Universal MCP server that emits Context Passport records for AI agent decisions and actions. Drop into any MCP-compatible client (Claude Code, Cursor, Cline, Continue, ChatGPT Desktop, Zed, Goose, and others) to give your agent a commit / verify / replay / export toolset for verifiable, tamper-evident records.

Built by DarkMatter. Implements Context Passport v1.0, an open CC0 standard.

Install

In your MCP client's config (claude_desktop_config.json, Cursor's mcp.json, etc.):

{
  "mcpServers": {
    "darkmatter": {
      "command": "npx",
      "args": ["-y", "@darkmatterhub/mcp-server"]
    }
  }
}

Restart the client. Five tools become available to your agent:

darkmatter_commit — record an agent decision or action
darkmatter_verify — check that the chain has not been tampered with
darkmatter_replay — walk the full chain in order
darkmatter_export — produce a portable proof bundle
darkmatter_list_sessions — see what sessions exist locally

What gets captured

Whatever the agent (or user) explicitly invokes via darkmatter_commit. Auto-capture of every tool call without explicit invocation is a separate component (see Auto-capture below).

Example agent flow:

User:    Approve the refund for order #1247 and record the decision.
Agent:   Calls refund_order(1247).
Agent:   Calls darkmatter_commit({
           input: "Approve refund for order #1247",
           output: "Approved. $84.00 refunded to original payment method.",
           role: "compliance",
           event_type: "commit"
         })
Result:  { ok: true, passport: {...}, verify_url: "https://darkmatterhub.ai/r/ctx_..." }

The passport is signed (if a key is configured), hash-chained to the previous commit in the session, and stored locally at ~/.darkmatter/mcp/<session_id>/chain.jsonl.

Storage

Default: local-only. Passports never leave the machine.

~/.darkmatter/mcp/
├── default/
│   ├── chain.jsonl        # append-only stream of all commits
│   └── latest.json        # most recent passport (used as parent for the next)
└── <other-session-id>/
    └── ...

To forward each passport to a DarkMatter receiving server in addition to local storage, set:

export DARKMATTER_API_KEY="dm_sk_..."

The forwarding is best-effort and never blocks the agent's tool call. Local storage remains the source of truth.

Auto-capture

The MCP server captures only what the agent explicitly invokes. To auto-capture every tool call and turn boundary in a specific dev tool (without the agent having to remember to call darkmatter_commit), install one of the dev-tool-specific adapters:

darkmatter-hub/claude-code — auto-capture for Claude Code (Anthropic)
Cursor adapter — planned
OpenAI Codex adapter — planned
Aider adapter — community-built welcome

Each adapter hooks into its specific dev tool's event lifecycle and routes events through this MCP server's darkmatter_commit tool. One canonical endpoint, many capture surfaces.

Verification

Records are valid Context Passport v1.0 artifacts. Verify with any conformant implementation:

pip install context-passport context-passport-conformance
context-passport-conformance --vectors-dir <your-chain-dir>

Or use the offline reference verifier directly on the JSONL file:

import json
from context_passport import verify_chain

with open("~/.darkmatter/mcp/default/chain.jsonl") as f:
    chain = [json.loads(line) for line in f]

print(verify_chain(chain))  # True if intact, False if tampered

Why MCP

MCP (Model Context Protocol) is becoming the universal interop layer for AI tools. Writing this server once means it works in every MCP-compatible client without per-client integration code. See the Context Passport for MCP proposal for the broader architectural rationale.