# Arcaeon

Keeps a log of what your agent did and checks it in one command. Useful when you have to show the history was not edited.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI · ★ 1
- Author: Arcaeon-io
- License: MIT · policy=link-only · description only; the file stays with the author
- Source: https://github.com/Arcaeon-io/arcaeon
- Updated: 2026-10-11
- HTML: https://affpapa.org/en/nevibecode/mcp/arcaeon

## What it does

Each row Arcaeon writes is hash-chained to the one before it. Edit a row, drop one, or swap two, and the check points at the line where the chain breaks. You can hand the file to somebody else and they run the same check on their own.

Install the server part with `pip install "arcaeon[mcp]"`; the base package pulls in nothing at all. Python 3.10 or newer is required. The heavy pieces sit in extras: `arcaeon[mcp]` brings the MCP Python SDK and roughly 30 packages, `arcaeon[ts]` adds tree-sitter for the TypeScript checks, `arcaeon[sign]` adds cryptography for signed reports. Without `ARCAEON_KEY`, `seal` and `pin --remote` send nothing to the hosted witness — you still get the free badge, and the command exits 3.

Run `arcaeon mcp` and the server comes up on stdio, handing the agent ledger, vet and witness tools. One gap: deleting the last rows slips past a plain check. `arcaeon pin` closes it by giving the ledger's current head to a witness. Treat `ARCAEON_KEY` like a password, since a leaked key lets someone pin under your name.

## Requirements
- Needs: Python and uv (commands run via uvx)
- Environment variables: `ARCAEON_KEY` — keys and tokens: ask the human for the values, never commit them or put them in shared files.

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add arcaeon -e ARCAEON_KEY=<ARCAEON_KEY> -- uvx arcaeon
```
Replace <…> with your own values. uvx runs the command named after the package; if the README names another one, use uvx --from arcaeon <command>

### Codex

**Platform CLI**
```bash
codex mcp add arcaeon --env ARCAEON_KEY=<ARCAEON_KEY> -- uvx arcaeon
```
Replace <…> with your own values. uvx runs the command named after the package; if the README names another one, use uvx --from arcaeon <command>

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "arcaeon": {
            "command": "uvx",
            "args": [
                "arcaeon"
            ],
            "env": {
                "ARCAEON_KEY": "<ARCAEON_KEY>"
            }
        }
    }
}
```
Replace <…> with your own values. uvx runs the command named after the package; if the README names another one, use uvx --from arcaeon <command>

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "arcaeon": {
            "type": "stdio",
            "command": "uvx",
            "args": [
                "arcaeon"
            ],
            "env": {
                "ARCAEON_KEY": "<ARCAEON_KEY>"
            }
        }
    }
}
```
Replace <…> with your own values. uvx runs the command named after the package; if the README names another one, use uvx --from arcaeon <command>

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add -e ARCAEON_KEY=<ARCAEON_KEY> arcaeon uvx arcaeon
```
Replace <…> with your own values. uvx runs the command named after the package; if the README names another one, use uvx --from arcaeon <command>

## When to use it
- record agent actions in a log that cannot be quietly rewritten
- find the exact line where a chain broke
- hand someone a portable receipt they can verify themselves
- confirm a refund or an email fired once, not twice
- capture every tool call made to an MCP server through a proxy

## Example prompts
- Start `arcaeon mcp` and list the ledger tools the agent can call
- Run `arcaeon verify` on `agent.jsonl` and tell me whether the chain broke
- Check with `arcaeon once` that the refund was recorded a single time

## Similar
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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md