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# agent_appkit

`agent_appkit` walks a live AppKit window into the [agent_core](/docs/packages/agent_core)
identity model and implements the common backend vtable used by `agent_mcp` and
`agent_inapp`.

```cplus
import "agent_appkit/agent_appkit" as agent;
import "agent_core/auth" as auth;
import "agent_core/identity" as identity;

agent::set_agent_id(button.as_view().raw(), "save");
agent::set_agent_policy(secret.as_view().raw(), identity::policy_protected());

var surface = agent::open(window.raw());
let nodes = surface.describe(auth::reader());
let result = surface.click(auth::operator(), "save");
```

The backend:

- derives stable ids from explicit tags and Facet keys;
- supports exposed and full descriptions without bypassing value grants;
- applies Open, Protected, Private, and excluded node policy;
- authorizes reads, actions, and versioned text writes before touching AppKit;
- translates native notifications into semantic events;
- marshals UI operations to AppKit's main thread; and
- exposes `mcp_backend()` for the platform-neutral adapters.

Use [facet_agent](/docs/packages/facet_agent) when a Facet application should
install this backend automatically. See [AppKit agent surface](/examples/appkit-agent-counter)
for a direct-window example.