# Block Invisible Unicode

Block Invisible Unicode: what it does, its label on each agent, what it misses, and examples.

Catalog policy block-invisible-unicode, version 0.1.1, labelled blocks on Claude Code.

> Ask the user before running any command on this page: each one changes how their agent or repository behaves.

## 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.

## On each agent

| Agent | Label | What it does there |
| --- | --- | --- |
| Claude Code | Blocks | Blocks on an agent's file writes and at turn end |
| Cursor | Blocks | Blocks on an agent's file writes and at turn end |
| Codex | 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) |
| GitHub Copilot | 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) |
| Devin | 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) |
| Grok | Not graded | Not graded yet for Grok |
| goose | Not graded | Not graded yet for goose |
| Antigravity | Not graded | Not graded yet for Antigravity |
| OpenHands | Not graded | Not graded yet for OpenHands |
| Kimi Code | Not graded | Not graded yet for Kimi Code |
| Factory Droid | Not graded | Not graded yet for Factory Droid |

## What it misses

This policy does not state what it misses.

## Examples from its eval suite

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.

## More

- [The policy on the catalog pages](https://chock.sh/coding/policies/block-invisible-unicode/)
- [Source at the pinned catalog commit](https://github.com/open-coder-ai/chock-catalog/tree/1e60d211c1bb767152c6ab0167932da06ab3a10f/base/block-invisible-unicode)


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