diff --git a/src/lib/onboard.ts b/src/lib/onboard.ts
index f0e9dd86444..c6b82d90c7c 100644
--- a/src/lib/onboard.ts
+++ b/src/lib/onboard.ts
@@ -3817,6 +3817,26 @@ async function createSandbox(
   if (process.env.NEMOCLAW_DASHBOARD_PORT) {
     envArgs.push(formatEnvAssignment("NEMOCLAW_DASHBOARD_PORT", String(DASHBOARD_PORT)));
   }
+  // When CHAT_UI_URL points to a non-loopback address (Brev Launchable,
+  // remote host, custom domain), pass NEMOCLAW_CORS_ORIGIN into the sandbox
+  // so nemoclaw-start.sh's apply_cors_override() adds the browser's origin
+  // to gateway.controlUi.allowedOrigins at startup. Without this, the
+  // Dockerfile-baked allowedOrigins only contains http://127.0.0.1:PORT
+  // and the gateway rejects WebSocket/API connections from the external URL.
+  const corsOrigin = process.env.NEMOCLAW_CORS_ORIGIN;
+  if (corsOrigin) {
+    envArgs.push(formatEnvAssignment("NEMOCLAW_CORS_ORIGIN", corsOrigin));
+  } else {
+    try {
+      const parsed = new URL(chatUiUrl);
+      if (!isLoopbackHostname(parsed.hostname)) {
+        const origin = `${parsed.protocol}//${parsed.host}`;
+        envArgs.push(formatEnvAssignment("NEMOCLAW_CORS_ORIGIN", origin));
+      }
+    } catch {
+      // Invalid chatUiUrl — skip CORS auto-detection
+    }
+  }
   if (webSearchConfig?.fetchEnabled) {
     const braveKey =
       getCredential(webSearch.BRAVE_API_KEY_ENV) || process.env[webSearch.BRAVE_API_KEY_ENV];
@@ -3926,14 +3946,33 @@ async function createSandbox(
   // Wait for NemoClaw dashboard to become fully ready (web server live)
   // This prevents port forwards from connecting to a non-existent port
   // or seeing 502/503 errors during initial load.
+  // Probe /health instead of / — the root path returns 401 when device auth
+  // is enabled (standard for Brev Launchable and headless deployments),
+  // causing this readiness check to false-negative for 30s. /health returns
+  // 200 unconditionally when the gateway is up. Falls back to accepting any
+  // HTTP response (including 401) from / as proof the server is listening.
   console.log("  Waiting for NemoClaw dashboard to become ready...");
   const openshellBin = getOpenshellBinary();
   for (let i = 0; i < 15; i++) {
-    const readyMatch = runCaptureOpenshell(
-      ["sandbox", "exec", sandboxName, "curl", "-sf", `http://localhost:${effectivePort}/`],
+    // Primary: /health endpoint (no auth required, returns 200 when gateway is up).
+    // Use -o /dev/null -w '%{http_code}' to check by status code, not output
+    // content — runCaptureOpenshell merges stdout/stderr so a failed curl can
+    // return non-empty error text that would incorrectly pass a truthy check.
+    const healthCode = runCaptureOpenshell(
+      ["sandbox", "exec", sandboxName, "curl", "-s", "-o", "/dev/null", "-w", "%{http_code}", `http://localhost:${effectivePort}/health`],
+      { ignoreError: true },
+    );
+    if (healthCode && String(healthCode).trim() === "200") {
+      console.log("  ✓ Dashboard is live");
+      break;
+    }
+    // Fallback: accept any HTTP response from / (including 401) as proof
+    // the server is listening — any 1xx-5xx means the gateway process is up.
