Error codes

Every error response from the Management API and the hosted flows has the same shape:

{
  "status": 400,
  "message": "Invalid phone number. Include the country code, for example +34600123456.",
  "error_code": "invalid_phone",
  "docs": "https://faable.com/docs/auth/errors#invalid_phone",
  "details": { "fields": ["phone"] }
}

• error_code is the field to branch on. It is stable: a code is never renamed or reused with another meaning, and each code maps to exactly one HTTP status.
• message is written for a person and may change between releases. Show it in a log; do not compare it, and do not show it to end users as it is — map the code to your own copy instead.
• details is optional and structured. validation_error and already_exists carry fields; validation_error also carries issues (one { path, message } per failing field).
• docs links to the entry for the code on this page.

A few codes carry a detail after a colon — sms_unavailable:plan, sms_unavailable:quota. Branch on the prefix.

The one exception is the OAuth token endpoint (POST /oauth/token), which answers in the RFC 6749 shape — { "error", "error_description" } — and carries error_code as an extension member when the canonical error is too coarse (for example invalid_grant with error_code: "user_suspended").

With the SDK

@faable/auth-sdk throws a FaableApiError on any non-2xx. The code is on the error, and every generated method lists the codes it can throw in its docstring:

import { FaableApiError, FaableAuthApi } from '@faable/auth-sdk'
 
try {
  await auth.userCreate({ name, email, phone })
} catch (e) {
  if (e instanceof FaableApiError) {
    switch (e.error_code) {
      case 'already_exists':
        return 'That email is already registered.'
      case 'invalid_phone':
        return 'Write the phone with its country code, e.g. +34 600 123 456.'
      case 'validation_error':
        return `Check ${e.details?.fields?.join(', ')}.`
    }
    if (e.isErrorCode('sms_unavailable'))
      return 'SMS is not available right now.'
  }
  throw e
}

ErrorCode is exported as a TypeScript union, so a switch over it is checked by the compiler.

The OpenAPI document

Every operation in /docs/json documents its error responses: one entry per status, with error_code restricted to the codes that operation can emit. Code generators pick them up from there.

Generic codes

When an error has no more specific code, error_code is derived from the status. You will always get one of these at minimum; the specific codes below are what you should reach for first.

All codes

Generated from the server’s catalogue (npm run dump-error-codes in the auth service); the list is the same one the OpenAPI ErrorCode schema enumerates.

Last updated on September 17, 2026