feat(task-scheduler): enable concurrent delegated task fan-out

apps/vscode-e2e/src/fixtures/search-files.ts

@@ -89,7 +89,7 @@ export function addSearchFilesResultFixtures(mock: InstanceType<typeof LLMock>)
 			toolName: "search_files",
 			arguments: '{"path":"search-files-tool-fixture","regex":"nonExistentPattern12345"}',
 			toolCallId: "call_search_files_no_match_001",
-			expected: ["No results found"],
+			expected: ["Found 0 results."],
 			result: "No matches were found for `nonExistentPattern12345` in the search fixture directory.",
 			id: "call_search_files_no_match_002",
 		},

apps/vscode-e2e/src/fixtures/subtasks.ts

@@ -14,13 +14,27 @@ const SUBTASK_FAST_CHILD_MARKER = "SUBTASK_CHILD_IMMEDIATE_COMPLETION"
 const SUBTASK_XPROFILE_PARENT_MARKER = "SUBTASK_PARENT_CROSS_PROFILE"
 const SUBTASK_XPROFILE_SAME_CHILD_MARKER = "SUBTASK_CHILD_SAME_PROFILE"
 const SUBTASK_XPROFILE_DIFFERENT_CHILD_MARKER = "SUBTASK_CHILD_DIFFERENT_PROFILE"
+const SUBTASK_FANOUT_PARENT_MARKER = "SUBTASK_PARENT_FANOUT_CONCURRENT"
+const SUBTASK_FANOUT_CHILD_MARKER = "SUBTASK_CHILD_FANOUT_CONCURRENT"
+const SUBTASK_FANOUT_XPROFILE_PARENT_MARKER = "SUBTASK_PARENT_FANOUT_CROSS_PROFILE"
+const SUBTASK_FANOUT_XPROFILE_CHILD_MARKER = "SUBTASK_CHILD_FANOUT_CROSS_PROFILE"
 
 const SUBTASK_CHILD_PROMPT = `${SUBTASK_CHILD_MARKER}: Ask the user exactly this follow-up question: What is the square root of 81? After the user answers, complete with only the answer.`
 export const SUBTASK_PARENT_PROMPT = `${SUBTASK_PARENT_MARKER}: Use the new_task tool exactly once. Create an ask-mode subtask with this exact message: "${SUBTASK_CHILD_PROMPT}" Do not answer directly.`
 export const SUBTASK_CHILD_FOLLOWUP_ANSWER = "9"
 export const SUBTASK_FAST_CHILD_RESULT = "Fast child completed"
 const SUBTASK_FAST_CHILD_PROMPT = `${SUBTASK_FAST_CHILD_MARKER}: Complete immediately with the exact result "${SUBTASK_FAST_CHILD_RESULT}".`
 export const SUBTASK_FAST_PARENT_PROMPT = `${SUBTASK_FAST_PARENT_MARKER}: Use the new_task tool exactly once. Create an ask-mode subtask with this exact message: "${SUBTASK_FAST_CHILD_PROMPT}" Do not answer directly.`
+export const SUBTASK_FANOUT_PARENT_FOLLOWUP = "Parent fan-out is still active?"
+export const SUBTASK_FANOUT_CHILD_RESULT = "Fan-out child completed"
+const SUBTASK_FANOUT_CHILD_PROMPT = `${SUBTASK_FANOUT_CHILD_MARKER}: Complete with the exact result "${SUBTASK_FANOUT_CHILD_RESULT}".`
+export const SUBTASK_FANOUT_PARENT_PROMPT = `${SUBTASK_FANOUT_PARENT_MARKER}: Use the new_task tool exactly once. Create an ask-mode subtask with this exact message: "${SUBTASK_FANOUT_CHILD_PROMPT}" After delegation, ask the user exactly this follow-up question: ${SUBTASK_FANOUT_PARENT_FOLLOWUP}`
+export const SUBTASK_FANOUT_XPROFILE_PARENT_MODEL = "openai/gpt-4.1"
+export const SUBTASK_FANOUT_XPROFILE_CHILD_MODEL = "openai/gpt-4.1-mini"
+export const SUBTASK_FANOUT_XPROFILE_PARENT_FOLLOWUP = "Parent cross-profile fan-out is still isolated?"
+export const SUBTASK_FANOUT_XPROFILE_CHILD_RESULT = "Fan-out cross-profile child completed"
+const SUBTASK_FANOUT_XPROFILE_CHILD_PROMPT = `${SUBTASK_FANOUT_XPROFILE_CHILD_MARKER}: Complete with the exact result "${SUBTASK_FANOUT_XPROFILE_CHILD_RESULT}".`
+export const SUBTASK_FANOUT_XPROFILE_PARENT_PROMPT = `${SUBTASK_FANOUT_XPROFILE_PARENT_MARKER}: Use the new_task tool exactly once. Create an ask-mode subtask with this exact message: "${SUBTASK_FANOUT_XPROFILE_CHILD_PROMPT}" After delegation, ask the user exactly this follow-up question: ${SUBTASK_FANOUT_XPROFILE_PARENT_FOLLOWUP}`
 
