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fix(core): decode byte-array encoded API error messages #19855

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fix(core): decode byte-array encoded API error messages #19855

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4a373f5
fix(core): decode byte-array encoded API error messages
Rohan-Mohite14 Feb 21, 2026
0412d47
Update packages/core/src/utils/errorParsing.ts
Rohan-Mohite14 Feb 22, 2026
e789c4b
Update packages/core/src/utils/errorParsing.ts
Rohan-Mohite14 Feb 22, 2026
a37c6c9
Update packages/core/src/utils/errorParsing.ts
Rohan-Mohite14 Feb 22, 2026
d776f0b
Merge branch 'main' into fix/decode-byte-array-errors
Rohan-Mohite14 Feb 22, 2026
3a5689d
Merge branch 'main' into fix/decode-byte-array-errors
Rohan-Mohite14 Feb 23, 2026
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16 changes: 16 additions & 0 deletions packages/core/src/utils/errorParsing.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -114,4 +114,20 @@ describe('parseAndFormatApiError', () => {
const expected = '[API Error: An unknown error occurred.]';
expect(parseAndFormatApiError(error)).toBe(expected);
});

it('should decode and format a byte-array encoded error message', () => {
const json = JSON.stringify({
error: {
code: 429,
message: 'No capacity available',
status: 'RESOURCE_EXHAUSTED',
},
});
const byteString = Array.from(json)
.map((c) => c.charCodeAt(0))
.join(',');
const result = parseAndFormatApiError(byteString);
expect(result).toContain('[API Error: No capacity available');
expect(result).toContain('RESOURCE_EXHAUSTED');
});
});
34 changes: 33 additions & 1 deletion packages/core/src/utils/errorParsing.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,18 @@ import { DEFAULT_GEMINI_FLASH_MODEL } from '../config/models.js';
import type { UserTierId } from '../code_assist/types.js';
import { AuthType } from '../core/contentGenerator.js';

function tryDecodeByteArray(s: string): string | null {
if (!/^\d+(,\d+)+$/.test(s)) {
return null;
}
try {
const bytes = new Uint8Array(s.split(',').map(Number));
return new TextDecoder().decode(bytes);
} catch {
return null;
}
}

const RATE_LIMIT_ERROR_MESSAGE_USE_GEMINI =
'\nPlease wait and try again later. To increase your limits, request a quota increase through AI Studio, or switch to another /auth method';
const RATE_LIMIT_ERROR_MESSAGE_VERTEX =
Expand Down Expand Up @@ -40,6 +52,16 @@ export function parseAndFormatApiError(
fallbackModel?: string,
): string {
if (isStructuredError(error)) {
const decoded = tryDecodeByteArray(error.message);
if (decoded) {
return parseAndFormatApiError(
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@mrpmohiburrahman mrpmohiburrahman Feb 28, 2026

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I noticed an edge case here.

When the code successfully decodes error.message and recursively calls
parseAndFormatApiError(decoded, ...), it passes only the new string and
leaves behind the original outer object, dropping error.status.

Timeline of what happens if the API returns a 429 Error:

  1. Input at line 47: { message: "78,111...", status: 429 }
  2. Line 55: tryDecodeByteArray decodes the message into the string
    "No capacity available".
  3. Line 57: The recursive call triggers, passing only the new string:
    parseAndFormatApiError("No capacity available", ...)
  4. The function restarts at line 47. Because the input is now a plain string
    instead of an object, status no longer exists.
  5. Line 66 (if (error.status === 429)) is never reached.

Actual Output: [API Error: No capacity available]

Expected Output:
[API Error: No capacity available]
Please wait and try again later. To increase your limits...

We should clone the error object here so we can preserve the original HTTP
status before recursing:

    if (decoded) {
      return parseAndFormatApiError(
        { ...error, message: decoded },
        authType,
        userTier,
        currentModel,
        fallbackModel,
      );

decoded,
authType,
userTier,
currentModel,
fallbackModel,
);
}
let text = `[API Error: ${error.message}]`;
if (error.status === 429) {
text += getRateLimitMessage(authType, fallbackModel);
Expand All @@ -49,9 +71,19 @@ export function parseAndFormatApiError(

// The error message might be a string containing a JSON object.
if (typeof error === 'string') {
const decoded = tryDecodeByteArray(error);
if (decoded) {
return parseAndFormatApiError(
decoded,
authType,
userTier,
currentModel,
fallbackModel,
);
}
const jsonStart = error.indexOf('{');
if (jsonStart === -1) {
return `[API Error: ${error}]`; // Not a JSON error, return as is.
return `[API Error: ${error}]`;
}

const jsonString = error.substring(jsonStart);
Expand Down