diff --git a/bin/lib/onboard.js b/bin/lib/onboard.js
index cf96d03f8..f68cce370 100644
--- a/bin/lib/onboard.js
+++ b/bin/lib/onboard.js
@@ -46,6 +46,22 @@ const nim = require("./nim");
 const onboardSession = require("./onboard-session");
 const policies = require("./policies");
 const { checkPortAvailable, ensureSwap, getMemoryInfo } = require("./preflight");
+function secureTempFile(prefix, ext = "") {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), `${prefix}-`));
+  return path.join(dir, `${prefix}${ext}`);
+}
+
+/**
+ * Safely remove a mkdtemp-created directory.  Guards against accidentally
+ * deleting the system temp root if a caller passes os.tmpdir() itself.
+ */
+function cleanupTempDir(filePath, expectedPrefix) {
+  const parentDir = path.dirname(filePath);
+  if (parentDir !== os.tmpdir() && path.basename(parentDir).startsWith(`${expectedPrefix}-`)) {
+    fs.rmSync(parentDir, { recursive: true, force: true });
+  }
+}
+
 const EXPERIMENTAL = process.env.NEMOCLAW_EXPERIMENTAL === "1";
 const USE_COLOR = !process.env.NO_COLOR && !!process.stdout.isTTY;
 const DIM = USE_COLOR ? "\x1b[2m" : "";
@@ -683,10 +699,7 @@ function getProbeRecovery(probe, options = {}) {
 
 // eslint-disable-next-line complexity
 function runCurlProbe(argv) {
-  const bodyFile = path.join(
-    os.tmpdir(),
-    `nemoclaw-curl-probe-${Date.now()}-${Math.random().toString(36).slice(2)}.json`,
-  );
+  const bodyFile = secureTempFile("nemoclaw-curl-probe", ".json");
   try {
     const args = [...argv];
     const url = args.pop();
@@ -739,7 +752,7 @@ function runCurlProbe(argv) {
       message: summarizeCurlFailure(error?.status || 1, error?.message || String(error)),
     };
   } finally {
-    fs.rmSync(bodyFile, { force: true });
+    cleanupTempDir(bodyFile, "nemoclaw-curl-probe");
   }
 }
 
@@ -2244,23 +2257,32 @@ async function recoverGatewayRuntime() {
 // ── Step 3: Sandbox ──────────────────────────────────────────────
 
 async function promptValidatedSandboxName() {
-  const nameAnswer = await promptOrDefault(
-    "  Sandbox name (lowercase, numbers, hyphens) [my-assistant]: ",
-    "NEMOCLAW_SANDBOX_NAME",
-    "my-assistant",
-  );
-  const sandboxName = (nameAnswer || "my-assistant").trim().toLowerCase();
+  while (true) {
+    const nameAnswer = await promptOrDefault(
+      "  Sandbox name (lowercase, numbers, hyphens) [my-assistant]: ",
+      "NEMOCLAW_SANDBOX_NAME",
+      "my-assistant",
+    );
+    const sandboxName = (nameAnswer || "my-assistant").trim().toLowerCase();
+
+    // Validate: RFC 1123 subdomain — lowercase alphanumeric and hyphens,
+    // must start and end with alphanumeric (required by Kubernetes/OpenShell)
+    if (/^[a-z0-9]([a-z0-9-]*[a-z0-9])?$/.test(sandboxName)) {
+      return sandboxName;
+    }
 
-  // Validate: RFC 1123 subdomain — lowercase alphanumeric and hyphens,
-  // must start and end with alphanumeric (required by Kubernetes/OpenShell)
-  if (!/^[a-z0-9]([a-z0-9-]*[a-z0-9])?$/.test(sandboxName)) {
     console.error(`  Invalid sandbox name: '${sandboxName}'`);
     console.error("  Names must be lowercase, contain only letters, numbers, and hyphens,");
     console.error("  and must start and end with a letter or number.");
-    process.exit(1);
-  }
 
-  return sandboxName;
+    // Non-interactive runs cannot re-prompt — abort so the caller can fix the
+    // NEMOCLAW_SANDBOX_NAME env var and retry.
+    if (isNonInteractive()) {
+      process.exit(1);
+    }
+
+    console.error("  Please try again.\n");
+  }
 }
 
 // ── Step 5: Sandbox ──────────────────────────────────────────────
@@ -3189,7 +3211,7 @@ async function setupOpenclaw(sandboxName, model, provider) {
         { stdio: ["ignore", "ignore", "inherit"] },
       );
     } finally {
-      fs.rmSync(path.dirname(scriptFile), { recursive: true, force: true });
+      cleanupTempDir(scriptFile, "nemoclaw-sync");
     }
   }
 
diff --git a/test/onboard.test.js b/test/onboard.test.js
index 820a0fae1..20f9a5c61 100644
--- a/test/onboard.test.js
+++ b/test/onboard.test.js
@@ -486,17 +486,23 @@ describe("onboard helpers", () => {
   });
 
   it("writes sandbox sync scripts to a temp file for stdin redirection", () => {
-    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-onboard-test-"));
+    const scriptFile = writeSandboxConfigSyncFile("echo test");
     try {
-      const scriptFile = writeSandboxConfigSyncFile("echo test", tmpDir);
-      expect(scriptFile).toMatch(/nemoclaw-sync-.*[/\\]sync\.sh$/);
+      expect(scriptFile).toMatch(/nemoclaw-sync.*\.sh$/);
       expect(fs.readFileSync(scriptFile, "utf8")).toBe("echo test\n");
+      // Verify the file lives inside a mkdtemp-created directory (not directly in /tmp)
+      const parentDir = path.dirname(scriptFile);
+      expect(parentDir).not.toBe(os.tmpdir());
+      expect(parentDir).toContain("nemoclaw-sync");
       if (process.platform !== "win32") {
         const stat = fs.statSync(scriptFile);
         expect(stat.mode & 0o777).toBe(0o600);
       }
     } finally {
-      fs.rmSync(tmpDir, { recursive: true, force: true });
+      const parentDir = path.dirname(scriptFile);
+      if (parentDir !== os.tmpdir() && path.basename(parentDir).startsWith("nemoclaw-sync-")) {
+        fs.rmSync(parentDir, { recursive: true, force: true });
+      }
     }
   });
 
@@ -1798,4 +1804,23 @@ const { setupInference } = require(${onboardPath});
     const commands = JSON.parse(result.stdout.trim().split("\n").pop());
     assert.equal(commands.length, 3);
   });
+
+  it("re-prompts on invalid sandbox names instead of exiting in interactive mode", () => {
+    const source = fs.readFileSync(
+      path.join(import.meta.dirname, "..", "bin", "lib", "onboard.js"),
+      "utf-8",
+    );
+    // Extract the promptValidatedSandboxName function body
+    const fnMatch = source.match(
+      /async function promptValidatedSandboxName\(\)\s*\{([\s\S]*?)\n\}/,
+    );
+    assert.ok(fnMatch, "promptValidatedSandboxName function not found");
+    const fnBody = fnMatch[1];
+    // Verify the retry loop exists within this function
+    assert.match(fnBody, /while\s*\(true\)/);
+    assert.match(fnBody, /Please try again/);
+    // Non-interactive still exits within this function
+    assert.match(fnBody, /isNonInteractive\(\)/);
+    assert.match(fnBody, /process\.exit\(1\)/);
+  });
 });