Middleware

When to use

Middleware is for cross-cutting behaviour that should apply consistently across many runs without changing the agent, model client, or tools themselves. Common use cases:

• Logging, tracing, timing
• Retry on transient failures
• Trim history before it reaches the model
• Cap or estimate token usage
• Rewrite tool arguments / results
• Enforce policies before a tool runs
• Audit human-input requests

Four hooks

BaseMiddleware exposes four async hooks. Implement only the ones you need: