ToolRetryMiddleware

Retries failed tool calls with exponential backoff. Use this when tools may experience transient failures (network timeouts, rate limits, temporary unavailability) and you want automatic recovery without surfacing errors to the model.

Constructor

use synaptic::middleware::ToolRetryMiddleware;

// Retry up to 3 times (4 total attempts including the first)
let mw = ToolRetryMiddleware::new(3);

Configuration

The base delay between retries defaults to 100ms and doubles on each attempt (exponential backoff). You can customize it with with_base_delay:

use std::time::Duration;

let mw = ToolRetryMiddleware::new(3)
    .with_base_delay(Duration::from_millis(500));
// Delays: 500ms, 1000ms, 2000ms

Usage with create_agent

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

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

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

How It Works

• Lifecycle hook: wrap_tool_call
• When a tool call fails, the middleware waits for base_delay * 2^attempt and retries.
• Retries continue up to max_retries times. If all retries fail, the last error is returned.
• If the tool call succeeds on any attempt, the result is returned immediately.

The backoff schedule with the default 100ms base delay:

Combining with Tool Call Limits

When both middlewares are active, the retry middleware operates inside the tool call limit. Each retry counts as a separate tool call:

let options = AgentOptions {
    middleware: vec![
        Arc::new(ToolCallLimitMiddleware::new(30)),
        Arc::new(ToolRetryMiddleware::new(3)),
    ],
    ..Default::default()
};

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