TruthGuard: Shell Script Hooks That Catch AI Coding Agent Lies

What TruthGuard Does

TruthGuard is a free, open-source tool built with Claude Code for Claude Code users. It addresses a documented problem where Claude Code makes false claims like "Done! All tests pass!" when tests were never run, or "I updated the file" when the file remains byte-for-byte identical. The creator notes that system prompts don't fix this issue—Claude ignores text instructions when it "decides" something is done.

What It Catches

• Phantom edits - Agent says "file updated" but SHA256 before and after is identical
• Exit code lies - Tests fail with exit 1, agent says they passed
• Dangerous shortcuts - Blocks --no-verify and --force push. Warns on reset --hard and clean -f
• Commits without tests - Auto-detects your test framework, runs tests before every git commit. Fails? Commit blocked
• "Done" without checking - After each commit, makes the agent stop and confirm the fix actually works before moving on

How It Works

Pure shell scripts plugged into Claude Code's hook pipeline. No backend, no API calls—just jq and bash. The workflow: Agent decides to edit a file → [PreToolUse] records SHA256 checksum → Agent edits the file → [PostToolUse] compares checksums → BLOCKS if unchanged. The agent can't argue with this—it's not a prompt it can ignore, it's a programmatic gate.

Dogfooding Results

After 2 days on a production Flutter project:

• 5 commits blocked because tests were failing
• 3 dangerous commands blocked (2x --force push, 1x --no-verify)
• 0 false positives - every block was a real problem

The pre-commit test hook alone kept the creator from shipping broken code five times in two days.

Installation

npx truthguard install && npx truthguard init

Or: brew tap spyrae/truthguard && brew install truthguard

Works with Claude Code and Gemini CLI. Same scripts for both—they're agent-agnostic (JSON in, JSON out).