Yammm

yammm Claude Code Plugin

Claude Code plugin for the yammm schema DSL, Go library, and CLI. Provides a holistic knowledge surface, schema authoring, quality review, and automatic validation hooks.

Prerequisites (Optional)

All tools are optional. The plugin provides full knowledge and review capabilities without them.

Tool	Enables	Install
yammm CLI	Schema compilation, formatting, export, auto-validation	/yammm:setup
yammm-lsp	Editor diagnostics, completions, hover, go-to-definition	/yammm:setup
jq	PostToolUse auto-validation hook	/yammm:setup

Installation

Primary: install from GitHub (recommended)

Inside any Claude Code session:

/plugin marketplace add simon-lentz/yammm
/plugin install yammm@yammm

The first command registers this repo as a marketplace via GitHub — Claude Code clones the repo, reads .claude-plugin/marketplace.json from the repo root, and caches the plugin locally. The second command installs the yammm plugin from that marketplace. After installation, the plugin is enabled in ~/.claude/settings.json as yammm@yammm and available in every Claude Code session.

To pin to a specific release rather than tracking the default branch, append @<ref> to the marketplace source:

/plugin marketplace add simon-lentz/yammm@v0.2.0

Refs can be branches, tags, or commit SHAs. Omit the ref to track the default branch.

Updates come via /plugin marketplace update yammm inside a Claude Code session, or automatically if you have plugin auto-updates enabled.

Alternative: install from a local clone

If you already have a local clone of the repo — for example, when working on a fork or in an offline environment — you can add the marketplace from the local path instead:

/plugin marketplace add /absolute/path/to/yammm
/plugin install yammm@yammm

Same installation result, but Claude Code reads the marketplace and plugin directly from your local working tree rather than cloning from GitHub. Useful when you need to test against a non-default branch you've checked out locally, or when GitHub is unreachable from your environment.

Dev iteration: per-session load without installing

For iterating on the plugin itself without installing, start Claude Code with --plugin-dir pointing at the plugin directory:

claude --plugin-dir /absolute/path/to/yammm/claude-plugin

This loads the plugin only for that session, additively alongside your installed plugins. Per the official docs, if a --plugin-dir plugin has the same name as an installed one, the local copy takes precedence for that session — useful for testing changes to an already-installed version. The flag is repeatable for loading multiple plugins at once.

Reloading changes

After edits to skill, hook, or LSP files, run /reload-plugins to pick up changes without restarting Claude Code.

Skills

yammm (Primary)

Holistic knowledge surface covering the full yammm ecosystem. Auto-triggers on any yammm-related question or when working with .yammm files. Includes an orientation layer and 9 reference files for progressive depth.

/yammm:author-schema [description]

Designs and writes .yammm schema files from requirements. Follows a 4-step process: understand, design, write, verify (compile-check). Also triggers on natural-language requests like "write me a schema" or "model this dataset."

/yammm:review-schema [path]

Structured schema quality review. Compiles the schema, applies a 10-item review checklist, and produces an Errors/Warnings/Suggestions/Summary report. Also triggers on natural-language requests like "review my schema."

/yammm:setup [tool-name]

Platform-aware toolchain installation guide. Detects your OS and currently installed tools, then provides download instructions for missing components.

Hooks

PostToolUse: Auto-validation

After any Edit or Write to a .yammm file, automatically runs yammm validate and feeds diagnostics back into the conversation. Requires yammm CLI and jq. Non-blocking (silently skips if tools are missing).

SessionStart: Environment check

On session start, checks for yammm, yammm-lsp, and jq. Reports missing tools as warnings (never blocks) and directs to /yammm:setup for installation.

Reference Files

File	Topic
dsl-syntax.md	Full grammar: types, properties, relationships, imports
expressions.md	Operators, pipeline, lambdas, built-in functions
type-system.md	Constraint types, aliases, abstract/part, inheritance
patterns.md	Common modeling patterns with examples
api-pipeline.md	Go API: load, validate, graph, snapshot
adapters.md	JSON/CSV/Neo4j adapter usage
diagnostics.md	Error codes and troubleshooting
cli.md	CLI commands and workflows

Troubleshooting

Skill not triggering: Ensure the plugin is installed and enabled (/plugin to inspect, or check enabledPlugins in ~/.claude/settings.json for yammm@yammm). The yammm skill should trigger on any question mentioning yammm, .yammm files, or yammm-related Go packages.

PostToolUse hook not running: Verify yammm and jq are installed (command -v yammm && command -v jq). The hook silently skips if either is missing.

LSP not working: Verify yammm-lsp is on PATH (command -v yammm-lsp). The .lsp.json configures yammm-lsp --stdio for .yammm files.

Reload after changes: Use /reload-plugins to pick up plugin modifications without restarting Claude Code.