src/middleware.rs

This file holds your middleware trait, the dispatch context and result carriers, and the pipeline builder. The layers themselves live in middleware/*.rs.

Key items

ToolMiddleware asks for name() plus dispatch(ctx, next) as a boxed async method, so you can pre-process, call next, post-process, or short-circuit.

ToolDispatchContext { tool_name, input, call_id, turn_number, cancel, permission, tool_context } carries everything a layer may read or rewrite.

ToolPipeline is a cursor-based chain where registration order equals execution order, so the first layer you register sits outermost. It offers invoke(ctx), dispatch_all which is all-or-nothing on cancel, and middleware_names().

ToolPipelineBuilder gives you with_middleware, with_middleware_arc, with_core(registry), and build(), failing with PipelineError { Empty, MissingCore }.

The module re-exports every shipped layer plus ToolDispatchResult, which is defined in tool.rs.

Behavior notes

Your core, ToolCallMiddleware in tool_call.rs, is always innermost. That is where the registry lookup and the actual tool call happen.

On the engine path, agent.set_pipeline(builder) injects the loop’s registry as the core, so do not call with_core yourself there.

Order guidance: keep permission outermost so deny happens before work, place redaction before verifiers, and put the shield inside renamers and outside memoize.

Deep dive: Middleware.