Errors

{
  "error": {
    "code": "preflight_failed",
    "message": "Post text is 312 graphemes; Bluesky allows at most 300.",
    "rule": "bluesky.text.max_graphemes",
    "platform": "bluesky",
    "platformVersion": "atproto-2026-04",
    "platformResponse": null,
    "remediation": "Shorten the post to 300 graphemes or fewer.",
    "requestId": "req_01HY6X4AWBJM2K9F2PTQMRD9JQ"
  }
}

const res = await fetch(url, init);
if (!res.ok) {
  const body = await res.json();
  // body.error is the envelope above.
  if (body.error.code === "preflight_failed") {
    // body.error.rule is the canonical rule id.
    // Look it up at /docs/preflight/<rule>/ for context.
    throw new PreflightError(body.error.rule, body.error.message);
  }
  if (body.error.code === "rate_limited") {
    const retry = Number(res.headers.get("retry-after") ?? 5);
    await sleep(retry * 1000);
    return retryOnce();
  }
  throw new Error(\`\${body.error.code}: \${body.error.message}\`);
}