How to Build a Self-Verification Loop in Claude Code (3 Layers, 20 Minutes)

Claude Code's Stop hook blocks the agent from finishing until verification passes. Combine it with PostToolUse feedback injection to build a 3-layer verification loop (syntax, intent, regression) in 20 minutes. The result: the agent can't say "done" until it actually is. Two hook setups. Same Claude Code session. Different outcomes: # What most devs have: a formatting hook # PostToolUse: runs prettier after file edits # What this post builds: a verification loop # PostToolUse: checks syntax on e