Refactor AI model routing and add ImageViewer portal rendering

[rossmanko]

Summary by CodeRabbit

Release Notes

• New Features

  • Implemented automatic fallback retry mechanism for interrupted streaming requests

• Bug Fixes

  • Fixed modal rendering issues within constrained containers
  • Improved error recovery with fallback model retries and enhanced logging

• Refactor

  • Streamlined AI model routing configuration
  • Updated default fallback model provider

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Project	Deployment	Actions	Updated (UTC)
hackerai	Ready	Preview, Comment	Jan 31, 2026 9:00pm

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR consolidates AI model provider routing by removing provider-level constraints and standardizing all model mappings to OpenRouter with Google's Gemini backend. A new fallback model (Moonshot's Kimi K2.5) is introduced, and direct gateway and Google SDK dependencies are removed. The chat handler is enhanced with expanded streaming lifecycle hooks for analytics and a fallback retry mechanism for incomplete streams. A UI modal is rendered via portal to escape CSS containment.

Changes

Cohort / File(s)	Summary
Model Provider Consolidation lib/ai/providers.ts, package.json	Removed provider-level routing constraints, simplified model mappings to use openrouter/google/gemini-3-flash-preview, introduced new fallback-model mapped to moonshot/kimi-k2.5, and removed @ai-sdk/gateway and @ai-sdk/google dependencies.
Streaming & Retry Logic lib/api/chat-handler.ts	Enhanced prepareStep with conditional system prompt caching; expanded streaming lifecycle with onChunk/onFinish/onError hooks for tool call tracking, analytics, and usage accounting; introduced fallback retry mechanism for incomplete streams with detailed metadata logging.
Provider Options Cleanup lib/api/chat-stream-helpers.ts	Removed GoogleGenerativeAIProviderOptions and GatewayProviderOptions imports; eliminated gateway and google provider configuration blocks from buildProviderOptions return value.
UI Portal Rendering app/components/FilePartRenderer.tsx	Updated ImageViewer modal rendering to use createPortal with document existence guard to escape CSS contentVisibility containment.
Test Formatting lib/rate-limit/__tests__/token-bucket.test.ts	Reformatted multi-line assertion statements for readability without logic changes.

Sequence Diagram(s)

sequenceDiagram
    participant Client
    participant ChatHandler
    participant Stream
    participant Providers
    
    Client->>ChatHandler: initiate chat request
    ChatHandler->>Providers: prepare with model config
    ChatHandler->>Stream: start streaming
    
    loop Stream Processing
        Stream->>Stream: receive chunk
        Stream-->>ChatHandler: onChunk event (tool calls)
        ChatHandler->>ChatHandler: log analytics
    end
    
    Stream-->>ChatHandler: onFinish event
    ChatHandler->>ChatHandler: record usage & cost
    
    alt Incomplete Stream (step-start only)
        ChatHandler->>ChatHandler: detect incomplete
        ChatHandler->>Providers: retry with fallback-model
        Providers-->>Stream: retry stream
        Stream-->>ChatHandler: onFinish (fallback response)
        ChatHandler->>ChatHandler: save new messages
        ChatHandler->>ChatHandler: log fallback metadata
    else Complete Stream
        ChatHandler->>ChatHandler: finalize response
    end
    
    ChatHandler-->>Client: emit completion event

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

• Daily branch 2026 01 28 #194: Modifies lib/ai/providers.ts and package.json to switch model provider endpoints toward OpenRouter while removing gateway/google dependencies, directly overlapping with this PR's provider consolidation.
• Daily branch 2026 12 06 #156: Modifies lib/api/chat-handler.ts streaming lifecycle and event handling, with overlapping changes to streaming behavior and retry logic.
• Daily branch 2025 10 27 #64: Removes @ai-sdk/gateway dependency and related Google/gateway provider imports and configuration, directly aligning with this PR's dependency cleanup.

Poem

🐰 With portals wide, we leap so free,
Models unified in harmony,
When streams falter, fallback springs,
Through OpenRouter's cleaner wings,
Fewer gates, more hops to see! 🌟

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title accurately describes the two main changes: refactoring AI model routing (lib/ai/providers.ts and related files) and adding ImageViewer portal rendering (app/components/FilePartRenderer.tsx).

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch daily-branch-2026-01-31

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