Problem

When switching between dynamic providers (like OpenRouter to Chutes), the extension would sometimes default to Claude Sonnet 4 instead of the provider's default model. This happened because configured model IDs from the previous provider were being used with the new provider, even when that model doesn't exist in the new provider's model list.

Additionally, when users switch providers after selecting a model, the router models for the new provider may not be loaded yet, causing a TypeError when the code tries to access properties on undefined objects (fixes #9047).

Root Cause

The issue was cross-contamination between providers. For example:

1. User selects OpenRouter with model anthropic/claude-sonnet-4.5
2. User switches to Chutes
3. apiConfiguration.apiModelId still contains anthropic/claude-sonnet-4.5
4. Chutes doesn't have this model, so it falls back to default
5. But the fallback was inconsistently applied

Solution

1. Created reusable validation helper

Added getValidatedModelId() function that ensures the configured model ID exists in the current provider's available models before using it.

2. Applied to ALL dynamic providers

Updated all 10 dynamic providers that use routerModels:

• OpenRouter
• Requesty
• Glama
• Unbound
• LiteLLM
• Chutes (the main culprit)
• DeepInfra
• IO Intelligence
• Roo
• Vercel AI Gateway

3. Centralized default model logic

Created getProviderDefaultModelId() function to centralize provider default model logic and reduce import bloat.

4. Added optional chaining for TypeError prevention

Added optional chaining (?.) to all router model accesses to safely handle cases where router models are undefined during provider transitions.

Benefits

• Consistent behavior: All dynamic providers handle model validation identically
• DRY principle: Single validation logic instead of 10+ repeated implementations
• Bug prevention: Eliminates cross-contamination when switching providers
• Maintainability: Future changes only need to be made in one place
• Type safety: All changes are properly typed
• Enhanced robustness: Prevents TypeError during provider transitions

Testing

• TypeScript compilation passes
• ESLint passes with no warnings
• All pre-commit hooks pass

Fixes #9047 and supersedes #9049