Retry behavior - Nito

Retryable

Status	Codes	How to retry
`429`	`rate_limited`	Wait for `Retry-After`, then retry. `insufficient_quota` shares the status but is a funding decision: do not retry it.
`502`	`provider_error`	Transient upstream failure. Retry with backoff.
`503`	`unavailable`	Transient. Retry with backoff.

Not retryable

Status	Meaning
`400`	The request is wrong (`invalid_request`, `model_unavailable`). Fix it first.
`401`	The credential is wrong (`unauthorized`). Fix the key.
`403`	Not permitted (`forbidden`, `registered_free_unavailable`).
`404`	Wrong path (`unknown_route`). Fix the base URL.
`429` `insufficient_quota`	Out of balance or allowance. Add funds or wait for the reset.

Streams

The gateway never replays a live stream. A failure after bytes were written arrives as a terminal error chunk (finish_reason: "error"); retry with a new request from the client.

Uncertain Outcomes

A failure after the provider may have started work is reported as uncertain. Those responses carry nito_operation_id, a durable ID to quote to support, not a status-lookup key. Do not blindly resend a request that may already have run.