fix: harden delegation lifecycle against race conditions with per-task metadata, mutual-exclusion guards, and multi-layer failure recovery (#11379)

* fix: race conditions in subtask delegation system

Comprehensive fix for race conditions and error handling gaps in the subtask
delegation system. Addresses multiple failure modes that could leave parent
tasks permanently stuck in 'delegated' status, causing nested subtasks to hang.

Key fixes:
- Remove initialStatus from taskMetadata rebuild (eliminates status overwrites)
- Persist delegation metadata to per-task files (resolves globalState eviction)
- Add delegationInProgress mutex guard (prevents concurrent delegation ops)
- TOCTOU race fixes with fresh re-reads before writes
- Abort-aware pWaitFor predicate (prevents false 60s timeout on user input)
- Remove silent .catch(() => {}) — all errors now logged unless task is aborting
- Single-attempt delegation with parent repair on failure (no retry band-aids)
- Cancel debouncedEmitTokenUsage in dispose() (prevents zombie callbacks)
- new_task isolation truncation for parallel tool calls

* fix: write all 6 delegation fields in every saveDelegationMeta call site

* fix: align delegation tests with single-attempt implementation (no retry)

Author: hannesrudolph

packages/types/src/task.ts

@@ -93,8 +93,6 @@ export interface CreateTaskOptions {
 	consecutiveMistakeLimit?: number
 	experiments?: Record<string, boolean>
 	initialTodos?: TodoItem[]
-	/** Initial status for the task's history item (e.g., "active" for child tasks) */
-	initialStatus?: "active" | "delegated" | "completed"
 	/** Whether to start the task loop immediately (default: true).
 	 *  When false, the caller must invoke `task.start()` manually. */
 	startTask?: boolean

src/__tests__/history-resume-delegation.spec.ts

@@ -38,6 +38,10 @@ vi.mock("../core/task-persistence", async (importOriginal) => {
 		saveTaskMessages: vi.fn().mockResolvedValue(undefined),
 	}
 })
+vi.mock("../core/task-persistence/delegationMeta", () => ({
+	readDelegationMeta: vi.fn().mockResolvedValue(null),
+	saveDelegationMeta: vi.fn().mockResolvedValue(undefined),
+}))
 
 import { ClineProvider } from "../core/webview/ClineProvider"
 import { readTaskMessages } from "../core/task-persistence/taskMessages"
@@ -149,6 +153,7 @@ describe("History resume delegation - parent metadata transitions", () => {
 				overwriteApiConversationHistory: vi.fn().mockResolvedValue(undefined),
 			}),
 			updateTaskHistory: vi.fn().mockResolvedValue([]),
+			log: vi.fn(),
 		} as unknown as ClineProvider
 
 		// Start with existing messages in history
@@ -232,6 +237,7 @@ describe("History resume delegation - parent metadata transitions", () => {
 				overwriteApiConversationHistory: vi.fn().mockResolvedValue(undefined),
 			}),
 			updateTaskHistory: vi.fn().mockResolvedValue([]),
+			log: vi.fn(),
 		} as unknown as ClineProvider
 
 		// Include an assistant message with new_task tool_use to exercise the tool_result path
@@ -320,6 +326,7 @@ describe("History resume delegation - parent metadata transitions", () => {
 				overwriteApiConversationHistory: vi.fn().mockResolvedValue(undefined),
 			}),
 			updateTaskHistory: vi.fn().mockResolvedValue([]),
+			log: vi.fn(),
 		} as unknown as ClineProvider
 
 		// No assistant tool_use in history
@@ -555,6 +562,7 @@ describe("History resume delegation - parent metadata transitions", () => {
 				overwriteApiConversationHistory: vi.fn().mockResolvedValue(undefined),
 			}),
 			updateTaskHistory: vi.fn().mockResolvedValue([]),
+			log: vi.fn(),
 		} as unknown as ClineProvider
 
 		vi.mocked(readTaskMessages).mockResolvedValue([])
@@ -754,6 +762,7 @@ describe("History resume delegation - parent metadata transitions", () => {
 				overwriteApiConversationHistory: vi.fn().mockResolvedValue(undefined),
 			}),
 			updateTaskHistory: vi.fn().mockResolvedValue([]),
+			log: vi.fn(),
 		} as unknown as ClineProvider
 
