diff --git a/backend/docker-compose.tunnel.yml b/backend/docker-compose.tunnel.yml
new file mode 100644
index 0000000..f3b1ce8
--- /dev/null
+++ b/backend/docker-compose.tunnel.yml
@@ -0,0 +1,24 @@
+# Overlay that adds a public Cloudflare tunnel so a patient's phone can scan the
+# wallet-import QR from ANY network (cellular, other Wi-Fi) — not just the LAN.
+#
+#   npm run docker:tunnel        # from backend/  (easiest)
+#   # equivalently:
+#   docker compose -f docker-compose.yml -f docker-compose.tunnel.yml up --build
+#
+# cloudflared opens a random https://<id>.trycloudflare.com URL to the backend
+# and exposes it on its metrics endpoint; the backend reads it from there and
+# bakes it into the QR (CLOUDFLARED_METRICS_URL below). Zero config — no
+# Cloudflare account or token needed for these quick tunnels.
+
+services:
+  cloudflared:
+    image: cloudflare/cloudflared:latest
+    restart: unless-stopped
+    depends_on:
+      - backend
+    command: tunnel --no-autoupdate --url http://backend:4000 --metrics 0.0.0.0:3333
+
+  backend:
+    environment:
+      # Where the backend reads its public quick-tunnel URL from.
+      CLOUDFLARED_METRICS_URL: http://cloudflared:3333
diff --git a/backend/package.json b/backend/package.json
index 66c8d4d..281ca59 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -11,6 +11,7 @@
   "scripts": {
     "dev": "tsx watch src/index.ts",
     "dev:tunnel": "node scripts/dev-tunnel.mjs",
+    "docker:tunnel": "docker compose -f docker-compose.yml -f docker-compose.tunnel.yml up --build",
     "build": "tsc -p tsconfig.json",
     "start": "node dist/index.js",
     "typecheck": "tsc --noEmit",
diff --git a/backend/src/env.ts b/backend/src/env.ts
index bea81a2..e29d6d3 100644
--- a/backend/src/env.ts
+++ b/backend/src/env.ts
@@ -25,6 +25,10 @@ const schema = z.object({
   // QR a patient scans. Optional — when unset we derive it from the request host
   // (so opening the web app over the LAN yields a reachable LAN URL).
   PUBLIC_RELAY_URL: z.string().optional(),
+  // Metrics URL of a cloudflared quick-tunnel sidecar (e.g. http://cloudflared:3333).
+  // When set and PUBLIC_RELAY_URL is unset, the backend discovers its public
+  // trycloudflare.com URL from there for Dockerized off-network testing.
+  CLOUDFLARED_METRICS_URL: z.string().optional(),
   PORT: z.coerce.number().int().positive().default(4000),
   NODE_ENV: z
     .enum(["development", "production", "test"])
diff --git a/backend/src/index.ts b/backend/src/index.ts
index c3ad156..6ace761 100644
--- a/backend/src/index.ts
+++ b/backend/src/index.ts
@@ -31,6 +31,7 @@ import { settingsRouter } from "./routes/settings.js";
 import { signingRouter } from "./routes/signing.js";
 import { staffRouter } from "./routes/staff.js";
 import { tasksRouter } from "./routes/tasks.js";
+import { discoverQuickTunnelUrl } from "./services/relay-url.js";
 import { sweepExpiredShares } from "./services/wallet-share.js";
 
 const app = express();
@@ -135,3 +136,10 @@ server.listen(env.PORT, () => {
   console.log(`  • signing:  /api/signing  (Ed25519 clinic key)`);
   console.log(`  • wallet:   /api/patients/wallet  (+ /wallet socket relay)`);
 });
+
+// Dockerized off-network testing: learn our public Cloudflare quick-tunnel URL
+// (from the `tunnel` compose profile) so the wallet-import QR points at it.
+// No-op unless a tunnel sidecar is configured and PUBLIC_RELAY_URL is unset.
+if (env.CLOUDFLARED_METRICS_URL && !env.PUBLIC_RELAY_URL) {
+  void discoverQuickTunnelUrl(env.CLOUDFLARED_METRICS_URL);
+}
diff --git a/backend/src/routes/patients-wallet.ts b/backend/src/routes/patients-wallet.ts
index fe3bba5..2f25053 100644
--- a/backend/src/routes/patients-wallet.ts
+++ b/backend/src/routes/patients-wallet.ts
@@ -18,6 +18,7 @@ import {
 import { emitToWallet } from "../realtime.js";
 import { recordActivity } from "../services/activity.js";
 import * as patientService from "../services/patients.js";
+import { getDiscoveredRelayUrl } from "../services/relay-url.js";
 import * as walletShare from "../services/wallet-share.js";
 
 export const patientsWalletRouter = Router();
@@ -29,6 +30,9 @@ patientsWalletRouter.use(requireAuth, requireOrg);
 // host so that opening the web app over the LAN yields a reachable LAN URL.
 function resolveRelayUrl(req: Request): string {
   if (env.PUBLIC_RELAY_URL) return env.PUBLIC_RELAY_URL;
+  // A cloudflared quick tunnel (Docker `--profile tunnel`), if one was found.
+  const tunnel = getDiscoveredRelayUrl();
+  if (tunnel) return tunnel;
   const host = req.get("host");
   if (host) {
     // Behind a TLS-terminating proxy (Fly/Render/etc.) req.protocol is "http";
diff --git a/backend/src/services/relay-url.ts b/backend/src/services/relay-url.ts
new file mode 100644
index 0000000..638b9a0
--- /dev/null
+++ b/backend/src/services/relay-url.ts
@@ -0,0 +1,43 @@
+// Discovers this backend's public relay URL from a cloudflared **quick tunnel**
+// so Dockerized off-network testing is zero-config: `docker compose --profile
+// tunnel up` starts a cloudflared sidecar that proxies a random
+// `https://<sub>.trycloudflare.com` URL to the backend, and we read that URL
+// from cloudflared's metrics endpoint (`GET /quicktunnel`) and bake it into the
+// wallet-import QR. An explicit PUBLIC_RELAY_URL always wins over this.
+
+let discovered: string | null = null;
+
+export function getDiscoveredRelayUrl(): string | null {
+  return discovered;
+}
+
+// Poll cloudflared's metrics `/quicktunnel` endpoint until it reports a
+// hostname, then cache `https://<hostname>`. Best-effort and quiet: if no
+// tunnel is running (e.g. plain `docker compose up`), it gives up after the
+// window without affecting normal request handling.
+export async function discoverQuickTunnelUrl(
+  metricsUrl: string,
+  { intervalMs = 2000, timeoutMs = 90_000 }: { intervalMs?: number; timeoutMs?: number } = {},
+): Promise<void> {
+  const base = metricsUrl.replace(/\/$/, "");
+  const deadline = Date.now() + timeoutMs;
+
+  while (Date.now() < deadline) {
+    try {
+      const res = await fetch(`${base}/quicktunnel`);
+      if (res.ok) {
+        const body = (await res.json()) as { hostname?: string };
+        const host = body.hostname?.trim();
+        if (host) {
+          discovered = host.startsWith("http") ? host : `https://${host}`;
+          console.log(`Wallet relay reachable via Cloudflare tunnel: ${discovered}`);
+          return;
+        }
+      }
+    } catch {
+      // cloudflared not up yet (or no tunnel profile) — keep trying until the
+      // deadline, then quietly stop.
+    }
+    await new Promise((r) => setTimeout(r, intervalMs));
+  }
+}