diff --git a/src/cli/tui/App.tsx b/src/cli/tui/App.tsx
index 81795d16d..65ff51050 100644
--- a/src/cli/tui/App.tsx
+++ b/src/cli/tui/App.tsx
@@ -10,6 +10,7 @@ import { ConfigBundleFlow } from './screens/config-bundle-hub';
 import { CreateScreen } from './screens/create';
 import { DatasetFlow } from './screens/dataset-hub';
 import { DeployScreen } from './screens/deploy/DeployScreen';
+import { DevScreen } from './screens/dev/DevScreen';
 import { EvalHubScreen, EvalScreen } from './screens/eval';
 import { ExportHarnessFlow } from './screens/export';
 import { FetchAccessScreen } from './screens/fetch-access';
@@ -52,6 +53,7 @@ type Route =
       autoSession?: boolean;
     }
   | { name: 'logs' }
+  | { name: 'dev' }
   | { name: 'create' }
   | { name: 'add' }
   | { name: 'status' }
@@ -142,9 +144,7 @@ function AppContent({
     }
 
     if (id === 'dev') {
-      setExitAction({ type: 'dev' });
-      exit();
-      return;
+      setRoute({ name: 'dev' });
     } else if (id === 'exec') {
       setExitAction({ type: 'exec' });
       exit();
@@ -271,6 +271,21 @@ function AppContent({
     return <LogsScreen isInteractive={isInteractive} onExit={handleBack} />;
   }
 
+  if (route.name === 'dev') {
+    // Render the dev picker in-TUI so agent-less projects get a guided error
+    // screen (Esc to go back) instead of crashing out of the TUI. When agents
+    // exist, the picker hands off to browser dev mode via the exit action.
+    return (
+      <DevScreen
+        onBack={handleBack}
+        onLaunchBrowser={() => {
+          setExitAction({ type: 'dev' });
+          exit();
+        }}
+      />
+    );
+  }
+
   if (route.name === 'status') {
     return <StatusScreen isInteractive={isInteractive} onExit={handleBack} />;
   }
diff --git a/src/cli/tui/screens/dev/__tests__/DevScreen.test.tsx b/src/cli/tui/screens/dev/__tests__/DevScreen.test.tsx
new file mode 100644
index 000000000..6e3adf790
--- /dev/null
+++ b/src/cli/tui/screens/dev/__tests__/DevScreen.test.tsx
@@ -0,0 +1,70 @@
+import { DevScreen } from '../DevScreen.js';
+import { render } from 'ink-testing-library';
+import React from 'react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+const { mockLoadProjectConfig, mockGetDevSupportedAgents } = vi.hoisted(() => ({
+  mockLoadProjectConfig: vi.fn(),
+  mockGetDevSupportedAgents: vi.fn(),
+}));
+
+vi.mock('../../../../operations/dev', () => ({
+  loadProjectConfig: mockLoadProjectConfig,
+  getDevSupportedAgents: mockGetDevSupportedAgents,
+  getEndpointUrl: vi.fn(),
+}));
+
+// The dev hooks would otherwise try to spin up a real dev server / deploy.
+vi.mock('../../../hooks/useDevServer', () => ({
+  useDevServer: () => ({
+    logs: [],
+    status: 'idle',
+    isStreaming: false,
+    conversation: [],
+    streamingResponse: null,
+    config: null,
+    configLoaded: true,
+    actualPort: 8080,
+    invoke: vi.fn(),
+    execCommand: vi.fn(),
+    execInContainer: vi.fn(),
+    isContainer: false,
+    clearConversation: vi.fn(),
+    restart: vi.fn(),
+    stop: vi.fn(),
+    logFilePath: undefined,
+    hasUndeployedMemory: false,
+    hasVpc: false,
+    protocol: undefined,
+    mcpTools: [],
+    fetchMcpTools: vi.fn(),
+    showMcpHint: false,
+    a2aAgentCard: undefined,
+    a2aStatus: undefined,
+    fetchAgentCard: vi.fn(),
+  }),
+}));
+
+vi.mock('../../../hooks/useDevDeploy', () => ({
+  useDevDeploy: () => ({ steps: [], deployMessages: [], isComplete: false, error: undefined }),
+}));
+
+const noop = () => undefined;
+
+describe('DevScreen', () => {
+  afterEach(() => vi.clearAllMocks());
+
+  // Regression: selecting "dev" in a project with no agents/harnesses must render
+  // the in-TUI error screen (not crash the TUI out to the shell). See issue #1588.
+  it('renders the in-TUI error when no agents or harnesses are defined', async () => {
+    mockLoadProjectConfig.mockResolvedValue({ runtimes: [], harnesses: [] });
+    mockGetDevSupportedAgents.mockReturnValue([]);
+
+    const onLaunchBrowser = vi.fn();
+    const { lastFrame } = render(<DevScreen onBack={noop} onLaunchBrowser={onLaunchBrowser} />);
+    await new Promise(r => setTimeout(r, 50));
+
+    expect(lastFrame()).toContain('No agents or harnesses defined in project.');
+    expect(onLaunchBrowser).not.toHaveBeenCalled();
+  });
+});