plugsdk

Embed Claude Code's plugin system in your own application.

npm install plugsdk

What it is

plugsdk is the host-side loader for Claude Code plugins. Drop it into any Node application and you can:

• Load plugins authored against Claude Code's plugin format from disk.
• Read every documented component — manifest, hooks, skills, commands, agents, MCP server configs, LSP server configs, monitors, themes, output styles, settings, marketplace catalogs.
• Dispatch your application's events through the plugins' hooks the same way Claude Code does, with subprocess execution, JSON I/O, matcher filtering, and result merging following the documented precedence rules.

plugsdk does not author plugins. It does not ship UI. It loads on-disk plugin directories and gives you their structure plus a hook dispatcher.

Reference: https://code.claude.com/docs/en/plugins-reference and https://code.claude.com/docs/en/hooks.

Quick start

import { loadClaudePlugin, createHookDispatcher } from 'plugsdk'

const plugin   = loadClaudePlugin('/path/to/some-plugin')
const dispatch = createHookDispatcher([plugin])

// Your app is about to run a tool. Ask plugins first:
const result = await dispatch('PreToolUse', {
    tool_name:  'Bash',
    tool_input: { command: 'rm -rf /' },
    cwd:        process.cwd(),
})

if (result.hookSpecificOutput?.permissionDecision === 'deny') {
    throw new Error(result.hookSpecificOutput.permissionDecisionReason)
}

What loadClaudePlugin(dir) returns

{
  root,                 // absolute plugin dir
  manifest,             // .claude-plugin/plugin.json
  hooks,                // { PreToolUse: [{ matcher, hooks: [...] }], ... }
  skills,               // [{ name, dir, file, fields, body }]
  commands,             // flat skills/commands
  agents,               // [{ name, file, fields, body }] — validated
  mcpServers,           // .mcp.json mcpServers map
  lspServers,           // .lsp.json
  monitors,             // monitors/monitors.json array
  themes,               // [{ slug, name, base, overrides }]
  outputStyles,         // output-styles/*.md
  settings,             // settings.json
  userConfig,           // manifest.userConfig
  channels,             // manifest.channels
  dependencies,         // manifest.dependencies
  binDir,               // bin/ if present
}

The manifest's custom-path fields (skills, commands, agents, outputStyles, themes, monitors, hooks, mcpServers, lspServers) are honored — when a manifest specifies a custom path, the default location is skipped, exactly as the Claude Code spec mandates.

Forbidden agent fields (hooks, mcpServers, permissionMode) and illegal isolation values cause the loader to throw at parse time so malformed plugins are rejected up front.

Loading marketplaces

import { loadClaudeMarketplace } from 'plugsdk'

const m = loadClaudeMarketplace('/path/to/some-marketplace')
// m.catalog: marketplace.json
// m.plugins: [{ entry, plugin: LoadedClaudePlugin | null }]
//            local-path sources auto-load; remote sources kept as metadata.

metadata.pluginRoot is honored when resolving local plugin paths.

Dispatching hooks

const dispatch = createHookDispatcher(plugins, { timeout: 60_000 })
const r = await dispatch('PreToolUse', payload)

For each loaded plugin whose hooks[event] entries match the payload's target (tool name / source / agent type / etc.), every command-type handler runs as a subprocess:

• The command string has ${CLAUDE_PLUGIN_ROOT}, ${CLAUDE_PLUGIN_DATA}, ${user_config.<key>}, and ${ENV_VAR} substituted.
• The full payload (with hook_event_name injected) is written to stdin as JSON.
• CLAUDE_PLUGIN_ROOT and CLAUDE_PROJECT_DIR are exported on the child's env.
• stdout JSON is parsed; stderr is captured for exit-code-2 blocks.

Returned shape:

{
  results: [{ plugin, exitCode, stdout, stderr, output, eventName, handler }, ...],
  unhandled: [...],          // non-command handlers (http/mcp_tool/prompt/agent)
  decision?: 'block', reason?: string,                    // top-level decision events
  hookSpecificOutput?: {                                  // permission events
    hookEventName,
    permissionDecision: 'allow' | 'deny' | 'ask' | 'defer',
    permissionDecisionReason,
    additionalContext,                                    // joined across plugins
    updatedInput,                                         // shallow-merged
  },
  continue?, stopReason?, suppressOutput?, systemMessage?,
}

Result merging follows the documented precedence:

• PreToolUse / PermissionRequest: deny > defer > ask > allow.
• Stop / UserPromptSubmit / PostToolBatch / etc.: first plugin emitting decision: 'block' (or exit code 2) wins.
• additionalContext entries are concatenated.
• continue: false / suppressOutput / systemMessage propagate.

Non-command handler types are returned in unhandled so your host can route them itself (HTTP webhook, an in-process MCP server call, etc).

Matcher rules

claudeAdapter.matches(matcher, target) implements Claude Code's documented matcher semantics:

matcher	meaning
omitted / '' / '*'	match every target
Bash	exact match
Bash|Edit	pipe-separated literal list
anything else	JavaScript regex

License

MIT © AnEntrypoint