 		// Mock read failures or empty returns

src/__tests__/provider-delegation.spec.ts

@@ -2,14 +2,20 @@
 
 import { describe, it, expect, vi } from "vitest"
 import { RooCodeEventName } from "@roo-code/types"
+
+vi.mock("../core/task-persistence/delegationMeta", () => ({
+	readDelegationMeta: vi.fn().mockResolvedValue(null),
+	saveDelegationMeta: vi.fn().mockResolvedValue(undefined),
+}))
+
 import { ClineProvider } from "../core/webview/ClineProvider"
 
 describe("ClineProvider.delegateParentAndOpenChild()", () => {
 	it("persists parent delegation metadata and emits TaskDelegated", async () => {
 		const providerEmit = vi.fn()
 		const parentTask = { taskId: "parent-1", emit: vi.fn() } as any
 
-		const childStart = vi.fn()
+		const childStart = vi.fn().mockResolvedValue(undefined)
 		const updateTaskHistory = vi.fn()
 		const removeClineFromStack = vi.fn().mockResolvedValue(undefined)
 		const createTask = vi.fn().mockResolvedValue({ taskId: "child-1", start: childStart })
@@ -48,6 +54,7 @@ describe("ClineProvider.delegateParentAndOpenChild()", () => {
 			updateTaskHistory,
 			handleModeSwitch,
 			log: vi.fn(),
+			contextProxy: { globalStorageUri: { fsPath: "/tmp" } },
 		} as unknown as ClineProvider
 
 		const params = {
@@ -63,18 +70,26 @@ describe("ClineProvider.delegateParentAndOpenChild()", () => {
 
 		// Invariant: parent closed before child creation
 		expect(removeClineFromStack).toHaveBeenCalledTimes(1)
-		// Child task is created with startTask: false and initialStatus: "active"
+		// Child task is created with startTask: false
 		expect(createTask).toHaveBeenCalledWith("Do something", undefined, parentTask, {
 			initialTodos: [],
-			initialStatus: "active",
 			startTask: false,
 		})
 
-		// Metadata persistence - parent gets "delegated" status (child status is set at creation via initialStatus)
-		expect(updateTaskHistory).toHaveBeenCalledTimes(1)
+		// Metadata persistence - child gets "active" status, parent gets "delegated" status
+		expect(updateTaskHistory).toHaveBeenCalledTimes(2)
 
-		// Parent set to "delegated"
-		const parentSaved = updateTaskHistory.mock.calls[0][0]
+		// Child set to "active" (first call)
+		const childSaved = updateTaskHistory.mock.calls[0][0]
+		expect(childSaved).toEqual(
+			expect.objectContaining({
+				id: "child-1",
+				status: "active",
+			}),
+		)
+
+		// Parent set to "delegated" (second call)
+		const parentSaved = updateTaskHistory.mock.calls[1][0]
 		expect(parentSaved).toEqual(
 			expect.objectContaining({
 				id: "parent-1",
@@ -99,7 +114,10 @@ describe("ClineProvider.delegateParentAndOpenChild()", () => {
 		const callOrder: string[] = []
 
 		const parentTask = { taskId: "parent-1", emit: vi.fn() } as any
-		const childStart = vi.fn(() => callOrder.push("child.start"))
+		const childStart = vi.fn(() => {
+			callOrder.push("child.start")
+			return Promise.resolve()
+		})
 
 		const updateTaskHistory = vi.fn(async () => {
 			callOrder.push("updateTaskHistory")
@@ -130,6 +148,7 @@ describe("ClineProvider.delegateParentAndOpenChild()", () => {
 			updateTaskHistory,
 			handleModeSwitch,
 			log: vi.fn(),
+			contextProxy: { globalStorageUri: { fsPath: "/tmp" } },
 		} as unknown as ClineProvider
 
 		await (ClineProvider.prototype as any).delegateParentAndOpenChild.call(provider, {
@@ -139,7 +158,7 @@ describe("ClineProvider.delegateParentAndOpenChild()", () => {
 			mode: "code",
 		})
 
