: {
+  flowId: string;
+  runtime: TaskRuntime;
+  sourceId?: string;
+  childSessionKey?: string;
+  parentTaskId?: string;
+  agentId?: string;
+  runId?: string;
+  label?: string;
+  task: string;
+  preferMetadata?: boolean;
+  notifyPolicy?: TaskNotifyPolicy;
+  deliveryStatus?: TaskDeliveryStatus;
+  status?: "queued" | "running";
+  startedAt?: number;
+  lastEventAt?: number;
+  progressSummary?: string | null;
+}): RunTaskInFlowResult {
+  const flow = getFlowById(params.flowId);
+  if (!flow) {
+    return {
+      found: false,
+      created: false,
+      reason: "Flow not found.",
+    };
+  }
+  if (flow.syncMode !== "managed") {
+    return {
+      found: true,
+      created: false,
+      reason: "Flow does not accept managed child tasks.",
+      flow,
+    };
+  }
+  if (flow.cancelRequestedAt != null) {
+    return {
+      found: true,
+      created: false,
+      reason: "Flow cancellation has already been requested.",
+      flow,
+    };
+  }
+  if (isTerminalFlowStatus(flow.status)) {
+    return {
+      found: true,
+      created: false,
+      reason: `Flow is already ${flow.status}.`,
+      flow,
+    };
+  }
+
+  const common = {
+    runtime: params.runtime,
+    sourceId: params.sourceId,
+    ownerKey: flow.ownerKey,
+    scopeKind: "session" as const,
+    requesterOrigin: flow.requesterOrigin,
+    parentFlowId: flow.flowId,
+    childSessionKey: params.childSessionKey,
+    parentTaskId: params.parentTaskId,
+    agentId: params.agentId,
+    runId: params.runId,
+    label: params.label,
+    task: params.task,
+    preferMetadata: params.preferMetadata,
+    notifyPolicy: params.notifyPolicy,
+    deliveryStatus: params.deliveryStatus ?? "pending",
+  };
+  let task: TaskRecord;
+  try {
+    task =
+      params.status === "running"
+        ? createRunningTaskRun({
+            ...common,
+            startedAt: params.startedAt,
+            lastEventAt: params.lastEventAt,
+            progressSummary: params.progressSummary,
+          })
+        : createQueuedTaskRun(common);
+  } catch (error) {
+    return mapRunTaskInFlowCreateError({
+      error,
+      flowId: flow.flowId,
+    });
+  }
+
+  return {
+    found: true,
+    created: true,
+    flow: getFlowById(flow.flowId) ?? flow,
+    task,
+  };
+}
+
+export function runTaskInFlowForOwner(params: {
+  flowId: string;
+  callerOwnerKey: string;
+  runtime: TaskRuntime;
+  sourceId?: string;
+  childSessionKey?: string;
+  parentTaskId?: string;
+  agentId?: string;
+  runId?: string;
+  label?: string;
+  task: string;
+  preferMetadata?: boolean;
+  notifyPolicy?: TaskNotifyPolicy;
+  deliveryStatus?: TaskDeliveryStatus;
+  status?: "queued" | "running";
+  startedAt?: number;
+  lastEventAt?: number;
+  progressSummary?: string | null;
+}): RunTaskInFlowResult {
+  const flow = getFlowByIdForOwner({
+    flowId: params.flowId,
+    callerOwnerKey: params.callerOwnerKey,
+  });
+  if (!flow) {
+    return {
+      found: false,
+      created: false,
+      reason: "Flow not found.",
+    };
+  }
+  return runTaskInFlow({
+    flowId: flow.flowId,
+    runtime: params.runtime,
