agent_winui_mcp

Optional HTTP transport for a standalone agent_winui::Surface. No Facet or Win32 control backend is used. Add agent_winui_mcp, agent_mcp and json to the app's dependency closure alongside the native agent dependencies.

import "agent_winui_mcp/agent_winui_mcp" as http;
import "agent_core/auth" as auth;

fn policy(request: auth::Request) -> auth::Grant { return auth::operator(); }

// On the Window's UI thread, with its own DispatcherQueue:
let port: i32 = http::start(surface_ptr, queue, "my-app", policy);
// A positive port means http://127.0.0.1:<port>/ is listening.
// Before closing the Surface or shutting down XAML, on that same UI thread:
http::stop();

start accepts an optional port: u16; zero selects the shared PID-derived port. It binds before returning and writes the shared discovery descriptor. Errors are -1/-2/-3 for socket/bind/listen, -10 for an active server or a reentrant start, -11 for an invalid id, -12 for invalid UI thread/queue/input, and -13 for failure to publish discovery. running() reports lifecycle state.

One server can run per process, matching shared MCP protocol state. The caller owns the Surface and must keep it alive through stop(). Start, stop and status calls belong to the owning UI thread. The worker handles sockets and framing; the DispatcherQueue handles protocol dispatch, the authorization policy and all native verbs. Do not run another MCP transport or call handle_request directly while this server is serving; embedded agent_inapp calls on the UI remain valid.

Stop cancels and joins the worker, closes all connections, and removes discovery. It works with an incomplete HTTP request and with a request queued behind a busy UI callback. Queued callbacks carry a server generation, not borrowed Surface or worker pointers; callbacks left behind by a stopped server cannot act after a restart. If an action or policy calls stop reentrantly, that current dispatch still unwinds on the UI thread: keep the Surface allocation alive until it returns, and restart from a later UI callback. The Facet connector owns a stable Surface allocation and performs this teardown automatically.

The transport inherits the shared MCP HTTP behavior: POST requests, JSON replies, 202 for notifications, and connection-scoped client identity over keep-alive. Client names are self-reported policy inputs, not authenticated identities. There is no bearer-token layer. The standalone API requires an explicit policy; the Facet connector uses facet_agent::effective_policy(). The server binds only to loopback. A partially received request occupies the single transport worker until it completes, disconnects or the server stops; it does not block the UI.

Verify real native and Facet apps with:

./tools/test_agent_winui.ps1
python tools/test_agent_winui_http.py

The HTTP harness checks MCP initialization/tools, notifications, Unicode edits, version conflicts, interleaved client grants, Facet replacement, pending-request cancellation/restart, interrupted body reads, and listener/discovery cleanup.