@rynfar/meridian-plugin-hermes-scrub

A Meridian plugin that strips Hermes Agent's coding-harness fingerprint from the system prompt before it reaches Claude.

Why

Hermes Agent (by Nous Research) can talk to an Anthropic-compatible endpoint via api_mode: anthropic_messages, so you can point it at Meridian and use your Claude Max subscription. Its system prompt contains self-management tool identifiers such as session_search and skill_manage.

Those identifiers have triggered Extra Usage metering in live Hermes requests. Once Extra Usage is depleted, affected requests fail with:

400 invalid_request_error: You're out of extra usage. Add more at claude.ai/settings/usage and keep going.

The plugin changes the distinctive underscored identifiers to spaced prose (session_search → session search). Live parent and subagent checks showed the requests succeeding under Max after that change. The prompt's guidance and structure remain intact:

• the user-editable persona (# Hermes Agent Persona, "You run on Hermes Agent…")
• the finishing-the-job, memory, session-recall, and skill guidance
• mid-turn user steering instructions
• the full <available_skills> list
• tools, guidelines, and any user- or harness-appended content

The scrub is content-scoped (it runs on every adapter and changes only the listed identifiers) and idempotent (running it twice is a no-op). Prompts without those identifiers are unchanged.

Install

Option 1: Local clone (recommended for dev)

git clone https://github.com/rynfar/meridian-plugin-hermes-scrub.git ~/repos/meridian-plugin-hermes-scrub
cd ~/repos/meridian-plugin-hermes-scrub
npm install
npm run build

Then point Meridian's plugin config at the built file:

mkdir -p ~/.config/meridian
# add this entry to ~/.config/meridian/plugins.json:
#   { "path": "/Users/YOU/repos/meridian-plugin-hermes-scrub/dist/index.js", "enabled": true }

Restart Meridian (or curl -X POST http://localhost:3456/plugins/reload).

Verify at http://localhost:3456/plugins — you should see hermes-scrub listed as active.

Option 2: Drop-in file

Symlink or copy dist/index.js into ~/.config/meridian/plugins/ for auto-discovery:

ln -s ~/repos/meridian-plugin-hermes-scrub/dist/index.js ~/.config/meridian/plugins/hermes-scrub.js

Point Hermes at Meridian

In ~/.hermes/config.yaml:

model:
  provider: custom
  base_url: http://localhost:3456     # your Meridian instance
  api_mode: anthropic_messages
  default: claude-opus-5-5            # or any model Meridian maps
  api_key: meridian-local            # any non-empty value; Meridian uses your Max auth

Behavior

| Input | Output | |---|---| | No system prompt | unchanged | | System prompt without the targeted identifiers | unchanged (idempotent) | | Hermes' default or subagent system prompt | Targeted tool identifiers changed to spaced prose; persona, guidance, steering, and skills preserved |

Test

bun test

License

MIT