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
HERMES_SESSION_INIT_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.
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.
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.
| Surface | Audience | Mechanism |
|---|---|---|
| MCP server (recommended for Claude Code) | Claude Code users | Native MCP tools — get_conventions / list_scopes. No CLAUDE.md mutation, no snapshot. See mcp-server/. |
Bash binary (CLAUDE.md fallback) |
Claude Code and other workflows that explicitly read a project's CLAUDE.md |
Inject the fragment into CLAUDE.md between markers. Snapshot semantics — re-inject to refresh. Other agent instruction formats are not included. |
Both share the same CLAUDE-fragment.md. They are independent surfaces; pick whichever fits your agent.
claude mcp add --scope local hermes-prime -- python3 "$PWD/mcp-server/hermes_prime_mcp.py"Run that command from the repository root. Local scope loads the server for the
current project. Use --scope user only if you intend to make the same command
available to your own sessions across projects. Then call get_conventions
from a session covered by the selected scope. Pure stdlib, no third-party
runtime dependencies. Full registration and removal instructions are in
mcp-server/README.md.
git clone https://github.com/hermes-labs-ai/hermes-prime.git
cd hermes-prime
ln -s "$PWD/bin/hermes-session-init" /usr/local/bin/hermes-session-init
hermes-session-init --checkOr symlink into ~/bin/. No package install — it is one bash script and one markdown fragment.
# Require the fragment; report optional companion tools as information
hermes-session-init --check
# Print the fragment to stdout (pipe-friendly)
hermes-session-init --print
# Inject the fragment into a project's CLAUDE.md (idempotent, backs up existing)
hermes-session-init --inject ~/Documents/projects/some-project
# Remove the fragment cleanly (anchored on the marker)
hermes-session-init --uninject ~/Documents/projects/some-project| Subcommand | Behavior | Exit |
|---|---|---|
--check |
Requires only the fragment file. Reports hermes-ground, hermes-rubric-blinded, and the handbook as optional informational companions. | 0 fragment present / 1 fragment missing |
--print |
Prints the CLAUDE-fragment to stdout. Useful for piping into --append-system-prompt or for inspection. |
0 |
--inject <project> |
Appends the fragment to <project>/CLAUDE.md between markers. Backs up existing CLAUDE.md to CLAUDE.md.bak.<timestamp>. Idempotent: re-running is a no-op. |
0 |
--uninject <project> |
Removes the exact suffix added by --inject, byte-restoring pre-existing content or removing a CLAUDE.md created by injection. Falls back to line-preserving marker removal for edited blocks, or the latest backup when no marker remains. |
0 ok / 1 not-found |
Note:
hermes-groundis an internal Hermes Labs grounding tool. It is not publicly released; the convention simply describes the orchestrator behavior it triggers.
A short markdown block containing:
- Grounding triggers — the 7 conditions under which the orchestrator should call
hermes-groundfor an external reality check. - Self-contained conventions — calibration, rubric pass-through, grounding, and name discipline.
- Tool map — functional categories, Hermes Labs implementations, and manual fallbacks.
- The rule most often forgotten mid-session — no noun-phrase label until a file exists at a path.
See CLAUDE-fragment.md for the full text. The fragment is the contract.
Three honest evals live in evals/:
- E1 — convention-recall test: does a fresh
claude --printsession injected with the fragment correctly identifyhermes-groundas the external-grounding tool, vs an un-injected session? - E2 — idempotency stress: inject 5x in a row, assert size delta ≤ 2 chars.
- E3 — uninject roundtrip: inject → uninject → require identical raw pre/post hashes.
Run them: bash evals/preliminary-bootstrap-eval.sh. Protocol in evals/EVAL-PROTOCOL.md. Run transcripts at evals/runs/. Null results published unredacted per the standing convention.
hermes-prime is a convention-delivery surface among the Hermes Labs open-source
tools. It does not replace companion tools and does not ensure that they are
called.
hermes-rubric— evidence-first scoring; the convention "every shippable artifact passes through a BLINDed rubric" points here.hermes-blind— a separately invoked multi-turn recovery scaffold.
Source version 0.2.1-alpha.1 — unreleased alpha candidate. There is no public 0.2.1-alpha.1 tag or GitHub release, and this branch does not authorize one. The mechanism suite contains 11 Bash assertions plus 10 MCP tests. E1 is one author-run three-question control/treatment observation; it is preliminary convention-recall evidence, not evidence that the tool prevents drift or improves downstream task performance.
If E1 returns a null result on a larger sweep, that gets published, not papered over. Same standing convention as the rest of the Hermes Labs open-source tools.
Before requesting any push or release, run the local mechanism gate:
./scripts/local-ci.shIt runs ShellCheck, the 11-assertion Bash suite, the 10-test MCP suite, and fragment size/marker checks. The proposed hosted workflow also runs MCP tests on macOS and Ubuntu. Exit 0 is evidence only for those named checks at the current tree; it is not push, release, or publication authorization.
MIT. See LICENSE.
Built by Hermes Labs.
Hermes Labs is an AI reliability engineering studio for product and engineering teams shipping production agents and LLM applications. This repository is one small mechanism in that portfolio; its claims are limited to behavior exercised by the checks above.
For enterprise deployments and AI-reliability engagements: roli@hermes-labs.ai · hermes-labs.ai
On naming. Hermes Labs is named for Hermes, the Greek messenger god — patron of communication and interpretation, the herald who carries meaning between worlds. The thread to the work: hermeneutics, the theory of interpretation that takes its name from Hermes, is the philosophical anchor for an AI reliability engineering studio whose substrate is linguistic. Not affiliated with NousResearch's Hermes LLM line or their hermes-agent framework — different companies, different work.
Founder: Rolando (Roli) Bosch. Site: hermes-labs.ai Citation: Bosch, R. (2026). Hermes Labs: AI reliability engineering for production agents and LLM applications. https://hermes-labs.ai