Struct M 

pub struct M;

The M namespace — static factory methods for middleware.

Implementations

impl M

pub fn log() -> MiddlewareComposite

Add logging middleware.

pub fn latency() -> MiddlewareComposite

Add latency tracking middleware.

pub fn timeout(duration: Duration) -> MiddlewareComposite

Bound the agent run to duration. The text agent enforces the tightest timeout across its middleware chain by wrapping the whole run; on elapse it emits AgentEvent::Timeout and returns an error.

pub fn retry(max_retries: u32) -> MiddlewareComposite

Add retry middleware — tracks errors and advises on retry.

pub fn tap( f: impl Fn(&AgentEvent) + Send + Sync + 'static, ) -> MiddlewareComposite

Add a custom event observer — called on every agent event.

pub fn before_tool( f: impl Fn(&FunctionCall) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Add a custom before-tool filter — called before every tool invocation.

pub fn after_tool( f: impl Fn(&FunctionCall, &Value) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Add a custom after-tool hook — called after every successful tool invocation.

pub fn on_error( f: impl Fn(&AgentError) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Add a custom error observer — called when an agent-level error occurs.

pub fn cost() -> MiddlewareComposite

Add cost tracking middleware — records token usage estimates.

pub fn rate_limit(rps: u32) -> MiddlewareComposite

Add rate-limiting middleware — spaces tool calls to at most rps per second by delaying before_tool (concurrent calls queue rather than burst).

pub fn circuit_breaker(threshold: u32) -> MiddlewareComposite

Add circuit breaker middleware — opens after consecutive failures.

pub fn trace() -> MiddlewareComposite

Add tracing span middleware — creates spans for distributed tracing.

pub fn audit() -> MiddlewareComposite

Add audit middleware — records all tool calls for review.

pub fn structured_log() -> MiddlewareComposite

Structured logging middleware — logs agent events as structured JSON.

pub fn dispatch_log() -> MiddlewareComposite

Dispatch logging middleware — logs dispatch/join events.

pub fn topology_log() -> MiddlewareComposite

Topology logging middleware — logs agent topology events.

pub fn validate( f: impl Fn(&FunctionCall) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Add a tool input validator middleware.

pub fn cache() -> MiddlewareComposite

Response caching middleware — caches model responses to avoid redundant calls.

pub fn dedup() -> MiddlewareComposite

Deduplicate consecutive identical requests.

pub fn sample(rate: f64) -> MiddlewareComposite

Sample/pass-through a fraction of requests (0.0–1.0).

pub fn metrics() -> MiddlewareComposite

Metrics collection middleware — tracks request counts, error counts, and latencies.

pub fn before_agent( f: impl Fn(&InvocationContext) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Shortcut for a before-agent hook.

pub fn after_agent( f: impl Fn(&InvocationContext) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Shortcut for an after-agent hook.

pub fn before_model( f: impl Fn(&LlmRequest) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Shortcut for a before-model hook.

pub fn after_model( f: impl Fn(&LlmRequest, &LlmResponse) -> Result<(), String> + Send + Sync + 'static, ) -> MiddlewareComposite

Shortcut for an after-model hook.

pub fn on_loop(f: impl Fn(u32) + Send + Sync + 'static) -> MiddlewareComposite

Loop iteration event hook — called on each iteration of a loop agent.

pub fn on_timeout(f: impl Fn() + Send + Sync + 'static) -> MiddlewareComposite

Timeout event hook — called when an agent times out.

pub fn on_route(f: impl Fn(&str) + Send + Sync + 'static) -> MiddlewareComposite

Route decision event hook — called when a route agent selects a branch.

pub fn on_fallback( f: impl Fn(&str) + Send + Sync + 'static, ) -> MiddlewareComposite

Fallback event hook — called when a fallback agent activates.