+    sourceId: params.sourceId,
+    childSessionKey: params.childSessionKey,
+    parentTaskId: params.parentTaskId,
+    agentId: params.agentId,
+    runId: params.runId,
+    label: params.label,
+    task: params.task,
+    preferMetadata: params.preferMetadata,
+    notifyPolicy: params.notifyPolicy,
+    deliveryStatus: params.deliveryStatus,
+    status: params.status,
+    startedAt: params.startedAt,
+    lastEventAt: params.lastEventAt,
+    progressSummary: params.progressSummary,
+  });
+}
+
 export async function cancelFlowById(params: {
   cfg: OpenClawConfig;
   flowId: string;
@@ -398,6 +639,25 @@ export async function cancelFlowById(params: {
       reason: "Flow not found.",
     };
   }
+  if (isTerminalFlowStatus(flow.status)) {
+    return {
+      found: true,
+      cancelled: false,
+      reason: `Flow is already ${flow.status}.`,
+      flow,
+      tasks: listTasksForFlowId(flow.flowId),
+    };
+  }
+  const cancelRequestedFlow = markFlowCancelRequested(flow);
+  if ("reason" in cancelRequestedFlow) {
+    return {
+      found: true,
+      cancelled: false,
+      reason: cancelRequestedFlow.reason,
+      flow: cancelRequestedFlow.flow,
+      tasks: listTasksForFlowId(flow.flowId),
+    };
+  }
   const linkedTasks = listTasksForFlowId(flow.flowId);
   const activeTasks = linkedTasks.filter((task) => isActiveTaskStatus(task.status));
   for (const task of activeTasks) {
@@ -413,48 +673,38 @@ export async function cancelFlowById(params: {
       found: true,
       cancelled: false,
       reason: "One or more child tasks are still active.",
-      flow: getFlowById(flow.flowId),
-      tasks: refreshedTasks,
-    };
-  }
-  if (isTerminalFlowStatus(flow.status)) {
-    return {
-      found: true,
-      cancelled: false,
-      reason: `Flow is already ${flow.status}.`,
-      flow,
+      flow: getFlowById(flow.flowId) ?? cancelRequestedFlow,
       tasks: refreshedTasks,
     };
   }
   const now = Date.now();
-  const refreshedFlow = getFlowById(flow.flowId) ?? flow;
-  const updatedFlowResult = updateFlowRecordByIdExpectedRevision({
-    flowId: refreshedFlow.flowId,
-    expectedRevision: refreshedFlow.revision,
-    patch: {
-      status: "cancelled",
-      blockedTaskId: null,
-      blockedSummary: null,
-      endedAt: now,
-      updatedAt: now,
-    },
-  });
-  if (!updatedFlowResult.applied) {
+  const refreshedFlow = getFlowById(flow.flowId) ?? cancelRequestedFlow;
+  if (isTerminalFlowStatus(refreshedFlow.status)) {
+    return {
+      found: true,
+      cancelled: refreshedFlow.status === "cancelled",
+      reason:
+        refreshedFlow.status === "cancelled"
+          ? undefined
+          : `Flow is already ${refreshedFlow.status}.`,
+      flow: refreshedFlow,
+      tasks: refreshedTasks,
+    };
+  }
+  const updatedFlow = cancelManagedFlowAfterChildrenSettle(refreshedFlow, now);
+  if ("reason" in updatedFlow) {
     return {
       found: true,
       cancelled: false,
-      reason:
-        updatedFlowResult.reason === "revision_conflict"
-          ? "Flow changed while cancellation was in progress."
