Fact-forcing gate that blocks Edit/Write/Bash (including MultiEdit) and demands concrete investigation (importers, data schemas, user instruction) before allowing the action. Measurably improves output quality by +2.25 points vs ungated agents.
A PreToolUse hook that forces Claude to investigate before editing. Instead of self-evaluation ("are you sure?"), it demands concrete facts. The act of investigation creates awareness that self-evaluation never did.
LLM self-evaluation doesn't work. Ask "did you violate any policies?" and the answer is always "no." This is verified experimentally.
But asking "list every file that imports this module" forces the LLM to run Grep and Read. The investigation itself creates context that changes the output.
Three-stage gate:
1. DENY — block the first Edit/Write/Bash attempt
2. FORCE — tell the model exactly which facts to gather
3. ALLOW — permit retry after facts are presented
No competitor does all three. Most stop at deny.
Two independent A/B tests, identical agents, same task:
| Task | Gated | Ungated | Gap |
|---|---|---|---|
| Analytics module | 8.0/10 | 6.5/10 | +1.5 |
| Webhook validator | 10.0/10 | 7.0/10 | +3.0 |
| Average | 9.0 | 6.75 | +2.25 |
Both agents produce code that runs and passes tests. The difference is design depth.
MultiEdit is handled identically — each file in the batch is gated individually.
Before editing {file_path}, present these facts:
1. List ALL files that import/require this file (use Grep)
2. List the public functions/classes affected by this change
3. If this file reads/writes data files, show field names, structure,
and date format (use redacted or synthetic values, not raw production data)
4. Quote the user's current instruction verbatim
Before creating {file_path}, present these facts:
1. Name the file(s) and line(s) that will call this new file
2. Confirm no existing file serves the same purpose (use Glob)
3. If this file reads/writes data files, show field names, structure,
and date format (use redacted or synthetic values, not raw production data)
4. Quote the user's current instruction verbatim
Triggers on: rm -rf, git reset --hard, git push --force, drop table, etc.
1. List all files/data this command will modify or delete
2. Write a one-line rollback procedure
3. Quote the user's current instruction verbatim
Quote the user's current instruction verbatim.
The hook at scripts/hooks/gateguard-fact-force.js is included in this plugin. Enable it via hooks.json.
pip install gateguard-ai
gateguard init
This adds .gateguard.yml for per-project configuration (custom messages, ignore paths, gate toggles).
%Y/%m/%d %H:%M. Checking data structure (with redacted values) prevents this entire class of bugs..gateguard.yml to ignore paths like .venv/, node_modules/, .git/.safety-guard — Runtime safety checks (complementary, not overlapping)code-reviewer — Post-edit review (GateGuard is pre-edit investigation)