Handle codes, not prose.

Eventium error responses use a stable envelope where implemented. Read the live operation schema for exact status codes.

{ "error": { "schema_version": "eventium.error.v1", "code": "AUTHENTICATION_REQUIRED", "message": "Authentication is required.", "retryable": false } }

Client behavior

Branch on the machine-readable code.
Show the safe message to the user when appropriate.
Retry only when retryable is true and the operation itself is safe to repeat.
Keep request or correlation identifiers in support evidence without logging credentials.

Common classes

Status	Meaning	Action
400	Contract validation failed	Correct the request.
401	Identity is absent or invalid	Sign in or rotate the credential.
403	Scope, role, entitlement, or policy denied	Request authorization; do not retry.
409	State or revision conflict	Refresh and reconcile.
429	Rate or quota boundary	Back off when allowed.
503	Required dependency unavailable	Retry only if marked retryable.