-          : "Flow not found.",
-      flow: updatedFlowResult.current ?? getFlowById(flow.flowId),
+      reason: updatedFlow.reason,
+      flow: updatedFlow.flow,
       tasks: refreshedTasks,
     };
   }
   return {
     found: true,
     cancelled: true,
-    flow: updatedFlowResult.flow,
+    flow: updatedFlow,
     tasks: refreshedTasks,
   };
 }
diff --git a/src/tasks/task-registry.test.ts b/src/tasks/task-registry.test.ts
index 8b246013a02..810f2a0c676 100644
--- a/src/tasks/task-registry.test.ts
+++ b/src/tasks/task-registry.test.ts
@@ -19,6 +19,7 @@ import {
   findTaskByRunId,
   getTaskById,
   getTaskRegistrySummary,
+  isParentFlowLinkError,
   listTasksForOwnerKey,
   listTaskRecords,
   linkTaskToFlowById,
@@ -379,6 +380,65 @@ describe("task-registry", () => {
     });
   });
 
+  it("rejects parent flow links once cancellation has been requested", async () => {
+    await withTaskRegistryTempDir(async (root) => {
+      process.env.OPENCLAW_STATE_DIR = root;
+      resetTaskRegistryForTests();
+      resetFlowRegistryForTests();
+
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/task-registry",
+        goal: "Cancelling flow",
+        cancelRequestedAt: 42,
+      });
+
+      try {
+        createTaskRecord({
+          runtime: "acp",
+          ownerKey: "agent:main:main",
+          scopeKind: "session",
+          parentFlowId: flow.flowId,
+          runId: "cancel-requested-link",
+          task: "Should be denied",
+        });
+        throw new Error("Expected createTaskRecord to throw.");
+      } catch (error) {
+        expect(isParentFlowLinkError(error)).toBe(true);
+        expect(error).toMatchObject({
+          code: "cancel_requested",
+          message: "Parent flow cancellation has already been requested.",
+        });
+      }
+    });
+  });
+
+  it("rejects parent flow links for terminal flows", async () => {
+    await withTaskRegistryTempDir(async (root) => {
+      process.env.OPENCLAW_STATE_DIR = root;
+      resetTaskRegistryForTests();
+      resetFlowRegistryForTests();
+
+      const flow = createManagedFlow({
+        ownerKey: "agent:main:main",
+        controllerId: "tests/task-registry",
+        goal: "Completed flow",
+        status: "cancelled",
+      });
+
+      expect(() =>
+        createTaskRecord({
+          runtime: "acp",
+          ownerKey: "agent:main:main",
+          scopeKind: "session",
+          parentFlowId: flow.flowId,
+          runId: "terminal-flow-link",
+          task: "Should be denied",
+        }),
+      ).toThrow("Parent flow is already cancelled.");
+    });
+  });
+
   it("delivers ACP completion to the requester channel when a delivery origin exists", async () => {
     await withTaskRegistryTempDir(async (root) => {
       process.env.OPENCLAW_STATE_DIR = root;
diff --git a/src/tasks/task-registry.ts b/src/tasks/task-registry.ts
index 7c087454fb5..c8d032159a0 100644
--- a/src/tasks/task-registry.ts
+++ b/src/tasks/task-registry.ts
@@ -9,7 +9,12 @@ import { createSubsystemLogger } from "../logging/subsystem.js";
 import { parseAgentSessionKey } from "../routing/session-key.js";
 import { normalizeDeliveryContext } from "../utils/delivery-context.js";
 import { isDeliverableMessageChannel } from "../utils/message-channel.js";
-import { getFlowById, syncFlowFromTask } from "./flow-runtime-internal.js";
+import type { FlowRecord } from "./flow-registry.types.js";
+import {
+  getFlowById,
+  syncFlowFromTask,
+  updateFlowRecordByIdExpectedRevision,
+} from "./flow-runtime-internal.js";
 import {
   formatTaskBlockedFollowupMessage,
   formatTaskStateChangeMessage,
@@ -63,6 +68,41 @@ type TaskDeliveryOwner = {
   flowId?: string;
 };
 
+export type ParentFlowLinkErrorCode =
+  | "scope_kind_not_session"
+  | "parent_flow_not_found"
+  | "owner_key_mismatch"
+  | "cancel_requested"
+  | "terminal";
+
+export class ParentFlowLinkError extends Error {
+  constructor(
+    public readonly code: ParentFlowLinkErrorCode,
+    message: string,
+    public readonly details?: {
