LLMWise/Learn/What Is AI Failover?
Glossary

What Is AI Failover?

AI failover is the automatic process of switching from a failing LLM to a healthy backup model, ensuring your AI features stay online during provider outages.

Definition

AI failover is a reliability pattern that automatically redirects requests from a failing or degraded LLM provider to a healthy alternative. When the primary model returns errors, times out, or exceeds latency thresholds, the failover system detects the problem and routes subsequent requests to a pre-configured backup model. This happens transparently, with no user-visible interruption. Failover is essential for production AI systems because LLM providers experience outages, rate limiting, and performance degradation regularly.

The circuit breaker pattern

A circuit breaker tracks consecutive failures for each model. When failures exceed a threshold, the circuit opens and the model is temporarily removed from rotation. After a cooldown period, the circuit enters a half-open state and sends a single test request. If the test succeeds, the circuit closes and normal traffic resumes. If it fails, the cooldown resets. LLMWise implements a three-strike circuit breaker with a 30-second open window, balancing fast failure detection with minimal false positives from transient errors.

Fallback chains and health checking

A fallback chain defines the priority order of models to try when the primary fails. Effective chains cross provider boundaries: if GPT-5.2 is primary, the first fallback should be from a different provider like Claude Sonnet 4.5 or Gemini 3 Flash. This protects against full provider outages, not just individual model issues. Health checking complements failover by proactively monitoring provider status and detecting degradation before user traffic is affected, enabling preemptive rerouting.

Implementing failover with LLMWise

LLMWise Mesh mode provides production-ready failover in a single API parameter. You specify a primary model and a fallback chain, and the platform handles circuit breaking, automatic rerouting, and recovery detection. Each failover event is logged with the failure reason, fallback model used, and added latency. The streaming protocol includes route events that tell your application exactly which model is handling the request and whether any failovers occurred, giving you full visibility without building custom monitoring.

How LLMWise implements this

LLMWise gives you five orchestration modes — Chat, Compare, Blend, Judge, and Mesh — with built-in optimization policy, failover routing, and replay lab. One API key, nine models, no separate subscriptions.

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Common questions

How often do LLM providers experience outages?
Major providers typically experience partial outages or degraded performance multiple times per month. Full outages are rarer but do occur. Rate limiting during peak hours is even more common. Failover ensures these events do not become outages for your users.
Does failover affect response quality?
The fallback model may produce slightly different output than the primary. The impact depends on how similar the models are. For most production use cases, getting a good response from a different model is far better than returning an error. LLMWise Replay Lab lets you test fallback quality against historical requests before deploying your failover chain.

Try it yourself

500 free credits. One API key. Nine models. No credit card required.