 const SUBTASK_INTERRUPT_CHILD_PROMPT = `${SUBTASK_INTERRUPT_CHILD_MARKER}: Ask the user exactly this follow-up question: What is the square root of 81? After the user answers, complete with only the answer.`
 export const SUBTASK_INTERRUPT_PARENT_PROMPT = `${SUBTASK_INTERRUPT_PARENT_MARKER}: Use the new_task tool exactly once. Create an ask-mode subtask with this exact message: "${SUBTASK_INTERRUPT_CHILD_PROMPT}" Do not answer directly. When the subtask returns, complete with the exact result "Interrupted parent resumed".`
@@ -38,6 +52,7 @@ export const SUBTASK_API_HANG_PARENT_RESULT = "API hang parent resumed"
 // Correctness depends on no flat `latency` (fixture or LLMock default) being set on that
 // fixture — a flat latency would apply to every chunk after the first, not just the ttft.
 export const SUBTASK_API_HANG_RESPONSE_LATENCY_MS = 15_000
+export const SUBTASK_FANOUT_CHILD_DELAY_MS = 15_000
 
 // Abandon-subtask scenario (#559) — separate markers to avoid sequenceIndex collisions with the
 // interrupted-child-resumes tests above, which exhaust the sequence count for INTERRUPT markers.
@@ -141,6 +156,120 @@ export function addSubtaskFixtures(mock: InstanceType<typeof LLMock>) {
 		},
 	})
 
