--- name: claude-code-plugin-reference description: Explain plugin, skill, command, agent, and hook mechanics used here. Use when authoring or debugging plugins. Do not use for ops; use night-market-operations. --- # Claude Code Plugin Reference (night-market edition) This is the domain pack for how Claude Code plugin machinery works in this repository. It covers manifests, skills, commands, agents, hooks, and the marketplace registry, with the local conventions layered on top. Every contract below was checked against a shipped plugin (mostly `plugins/imbue`, `plugins/abstract`, and `plugins/herald`) on 2026-07-02 at repo v1.9.15. When another night-market skill says "see the plugin reference for what a hook payload is," this is the file it means. ## Vocabulary Each term is defined once here and used without redefinition below. | Term | Meaning in this repo | |------|----------------------| | Plugin | A directory under `plugins/` shipping skills, commands, agents, and hooks, with its own tests, Makefile, and pyproject.toml. Independently deployable (ADR-0001). | | Skill | A directory `skills//` containing `SKILL.md`. Loaded by the model on demand, invoked as `Skill(plugin:name)`. | | Module | A file under a skill's `modules/` subdirectory. Loaded only when the hub `SKILL.md` routes to it (progressive loading). | | Command | A markdown file under `commands/`. Surfaces as a slash command the user types. Repo docs refer to the namespaced form, e.g. `/sanctum:sync-capabilities`. | | Agent | A markdown file under `agents/` defining a dispatchable subagent: frontmatter plus a system-prompt body. | | Hook | An executable script Claude Code runs on a lifecycle event, registered in the plugin's `hooks/hooks.json`. | | Hook event | The lifecycle point a hook fires on: `PreToolUse`, `PostToolUse`, `Stop`, `SessionStart`, `UserPromptSubmit`, and others (full table in `modules/hooks.md`). | | Manifest | `.claude-plugin/plugin.json`: the file Claude Code reads to register a plugin's components. | | Marketplace | The root `.claude-plugin/marketplace.json` registry listing all plugins, installed via `/plugin marketplace add`. | | Plugin cache | The directory Claude Code copies installed plugins into and executes them from. It is NOT the repo checkout. | | `${CLAUDE_PLUGIN_ROOT}` | Placeholder Claude Code expands to the plugin's cache path. The only safe way to reference plugin files from hooks. | | Host Python | The system Python interpreter that runs hook scripts. Assume 3.9, even though plugin package code targets 3.12. | ## Anatomy of a night-market plugin Verified tree (imbue, trimmed): ``` plugins/imbue/ ├── .claude-plugin/ │ ├── plugin.json # Claude Code manifest: registers everything │ └── metadata.json # inter-plugin dependency manifest ├── openpackage.yml # cross-framework export manifest ├── skills// │ ├── SKILL.md # hub document with frontmatter │ └── modules/*.md # spokes, loaded on demand ├── commands/*.md # slash commands ├── agents/*.md # subagents ├── hooks/ │ ├── hooks.json # hook registration (auto-loaded) │ ├── *.py, *.sh # hook scripts │ └── shared/ # vendored helpers (hook_io, vow_utils, ...) ├── scripts/ # Python utilities skills shell out to ├── tests/ # pytest suite, run per plugin ├── Makefile # per-plugin test/lint/typecheck targets ├── pyproject.toml # package config, per-plugin coverage threshold └── README.md ``` ### plugin.json field contract | Field | What it does | Local rule | |-------|--------------|------------| | `name` | Plugin identity and namespace prefix for skills/commands | Matches directory name | | `version` | Plugin version | Lockstep with marketplace version (1.9.15). Never hand-edit, use the bumper (below) | | `description` | Marketplace listing text | Two-part style per ADR-0003 | | `skills` | Array of `"./skills/"` paths. Each dir must contain a `SKILL.md`. Registration makes `Skill(plugin:name)` resolvable | Keep in sync with disk via `/sanctum:update-plugins` | | `commands` | Array of `"./commands/.md"` paths, each becoming a slash command | Same sync rule | | `agents` | Array of `"./agents/.md"` paths, each a dispatchable subagent | Same sync rule | | `hooks` | Paths to ADDITIONAL hook files only. `./hooks/hooks.json` is auto-loaded and must never appear here | Every plugin in this repo keeps `"hooks": []` (verified across all 23 manifests). See the hooks section for why | | `keywords` | Marketplace search and discovery terms | Free-form | | `dependencies` / `metadata.optional_dependencies` | Names of other night-market plugins | Informational plus runtime detection only. ADR-0001 forbids import coupling: plugins detect each other via the filesystem and degrade gracefully. A top-level `optional_dependencies` is not a manifest field and