+    const httpCode = runCaptureOpenshell(
+      ["sandbox", "exec", sandboxName, "curl", "-s", "-o", "/dev/null", "-w", "%{http_code}", `http://localhost:${effectivePort}/`],
       { ignoreError: true },
     );
-    if (readyMatch) {
+    if (httpCode && /^[1-5]\d\d$/.test(String(httpCode).trim())) {
       console.log("  ✓ Dashboard is live");
       break;
     }
diff --git a/test/onboard.test.ts b/test/onboard.test.ts
index bd888763f6d..6e3df2ad89e 100644
--- a/test/onboard.test.ts
+++ b/test/onboard.test.ts
@@ -2378,7 +2378,7 @@ runner.run = (command, opts = {}) => {
 runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };
@@ -2486,7 +2486,7 @@ runner.run = (command, opts = {}) => {
 runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };
@@ -2542,6 +2542,190 @@ const { createSandbox } = require(${onboardPath});
     );
   });
 
+  it("injects NEMOCLAW_CORS_ORIGIN into sandbox envArgs when CHAT_UI_URL is non-loopback (#2342)", async () => {
+    const repoRoot = path.join(import.meta.dirname, "..");
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-onboard-cors-origin-"));
+    const fakeBin = path.join(tmpDir, "bin");
+    const scriptPath = path.join(tmpDir, "cors-origin-envargs.js");
+    const onboardPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "onboard.js"));
+    const runnerPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "runner.js"));
+    const registryPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "registry.js"));
+    const preflightPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "preflight.js"));
+    const credentialsPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "credentials.js"));
+
+    fs.mkdirSync(fakeBin, { recursive: true });
+    fs.writeFileSync(path.join(fakeBin, "openshell"), "#!/usr/bin/env bash\nexit 0\n", {
+      mode: 0o755,
+    });
+
+    const script = String.raw`
+const runner = require(${runnerPath});
+const _n = (c) => (Array.isArray(c) ? c.join(" ") : String(c)).replace(/'/g, "");
+const registry = require(${registryPath});
+const preflight = require(${preflightPath});
+const credentials = require(${credentialsPath});
+const childProcess = require("node:child_process");
+const { EventEmitter } = require("node:events");
+
+const commands = [];
+runner.run = (command, opts = {}) => {
+  commands.push({ command: _n(command), env: opts.env || null });
+  return { status: 0 };
+};
+runner.runCapture = (command) => {
+  if (_n(command).includes("sandbox get my-assistant")) return "";
+  if (_n(command).includes("sandbox list")) return "my-assistant Ready";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
+  if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
+  return "";
+};
+registry.registerSandbox = () => true;
+registry.removeSandbox = () => true;
+preflight.checkPortAvailable = async () => ({ ok: true });
+credentials.prompt = async () => "";
+
+childProcess.spawn = (...args) => {
+  const child = new EventEmitter();
+  child.stdout = new EventEmitter();
+  child.stderr = new EventEmitter();
+  commands.push({ command: _n(args[1][1]), env: args[2]?.env || null });
+  process.nextTick(() => {
+    child.stdout.emit("data", Buffer.from("Created sandbox: my-assistant\n"));
+    child.emit("close", 0);
+  });
+  return child;
+};
+
+const { createSandbox } = require(${onboardPath});
+
+(async () => {
+  process.env.OPENSHELL_GATEWAY = "nemoclaw";
+  process.env.CHAT_UI_URL = "https://nemoclaw0-abc123.brevlab.com";
+  await createSandbox(null, "gpt-5.4");
+  console.log(JSON.stringify(commands));
+})().catch((error) => {
+  console.error(error);
+  process.exit(1);
+});
+`;
+    fs.writeFileSync(scriptPath, script);
+
+    const result = spawnSync(process.execPath, [scriptPath], {
+      cwd: repoRoot,
+      encoding: "utf-8",
+      env: {
+        ...process.env,
+        HOME: tmpDir,
+        PATH: `${fakeBin}:${process.env.PATH || ""}`,
+        NEMOCLAW_NON_INTERACTIVE: "1",
+        NEMOCLAW_CORS_ORIGIN: "",
+      },
+    });
+
+    assert.equal(result.status, 0, result.stderr);
+    const commands = JSON.parse(result.stdout.trim().split("\n").pop());
+    // The sandbox create command should include NEMOCLAW_CORS_ORIGIN with the
+    // Brev public URL origin so apply_cors_override() adds it to allowedOrigins.
