proof

proof is a skill for Claude Code, Codex from tajmahal226/compound-engineering-plugin. It costs 64 tokens per session (1,824 once invoked), scanned A, a copy of proof, MIT.

A way to create, edit, review, and share Markdown documents through Proof, a collaborative editor for people and AI agents.

In plain words
What is it for?
Use it to create shareable documents, read their contents, apply edits, add comments, and suggest revisions through Proof’s web service or local Mac app connection.
Why use it?
It gives agents a shared document space for drafting, feedback, and revisions instead of keeping changes isolated in chat.

Skill for Claude CodeCodex

Part of the compound-engineering plugin — 20 skills, 17 commands, 1 MCP server shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/tajmahal226/compound-engineering-plugin/proof
Any agent
npx skills add tajmahal226/compound-engineering-plugin --skill proof
Clone the repo
git clone --depth 1 https://github.com/tajmahal226/compound-engineering-plugin

Made for: Claude Code, Codex.

Or install compound-engineering, the plugin that ships this one along with the rest of its 20 skills, 17 commands, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for proof

README.md
[![agentmods](https://agentmods.dev/badge/skills/tajmahal226/compound-engineering-plugin/proof.svg)](https://agentmods.dev/skills/tajmahal226/compound-engineering-plugin/proof)
Your own site
<a href="https://agentmods.dev/skills/tajmahal226/compound-engineering-plugin/proof"><img src="https://agentmods.dev/badge/skills/tajmahal226/compound-engineering-plugin/proof.svg" alt="Measured on agentmods" height="20"></a>
Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,824 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00064 $0.01824
Opus 5 $0.00032 $0.00912
Sonnet 5 $0.00013 $0.00365
Haiku 4.5 $0.00006 $0.00182

Measured 5d ago against content hash f673b6551982, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

proof scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -X POST https://www.proofeditor.ai/share/markdown \
Origin

This is a copy

100% identical to proof — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/compound-engineering/skills/proof/SKILL.md · 186 lines

How it starts

The opening of the file, as written. The whole thing — 186 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Proof - Collaborative Markdown Editor

Proof is a collaborative document editor for humans and agents. It supports two modes:

  1. Web API - Create and edit shared documents via HTTP (no install needed)
  2. Local Bridge - Drive the macOS Proof app via localhost:9847

Web API (Primary for Sharing)

Create a Shared Document

No authentication required. Returns a shareable URL with access token.

curl -X POST https://www.proofeditor.ai/share/markdown \
  -H "Content-Type: application/json" \
  -d '{"title":"My Doc","markdown":"# Hello\n\nContent here."}'

Response format:

{
  "slug": "abc123",
  "tokenUrl": "https://www.proofeditor.ai/d/abc123?token=xxx",
  "accessToken": "xxx",
  "ownerSecret": "yyy",
  "_links": {
    "state": "https://www.proofeditor.ai/api/agent/abc123/state",
    "ops": "https://www.proofeditor.ai/api/agent/abc123/ops"
  }
}

Use the tokenUrl as the shareable link. The _links give you the exact API paths.

Read a Shared Document

curl -s "https://www.proofeditor.ai/api/agent/{slug}/state" \
  -H "x-share-token: <token>"

Edit a Shared Document

All operations go to POST https://www.proofeditor.ai/api/agent/{slug}/ops

Note: Use the /api/agent/{slug}/ops path (from _links in create response), NOT /api/documents/{slug}/ops.

Authentication for protected docs:

  • Header: x-share-token: <token> or Authorization: Bearer <token>
  • Token comes from the URL parameter: ?token=xxx or the accessToken from create response

Comment on text:

{"op": "comment.add", "quote": "text to comment on", "by": "ai:<agent-name>", "text": "Your comment here"}

Reply to a comment:

{"op": "comment.reply", "markId": "<id>", "by": "ai:<agent-name>", "text": "Reply text"}

Resolve a comment:

{"op": "comment.resolve", "markId": "<id>", "by": "ai:<agent-name>"}

Suggest a replacement:

{"op": "suggestion.add", "kind": "replace", "quote": "original text", "by": "ai:<agent-name>", "content": "replacement text"}

Read the full file on GitHub · 186 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 186 lines · 64 tokens per session scan A f673b6551982

Subscribe to this mod's changes

proof is a skill published in the GitHub repository tajmahal226/compound-engineering-plugin (4 stars, last pushed 6mo ago), licensed MIT. It adds 64 tokens to every session and 1,824 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to proof, differing in 0 lines, and is treated as a copy.

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