+	mock.addFixture({
+		match: {
+			userMessage: new RegExp(SUBTASK_FANOUT_PARENT_MARKER),
+			sequenceIndex: 0,
+		},
+		response: {
+			toolCalls: [
+				{
+					name: "new_task",
+					arguments: JSON.stringify({
+						mode: "ask",
+						message: SUBTASK_FANOUT_CHILD_PROMPT,
+					}),
+					id: "call_subtasks_fanout_parent_new_task_001",
+				},
+			],
+		},
+	})
+
+	mock.addFixture({
+		match: {
+			predicate: (req: ChatCompletionRequest) =>
+				lastUserMessageContains(req, SUBTASK_FANOUT_CHILD_MARKER) &&
+				!requestContains(req, [SUBTASK_FANOUT_PARENT_MARKER]),
+		},
+		streamingProfile: { ttft: SUBTASK_FANOUT_CHILD_DELAY_MS },
+		response: {
+			toolCalls: [
+				{
+					name: "attempt_completion",
+					arguments: JSON.stringify({ result: SUBTASK_FANOUT_CHILD_RESULT }),
+					id: "call_subtasks_fanout_child_completion_002",
+				},
+			],
+		},
+	})
+
+	mock.addFixture({
+		match: {
+			predicate: (req: ChatCompletionRequest) =>
+				requestContains(req, [SUBTASK_FANOUT_PARENT_MARKER, "Delegated to child task"]) &&
+				!requestContains(req, [SUBTASK_RESULT_INJECTION]),
+		},
+		response: {
+			toolCalls: [
+				{
+					name: "ask_followup_question",
+					arguments: JSON.stringify({
+						question: SUBTASK_FANOUT_PARENT_FOLLOWUP,
+						follow_up: [{ text: "continue" }],
+					}),
+					id: "call_subtasks_fanout_parent_followup_003",
+				},
+			],
+		},
+	})
+
+	mock.addFixture({
+		match: {
+			userMessage: new RegExp(SUBTASK_FANOUT_XPROFILE_PARENT_MARKER),
+			sequenceIndex: 0,
+		},
+		response: {
+			toolCalls: [
+				{
+					name: "new_task",
+					arguments: JSON.stringify({
+						mode: "ask",
+						message: SUBTASK_FANOUT_XPROFILE_CHILD_PROMPT,
+					}),
+					id: "call_subtasks_fanout_xprofile_parent_new_task_001",
+				},
+			],
+		},
+	})
+
+	mock.addFixture({
+		match: {
+			predicate: (req: ChatCompletionRequest) =>
+				lastUserMessageContains(req, SUBTASK_FANOUT_XPROFILE_CHILD_MARKER) &&
+				!requestContains(req, [SUBTASK_FANOUT_XPROFILE_PARENT_MARKER]),
+		},
+		streamingProfile: { ttft: SUBTASK_FANOUT_CHILD_DELAY_MS },
+		response: {
+			toolCalls: [
+				{
+					name: "attempt_completion",
+					arguments: JSON.stringify({ result: SUBTASK_FANOUT_XPROFILE_CHILD_RESULT }),
+					id: "call_subtasks_fanout_xprofile_child_completion_002",
+				},
+			],
+		},
+	})
+
+	mock.addFixture({
+		match: {
+			predicate: (req: ChatCompletionRequest) =>
+				requestContains(req, [SUBTASK_FANOUT_XPROFILE_PARENT_MARKER, "Delegated to child task"]) &&
+				!requestContains(req, [SUBTASK_RESULT_INJECTION]),
+		},
+		response: {
+			toolCalls: [
+				{
+					name: "ask_followup_question",
+					arguments: JSON.stringify({
+						question: SUBTASK_FANOUT_XPROFILE_PARENT_FOLLOWUP,
+						follow_up: [{ text: "continue" }],
+					}),
+					id: "call_subtasks_fanout_xprofile_parent_followup_003",
+				},
+			],
+		},
+	})
+
 	// The parent prompt embeds SUBTASK_FAST_CHILD_MARKER verbatim, so parent-resume turns
 	// can also match a bare substring check (same collision class as #561). Exclude the
 	// parent marker so those turns fall through to the parent-resume fixture below.

apps/vscode-e2e/src/fixtures/terminal-reuse-shell-race.ts

@@ -4,10 +4,19 @@ import { toolResultContains } from "./tool-result"
 
 export function addTerminalReuseShellRaceFixtures(mock: InstanceType<typeof LLMock>) {
 	// First command completes — model issues a second command on the same terminal.
-	// With the temp-script fix, both commands now deliver real output.
 	mock.addFixture({
 		match: {
-			predicate: (req) => toolResultContains(req, "call_terminal_reuse_001", ["first", "Exit code: 0"]),
+			predicate: (req) => {
+				const messages = Array.isArray(req?.messages) ? req.messages : []
+				const lastToolMsg = messages.filter((message) => message?.role === "tool").at(-1)
+
+				return (
+					lastToolMsg?.tool_call_id === "call_terminal_reuse_001" &&
+					toolResultContains(req, "call_terminal_reuse_001", [
+						"Command was submitted in the VS Code terminal",
+					])
+				)
+			},
 		},
 		response: {
 			toolCalls: [
@@ -25,7 +34,17 @@ export function addTerminalReuseShellRaceFixtures(mock: InstanceType<typeof LLMo
 	// Second command on the reused terminal also completes.
 	mock.addFixture({
 		match: {
-			predicate: (req) => toolResultContains(req, "call_terminal_reuse_002", ["second", "Exit code: 0"]),
+			predicate: (req) => {
+				const messages = Array.isArray(req?.messages) ? req.messages : []
+				const lastToolMsg = messages.filter((message) => message?.role === "tool").at(-1)
+
+				return (
+					lastToolMsg?.tool_call_id === "call_terminal_reuse_002" &&
+					toolResultContains(req, "call_terminal_reuse_002", [
+						"Command was submitted in the VS Code terminal",
+					])
+				)
+			},
 		},
 		response: {
 			toolCalls: [