+    const createCmd = commands.find((entry) => entry.command.includes("sandbox create"));
+    assert.ok(createCmd, "expected a sandbox create command");
+    assert.ok(
+      createCmd.command.includes("NEMOCLAW_CORS_ORIGIN=https://nemoclaw0-abc123.brevlab.com"),
+      `expected NEMOCLAW_CORS_ORIGIN in sandbox create envArgs, got: ${createCmd.command}`,
+    );
+  });
+
+  it("does not inject NEMOCLAW_CORS_ORIGIN when CHAT_UI_URL is loopback (#2342)", async () => {
+    const repoRoot = path.join(import.meta.dirname, "..");
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-onboard-cors-loopback-"));
+    const fakeBin = path.join(tmpDir, "bin");
+    const scriptPath = path.join(tmpDir, "cors-loopback-envargs.js");
+    const onboardPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "onboard.js"));
+    const runnerPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "runner.js"));
+    const registryPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "registry.js"));
+    const preflightPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "preflight.js"));
+    const credentialsPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "credentials.js"));
+
+    fs.mkdirSync(fakeBin, { recursive: true });
+    fs.writeFileSync(path.join(fakeBin, "openshell"), "#!/usr/bin/env bash\nexit 0\n", {
+      mode: 0o755,
+    });
+
+    const script = String.raw`
+const runner = require(${runnerPath});
+const _n = (c) => (Array.isArray(c) ? c.join(" ") : String(c)).replace(/'/g, "");
+const registry = require(${registryPath});
+const preflight = require(${preflightPath});
+const credentials = require(${credentialsPath});
+const childProcess = require("node:child_process");
+const { EventEmitter } = require("node:events");
+
+const commands = [];
+runner.run = (command, opts = {}) => {
+  commands.push({ command: _n(command), env: opts.env || null });
+  return { status: 0 };
+};
+runner.runCapture = (command) => {
+  if (_n(command).includes("sandbox get my-assistant")) return "";
+  if (_n(command).includes("sandbox list")) return "my-assistant Ready";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
+  if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
+  return "";
+};
+registry.registerSandbox = () => true;
+registry.removeSandbox = () => true;
+preflight.checkPortAvailable = async () => ({ ok: true });
+credentials.prompt = async () => "";
+
+childProcess.spawn = (...args) => {
+  const child = new EventEmitter();
+  child.stdout = new EventEmitter();
+  child.stderr = new EventEmitter();
+  commands.push({ command: _n(args[1][1]), env: args[2]?.env || null });
+  process.nextTick(() => {
+    child.stdout.emit("data", Buffer.from("Created sandbox: my-assistant\n"));
+    child.emit("close", 0);
+  });
+  return child;
+};
+
+const { createSandbox } = require(${onboardPath});
+
+(async () => {
+  process.env.OPENSHELL_GATEWAY = "nemoclaw";
+  process.env.CHAT_UI_URL = "http://127.0.0.1:18789";
+  await createSandbox(null, "gpt-5.4");
+  console.log(JSON.stringify(commands));
+})().catch((error) => {
+  console.error(error);
+  process.exit(1);
+});
+`;
+    fs.writeFileSync(scriptPath, script);
+
+    const result = spawnSync(process.execPath, [scriptPath], {
+      cwd: repoRoot,
+      encoding: "utf-8",
+      env: {
+        ...process.env,
+        HOME: tmpDir,
+        PATH: `${fakeBin}:${process.env.PATH || ""}`,
+        NEMOCLAW_NON_INTERACTIVE: "1",
+        NEMOCLAW_CORS_ORIGIN: "",
+      },
+    });
+
+    assert.equal(result.status, 0, result.stderr);
+    const commands = JSON.parse(result.stdout.trim().split("\n").pop());
+    // Loopback CHAT_UI_URL should NOT inject NEMOCLAW_CORS_ORIGIN —
+    // the Dockerfile-baked allowedOrigins already contains the loopback origin.
+    const createCmd = commands.find((entry) => entry.command.includes("sandbox create"));
+    assert.ok(createCmd, "expected a sandbox create command");
+    assert.ok(
+      !createCmd.command.includes("NEMOCLAW_CORS_ORIGIN"),
+      `NEMOCLAW_CORS_ORIGIN should not be set for loopback URL, got: ${createCmd.command}`,
+    );
+  });
+
   it("injects NEMOCLAW_DASHBOARD_PORT into sandbox create envArgs when set (#1925)", async () => {
     const repoRoot = path.join(import.meta.dirname, "..");
     const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-onboard-dashboard-port-"));
@@ -2580,7 +2764,7 @@ runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
   // Custom port: dashboard readiness curl uses 19000 (DASHBOARD_PORT from env)
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:19000/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:19000/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 19000 12345 running";
   return "";
 };
@@ -4087,7 +4271,7 @@ runner.runCapture = (command) => {
     sandboxListCalls += 1;
     return sandboxListCalls >= 2 ? "my-assistant Ready" : "my-assistant Pending";
   }
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };
@@ -4476,7 +4660,7 @@ runner.run = (command, opts = {}) => {
 runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };
@@ -4604,7 +4788,7 @@ runner.run = (command, opts = {}) => {
 runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };
@@ -4880,7 +5064,7 @@ runner.run = (command, opts = {}) => {
 runner.runCapture = (command) => {
   if (_n(command).includes("sandbox get my-assistant")) return "";
   if (_n(command).includes("sandbox list")) return "my-assistant Ready";
-  if (_n(command).includes("sandbox exec my-assistant curl -sf http://localhost:18789/")) return "ok";
+  if (_n(command).includes("sandbox exec my-assistant curl -s -o /dev/null -w %{http_code} http://localhost:18789/health")) return "200";
   if (_n(command).includes("forward list")) return "my-assistant 127.0.0.1 18789 12345 running";
   return "";
 };