- Update model ID to claude-sonnet-4-6 (latest, Feb 2026)
- Add Relay/Proxy API Configuration section with apiBaseUrl patterns
- Document that maxConcurrency MUST be under commandLineOptions (not top-level)
- Add LLM-as-judge relay provider config (apiBaseUrl not inherited)
- Add 5 new Troubleshooting entries from real-world title-agent eval
- Add Concurrency Control section to API reference
- Clarify file:// path resolution (always relative to promptfooconfig.yaml)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>