Use a model

Select, verify, and observe a model without working on PtcRunner's provider implementation.

ptc-host.json installs a model under a stable alias, and ptc.json selects it for trusted workflow code. Generated mission code never receives the route.

What must the model support?

An agent loop needs an endpoint that accepts tools. PtcRunner distinguishes an unsupported tool contract from a missing model or credential.

How do I choose one?

Start with the shipped example model: OpenRouter's deepseek/deepseek-v4-flash. Catalogs and routing change, so choose a model advertised for tool use and confirm its exact route with ptc doctor PROJECT.json --connect.

Two aliases share the public llm-request call budget. config.max_calls additionally caps an alias only when it is stricter than that shared budget.

Where do credentials belong?

Bind credentials outside the application, preferably through a named source in ptc-host.json. Inspect the public installation without revealing its credential or private endpoint:

ptc models ptc-project.json
ptc doctor ptc-project.json

models names each LLM selector but withholds an endpoint-bearing openai-compat: selector because it carries a private address.

What can I check before a run?

Plain doctor is inert. Use the active connectivity probe only when a remote request is intended:

ptc doctor ptc-project.json --connect

ptc models, ptc validate, and ptc doctor do not provide a pre-run price quote. Use the optional reservation budget described in Size an LLM cost budget; a refusal names the next call's exact requirement.

What does a run record?

After a run, the trace records how many model calls were made, which alias they used, reported token usage and cost, timing, and a safe failure class. Prompts and responses are private and appear only when private inspection is enabled.

Start with Install models and tools for one complete workflow. The model and host reference owns selector forms, credentials, cache policy, request parameters, ceilings, diagnostics, and connectivity behavior. See Customize an agent for the model-neutral loop.