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block-invisible-unicode

100 / 100 · Low risk

Fine to try.

By open-coder-ai/chock (GitHub) · coding · 10 stars · scanned at commit 9fe0a59

The mechanizable slice of prompt-injection defense, enforced at two points: at commit (the git hook, over staged changes) and at agent tool-use (over a tool call's arguments, as the agent writes) -- invisible and direction-override Unicode. Bidi controls make code read differently than it parses (Trojan Source, CVE-2021-42574); Unicode tag-block characters smuggle instructions that are invisible to a human reviewer but fully legible to the agent reading the file. Zero-width joiners and bidi mar…

Works with any agent that supports SKILL.md skills.

What this skill can do

We found nothing in the files we read that matches our rules. That does not prove the skill is safe: see the limits of static scanning.

Install

Paste this into your terminal. It downloads exactly the version we scanned, not whatever is newest.

if [ -e ~/.agents/skills/'block-invisible-unicode' ] || [ -L ~/.agents/skills/'block-invisible-unicode' ]; then echo 'A skill folder named block-invisible-unicode already exists — not replacing it' >&2; false; else d=$(mktemp -d) && git clone --quiet --filter=blob:none --no-checkout 'https://github.com/open-coder-ai/chock' "$d" && git -C "$d" checkout --quiet '9fe0a59174384230f02faeecbe4a837ff3e96b9a' -- '.agents/policies/block-invisible-unicode/skills/block-invisible-unicode' && mkdir -p ~/.agents/skills && cp -R "$d"/'.agents/policies/block-invisible-unicode/skills/block-invisible-unicode' ~/.agents/skills/'block-invisible-unicode' && rm -rf "$d"; fi

Codex reads ~/.agents/skills directly. For Claude Code, Cursor, Copilot, Gemini CLI, Antigravity or OpenCode, also link it. For Claude Code: ln -s ~/.agents/skills/'block-invisible-unicode' ~/.claude/skills/'block-invisible-unicode' (other agents: ~/.cursor/skills, ~/.copilot/skills, ~/.gemini/skills, ~/.gemini/config/skills, ~/.config/opencode/skills). Or install through the finder skill, which does both.

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