NVIDIA NeMo Switchyard

Switchyard is an open-source library that helps an AI agent choose which model handles each request. It combines efficient models with more capable models so you can balance task success, cost, and latency on your workload.

Adopt Switchyard by embedding its Rust core, libsy, in your gateway or agent harness. You own the model clients, credentials, and service. Switchyard supplies the routing decision.

How it works

1. Configure the models an agent can use and choose a routing algorithm.
2. The algorithm examines the request or the agent's recent tool activity. Some algorithms call a model to judge the task.
3. A gateway or agent sends the request to the selected model. Routing can change as the agent continues its work.

Evaluate the complete agent, model pool, and routing configuration against your single-model baseline. A cheaper model call does not guarantee a cheaper successfully completed task. The tuning loop gives the steps for that evaluation, and Troubleshooting lists the settings that disable routing without an error.

How to use it

• Through an existing gateway: Use an available gateway integration.
• Embed libsy in your harness: Add libsy to a service you operate.
• Evaluate Switchyard locally: Compare routing configurations with your own model pool using the demo server.

Through an existing gateway

Gateway	Start here	Deployment and limits
Agent Router	Agent Router	Open-source and self-hosted. It provides an OpenAI-compatible API and runs on Envoy.
LiteLLM	Run the Switchyard routing-plugin example	Experimental and checkout-only. The example pins LiteLLM 1.102.0 and supports Stage routing based on request history, plus Random routing. It cannot service intermediate model calls required by classifier or escalation algorithms.
NeMo Relay	Build and configure the native plugin	Requires Relay >=0.10.0, <1.0.0. The source-build path requires a Rust toolchain and Python 3.
OpenRouter	Use Switchyard through OpenRouter	Hosted by OpenRouter. Set model to nvidia/switchyard in API requests.

Relay 0.8.x and 0.9.0 can lose upstream error status and details when the plugin is enabled, even for models outside its routes. Review the upstream error compatibility note before enabling the plugin.

LiteLLM and NeMo Relay run in your own deployment. Follow each gateway's guidance for credentials and service operation.

Embed libsy in your harness

Algorithm::run_stream hands model calls and the final routing outcome back to your application. In this development-API outline, comments mark the work your code supplies:

let mut steps = algorithm.run_stream(request, models, state);
while let Some(step) = steps.next().await {
    match step? {
        Step::CallModel(call) => {
            // Send call.request through your LLM client.
            // Give the call future to call.respond(...).await.
        }
        Step::CallDecision(call) => {
            // Send call.request through your decision-model client.
            // Give its typed response future to call.respond(...).await.
        }
        Step::Done(outcome) => {
            match outcome.response {
                Some(response) => {
                    // Return this answer; no final LLM call is needed.
                }
                None => {
                    // Send outcome.request through your client for the final answer,
                    // or pass it to your gateway to make that call later.
                }
            }
        }
    }
}

• Inputs: supply an algorithm, model pool, request, and state.
• Calls: your clients handle model calls. Stage returns a selection; other algorithms may return an answer.
• Start here: Rust quickstart · Python bindings.

Evaluate Switchyard locally

The standalone server is provided only for demos and local evaluation. It is not a supported production deployment path.

Evaluate routing locally with the standalone server and your own model pool, then verify routing is active.

The experimental desktop and terminal quickstart covers local installation, coding-tool connections, sessions, usage, recovery, and uninstall.

Agent-specific guides are available for pi and Oh My Pi.

Routing algorithms

Start with Auto. Choose Task, Execution, or Composite when you need more control. These names describe routing choices. The configuration keys are unchanged.

This is the beginning of the README. Read the rest at the original. Read the full README ↗