llm-errors

Normalize OpenAI, Anthropic and Gemini API errors into one shape: category, retryable flag and Retry-After delay. Zero dependencies.

Security posture is tracked in docs/security-posture.md, including CodeQL, OpenSSF Scorecard, Dependabot and branch rules.

Every LLM provider fails differently. OpenAI nests { error: { type, code, param } }, Anthropic wraps { type: "error", error: { type } }, Gemini speaks Google RPC status strings, and each puts retry hints in a different place. Generic HTTP failures add their own wrinkles with status-only errors and Retry-After headers. llm-errors collapses all of that into a single, predictable object so your retry and error-handling code stays provider-agnostic.

import { normalizeError, getRetryDelayMs } from 'llm-errors';

try {
  await client.chat.completions.create(params);
} catch (err) {
  const e = normalizeError(err);
  // -> { provider: 'openai', category: 'rate_limit', retryable: true, retryAfterMs: 2000, ... }

  if (e.category === 'context_length_exceeded') trimHistory();
  else if (e.retryable) await sleep(getRetryDelayMs(e, attempt));
  else throw err;
}

Why

• One switch, not three. A rate_limit is a rate_limit whether it came from OpenAI's code, Anthropic's type, or Gemini's RESOURCE_EXHAUSTED.
• Correct retry decisions. insufficient_quota and context_length_exceeded look like other 4xx/429s but are not worth retrying. llm-errors separates them out.
• Honours Retry-After safely. Reads the Retry-After header (seconds or HTTP date), retry-after-ms, and Google's RetryInfo.retryDelay for retryable errors — then falls back to exponential backoff with jitter when none is given.
• Never throws. Feed it an SDK error, a raw fetch response, plain JSON, null, or a string — it always returns a NormalizedError.
• Transport errors too. Connection timeouts, resets and DNS failures (ETIMEDOUT, ECONNRESET, AbortError, …) have no HTTP status, yet they are retryable — llm-errors classifies them as timeout / server_error instead of dropping them.
• Zero dependencies, ESM + CJS, fully typed.

Install

npm install llm-errors

Fixture corpus

The npm package includes a public fixture corpus under fixtures/. It pairs raw SDK-like, fetch-like and transport-level provider errors with the normalized output expected from normalizeError.

These fixtures are useful for downstream regression tests when you want to verify provider-portable retry and error handling without importing OpenAI, Anthropic or Gemini SDKs.

API

normalizeError(error, options?) => NormalizedError

Classifies any value into:

interface NormalizedError {
  provider: 'openai' | 'anthropic' | 'gemini' | 'unknown';
  category: ErrorCategory;
  message: string;
  status?: number; // HTTP status, when available
  code?: string; // provider-specific code / type
  retryable: boolean;
  retryAfterMs?: number; // provider-supplied delay for retryable errors, if any
  raw: unknown; // the original input
}

The provider is auto-detected from SDK errors, parsed fetch envelopes and direct provider error bodies. Pass { provider } to force it when you already know which client threw or the shape is ambiguous:

normalizeError(err, { provider: 'anthropic' });

Unknown providers still get safe status-based behavior. For example, a plain { status: 503, headers: { "Retry-After": "4" } } normalizes to provider: "unknown", category: "overloaded", retryable: true and retryAfterMs: 4000. A non-retryable unknown status ignores the same header.

ErrorCategory

Category	Retryable	Typical cause
authentication	no	Missing / invalid API key (401)
permission	no	Key valid but not allowed (403)
rate_limit	yes	Too many requests (429)
insufficient_quota	no	Billing / credits exhausted (429)
context_length_exceeded	no	Prompt + completion over the context window
request_too_large	no	Payload too large (413)
invalid_request	no	Malformed request (400 / 422)
not_found	no	Unknown model or resource (404)
content_filter	no	Blocked by a safety policy
timeout	yes	Request / upstream timeout (504)
server_error	yes	Upstream failure (500)
overloaded	yes	Provider temporarily overloaded (503 / 529)
unknown	no	Could not be classified

Only rate_limit, server_error, overloaded and timeout are retryable. unknown is deliberately not retryable, so unrecognized shapes fail closed instead of causing accidental retry storms.

isRetryableError(error, options?) => boolean

Shorthand for normalizeError(error).retryable.

getRetryDelayMs(error, attempt, options?) => number

Returns the delay to wait before the next attempt. Non-retryable errors return 0. If the provider supplied a valid retryAfterMs, that wins. Otherwise it computes exponential backoff baseMs * 2 ** attempt, capped at maxMs, with full jitter by default.

getRetryDelayMs(e, attempt, { baseMs: 500, maxMs: 60_000, jitter: 'full' });

parseRetryAfter / parseGoogleRetryDelay

The low-level helpers, exported for advanced use.

Example: a provider-agnostic retry loop

import { normalizeError, getRetryDelayMs } from 'llm-errors';

async function withRetries<T>(call: () => Promise<T>, max = 5): Promise<T> {
  for (let attempt = 0; ; attempt++) {
    try {
      return await call();
    } catch (err) {
      const e = normalizeError(err);
      if (!e.retryable || attempt >= max) throw err;
      await new Promise((r) => setTimeout(r, getRetryDelayMs(e, attempt)));
    }
  }
}

Related

• tool-schema — convert a JSON Schema into OpenAI / Anthropic / Gemini / MCP tool schemas.
• llm-messages — convert conversations and responses between providers.

License

MIT © Sebastian Legarraga