Errors

400 — validation. Two alternative shapes, never combined in one response. Field validation failures — each offending field maps to a list of messages:

{
  "plaintiff_name": ["This field is required."]
}

Cross-field rule violations (the conditional-requirement rules — “required when”, “at least one of”, etc.) arrive under non_field_errors, and are returned only once field-level validation passes:

{
  "non_field_errors": [
    "Fields 'policy_number' and 'claim_number' can not both be empty.You must define one (or both) of the fields."
  ]
}

401 — missing or bad token. No Authorization header: {"detail": "Authentication credentials were not provided."}. Header present but the token is invalid or expired: {"detail": "Invalid token."}.
403 — not currently returned by the partner API. Every partner endpoint only requires an authenticated user; cross-organization access to a case is reported as 404 (below), not 403, so as not to leak whether a case exists outside your organization.
404 — unknown case_ref, a case your organization can’t access, or results not yet available on the results endpoint.
409 — two sources with different bodies. Cancel returns it for a non-cancellable state (already closed, substantially complete, or intake still processing) with an error-keyed body — see the endpoint’s schema for the specific error code. The file-append endpoint returns it when the per-case cap is reached (25 files or 100 MB total per case) with a detail-keyed body: {"detail": "Per-case file limit reached (25 files / 104857600 bytes)."}.
429 — rate limited. Most endpoints allow 100/min per authenticated user; the file-append endpoint (POST .../cases/{case_ref}/files) is capped separately at 60/min. Body: {"detail": "Request was throttled. Expected available in <N> seconds."}. Honor Retry-After when present and retry with exponential backoff.
File-level failures are reported differently by endpoint: case creation reports each file’s outcome per-file in the attachments array via error_code — the case itself still succeeds. The single-file append endpoint instead fails the whole request with 400 and {"detail": ..., "error_code": ...}. See each endpoint’s error_code table.