+      flowId?: string;
+      status?: FlowRecord["status"];
+    },
+  ) {
+    super(message);
+    this.name = "ParentFlowLinkError";
+  }
+}
+
+export function isParentFlowLinkError(error: unknown): error is ParentFlowLinkError {
+  return error instanceof ParentFlowLinkError;
+}
+
+function isActiveTaskStatus(status: TaskStatus): boolean {
+  return status === "queued" || status === "running";
+}
+
+function isTerminalFlowStatus(status: FlowRecord["status"]): boolean {
+  return (
+    status === "succeeded" || status === "failed" || status === "cancelled" || status === "lost"
+  );
+}
+
 function assertTaskOwner(params: { ownerKey: string; scopeKind: TaskScopeKind }) {
   const ownerKey = params.ownerKey.trim();
   if (!ownerKey && params.scopeKind !== "system") {
@@ -85,14 +125,37 @@ function assertParentFlowLinkAllowed(params: {
     return;
   }
   if (params.scopeKind !== "session") {
-    throw new Error("Only session-scoped tasks can link to flows.");
+    throw new ParentFlowLinkError(
+      "scope_kind_not_session",
+      "Only session-scoped tasks can link to flows.",
+      { flowId },
+    );
   }
   const flow = getFlowById(flowId);
   if (!flow) {
-    throw new Error(`Parent flow not found: ${flowId}`);
+    throw new ParentFlowLinkError("parent_flow_not_found", `Parent flow not found: ${flowId}`, {
+      flowId,
+    });
   }
   if (normalizeOwnerKey(flow.ownerKey) !== normalizeOwnerKey(params.ownerKey)) {
-    throw new Error("Task ownerKey must match parent flow ownerKey.");
+    throw new ParentFlowLinkError(
+      "owner_key_mismatch",
+      "Task ownerKey must match parent flow ownerKey.",
+      { flowId },
+    );
+  }
+  if (flow.cancelRequestedAt != null) {
+    throw new ParentFlowLinkError(
+      "cancel_requested",
+      "Parent flow cancellation has already been requested.",
+      { flowId, status: flow.status },
+    );
+  }
+  if (isTerminalFlowStatus(flow.status)) {
+    throw new ParentFlowLinkError("terminal", `Parent flow is already ${flow.status}.`, {
+      flowId,
+      status: flow.status,
+    });
   }
 }
 
@@ -694,6 +757,55 @@ function resolveTaskDeliveryOwner(task: TaskRecord): TaskDeliveryOwner {
   };
 }
 
+function syncManagedFlowCancellationFromTask(task: TaskRecord): void {
+  const flowId = task.parentFlowId?.trim();
+  if (!flowId) {
+    return;
+  }
+  let flow = getFlowById(flowId);
+  if (
+    !flow ||
+    flow.syncMode !== "managed" ||
+    flow.cancelRequestedAt == null ||
+    isTerminalFlowStatus(flow.status)
+  ) {
+    return;
+  }
+  if (listTasksForFlowId(flowId).some((candidate) => isActiveTaskStatus(candidate.status))) {
+    return;
+  }
+  const endedAt = task.endedAt ?? task.lastEventAt ?? Date.now();
+  for (let attempt = 0; attempt < 2; attempt += 1) {
+    const result = updateFlowRecordByIdExpectedRevision({
+      flowId,
+      expectedRevision: flow.revision,
+      patch: {
+        status: "cancelled",
+        blockedTaskId: null,
+        blockedSummary: null,
+        waitJson: null,
+        endedAt,
+        updatedAt: endedAt,
+      },
+    });
+    if (result.applied || result.reason === "not_found") {
+      return;
+    }
+    flow = result.current;
+    if (
+      !flow ||
+      flow.syncMode !== "managed" ||
+      flow.cancelRequestedAt == null ||
+      isTerminalFlowStatus(flow.status)
+    ) {
+      return;
+    }
+    if (listTasksForFlowId(flowId).some((candidate) => isActiveTaskStatus(candidate.status))) {
+      return;
+    }
+  }
+}
+
 function restoreTaskRegistryOnce() {
   if (restoreAttempted) {
     return;
@@ -767,6 +879,15 @@ function updateTask(taskId: string, patch: Partial<TaskRecord>): TaskRecord | nu
       error,
     });
   }
+  try {
+    syncManagedFlowCancellationFromTask(next);
+  } catch (error) {
+    log.warn("Failed to finalize managed flow cancellation from task update", {
+      taskId,
+      flowId: next.parentFlowId,
+      error,
+    });
+  }
   emitTaskRegistryHookEvent(() => ({
     kind: "upserted",
     task: cloneTaskRecord(next),