GitHub Copilot agentic harness performance data

GitHub Copilot's agentic harness improves efficiency across four leading models: Claude Sonnet 4.6, Claude Opus 4.7, GPT-5.4, and GPT-5.5. The harness powers Copilot CLI, app, and code review. Benchmarks compare GitHub Copilot CLI against native model-vendor harnesses like Claude Code, controlling for model, task, context window, and reasoning efforts.