dispose terminal bg event listeners if session is cancelled

src/vs/workbench/contrib/terminalContrib/chatAgentTools/browser/tools/monitoring/outputMonitor.ts

@@ -468,8 +468,9 @@ export function matchTerminalPromptOption(options: readonly string[], suggestedO
 export function detectsInputRequiredPattern(cursorLine: string): boolean {
 	return [
 		// PowerShell-style multi-option line (supports [?] Help and optional default suffix) ending
-		// in whitespace
-		/\s*(?:\[[^\]]\]\s+[^\[\s][^\[]*\s*)+(?:\(default is\s+"[^"]+"\):)?\s+$/,
+		// in whitespace.  The label part uses [^\[\s]+(?:\s+[^\[\s]+)* to support multi-word
+		// labels (e.g. "Yes to All") while avoiding overlap with \s* that caused ReDoS.
+		/\s*(?:\[[^\]]\]\s+[^\[\s]+(?:\s+[^\[\s]+)*\s*)+(?:\(default is\s+"[^"]+"\):)?\s+$/,
 		// Bracketed/parenthesized yes/no pairs at end of line: (y/n), [Y/n], (yes/no), [no/yes]
 		/(?:\(|\[)\s*(?:y(?:es)?\s*\/\s*n(?:o)?|n(?:o)?\s*\/\s*y(?:es)?)\s*(?:\]|\))\s+$/i,
 		// Same as above but allows a preceding '?' or ':' and optional wrappers e.g.

src/vs/workbench/contrib/terminalContrib/chatAgentTools/browser/tools/runInTerminalTool.ts

@@ -28,7 +28,7 @@ import { ITerminalLogService, ITerminalProfile } from '../../../../../../platfor
 import { IRemoteAgentService } from '../../../../../services/remote/common/remoteAgentService.js';
 import { TerminalToolConfirmationStorageKeys } from '../../../../chat/browser/widget/chatContentParts/toolInvocationParts/chatTerminalToolConfirmationSubPart.js';
 import { IChatService, ChatRequestQueueKind, ElicitationState, type IChatExternalToolInvocationUpdate, type IChatTerminalToolInvocationData } from '../../../../chat/common/chatService/chatService.js';
-import { constObservable, type IObservable } from '../../../../../../base/common/observable.js';
+import { autorun, constObservable, type IObservable } from '../../../../../../base/common/observable.js';
 import { ChatModel, type IChatRequestModeInfo } from '../../../../chat/common/model/chatModel.js';
 import type { UserSelectedTools } from '../../../../chat/common/participants/chatAgents.js';
 import { CountTokensCallback, ILanguageModelToolsService, IPreparedToolInvocation, IToolConfirmationMessages, IStreamedToolInvocation, IToolData, IToolImpl, IToolInvocation, IToolInvocationPreparationContext, IToolInvocationStreamContext, IToolResult, ToolDataSource, ToolInvocationPresentation, ToolProgress } from '../../../../chat/common/tools/languageModelToolsService.js';
@@ -2111,6 +2111,33 @@ export class RunInTerminalTool extends Disposable implements IToolImpl {
 		// stops asking questions and lets the user finish interacting with the terminal.
 		let userIsReplyingDirectly = false;
 
+		const disposeNotification = () => this._backgroundNotifications.deleteAndDispose(termId);
+
+		// If the user manually stopped the agent, suppress background
+		// steering requests and tear down the notification listeners.
+		const handleSessionCancelled = (): boolean => {
+			if (sessionRef.object.lastRequest?.response?.isCanceled) {
+				disposeNotification();
+				return true;
+			}
+			return false;
+		};
+
+		// Proactively detect session cancellation so that all background
+		// listeners are torn down immediately, rather than waiting for the
+		// next terminal event to fire and discover the cancelled state.
+		store.add(autorun(reader => {
+			const request = sessionRef.object.lastRequestObs.read(reader);
+			if (!request?.response) {
+				return;
+			}
+			reader.store.add(request.response.onDidChange(ev => {
+				if (ev.reason === 'completedRequest' && request.response!.isCanceled) {
+					disposeNotification();
+				}
+			}));
+		}));
+
 		if (outputMonitor) {
 			let lastInputNeededOutput = '';
 			let lastInputNeededNotificationTime = 0;
@@ -2132,6 +2159,10 @@ export class RunInTerminalTool extends Disposable implements IToolImpl {
 					return;
 				}
 
+				if (handleSessionCancelled()) {
+					return;
+				}
+
 				const execution = RunInTerminalTool._activeExecutions.get(termId);
 				if (!execution) {
 					return;
@@ -2176,15 +2207,17 @@ export class RunInTerminalTool extends Disposable implements IToolImpl {
 
 		store.add(sessionRef);
 
-		const disposeNotification = () => this._backgroundNotifications.deleteAndDispose(termId);
-
 		store.add(commandDetection.onCommandFinished(command => {
 			const execution = RunInTerminalTool._activeExecutions.get(termId);
 			if (!execution) {
 				disposeNotification();
 				return;
 			}
 
+			if (handleSessionCancelled()) {
+				return;
+			}
+
 			// Dispose after first notification to avoid chatty repeated messages
 			// if the user runs additional commands via send_to_terminal.
 			disposeNotification();

src/vs/workbench/contrib/terminalContrib/chatAgentTools/test/browser/outputMonitor.test.ts

@@ -271,6 +271,15 @@ suite('OutputMonitor', () => {
 				false
 			);
 		});
+		test('PowerShell regex does not cause catastrophic backtracking (ReDoS)', () => {
+			// Pathological input: many spaces not followed by a bracket.
+			// With the old overlapping regex this would hang; it must return promptly.
+			const start = performance.now();
+			const pathological = '[Y] Yes' + ' '.repeat(200) + 'x';
+			detectsInputRequiredPattern(pathological);
+			const elapsed = performance.now() - start;
+			assert.ok(elapsed < 500, `Regex took ${elapsed}ms on pathological input, expected < 500ms`);
+		});
 		test('Line ends with colon', () => {
 			assert.strictEqual(detectsInputRequiredPattern('Enter your name: '), true);
 			assert.strictEqual(detectsInputRequiredPattern('Password: '), true);

src/vs/workbench/contrib/terminalContrib/chatAgentTools/test/electron-browser/runInTerminalTool.test.ts

@@ -7,6 +7,7 @@ import { ok, strictEqual } from 'assert';
 import { Separator } from '../../../../../../base/common/actions.js';
 import { CancellationToken } from '../../../../../../base/common/cancellation.js';
 import { Emitter, Event } from '../../../../../../base/common/event.js';
+import { constObservable } from '../../../../../../base/common/observable.js';
 import { Schemas } from '../../../../../../base/common/network.js';
 import { isLinux, isWindows, OperatingSystem } from '../../../../../../base/common/platform.js';
 import { count } from '../../../../../../base/common/strings.js';
@@ -150,6 +151,7 @@ suite('RunInTerminalTool', () => {
 			acquireExistingSession: () => ({
 				object: {
 					lastRequest: undefined,
+					lastRequestObs: constObservable(undefined),
 					onDidChange: Event.None,
 				},
 				dispose: () => { },