---
id: block-invisible-unicode
track: coding
version: 0.1.1
label: blocks
keyword: block
where: write turn-end
sha256: 518f716868c54ba0207b09ce633758471cca37ad63a2d88c67f7be56836fa662
source: https://github.com/open-coder-ai/chock-catalog/tree/1e60d211c1bb767152c6ab0167932da06ab3a10f/base/block-invisible-unicode
catalog_ref: 1e60d211c1bb767152c6ab0167932da06ab3a10f
---

# Block Invisible Unicode

block-invisible-unicode · version 0.1.1

Blocks — Blocks on an agent's file writes and at turn end. Chock adds friction. It is not a security boundary. 

In a git repo: at commit (Chock refuses the commit, locally and in CI.)



## What it does

Blocks hidden Unicode in added lines: bidi, tag and plane-14 chars, word joiner, chained invisibles, zero-width/joiners/fillers by ASCII, mid-line BOM, LRM/RLM outside RTL text, selectors after ASCII, private-use runs of 16+. Allows emoji, RTL/Indic/Thai/CJK text, line-start BOM. Not caught: homoglyphs, a joiner between non-ASCII, binary files and text after U+2028 at commit. Runs: commit, agent write, turn's end. Waiver: 'pragma: allowlist invisible-unicode' same line; agent: HEAD only.

## Its label on each agent

- Claude Code (tested): Blocks — Blocks on an agent's file writes and at turn end. Builder: /coding/builder/#client=claude-code&p=block-invisible-unicode
- Cursor (tested): Blocks — Blocks on an agent's file writes and at turn end. Builder: /coding/builder/#client=cursor&p=block-invisible-unicode
- Codex (tested): Blocks — Blocks on an agent's file writes and at turn end. If the hook errors, the action goes through (not witnessed; the vendor's row is only partly live-run). Builder: /coding/builder/#client=codex&p=block-invisible-unicode
- GitHub Copilot (tested): Blocks — Blocks at turn end only. It does not check a file write when it happens. If the hook errors, the action goes through (not witnessed; the vendor's row is only partly live-run). Builder: /coding/builder/#client=copilot&p=block-invisible-unicode
- Devin (tested): Blocks — Blocks at turn end only. It does not check a file write when it happens. If the hook errors, the action goes through (vendor docs only, not witnessed). Builder: /coding/builder/#client=devin&p=block-invisible-unicode
- Grok (tested): Not graded yet for Grok. Builder: /coding/builder/#client=grok&p=block-invisible-unicode
- goose (tested): Not graded yet for goose. Builder: /coding/builder/#client=goose&p=block-invisible-unicode
- Antigravity (tested): Not graded yet for Antigravity. Builder: /coding/builder/#client=antigravity&p=block-invisible-unicode
- OpenHands (untested): Not graded yet for OpenHands. Builder: /coding/builder/#client=openhands&p=block-invisible-unicode
- Kimi Code (untested): Not graded yet for Kimi Code. Builder: /coding/builder/#client=kimi-code&p=block-invisible-unicode
- Factory Droid (untested): Not graded yet for Factory Droid. Builder: /coding/builder/#client=factory-droid&p=block-invisible-unicode

## What it misses

This policy does not state what it misses.

## Examples

- Refused: A staged source file uses a right-to-left override to disguise code (Trojan Source).
- Allowed: A staged file contains ordinary ASCII source code.

## Latest change

0.1.1 · 2026-10-07 — Promoted from draft to production: every test case ran and passed, and no bug report was open. Behaviour unchanged.

## Provenance

- Tested by 72 of 72 cases run automatically
- SHA-256: `518f716868c54ba0207b09ce633758471cca37ad63a2d88c67f7be56836fa662`
- Catalog commit: https://github.com/open-coder-ai/chock-catalog/commit/1e60d211c1bb767152c6ab0167932da06ab3a10f
- Source: https://github.com/open-coder-ai/chock-catalog/tree/1e60d211c1bb767152c6ab0167932da06ab3a10f/base/block-invisible-unicode (catalog path `base/block-invisible-unicode`)
- Presets: Prompt injection and memory
- JSON: `/api/coding/policies/block-invisible-unicode.json`
- Report a problem: https://chock.sh/report/?policy=block-invisible-unicode&version=0.1.1&page=%2Fcoding%2Fpolicies%2Fblock-invisible-unicode%2F