is stripped at load | | `author`, `license` | Attribution | MIT throughout | | `homepage`, `repository` | Listing links | `homepage` must parse as a URL or the plugin fails to load. Pinned by `tests/test_plugin_manifest_contract.py` | ### metadata.json Second manifest in `.claude-plugin/`. Fields verified on imbue: `name`, `version` (lockstep), `main`, a `skills` subset, `dependencies`, `provides` (infrastructure/patterns/tools), and a `claude` block (`skill_prefix`, `auto_load`, `categories`). One trap: dependency ranges here use their own semver namespace. imbue declares `"abstract": ">=2.0.0"` while every plugin ships 1.9.15. The range is not compared against the marketplace version, so do not "fix" it to 1.9.15 during a bump. The `update_versions.py` bumper knows which fields to touch. ### openpackage.yml Cross-framework manifest consumed by the export pipeline (`make cross-framework`, `scripts/clawhub_export.py`). Lists the skills exported outside Claude Code and dependency sources in `gh@athola/claude-night-market` form. Its `version` is also lockstep. ## SKILL.md contract ### Frontmatter Fields verified on `plugins/imbue/skills/proof-of-work/SKILL.md`. Only `name` and `description` are consumed by Claude Code itself. The rest are house conventions read by repo tooling. | Field | Purpose | |-------|---------| | `name` | Skill identity. `Skill(plugin:name)` resolves against it | | `description` | Loading trigger. Hard cap 160 chars, enforced by `plugins/abstract/scripts/validate_budget.py` (`DESCRIPTION_MAX = 160`, ecosystem budget 90,000 chars per ADR-0004). House template: verb phrase, then "Use when [trigger].", then "Do not use when [negative]; use [sibling] instead." | | `role` | One of `entrypoint`, `library`, `hook-target` (taxonomy below) | | `modules` | List of `modules/*.md` spokes this hub can load | | `dependencies`, `tags`, `category`, `usage_patterns` | Discovery metadata | | `estimated_tokens`, `complexity`, `model_hint`, `alwaysApply`, `tools` | Advisory metadata for tooling and audits | Role taxonomy (from `docs/skill-integration-guide.md`): | Role | Inbound refs | User-invoked | Example | |------|--------------|--------------|---------| | `entrypoint` | low (0-3) | yes | `sanctum:do-issue` | | `library` | high (4+) | rarely | `imbue:proof-of-work` | | `hook-target` | varies | no | `imbue:vow-enforcement` | ### Progressive loading (hub-and-spoke) A skill's `SKILL.md` is the hub: it carries the always-loaded core and a routing table into `modules/*.md` spokes. The model loads a spoke only when the hub tells it to. This keeps the initial token cost near the `estimated_tokens` value instead of the whole directory. The pattern is specified in `Skill(leyline:progressive-loading)`. ### Required sections and ratchets - Every new or modified `SKILL.md` needs a `## Exit Criteria` section with concrete, observable, falsifiable checkboxes (`.claude/rules/skill-exit-criteria.md`). A pre-commit ratchet, `scripts/check_skill_exit_criteria_drift.py`, fails when the count of missing sections rises above `scripts/skill_exit_criteria_baseline.json`. - `Skill(plugin:name)` references in prose are scanned by `plugins/abstract/scripts/skill_graph.py`. A second ratchet, `scripts/check_skill_graph_drift.py`, blocks commits that add dangling references (the `bugs` category) above `scripts/skill_graph_baseline.json`. When your change lowers the count, lower the baseline too so the ratchet tightens. - CONSTITUTION.md rule 3 exempts skill prose from TDD but requires a structural validation test per new skill (constitution names the pattern `test_skill_.py`; in practice imbue keeps them at `tests/unit/skills/test_.py`, e.g. `test_proof_of_work.py`). ### How Skill() invocation resolves `Skill(imbue:proof-of-work)` resolves `imbue` to the plugin registered in the marketplace, then `proof-of-work` to the directory listed in that plugin's `plugin.json` `skills` array. If the directory or the manifest entry is missing, the reference is dangling and the skill-graph ratchet will flag it. ## Commands Frontmatter verified on `plugins/imbue/commands/justify.md` and `plugins/sanctum/commands/fixit.md`: ```yaml --- name: fixit description: Fix broken functionality from pasted error output... usage: /fixit [--file ] ... extends: "imbue:proof-of-work" --- ``` - `name` and `description` are required. `usage` documents the argument shape. `extends` (optional) names the skill the command routes into. - `$ARGUMENTS` in the body is replaced with the raw argument string the user typed after the command (see fixit: "The input is `$ARGUMENTS` (a paste) or the contents of `--file `"). When to write a command versus a skill: | Write a | When | |---------|------| | Command | The user should type it