[Code Quality] Add named type LLMProvider string in pkg/workflow/llm_provider.go

[github-actions]

Description

The LLM provider identifiers (LLMProviderGitHub, LLMProviderAnthropic, LLMProviderOpenAI) in pkg/workflow/llm_provider.go are declared as plain string constants. This closed enum is threaded as a bare string through the ResolveLLMProvider(...) string interface method, its 5 engine implementations, the EngineConfig.LLMProvider string field, and four switch normalizeLLMProvider(...) sites — allowing arbitrary strings to be passed without compile-time safety.

Suggested Changes

1. Add type LLMProvider string in pkg/workflow/llm_provider.go
2. Type the three constants: LLMProviderGitHub LLMProvider = "github" etc.
3. Update EngineConfig.LLMProvider field from string to LLMProvider
4. Update ResolveLLMProvider(...) string interface method to return LLMProvider
5. Update all engine implementations (claude, codex, copilot, pi engines)
6. Update normalizeLLMProvider return type

Files Affected

• pkg/workflow/llm_provider.go (add type, re-type constants)
• pkg/workflow/engine.go (EngineConfig.LLMProvider field)
• pkg/workflow/agentic_engine.go (interface method signature)
• Engine implementation files (claude/codex/copilot/pi engines)

Success Criteria

• type LLMProvider string defined
• All call sites use LLMProvider type (no implicit string conversions)
• All tests pass
• make fmt green

Source

Extracted from [typist] 🔤 Typist — Go Type Consistency Analysis #47070

Priority

High — prevents arbitrary provider strings, improves contract clarity across 5 engine implementations

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• expires on Jul 22, 2026, 5:16 PM UTC-08:00