Handle stringified forwarded chatError

src/vs/workbench/contrib/chat/common/chatErrorMessages.ts

@@ -354,7 +354,19 @@ function isForwardedChatError(value: unknown): value is IForwardedChatError {
  */
 export function getChatErrorDetailsFromMeta(error: ErrorInfo | undefined, context?: IChatErrorContext): IChatResponseErrorDetails | undefined {
 	const meta = error?._meta;
-	const chatError = meta?.chatError;
+	let chatError = meta?.chatError;
+	// In some hosts the forwarded chat error may be JSON-stringified. Accept
+	// either the raw object or a stringified payload and try to parse it so we
+	// can render friendly messages instead of falling back to generic errors.
+	if (typeof chatError === 'string') {
+		try {
+			chatError = JSON.parse(chatError);
+		} catch {
+			// If parsing fails, fall back to undefined so callers use their
+			// existing generic handling.
+			return undefined;
+		}
+	}
 	if (!isForwardedChatError(chatError)) {
 		return undefined;
 	}

src/vs/workbench/contrib/chat/test/common/chatErrorMessages.stringified.malformed.test.ts

@@ -0,0 +1,25 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../base/test/common/utils.js';
+import { getChatErrorDetailsFromMeta } from '../../common/chatErrorMessages.js';
+import type { ErrorInfo } from '../../../../../platform/agentHost/common/state/protocol/state.js';
+
+function errorInfo(meta: Record<string, unknown> | undefined): ErrorInfo {
+	return { errorType: 'e', message: 'm', _meta: meta };
+}
+
+suite('ChatErrorMessages (malformed stringified payload)', () => {
+	ensureNoDisposablesAreLeakedInTestSuite();
+
+	test('invalid JSON in forwarded chatError returns undefined (safe fallback)', () => {
+		// Malformed JSON string should not throw; the helper should return undefined
+		// so callers fall back to generic error handling.
+		const payload = '{ fetchError: { type: "rateLimited", retryAfter: 60 }'; // missing closing brace
+		const details = getChatErrorDetailsFromMeta(errorInfo({ chatError: payload }));
+		assert.strictEqual(details, undefined);
+	});
+});

src/vs/workbench/contrib/chat/test/common/chatErrorMessages.stringified.test.ts

@@ -0,0 +1,37 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../base/test/common/utils.js';
+import { ChatFetchResponseType, getChatErrorDetailsFromMeta } from '../../common/chatErrorMessages.js';
+import { ChatErrorLevel } from '../../common/chatService/chatService.js';
+import type { ErrorInfo } from '../../../../../platform/agentHost/common/state/protocol/state.js';
+
+function errorInfo(meta: Record<string, unknown> | undefined): ErrorInfo {
+	return { errorType: 'e', message: 'm', _meta: meta };
+}
+
+suite('ChatErrorMessages (stringified payload)', () => {
+	ensureNoDisposablesAreLeakedInTestSuite();
+
+	test('parses stringified forwarded chatError', () => {
+		const payload = JSON.stringify({
+			fetchError: {
+				type: ChatFetchResponseType.RateLimited,
+				retryAfter: 60,
+				capiError: { code: 'user_global_rate_limited', message: 'slow down' },
+			},
+			copilotPlan: 'free',
+		});
+
+		const details = getChatErrorDetailsFromMeta(errorInfo({ chatError: payload }));
+		assert.deepStrictEqual(details, {
+			code: ChatFetchResponseType.RateLimited,
+			message: 'You\'ve hit your session rate limit. Please upgrade your plan or wait 60 seconds for your limit to reset. [Learn More](https://aka.ms/github-copilot-rate-limit-error)',
+			level: ChatErrorLevel.Info,
+			isRateLimited: true,
+		});
+	});
+});