Plugin and Engine
The $.plugin noun, the plugin.register and engine.create events, and the types that describe a plugin and the engine object.
Model, Audio, and MCP
The $.model, $.audio, and $.mcp nouns - ask a model, play or speak sound, and call a tool of a connected MCP server.
Session
The $.session noun that reads the running session, compacts it, and sends messages, plus the session events.
Turn and Prompt
The $.turn and $.prompt nouns, and the events that follow a turn from start to end, including the system prompt, context blocks, and attachments.
Tool, Command, and Config
The $.tool, $.command, and $.config nouns that list, check, call, and register tools and slash commands, and change /config rows.
Agent
The $.agent noun that starts, lists, and registers subagents, the agent.offer and agent.spawn events, and the agent types.
Files, Store, and State
The $.fs, $.store, and $.state nouns, the state helpers you import from claude-code, and the events these calls raise.
Clock, HTTP, Process, Env, and Settings
The five $ nouns that reach the machine - time and timers, web requests, commands, environment variables, and merged settings.
Telemetry
The $.telemetry noun, the telemetry.log and telemetry.mark events, and the record types.
The Testing Module
The claude-code/testing module that test files import, and the claude plugin test command that runs them.