Error format

Every error shares one flat envelope:

{
  "error": "validation_failed",
  "message": "validation failed",
  "fields": {
    "slug": "slug is required",
    "outputOptions.pdf.format": "format \"A9\" is not supported (allowed: A0, A1, …)"
  }
}

fields is present only for field-level validation errors. Common codes:

HTTP	error code	When
400	kind_mismatch	Endpoint doesn't match the active template kind.
400	invalid_json	Request body isn't valid JSON (or is empty when required).
400	name_mismatch	PUT template: filename in the body doesn't match the URL.
403	csrf_blocked	Sec-Fetch-Site: cross-site on a mutating call.
404	not_found	Report, template, or version doesn't exist.
409	duplicate_slug	A report with that slug already exists.
413	upload_too_large	Template upload exceeds MAX_BINARY_UPLOAD_BYTES.
415	unsupported_media_type	Body present with an unsupported Content-Type.
422	validation_failed	Field validation failed (see fields).
422	invalid_template_name	Asset name has illegal characters or hits a reserved name.
422	invalid_template	Uploaded content is invalid — bad UTF-8 HTML, or not a real .docx/.xlsx.
422	template_missing	Render/preview called with no active template selected.
422	html_preview_unavailable	preview-html called on a non-HTML active template.
422	empty_template	The rendered output was empty.
422	template_error	Handlebars failed to compile/execute (also covers JS helper errors).
422	empty_commit	A commit would record zero changed files.
500	internal_error	Unexpected server error.
503	*_renderer_unavailable	The PDF/DOCX/XLSX renderer isn't configured on the server.
503	versions_unavailable	Commit/history store not configured.