-		// Verify ordering: createTask → updateTaskHistory → child.start
-		expect(callOrder).toEqual(["createTask", "updateTaskHistory", "child.start"])
+		// Verify ordering: createTask → updateTaskHistory (child) → updateTaskHistory (parent) → child.start
+		expect(callOrder).toEqual(["createTask", "updateTaskHistory", "updateTaskHistory", "child.start"])
 	})
 })

src/__tests__/removeClineFromStack-delegation.spec.ts

@@ -1,6 +1,12 @@
 // npx vitest run __tests__/removeClineFromStack-delegation.spec.ts
 
 import { describe, it, expect, vi } from "vitest"
+
+vi.mock("../core/task-persistence/delegationMeta", () => ({
+	readDelegationMeta: vi.fn().mockResolvedValue(null),
+	saveDelegationMeta: vi.fn().mockResolvedValue(undefined),
+}))
+
 import { ClineProvider } from "../core/webview/ClineProvider"
 
 describe("ClineProvider.removeClineFromStack() delegation awareness", () => {
@@ -38,6 +44,7 @@ describe("ClineProvider.removeClineFromStack() delegation awareness", () => {
 			log: vi.fn(),
 			getTaskWithId,
 			updateTaskHistory,
+			contextProxy: { globalStorageUri: { fsPath: "/tmp" } },
 		}
 
 		return { provider, childTask, updateTaskHistory, getTaskWithId }
@@ -183,6 +190,7 @@ describe("ClineProvider.removeClineFromStack() delegation awareness", () => {
 			log: vi.fn(),
 			getTaskWithId: vi.fn(),
 			updateTaskHistory: vi.fn(),
+			contextProxy: { globalStorageUri: { fsPath: "/tmp" } },
 		}
 
 		// Should not throw
@@ -263,6 +271,7 @@ describe("ClineProvider.removeClineFromStack() delegation awareness", () => {
 			log: vi.fn(),
 			getTaskWithId,
 			updateTaskHistory,
+			contextProxy: { globalStorageUri: { fsPath: "/tmp" } },
 		}
 
 		// Simulate what delegateParentAndOpenChild does: pop B with skipDelegationRepair

src/core/assistant-message/presentAssistantMessage.ts

@@ -60,7 +60,7 @@ import { sanitizeToolUseId } from "../../utils/tool-id"
  */
 
 export async function presentAssistantMessage(cline: Task) {
-	if (cline.abort) {
+	if (cline.abort || cline.abandoned) {
 		throw new Error(`[Task#presentAssistantMessage] task ${cline.taskId}.${cline.instanceId} aborted`)
 	}
 
@@ -938,6 +938,15 @@ export async function presentAssistantMessage(cline: Task) {
 	// locked.
 	cline.presentAssistantMessageLocked = false
 
+	// Early exit if task was aborted/abandoned during tool execution (e.g., new_task delegation).
+	// Prevents unhandled promise rejections from recursive calls hitting the abort check.
+	if (cline.abort || cline.abandoned) {
+		if (cline.didCompleteReadingStream) {
+			cline.userMessageContentReady = true
+		}
+		return
+	}
+
 	// NOTE: When tool is rejected, iterator stream is interrupted and it waits
 	// for `userMessageContentReady` to be true. Future calls to present will
 	// skip execution since `didRejectTool` and iterate until `contentIndex` is
@@ -965,7 +974,11 @@ export async function presentAssistantMessage(cline: Task) {
 		if (cline.currentStreamingContentIndex < cline.assistantMessageContent.length) {
 			// There are already more content blocks to stream, so we'll call
 			// this function ourselves.
-			presentAssistantMessage(cline)
+			presentAssistantMessage(cline).catch((err) => {
+				if (!cline.abort) {
+					console.error("[presentAssistantMessage] Unhandled error:", err)
+				}
+			})
 			return
 		} else {
 			// CRITICAL FIX: If we're out of bounds and the stream is complete, set userMessageContentReady
@@ -978,7 +991,11 @@ export async function presentAssistantMessage(cline: Task) {
 
 	// Block is partial, but the read stream may have finished.
 	if (cline.presentAssistantMessageHasPendingUpdates) {
-		presentAssistantMessage(cline)
+		presentAssistantMessage(cline).catch((err) => {
+			if (!cline.abort) {
+				console.error("[presentAssistantMessage] Unhandled error:", err)
+			}
+		})
 	}
 }