Error Handling

llm-exe uses LlmExeError for errors created by the library.

import {
  LlmExeError,
  isLlmExeError,
  serializeLlmExeError,
  formatLlmExeErrorForLog,
} from "llm-exe";

Error Shape

LlmExeError exposes these fields:

try {
  await executor.execute(input);
} catch (error) {
  if (isLlmExeError(error)) {
    console.log(error.code);
    console.log(error.category);
    console.log(error.context);
    console.log(error.cause);
  }
}

Field	Description
code	Machine-readable error code, such as parser.parse_failed
category	The prefix of the code, such as parser, prompt, or llm
context	Extra metadata about the failure
cause	Original error, when available

Branching on Codes

Use isLlmExeError(error, code) to check error codes.

try {
  const result = parser.parse(output);
} catch (error) {
  if (isLlmExeError(error, "parser.schema_validation_failed")) {
    // The output parsed, but did not match the schema.
  }

  if (isLlmExeError(error, "parser.parse_failed")) {
    // The output could not be parsed.
  }
}

You can also pass a list of codes.

if (
  isLlmExeError(error, [
    "llm.provider_rate_limited",
    "llm.provider_unavailable",
  ])
) {
  // Retry, queue, or fall back.
}

Common Categories

Known error categories include:

• configuration
• parser
• prompt
• llm
• embedding
• executor
• callable
• state
• request
• auth
• template
• internal

Provider Errors

HTTP failures from LLM providers use typed llm-exe errors:

Code	Typical cause
llm.provider_rate_limited	Provider returned a rate-limit status
llm.provider_auth_failed	Missing, invalid, or unauthorized credentials
llm.provider_invalid_request	Provider rejected the request body or model/options
llm.provider_unavailable	Timeout, unavailable provider, or server-side failure
llm.provider_http_error	Other provider HTTP error

Embedding providers use the same pattern with the embedding. prefix.

Provider error context may include:

• status
• statusText
• url
• providerError
• providerErrorBody
• responseHeaders

Secrets are redacted before provider error data is added to context.

Serialization

Use serializeLlmExeError when sending errors to logs, queues, or telemetry.

const payload = serializeLlmExeError(error);

Use formatLlmExeErrorForLog for compact logs.

logger.error(formatLlmExeErrorForLog(error));

error.toJSON() also returns the serialized value for LlmExeError instances.