Hermes Prime MCP server

hermes-prime

Deliver a versioned convention card to a fresh Claude Code session. The Bash surface snapshots the card into a project's CLAUDE.md; the read-only MCP surface returns the same card over stdio. The mechanism makes conventions available. It does not prove that a model will follow them or prevent drift.

This is a small transport, not an enforcement layer. Hermes Labs ships the convention card it uses itself; fork it or select another fragment with HERMESSESSIONINIT_FRAGMENT=/path/to/custom.md.

Two surfaces share one fragment: a four-subcommand Bash tool for CLAUDE.md-based workflows and a Claude-Code-native MCP server that does not mutate CLAUDE.md. Neither surface calls a model or a network service. The Bash path makes no global configuration change; MCP registration uses the scope the user selects.

Pain

Conventions can fall out of visible context between sessions. A versioned card gives a new session one concrete artifact to read instead of requiring it to reconstruct those conventions from scattered notes.

The discipline rules normally live in scattered handbook docs, feedback files, or session-end retros — places a fresh session never reads. hermes-prime packages them as a single self-contained card the orchestrator opens with.

How it's different

Most "set up the agent" tools either (a) ship a giant prompt file you copy-paste, or (b) install a global hook that runs on every session whether you want it or not. hermes-prime is per-project, marker-anchored, and idempotent. Unedited injected suffixes are byte-reversible; edited blocks use the documented marker/backup fallback.

The fragment is a snapshot, not a live reference. Re-inject to refresh. The marker (<!-- session-init: BEGIN/END -->) means uninject is byte-clean.

Two surfaces

Both share the same CLAUDE-fragment.md. They are independent surfaces; pick whichever fits your agent.

MCP server (Claude Code native)

claude mcp add --scope local hermes-prime -- python3 "$PWD/mcp-server/hermes_prime_mcp.py"

Run that command from the repository root. Local scope loads the server for the current project. Last verified against Claude Code 2.1.268 on 2026-09-11: claude mcp list reports the server as Connected. The server's initialize response carries a short instructions string, which Claude Code shows to the model so a fresh session knows to call getconventions. Use --scope user only if you intend to make the same command available to your own sessions across projects. Then call getconventions from a session covered by the selected scope. Pure stdlib, no third-party runtime dependencies. Full registration and removal instructions, plus the packaged pip install hermes-prime-mcp console-script path and the server.json MCP Registry manifest, are documented in mcp-server/README.md.

Install (bash binary)

git clone https://github.com/hermes-labs-ai/hermes-prime.git
cd hermes-prime
ln -s "$PWD/bin/hermes-session-init" /usr/local/bin/hermes-session-init
hermes-session-init --check

Shortened. The full README is on GitHub.