Function surfaceOauthError

apps/sim/app/api/mcp/oauth/start/route.ts:29–53

(error: unknown)

const MAX_SURFACED_ERROR_LENGTH = 250

export function surfaceOauthError(error: unknown): string {
  // Spec-compliant OAuth servers throw typed subclasses with clean RFC 6749 fields.
  if (error instanceof OAuthError && !(error instanceof ServerError)) {
    return truncate(`${error.errorCode}: ${error.message}`)
  }

  // ServerError wraps non-spec response bodies as "HTTP N: Invalid OAuth error
  // response: ... Raw body: {...}". Dig the vendor message out of the JSON tail.
  if (error instanceof Error) {
    const rawBodyMatch = error.message.match(/Raw body:\s*(\{[\s\S]*\})\s*$/)
    if (rawBodyMatch) {
      try {
        const body = JSON.parse(rawBodyMatch[1]) as Record<string, unknown>
        const vendorMessage =
          (typeof body.error_description === 'string' && body.error_description) ||
          (typeof body.message === 'string' && body.message) ||
          (typeof body.error === 'string' && body.error) ||
          null
        if (vendorMessage) return truncate(`Authorization server: ${vendorMessage}`)
      } catch {}
    }
    return truncate(error.message.split('\n')[0] || 'Failed to start OAuth flow')
  }
  return 'Failed to start OAuth flow'
}

function truncate(message: string): string {
  return message.length > MAX_SURFACED_ERROR_LENGTH