diff --git a/app/gateway/index.ts b/app/gateway/index.ts
index 9adf3ed..c306dff 100644
--- a/app/gateway/index.ts
+++ b/app/gateway/index.ts
@@ -16,6 +16,14 @@ export interface GatewayDeps {
 export function createGateway(deps: GatewayDeps): Hono {
 	const app = new Hono();
 
+	// The gateway has no UI; people who open its URL in a browser should see that it's running, not a 404.
+	app.get("/", (c) =>
+		c.text(
+			"software-factory gateway is running.\n\n" +
+				"It has no web UI. GitHub sends webhooks to POST /webhooks/github, and the factory replies on issues and pull requests.\n" +
+				"Health checks: GET /health and GET /ready. Setup and usage: docs/quickstart.md in your software-factory repository.\n",
+		),
+	);
 	app.get("/health", (c) => c.json({ status: "ok" }));
 	app.get("/ready", (c) => c.json({ status: "ready" }));
 
diff --git a/docs/quickstart.md b/docs/quickstart.md
index a0c2da4..7512d49 100644
--- a/docs/quickstart.md
+++ b/docs/quickstart.md
@@ -59,6 +59,10 @@ Setup is complete when:
 - applying `factory:triage` produces an App-authored status comment and a
   useful outcome.
 
+software-factory has no web UI. You use it through labels and comments in
+GitHub. Opening the `factory-gateway` URL in a browser shows only a short
+message that the gateway is running.
+
 ## Next steps
 
 - [Configuration](configuration.md) — change settings, follow or cancel runs,
diff --git a/docs/runbooks/setup.md b/docs/runbooks/setup.md
index 5656ee5..577da6a 100644
--- a/docs/runbooks/setup.md
+++ b/docs/runbooks/setup.md
@@ -244,6 +244,9 @@ and apply it. The form asks for no values.
 
 Continue when both services have deployed and the gateway is live.
 
+The gateway has no web UI. Opening its URL in a browser shows a short
+message that it is running; that is expected, not a failed deploy.
+
 ## Phase 8: Configure GitHub
 
 Ask for the public gateway URL. It is not a secret. Run:
diff --git a/tests/gateway.test.ts b/tests/gateway.test.ts
index 2ab2390..d91b6f7 100644
--- a/tests/gateway.test.ts
+++ b/tests/gateway.test.ts
@@ -44,6 +44,16 @@ describe("gateway", () => {
 		expect(await ready.json()).toEqual({ status: "ready" });
 	});
 
+	it("tells a browser at / that the headless gateway is running, without revealing its secret", async () => {
+		const res = await app.request("/");
+		expect(res.status).toBe(200);
+		const text = await res.text();
+		expect(text).toContain("software-factory gateway is running");
+		expect(text).toContain("no web UI");
+		expect(text).not.toContain(SECRET);
+		expect(startTask).not.toHaveBeenCalled();
+	});
+
 	it("rejects a bad signature before parsing the body", async () => {
 		const parse = vi.spyOn(JSON, "parse");
 		const res = await app.fetch(webhook("{not json", { signature: sign("{not json", "wrong") }));