Errors

Errors before the stream opens are JSON with an HTTP status. Errors after it has opened arrive as {"type":"error","message":"..."} inside the stream — by then the status line is already 200 and cannot be changed.

Statuses

Status	code	Cause	Do
400	—	Validation. Missing text, unknown register, bad mode	Fix the request
400	notes_too_short	fromNotes with too little to work from	Give it more notes
401	unauthorized	Bad or revoked API key	Check the key. Do not retry
402	quota_exceeded	Included allowance gone, no wallet fallback	Wait for resetAt, or upgrade
402	credits_required	Allowance gone and the wallet is short	Buy credits
402	expand_pro	mode: "expand" on a non-Pro plan	Upgrade, or use rewrite
413	word_cap	Draft is longer than the plan's per-request cap	Split the draft
413	—	Body too large — text or previousRewrite over the byte limit	Split the draft
429	rate_limit	Too many requests per minute	Back off, respect the headers
429	concurrency	Too many rewrites in flight for the plan	Wait for one to finish
503	kill_switch	HUMANIZE_DISABLED is set	Nothing. Try later
503	spend_cap	Daily spend breaker tripped	Nothing. Try later

The 402 body

{
  "error": "Your included allowance is used and your credit balance is too low.",
  "code": "credits_required",
  "reason": "credits",
  "plan": "free",
  "resetAt": "2026-09-01T00:00:00.000Z",
  "upgrade": true,
  "buyCredits": true,
  "requiredCredits": 4,
  "creditBalance": 1,
  "usage": { "requests": 40, "inputTokens": 198234 }
}

reason is requests, tokens, or credits — which limit you actually hit. upgrade and buyCredits say which routes out exist for this subject; an API key owned by an anonymous subject cannot buy credits, so buyCredits is false.

Retrying

• 429 — back off. Concurrency clears in seconds; a rate limit clears at the minute boundary.
• 503 — retry with a long delay. Both causes are operator-side and neither clears because you asked again.
• 401, 400, 402 — do not retry the same request. Nothing about it will change on its own.
• A mid-stream error event — safe to retry once. Partial output before it is incomplete, not wrong; discard it.

What you will not get

There is no error that means your draft was rejected on content. The endpoint does not moderate, classify, or refuse drafts. If something fails, it is a limit, a credential, or the service.