feat: Adopt ModelCapabilitiesOverride for vision-capable model switching

[PureWeen]

Context

SDK v0.2.2 added ModelCapabilitiesOverride to ModelApi.SwitchToAsync(). Currently we pass null (PR #641).

Opportunity

When switching to a vision-capable model (e.g., GPT-4o, Claude with vision), we could pass ModelCapabilitiesOverride with:

• Limits.Vision.SupportedMediaTypes — MIME types the model accepts
• Limits.Vision.MaxPromptImages — image count limit
• Limits.Vision.MaxPromptImageSize — size limit per image
• Limits.MaxContextWindowTokens — context window for the specific model

This would enable the CLI to enforce proper image limits and token budgets per model rather than using server defaults.

Current State

// CopilotService.cs:3316
await state.Session.Rpc.Model.SwitchToAsync(normalizedModel, reasoningEffort, null, cancellationToken);

Priority

Low — only relevant if custom model limits are needed. Server defaults work fine for now.

[github-actions]

✅ Agent Fix completed successfully!

[github-actions]

Pull request created: #824

Generated by Agent Fix

[github-actions]

Implementation Summary

PR created to adopt ModelCapabilitiesOverride when switching models mid-session.

Changes

1. ModelCapabilities.GetCapabilitiesOverride() — new method that maps existing ModelCapability flags to SDK ModelCapabilitiesOverride:

   • Vision models (gemini-3-pro, etc.): Supports.Vision = true + image limits (PNG/JPEG/GIF/WebP, max 10 images, 20 MB)
   • Reasoning models (claude-opus, gpt-5, etc.): Supports.ReasoningEffort = true
   • Other models: returns null (server defaults apply)

2. CopilotService.ChangeModelAsync() — now passes capabilities to SwitchToAsync instead of null

Test Results

• ✅ 3686 tests passed, 0 failed (includes 9 new tests for GetCapabilitiesOverride)
• ✅ Integration test builds successfully
• 🚀 Expert review and CI dispatched

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Generated by Agent Fix for issue #643 · ● 23.3M · ◷