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. To send your gateway key through a route that forwards it, see Forwarded keys.
• 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 and Responses APIs, 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.

Claude through an LLM gateway

The pi guide's Claude through an LLM gateway section applies to omp: give Claude targets an LLM client with format = "anthropic_messages". It shows how to check prompt caching and estimate the cost. This section covers what differs for omp, tested with Oh My Pi 18.2.11.

Thinking on anthropic-messages

On openai-completions and openai-responses, Switchyard turns omp's thinking level into adaptive thinking for an anthropic_messages target. On anthropic-messages, Switchyard sends omp's own thinking object unchanged. omp does not recognize a route ID such as switchyard as a Claude model. With thinking on, it sends thinking: {type: "enabled"}, and Claude Opus 5.5 and Sonnet 5 return HTTP 400. Set adaptive thinking on the model entry:

      - id: switchyard
        reasoning: true
        thinking:
          mode: anthropic-adaptive
          efforts: [low, medium, high]

omp requires efforts next to mode. With both set, it sends thinking: {type: "adaptive"} and output_config.effort.

Forwarded keys

To forward omp's key, remove auth: none and set apiKey: GATEWAY_API_KEY, the name of the environment variable that holds your gateway key. Unlike pi, omp reads the name without a leading $. With auth: none, omp sends no key, and the gateway returns HTTP 401. Only standalone switchyard-server forwards keys. The native Nemo Relay plugin rejects routes that use forward_auth = true (see Request Handling).

The pi guide's Forwarded keys table shows which request APIs a route accepts when it forwards the key. A route that forwards the key to an OpenAI-format LLM client, such as a classifier's GPT judge, accepts only openai-completions and openai-responses requests.