Add setModel, getThinkingLevel, setThinkingLevel to ExtensionAPI

[badlogic]

Summary

Add three methods to ExtensionAPI to enable extensions to change model and thinking level at runtime. This unblocks implementing preset configurations (#347) as an extension rather than built-in.

Motivation

Issue #347 requests preset configurations. Analysis showed that an extension can already:

• Read config files (Node.js fs)
• Register CLI flags (--preset)
• Change active tools (setActiveTools)
• Append to system prompt (before_agent_start event)
• Show UI selectors (ctx.ui.select)
• Find models (ctx.modelRegistry.find)

But it cannot:

• Set the current model
• Get/set thinking level

Proposed API Additions

interface ExtensionAPI {
  // ... existing ...

  /** Set the current model. Returns false if model not found or no API key. */
  setModel(model: Model<any>): Promise<boolean>;

  /** Get current thinking level */
  getThinkingLevel(): ThinkingLevel;

  /** Set thinking level (clamped to model capabilities) */
  setThinkingLevel(level: ThinkingLevel): void;
}

Implementation

1. types.ts - Add API methods and handler types
2. loader.ts - Wire up handlers in loadExtension()
3. runner.ts - Accept and distribute handlers in initialize()
4. agent-session.ts - Provide actual implementations

TUI Reflection

The footer already reads model/thinking from session state on each render. No TUI changes needed.

Related

• Preset configurations #347 - Preset configurations (will be implementable as extension after this)