UI Test Guard

ui-test-guard — Stop Hook for Honest UI Testing

A Claude Code Stop hook that intercepts replies claiming a UI change is complete and asks: did you actually run a real-browser test? If not, it injects a system-reminder so Claude has to either run the test or admit it skipped.

The problem

Claude will happily report a UI change as "deployed and verified" after running only curl | grep "expected text". Curl can confirm the server returns a 200 with the right string in its body, but it cannot catch:

• CSS layout breakage
• React hydration errors
• RSC flight payloads served as raw text instead of rendered HTML
• Blank screens caused by JS runtime errors
• Visual regressions
• Missing fonts, broken images, overflow, mobile-only bugs

A user can spend hours trusting "verified" reports that were never actually verified.

The fix

A Stop hook scans Claude's last reply. If it contains:

• A claim word: deployed, verified, done, shipped, live, tested, complete, works, ALL PASSED
• AND a URL or known web route: https://..., /login, /dashboard, /portfolio, etc.
• AND no evidence of a real-browser test: ui-test, run_tests.py, ALL PASSED, playwright, cypress

…the hook returns exit 2 with a reminder. Claude sees the reminder on the next turn and has to either run the test or explicitly say it skipped.

How it works

Fail-open by design: if jq is missing, the transcript is unreadable, or anything else goes wrong, the hook exits 0. No false positives blocking real work.

Install

1. Copy the hook

mkdir -p ~/.claude/hooks/ui-test-guard
cp skills/ui-test-guard/hooks/ui-test-guard.sh ~/.claude/hooks/ui-test-guard/
chmod +x ~/.claude/hooks/ui-test-guard/ui-test-guard.sh

2. Register in settings.json

Add this to ~/.claude/settings.json under hooks:

{
  "hooks": {
    "Stop": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "/home/<you>/.claude/hooks/ui-test-guard/ui-test-guard.sh",
            "timeout": 5
          }
        ]
      }
    ]
  }
}

See settings.example.json for the project-relative path version.

3. Verify

# Synthetic transcript that should trigger
mkdir -p /tmp/guard-test
cat > /tmp/guard-test/bad.jsonl <<'EOF'
{"type":"assistant","message":{"content":[{"type":"text","text":"I deployed the fix to /dashboard and verified it works."}]}}
EOF
echo '{"transcript_path":"/tmp/guard-test/bad.jsonl"}' | bash ~/.claude/hooks/ui-test-guard/ui-test-guard.sh
echo "exit=$?"
# Expected: prints reminder to stderr, exit=2

Customize the regexes

Override any regex via environment variables before the hook runs. Useful when you want to scope to a specific project URL:

Wrap the hook in a wrapper script to apply the env, e.g.:

#!/bin/bash
export UI_TEST_GUARD_URL_RE='(myapp\.example\.com|/dashboard|/admin)'
exec ~/.claude/hooks/ui-test-guard/ui-test-guard.sh

Pair this with a real-browser test runner

This hook only nags. It does not run the test. You still need a test harness. Pairs well with:

• ui-test skill (AWS AgentCore Browser, in this repo)
• Playwright
• Cypress
• Selenium

The EVIDENCE_RE matches the names of the most common harnesses, so it stays quiet when any of them are mentioned in the reply.

Why a Stop hook, not PreToolUse

Two design choices were considered:

Stop hook (this skill): soft, advisory. Reminds Claude after the fact. Does not block any tool. Lets Claude finish a thought, then nudges. Best for repeated education.

PreToolUse hook (alternative): hard block. Refuses git commit or aws ssm send-command if recent test results don't show pass. Stronger, but risks blocking legitimate non-UI work and frustrating the user.

This skill picks the soft path. Upgrade to PreToolUse only if Stop reminders aren't enough.

File layout

ui-test-guard/
├── SKILL.md                      # this file
├── settings.example.json         # hooks block to merge into settings.json
└── hooks/
    └── ui-test-guard.sh          # the hook itself (one Bash script)

Limitations

• Only as good as the regexes. If Claude phrases its claim creatively, the hook won't fire.
• Reads the JSONL transcript — sensitive to changes in Claude Code's transcript schema. Tested on Claude Code 2.x.
• One hook per Stop event. If you have other Stop hooks, register them all in the same array.