diff --git a/harness/.pi/extensions/gate/__tests__/gate_roundtrip.test.js b/harness/.pi/extensions/gate/__tests__/gate_roundtrip.test.js
new file mode 100644
index 00000000..c8d717ef
--- /dev/null
+++ b/harness/.pi/extensions/gate/__tests__/gate_roundtrip.test.js
@@ -0,0 +1,25 @@
+const test = require("node:test");
+const assert = require("node:assert");
+const { createFakePi } = require("./fake_pi_runtime.js");
+const { emitAndWait } = require("../../tht-gate.js");
+
+test("emitAndWait trasporta il descriptor come JSON nel title e ritorna la ui_response parsata", async () => {
+  const { ctx, enqueueUi } = createFakePi();
+  const descriptor = { id: "u1", widget: "select", options: [{ id: "a", label: "A" }] };
+  enqueueUi(JSON.stringify({ id: "u1", choices: ["a"] }));
+  const resp = await emitAndWait(ctx, descriptor);
+  assert.deepEqual(resp, { id: "u1", choices: ["a"] });
+  assert.equal(ctx.uiCalls[0].method, "input");
+  assert.equal(ctx.uiCalls[0].title, JSON.stringify(descriptor));
+});
+
+test("no-limbo: undefined (cancel) ri-presenta lo stesso widget", async () => {
+  const { ctx, enqueueUi } = createFakePi();
+  const descriptor = { id: "u1", widget: "select", options: [] };
+  enqueueUi(undefined);                                   // 1° giro: cancel
+  enqueueUi(JSON.stringify({ id: "u1", choices: ["a"] })); // 2° giro: risposta valida
+  const resp = await emitAndWait(ctx, descriptor);
+  assert.deepEqual(resp, { id: "u1", choices: ["a"] });
+  assert.equal(ctx.uiCalls.length, 2);                    // ri-presentato una volta
+  assert.ok(ctx.notifications.some((n) => /Esc non chiude/.test(n.message)));
+});
diff --git a/harness/.pi/extensions/tht-gate.js b/harness/.pi/extensions/tht-gate.js
index c190472e..07695859 100644
--- a/harness/.pi/extensions/tht-gate.js
+++ b/harness/.pi/extensions/tht-gate.js
@@ -133,46 +133,30 @@ function advanceIfReady(ctx, session) {
 	}
 }
 
-// --- widget emission + wait (NEW: replaces ctx.ui.* blocking primitives) -------
+// --- widget emission + wait — usa l'API UI NATIVA di Pi (ctx.ui.input) --------
 //
-// emitAndWait(ctx, descriptor) sends a ui_request widget and awaits the correlated
-// ui_response by id. This is the correlation-by-id layer the reference implementation never had (its
-// native TUI primitives handled it implicitly). The descriptor is built by the pure
-// ./gate/builders.js (L1-tested).
+// emitAndWait(ctx, descriptor) sends the widget-descriptor as JSON in the `title`
+// of ctx.ui.input and awaits the response as a parsed string value. No ctx.sendRaw,
+// no pi.on("extension_ui_response"): Pi routes the response via pendingExtensionRequests.
 //
-// The no-limbo invariant: a control response of "cancel"/undefined is NEVER accepted
-// as a final answer -- the widget is re-presented. Real escapes (Back/Exit/Other) are
-// always present as selectable options in the descriptor (reserved field), so cancel
-// has no legitimate meaning.
-let _pending = new Map(); // id -> {resolve, reject}
-
-async function emitAndWait(ctx, descriptor) {
+// The no-limbo invariant: undefined/null/invalid-JSON/control:"cancel" are NEVER
+// accepted as a final answer — the widget is re-presented. Real escapes (Back/Exit/Other)
+// are always present as selectable options in the descriptor, so cancel has no
+// legitimate meaning.
+export async function emitAndWait(ctx, descriptor) {
 	for (;;) {
-		const promise = new Promise((resolve, reject) => {
-			_pending.set(descriptor.id, { resolve, reject });
-		});
-		ctx.sendRaw({ type: "extension_ui_request", ui_request: descriptor });
-		const resp = await promise;
-		// no-limbo: a cancel/undefined response re-presents the same widget
-		if (resp && resp.control !== "cancel" && resp.id === descriptor.id) {
-			return resp;
-		}
-		if (ctx.hasUI) {
-			await ctx.ui.notify(
-				"Esc non chiude il gate: usa Torna indietro / Esci / Altro dalle opzioni.",
-				"warning",
-			);
-		}
+		const value = await ctx.ui.input(JSON.stringify(descriptor), "");
+		if (value === undefined || value === null) { await reLoop(ctx); continue; }
+		let resp;
+		try { resp = JSON.parse(value); } catch { await reLoop(ctx); continue; }
+		if (resp && resp.control !== "cancel" && resp.id === descriptor.id) return resp;
+		await reLoop(ctx);
 	}
 }
 
-// The runtime invokes this when a ui_response arrives (RPC reply or SSE from FE).
-function handleUiResponse(event) {
-	const slot = _pending.get(event.id);
-	if (slot) {
-		_pending.delete(event.id);
-		slot.resolve(event);
-	}
+async function reLoop(ctx) {
+	if (ctx.hasUI) await ctx.ui.notify(
+		"Esc non chiude il gate: usa Torna indietro / Esci / Altro dalle opzioni.", "warning");
 }
 
 // --- the extension ------------------------------------------------------------
@@ -284,9 +268,6 @@ export default function (pi) {
 		}
 	});
 
-	// 6) UI_RESPONSE dispatch: correlate an incoming response to its awaiting widget.
-	pi.on("extension_ui_response", handleUiResponse);
-
 	// --- the four reviewer tools (widget-descriptor emit + await) ---------------
 
 	pi.registerTool({