integrate-arcjet-guard-google-adk

Integrate Arcjet Guard into Google ADK JS

@arcjet/guard's Google ADK v2 namespace wraps the agent's existing Arcjet client. It never talks to the Arcjet API itself. Two surfaces, one decision rule:

• Tool calls → guardPlugin(). A Runner BasePlugin whose beforeToolCallback is the run-wide gate. DENY is a dictionary (ArcjetDenialResult) so ADK skips runAsync and the model sees the payload. undefined lets the tool execute. Do not throw from the callback — PluginManager treats a throw as a plugin error, not skip. Tools already branded by a sibling guardTool are skipped so Guard is not double-called. Inbound guard() before Runner.runAsync does not brand tools and does not skip this gate. The plugin does not screen inbound (onUserMessageCallback / beforeModelCallback are no-ops) so a preceding guard() does not double-call.
• Correlation → googleAdkContext() reads a caller-owned id from helper options (guardPlugin({ sessionId })) or a wrap (googleAdkContext({ context: appContext })). ADK Context has no nested context field. Durable session state loses to helper options. It never mints a new id. It never reads invocationId (ADK always generates it). It never reads traceId. It never reads toolContext.sessionId / session.id (session auto-ids).

There is no guardTool. Skip is the plugin return, not throw-from-execute. There is no guardInbound, no guardApproval, and this namespace does not use ADK SecurityPlugin as the Arcjet policy gate.

This namespace is Google ADK JS Runner + BasePlugin.beforeToolCallback. Not @google/genai. Not the Python SDK. Do not also wrap with @arcjet/guard/vercel-ai/v7 or @arcjet/guard/claude-managed-agents/v0.

Docs live at docs.arcjet.com/guards/google-adk/. Do not overwrite any other /guards/... slug.

Put Arcjet first in new Runner({ plugins }). PluginManager is first-win; if another plugin (including SecurityPlugin) returns a value first, Guard never runs.