ModelCallLimitMiddleware

Limits the number of model invocations during a single agent run, preventing runaway loops. Use this when you want a hard cap on how many times the LLM is called per invocation.

Constructor

use synaptic::middleware::ModelCallLimitMiddleware;

let mw = ModelCallLimitMiddleware::new(10); // max 10 model calls

The middleware also exposes call_count() to inspect the current count and reset() to zero it out.

Usage with create_agent

use std::sync::Arc;
use synaptic::graph::{create_agent, AgentOptions};
use synaptic::middleware::ModelCallLimitMiddleware;

let options = AgentOptions {
    middleware: vec![
        Arc::new(ModelCallLimitMiddleware::new(5)),
    ],
    ..Default::default()
};

let graph = create_agent(model, tools, options)?;

How It Works

• Lifecycle hook: wrap_model_call
• Before delegating to the next layer, the middleware atomically increments an internal counter.
• If the counter has reached or exceeded max_calls, it returns SynapticError::MaxStepsExceeded immediately without calling the model.
• Otherwise, it delegates to next.call(request) as normal.

This means the agent loop terminates with an error once the limit is hit. The counter persists across the entire agent invocation (all steps in the agent loop), so a limit of 5 means at most 5 model round-trips total.

Example: Combining with Other Middleware

let options = AgentOptions {
    middleware: vec![
        Arc::new(ModelCallLimitMiddleware::new(10)),
        Arc::new(ToolRetryMiddleware::new(3)),
    ],
    ..Default::default()
};

let graph = create_agent(model, tools, options)?;

The model call limit is checked on every model call regardless of whether other middlewares modify the request or response.