> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neuraltrust.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Fallback

> Retry across registries when an upstream fails — configurable triggers, an attempt/latency budget, and an ordered fallback chain.

**Fallback** turns a single upstream failure into a retry on the next registry instead of
an error to the client. It is configured per [consumer](/trustgate/concepts/consumers)
(inline routing) and engages when a forward fails with a matching trigger.

```json theme={null}
"fallback": {
  "enabled": true,
  "triggers": ["http_5xx", "http_429", "timeout", "provider_error"],
  "budget": { "max_attempts": 3, "max_total_latency": "20s" },
  "chain": ["<primary_registry>", "<secondary_registry>", "<tertiary_registry>"]
}
```

## Triggers

A retry only happens when the failure matches a configured trigger:

| Trigger            | Fires on                                                                 |
| ------------------ | ------------------------------------------------------------------------ |
| `http_5xx`         | Upstream 5xx responses.                                                  |
| `http_429`         | Upstream rate-limit responses.                                           |
| `timeout`          | Upstream timeouts.                                                       |
| `provider_error`   | Provider-reported errors.                                                |
| `plugin_rejection` | A policy rejected the request (the trigger value is `plugin_rejection`). |

## Budget

The `budget` caps how hard TrustGate tries:

* **`max_attempts`** — total forward attempts (including the first).
* **`max_total_latency`** — wall-clock ceiling across all attempts.

When either limit is reached, the last error is returned to the client.

## The chain

`chain` is the ordered list of registries to try. On each failure TrustGate moves to the
next entry and adds the failed registry to an **exclude set**, so the
[load balancer](/trustgate/routing/load-balancing) never re-picks an already-failed
registry within the same request.

> Use fallback to span providers (e.g. OpenAI → Azure OpenAI → Bedrock) for resilience, or
> to degrade from a premium model to a cheaper one under load.