session.set({ model })

session.set({ model }) is one of the explicit ways to bind a model instance in local SDK usage.

await session.set({
  model: openai.responses("gpt-5"),
});

When you need it

This is useful when:

• you are using @downcity/agent in pure SDK embedding mode
• you did not provide a default model through new Agent({ model })
• you want to override the model for one specific session

When you may not need it

If you already wrote:

const agent = new Agent({
  id: "repo-helper",
  path: "/path/to/project",
  model: openai.responses("gpt-5"),
});

then new sessions automatically receive that default model, so you usually do not need another explicit set.

Why it works this way

The local SDK behaves more like an embedded execution shell:

• the agent handles path, tools, plugins, and session storage
• the caller decides which live model instance should be used

That makes the local SDK more flexible, but it also makes the caller responsible for model readiness.

What happens if you skip it

If a local session has neither:

• new Agent({ model })

nor:

• session.set({ model })

then execution fails because the session has no default model.

What about remote sessions

Remote sessions do not currently support setting the model this way from the client side.

What about Downcity Agent projects

If you are working inside a normal Downcity Agent project, the model should usually come from:

• downcity.json.execution.modelId
• the connected Federation AIService

In that case, session.set({ model }) should not be treated as the default path.