GitHub Copilot CLI gets HydraFusion multi-model routing

GitHub launched Project HydraFusion, a research preview in Copilot CLI that decides how to solve a task rather than just which model to call: a single model, a cascade with escalation to a stronger model, or a critique from a different model family. In offline evals against always running Claude Opus 5 it costs less, though it can cost more than a simple cheap pick.

• Three patterns: Single, Cascade with escalation, and Critique by another model
• Reviews run isolated and tool-less, so the critic cannot mutate the tree
• Failed or cancelled workflows apply no patch; cost is counted across every leg
• Still a research preview, best for first-turn, well-scoped coding tasks