deliberately with arguments (an entrypoint with a CLI-like contract) | | Skill | The model should load it when a trigger matches (knowledge, procedure, or a library other skills compose) | | Both | Common pattern here: a thin command that `extends` or routes into a skill (`/imbue:justify` wraps `imbue:justify`) | The Exit Criteria rule does not apply to command files. ## Agents Frontmatter verified on `plugins/imbue/agents/review-analyst.md`: ```yaml --- name: review-analyst description: Autonomous agent for conducting structured reviews with evidence gathering. Use when detailed code reviews requiring evidence trails... Do not use when quick code check without formal review... model: opus tools: - Read - Glob - Grep - Bash skills: imbue:review-core, imbue:proof-of-work, ... --- ``` - The `description` drives dispatch: Claude decides whether to hand a task to the agent by matching it, so it must carry "Use when" and "Do not use when" clauses just like a skill description. - `tools` is the allowlist the subagent gets. `model` pins the model tier. - `skills` lists skills the agent should load. The body below the frontmatter is the agent's system prompt. Plugin agents read a fixed field set (code.claude.com/docs/en/plugins/ components, "Frontmatter fields in plugin agents"): `name`, `description`, `model`, `effort`, `maxTurns`, `tools`, `disallowedTools`, `skills`, `memory`, `background`, `omitClaudeMd`, `isolation` (`worktree` only), `color`, and `experimental.cacheTtl`. They ignore `permissionMode`, `hooks`, `mcpServers` and `initialPrompt` without an error, and never read `allowed-tools` (a skill field) or `max_iterations`. Seven agents here ran with every tool for months because they wrote `allowed-tools`. `FrontmatterProcessor.validate_plugin_agent` reports each case, and `plugins/abstract/tests/test_every_plugin_agent_uses_read_fields.py` runs it over every agent. Hooks an agent needs go in the plugin's `hooks/hooks.json`, matched with `SubagentStart`/`SubagentStop` on the agent's scoped name. `omitClaudeMd: true` (2.1.271) suits an agent whose delegation prompt carries everything it needs: it skips about 79 KB of CLAUDE.md and rules here. Agents that must apply repo rules keep loading them. ## Hooks The hardest-won knowledge in the repo. Read `modules/hooks.md` whole before writing or editing any hook. It carries the events registered here, registration through `hooks/hooks.json` with empty `plugin.json` `hooks` arrays, the stdin payload contract, exit-code and verdict semantics, timeout budgets, the Python 3.9 floor, cache-dir execution and hook testing. ## Workflows: one per plugin, discovered by convention Every plugin ships dynamic-workflow scripts under `workflows/`, invoked as `/plugin-name:workflow-name`. Location, the `meta` format, the forbidden calls and the refuse-with-`next` convention are in `modules/workflows.md`. ## Marketplace mechanics - Registry: root `.claude-plugin/marketplace.json`. Top-level `name`, `version`, `description`, `owner`, and a `plugins` array of `{name, source: "./plugins/", description, version, keywords}`. - Install: `/plugin marketplace add athola/claude-night-market` (README quick start), then `/plugin install @claude-night-market`. The install form is documented in the book's getting-started pages; re-verify there if it fails. - Version lockstep: one ecosystem version fans out from marketplace.json to every plugin's `plugin.json`, `metadata.json`, `openpackage.yml`, `pyproject.toml`, and package `__init__.py`. Bump with: ```bash uv run python plugins/sanctum/scripts/update_versions.py 1.9.16 --dry-run uv run python plugins/sanctum/scripts/update_versions.py 1.9.16 ``` - Drift tooling: `/sanctum:update-plugins [plugin] [--fix]` audits `plugin.json` arrays against disk contents. `make docs-sync-check` (and the `capabilities-sync.yml` CI job) verifies `book/src/reference/capabilities-*.md` matches registrations. Fix drift with `/sanctum:sync-capabilities --fix`, never by hand-editing the generated capabilities files. ## Mods: TypeScript function hooks (2.1.287) A mod is a plugin whose `hooks/hooks.json` names a TypeScript module under `"modules"`. Its `register(on, options)` API, the events it can hook and how mods are tested are in `modules/mods.md`. ## Release tooling (2.1.259 to 2.1.285) - `claude plugin validate [--json] [--strict]`: manifests, hooks, agent and skill frontmatter, MCP entries, unquoted `${CLAUDE_PLUGIN_ROOT}`. `make validate-plugins` runs it over every plugin. - `claude plugin eval`: scored eval suites run against a no-plugin baseline. Runs are billed. - `/skill-doctor`: loaded skills that go unused, and what they cost in context. - `/doctor prompt-audit`: prompting written for older models. ## Where the authoritative docs live - Repo book: `book/src/` (mdBook, published by `deploy-book.yml`). `book/src/reference/capabilities-*.md` are generated by the sync tooling. Getting-started and plugin pages are hand-written. - Local deep dives: `docs/plugin-development-guide.md`, `docs/skill-description-guide.md`, `docs/skill-integration-guide.md`. Note: the dev guide's `make create-plugin NAME=...