Architecture improvements:
- Extract ProviderService with switch/backfill/write methods
- Reduce command layer from 160 to 13 lines via delegation
- Separate business logic (services) from state management (commands)
- Introduce precise error handling with structured validation
Refactoring details:
- Split Codex/Claude switching into symmetric private methods
- Add multi-layer validation for Codex auth field (existence + type)
- Extract import_config_from_path for command and test reuse
- Expose export_config_to_file and ProviderService in public API
Test coverage:
- Add 10+ integration tests for Claude/Codex switching flows
- Cover import/export success and failure scenarios (JSON parse, missing file)
- Verify state consistency on error paths (current remains unchanged)
- Test snapshot backfill for both old and new providers after switching
Key improvements:
- Extract switch_provider_internal() returning AppError for better testability
- Fix backup mtime inheritance: use read+write instead of fs::copy to ensure latest backup survives cleanup
- Add 15+ integration tests covering provider commands, atomic writes, and rollback scenarios
- Expose write_codex_live_atomic, AppState, and test hooks in public API
- Extract tests/support.rs with isolated HOME and mutex utilities
Test coverage:
- Provider switching with live config backfill and MCP sync
- Codex atomic write success and failure rollback
- Backup retention policy with proper mtime ordering
- Negative cases: missing auth field, invalid provider ID
