Use Switchyard with Oh My Pi

Oh My Pi (omp) is a coding agent based on pi. It reads its model providers from ~/.omp/agent/models.yml. Add Switchyard there and omp sends every model call to switchyard-server. omp has no --base-url flag, and setting OPENAI_BASE_URL does not change the address of its built-in openai provider. This page was tested with Oh My Pi 18.1.21 against the Getting Started server on http://localhost:4000 with route id switchyard.

Configure

~/.omp/agent/models.yml:

providers:
  switchyard:
    baseUrl: http://localhost:4000/v1
    api: openai-completions
    auth: none
    models:
      - id: switchyard
        name: Switchyard stage router
        reasoning: true
        input: [text, image]
        contextWindow: 200000
        maxTokens: 32000

• auth: none marks the provider as keyless. Switchyard ignores client keys unless an LLM client sets forward_auth = true. Without auth: none, omp refuses to send a request.
• models[].id must equal a route id from your TOML file. contextWindow and maxTokens set omp's compaction limit and output cap. reasoning: true turns on the --thinking flag.
• omp models find switchyard shows the loaded entry.

Or let omp list the routes

providers:
  switchyard:
    baseUrl: http://localhost:4000/v1
    api: openai-completions
    auth: none
    discovery:
      type: openai-models-list

omp reads GET /v1/models and adds one model per route. For routes that declare context_window, omp takes the context window from the context_length field that the server reports. Other routes get omp's default of 128K tokens. Discovered models have no thinking controls and accept text only. List the models by hand when you need --thinking or image input. omp caches the list for a day, so run omp models refresh after you change the routes.

Run

omp --model switchyard/switchyard
omp -p --model switchyard/switchyard "List the files in this directory."

--thinking off|minimal|low|medium|high|xhigh sets the reasoning level. Setting modelRoles.default: switchyard/switchyard in ~/.omp/agent/config.yml makes the route the default model.

Check the routing

The checks in Use Switchyard with pi work the same way for omp. On the Chat Completions API, omp sends no session header for a custom provider, so the routing log records "session_id": null. Routes with classify_trigger = "user_turn" or "new_session", advisor budgets, and the stage router's capable_hold_turns then treat each request as its own session. If you need per-session routing, use anthropic-messages. On that API omp sends the X-Claude-Code-Session-Id header, which Switchyard reads as the session id.

Which request API

api	Endpoint	Use it when
openai-completions	/v1/chat/completions	Default. The targets use format = "openai_chat", for example OpenRouter.
openai-responses	/v1/responses	The targets use format = "openai_responses". omp sends store: false and the full history every turn.
anthropic-messages	/v1/messages	You need per-session routing. Set baseUrl: http://localhost:4000 and keep auth: none.

When the route's LLM client uses the same format as the request, Switchyard forwards the body unchanged except for model. When the client uses another format, Switchyard translates the request. Unlike pi, omp keeps the local model id switchyard on stored messages, so the served target's name in the response does not affect its thinking replay or compaction.

Port 4000 is also the default port for omp's litellm provider and for omp auth-gateway. If LITELLM_API_KEY is set, omp probes http://localhost:4000/v1 as a LiteLLM proxy. In that case, run Switchyard on another port or set LITELLM_BASE_URL. Set cost on the model entry if you want omp to show a non-zero cost.