Errors

Helium MVNE returns errors in RFC 9457 Problem Details format:

{
  "type": "https://errors.mvne.example/validation",
  "title": "Validation failed",
  "status": 422,
  "code": "validation_failed",
  "detail": "email is required",
  "instance": "/v1/subscribers",
  "errors": [
    { "path": "/email", "code": "required", "message": "email is required" }
  ]
}

Common status codes

Status	When	Retry?
`400`	Malformed request	No
`401`	Missing or invalid API key	No
`403`	Key missing a required capability	No
`404`	Resource not found (or wrong environment)	No
`409`	Idempotency key in-flight	Yes, after delay
`422`	Validation failed	No
`429`	Rate limited	Yes, honor `Retry-After`
`5xx`	Helium MVNE-side error	Yes, backoff

Error code catalog

Codes are stable strings — they're safe to branch on. The catalog is generated from the OpenAPI spec; see the Errors section in the API reference for the complete list with per-endpoint applicability.