` target does not exist in the root Makefile as of 2026-07-02 (stale doc). Scaffold with `Skill(abstract:create-skill)` and copy an existing plugin's layout. - Upstream: https://code.claude.com/docs (linked from the dev guide and README badge). Consult upstream when the question is about harness behavior this repo only records as code comments: full event payload schemas, new hook events, or exit-code semantics changing across Claude Code versions. ## When NOT to use | You need | Use instead | |----------|-------------| | Run tests, lint, typecheck, release, publish | night-market-operations | | Classify or gate a change, review rules | night-market-change-control | | Recreate the dev environment (uv, tool pins) | night-market-build-and-env | | Triage a failing hook or CI job by symptom | night-market-debugging-playbook | | History of why a hook or pattern exists | night-market-failure-archaeology | | Design invariants across plugins (isolation, lockstep rationale) | night-market-architecture-contract | | Config axes and env vars (VOW_SHADOW_MODE and friends) | night-market-config-catalog | | Evidence bar and test-discipline policy | night-market-validation-and-qa | ## Exit Criteria - [ ] Given a new hook idea, you register it by editing that plugin's `hooks/hooks.json` only, and `python3 scripts/check_plugin_hooks.py` exits 0 afterward. - [ ] A hook you author reads its payload from stdin JSON (no `CLAUDE_TOOL_*` env vars) and exits 0 when fed malformed input: `echo not-json | python3 .py; echo $?` prints 0. - [ ] Every subprocess timeout inside your hook is asserted in a test to be strictly less than the `timeout` registered in `hooks.json`. - [ ] Your hook file starts with `from __future__ import annotations`, uses `timezone.utc` rather than `datetime.UTC`, imports no unguarded third-party package, and the `python39-compat.yml` gates pass. - [ ] A new skill you add appears in its plugin's `plugin.json` `skills` array, its description is at most 160 characters, it has an `## Exit Criteria` section, and both ratchet scripts (`check_skill_graph_drift.py`, `check_skill_exit_criteria_drift.py`) pass. - [ ] You can state from memory why `plugin.json` `hooks` arrays are empty in this repo and what error appears if they are not. - [ ] An agent you add or edit passes `plugins/abstract/tests/test_every_plugin_agent_uses_read_fields.py`. - [ ] A hook command you add passes `tests/test_hook_commands_quote_plugin_root.py`, and `claude plugin validate` on its plugin reports no warnings for it. ## Provenance and maintenance Compiled 2026-07-02 against repo v1.9.15 (branch discussions-fix-1.9.14). PreToolUse verdict contract corrected to `allow|deny|ask` and the imbue vow-hook `warn`/`block` anomaly flagged on 2026-07-03. Volatile facts and how to re-verify them: ```bash # Hook events per plugin for f in plugins/*/hooks/hooks.json; do echo "$f" python3 -c "import json,sys; print(list(json.load(open(sys.argv[1]))['hooks']))" "$f" done # All plugin.json hooks arrays empty (exit 0 = clean) python3 scripts/check_plugin_hooks.py rg '"hooks": \[' plugins/*/.claude-plugin/plugin.json # 160-char description cap still in force rg -n 'DESCRIPTION_MAX' plugins/abstract/scripts/validate_budget.py # Payload-on-stdin contract (read the module docstring) head -15 plugins/abstract/hooks/shared/hook_io.py # Exit-2 semantics comment rg -n 'exit 2 blocks' plugins/imbue/hooks/tdd_bdd_gate.py # permissionDecision values in repo hooks (deny is correct; the # warn/block hits in vow_no_ai_attribution.py are the known anomaly) rg -n '"permissionDecision"' plugins/*/hooks/*.py # Herald timeout pairing (registered 10s vs internal 8s) rg -n 'LLM_TIMEOUT_SECONDS|timeout' plugins/herald/hooks/ # py39 gates and covered plugins head -50 .github/workflows/python39-compat.yml # Version lockstep fields touched by the bumper rg -n 'def main' -A 12 plugins/sanctum/scripts/update_versions.py # Marketplace entry shape head -60 .claude-plugin/marketplace.json # Stale make create-plugin claim (doc says it exists, Makefile disagrees) rg -n 'create-plugin' Makefile docs/plugin-development-guide.md ``` Unverified/candidate items are labeled inline: the `/plugin install @claude-night-market` form (book-documented, not exercised here) and the explanation that metadata.json dependency ranges form a separate semver namespace (observed, not specified anywhere).