A workflow for adding one Claude Code plugin to a Hermes installation. Hermes is a command-line tool that manages plugins through a file named plugin-sync.yaml.

Use it to add, install, register, or synchronize one plugin from a repository. It collects the repository URL, branch, layout details, and Hermes location, then stops for approval before syncing.

It checks the required setup and shows the proposed configuration change before synchronization. This lets the user approve the plugin entry before any sync is run.

How futuretyler/hermetic configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to futuretyler/hermetic. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/futuretyler/hermetic/main/.claude/skills/add-plugin/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/futuretyler/hermetic

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/futuretyler/hermetic/add-plugin/github.svg)](https://agentmods.dev/skills/futuretyler/hermetic/add-plugin)

Your own site

<a href="https://agentmods.dev/skills/futuretyler/hermetic/add-plugin"><img src="https://agentmods.dev/badge/skills/futuretyler/hermetic/add-plugin/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/futuretyler/hermetic/add-plugin"><img src="https://agentmods.dev/badge/skills/futuretyler/hermetic/add-plugin.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 89 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,311 The whole file, excluding the scripts and references it only reads on demand.

Security scan C 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00089	$0.01311
Opus 5.5	$0.00036	$0.00524
Sonnet 5.5	$0.00018	$0.00262
Haiku 4.5	$0.00009	$0.00131

Measured 2mo ago against content hash 9f4128a96b24, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

add-plugin scanned grade C with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

rm -rf /tmp/hermetic-probe

.claude/skills/add-plugin/SKILL.md · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Add a plugin via hermetic

Walks the user through appending one new plugin entry to an existing plugin-sync.yaml, then running hermetic sync. The skill stops and shows the diff before any network or filesystem work — the user must explicitly approve the YAML change before hermetic sync runs.

Preconditions (verify before anything else)

hermetic is installed. Run hermetic --version. If missing, tell the user to uv pip install hermetic-cli (or pip install hermetic-cli) and stop.
A plugin-sync.yaml exists. Check, in order:
- the path the user named in their message
- ./plugin-sync.yaml (cwd)
If neither exists, ask the user where the config lives or should be created. Do not guess a path.
Hermes home is resolved. Priority: --hermes-home flag in play > $HERMES_HOME env var > default ~/.hermes. Name the resolved path in the approval summary so the user can confirm.

Gather plugin details

Collect (ask only what the user hasn't already told you):

Repo URL — required. Any URL git clone accepts (https, ssh, file://).
Branch — default main. Don't prompt unless the user mentioned a non-default.
Monorepo layout? — many Claude Code plugin repos nest plugins under plugins/<name>/. See "Monorepo detection" below.
Plugin name — the subdirectory created under <hermes_home>/skills/<name>/. Prefer the user's stated name; otherwise use the monorepo subdir leaf or the repo's last path segment.

Monorepo detection

If the user already knows the layout, use what they said. Otherwise, the cheapest probe is a shallow treeless clone:

git clone --depth 1 --filter=tree:0 <url> /tmp/hermetic-probe
ls /tmp/hermetic-probe              # skills/ and agents/ at root?
ls /tmp/hermetic-probe/plugins 2>/dev/null  # monorepo layout?
rm -rf /tmp/hermetic-probe

skills/ and/or agents/ at the root → no subdir: needed.
plugins/<name>/ tree → set subdir: plugins/<name>.
Neither obvious → ask the user.

Read the full file on GitHub · 127 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 127 lines · 89 tokens per session scan C 9f4128a96b24

Subscribe to this mod's changes

add-plugin is a skill published in the GitHub repository futuretyler/hermetic (2 stars, last pushed 4mo ago), licensed MIT. It adds 89 tokens to every session and 1,311 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Building agents

add-plugin next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
add-pluginfuturetyler/hermetic	Skill	2	4mo ago	MIT	C	89	Claude Code
imagegenopenai/codex	Skill	134k	today	Apache-2.0	A	113	Codex
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	yesterday	MIT	A	200	Claude Code, Codex
playwright-climicrosoft/playwright	Skill	100k	yesterday	Apache-2.0	A	19	Claude Code
browser-automationopenclaw/openclaw	Skill	394k	today	MIT	A	36	Claude Code
systematic-debuggingobra/superpowers	Skill	314k	4d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code

hermetic: Skill for Claude Code