- Extend Usage struct with cache_creation_tokens and cache_read_tokens fields
- Parse Anthropic cache_creation_input_tokens and cache_read_input_tokens
- Parse OpenAI prompt_tokens_details.cached_tokens for automatic prefix caching
- Add CacheStats struct to Agent for cumulative tracking across API calls
- Add "Prompt Cache Statistics" section to /stats output showing:
- API call count and cache hit count
- Hit rate percentage
- Total input tokens and cache read/creation tokens
- Cache efficiency (% of input served from cache)
- Update all provider implementations and test files
Extract the get_stats() function (158 lines) from lib.rs to a new stats.rs module.
Changes:
- Create stats.rs with AgentStatsSnapshot struct for capturing agent state
- Replace inline formatting logic with delegation to snapshot.format()
- Add unit tests for stats formatting (empty and populated states)
- Reduce lib.rs from 2961 to 2818 lines (-143 lines)
The new module improves:
- Testability: Stats formatting can now be unit tested in isolation
- Separation of concerns: Formatting logic is decoupled from Agent struct
- Readability: lib.rs is more focused on core agent behavior
All 271 workspace tests pass.
Agent: fowler
