diff --git a/src/sdk/devbox.ts b/src/sdk/devbox.ts
index df25963c9..e34a938d3 100644
--- a/src/sdk/devbox.ts
+++ b/src/sdk/devbox.ts
@@ -838,7 +838,9 @@ export class Devbox {
     if (!tunnel) {
       throw new RunloopError('No tunnel has been enabled for this devbox. Call net.enableTunnel() first.');
     }
-    return `https://${port}-${tunnel.tunnel_key}.tunnel.runloop.ai`;
+    const apiHost = new URL(this.client.baseURL).hostname;
+    const baseDomain = apiHost.startsWith('api.') ? apiHost.slice(4) : apiHost;
+    return `https://${port}-${tunnel.tunnel_key}.tunnel.${baseDomain}`;
   }
 
   /**
diff --git a/tests/objects/devbox.test.ts b/tests/objects/devbox.test.ts
index 4a9fadfa9..2cb930c97 100644
--- a/tests/objects/devbox.test.ts
+++ b/tests/objects/devbox.test.ts
@@ -11,6 +11,7 @@ describe('Devbox (New API)', () => {
   beforeEach(() => {
     // Create mock client instance with proper structure
     mockClient = {
+      baseURL: 'https://api.runloop.ai',
       devboxes: {
         createAndAwaitRunning: jest.fn(),
         retrieve: jest.fn(),
@@ -303,6 +304,24 @@ describe('Devbox (New API)', () => {
         expect(url).toBe('https://3000-mykey456.tunnel.runloop.ai');
       });
 
+      it('should derive tunnel domain from client baseURL', async () => {
+        const mockTunnel = {
+          tunnel_key: 'abc123xyz',
+          auth_mode: 'open' as const,
+          create_time_ms: Date.now(),
+        };
+        const dataWithTunnel = { ...mockDevboxData, tunnel: mockTunnel };
+        mockClient.devboxes.retrieve.mockResolvedValue(dataWithTunnel);
+
+        mockClient.baseURL = 'https://api.runloop.pro';
+        expect(await devbox.getTunnelUrl(8080)).toBe('https://8080-abc123xyz.tunnel.runloop.pro');
+
+        mockClient.baseURL = 'http://127.0.0.1:8080';
+        expect(await devbox.getTunnelUrl(8080)).toBe('https://8080-abc123xyz.tunnel.127.0.0.1');
+
+        mockClient.baseURL = 'https://api.runloop.ai';
+      });
+
       it('should throw RunloopError when no tunnel has been enabled', async () => {
         const dataWithoutTunnel = { ...mockDevboxData, tunnel: null };
         mockClient.devboxes.retrieve.mockResolvedValue(dataWithoutTunnel);
diff --git a/tests/smoketests/object-oriented/devbox.test.ts b/tests/smoketests/object-oriented/devbox.test.ts
index 603128f30..8d8598cbd 100644
--- a/tests/smoketests/object-oriented/devbox.test.ts
+++ b/tests/smoketests/object-oriented/devbox.test.ts
@@ -413,10 +413,10 @@ describe('smoketest: object-oriented devbox', () => {
         expect(tunnel.tunnel_key).toBeTruthy();
 
         const url = await devbox.getTunnelUrl(8080);
-        expect(url).toBe(`https://8080-${tunnel.tunnel_key}.tunnel.runloop.ai`);
+        expect(url).toContain(`https://8080-${tunnel.tunnel_key}.tunnel.runloop.`);
 
         const url3000 = await devbox.getTunnelUrl(3000);
-        expect(url3000).toBe(`https://3000-${tunnel.tunnel_key}.tunnel.runloop.ai`);
+        expect(url3000).toContain(`https://3000-${tunnel.tunnel_key}.tunnel.runloop.`);
       } finally {
         await devbox.shutdown();
       }