> ## Documentation Index
> Fetch the complete documentation index at: https://agentclientprotocol.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Model Config Option Category

* Author(s): [anna239](https://github.com/anna239)

## Elevator pitch

Add a new `model_config` category to session configuration options, so that agents can expose model-related parameters (context size, speed/quality trade-offs, etc) and clients can group them alongside the main model selector in the UI.

## Status quo

The `category` field on `SessionConfigOption` currently supports three values: `mode`, `model`, and `thought_level`. This works well when the model is a single selector, but some agents expose many model configurations — context window size, speed tier, and similar settings that logically belong next to the model picker.

## What we propose to do about it

Add a `model_config` variant to `SessionConfigOptionCategory`.

Agents tag any model-related parameters with `"category": "model_config"`, and clients render them near the primary `model` selector — for example as secondary controls within a model-picker popover or panel.

### Relationship to `thought_level`

Once `model_config` exists, `thought_level` is semantically a special case of a model configuration parameter. We keep `thought_level` as-is for backward compatibility — existing clients already handle it — but new model-related options should use `model_config`.

## Shiny future

Agents expose rich, parameterized model configurations over ACP.

## Implementation details and plan

### JSON format

An agent declares model-config options in `configOptions`:

```json theme={null}
{
  "configOptions": [
    {
      "id": "model",
      "name": "Model",
      "category": "model",
      "type": "select",
      "currentValue": "sonnet-4.5",
      "options": [
        { "value": "sonnet-4.5", "name": "Sonnet 4.5" },
        { "value": "opus-4.6", "name": "Opus 4.6" }
      ]
    },
    {
      "id": "context_size",
      "name": "Context Size",
      "category": "model_config",
      "type": "select",
      "currentValue": "200k",
      "options": [
        { "value": "200k", "name": "200K" },
        { "value": "1m", "name": "1M" }
      ]
    },
    {
      "id": "fast_mode",
      "name": "Fast Mode",
      "category": "model_config",
      "type": "boolean",
      "currentValue": false
    }
  ]
}
```

### Client behavior

* Clients SHOULD render `model_config` options near the `model` selector (e.g., in the same popover or panel).
* Clients that do not recognize the category MUST handle it gracefully per the existing spec — the option still renders, just without special placement.
* No new client capability negotiation is needed.

### Should `thought_level` move under `model_config`?

Not now. Existing clients already handle `thought_level`, so changing its semantics would be a breaking change. New model-related parameters should use `model_config`; `thought_level` remains for backward compatibility.

## Revision history

* 2026-04-08: Initial proposal