Run Claude Code hooks async and over HTTP — and put heavy work on Stop, not PostToolUse

Claude Code Docs·medium signal

Anthropic's January 2026 hooks update adds async: true (background hooks that don't block Claude's turn) and HTTP hooks that POST lifecycle events to a remote server for team-wide policy enforcement instead of local scripts. The discipline that keeps hooks fast: use PostToolUse with a Write|Edit matcher only for cheap per-edit ops like formatting, and move full test suites/builds to the Stop hook so you don't re-run them on every file write. Hooks are deterministic shell automations, so they're more reliable than asking the model to remember to format/test.