diff --git a/bin.ts b/bin.ts
index f4bb1bd5..b03b11ab 100644
--- a/bin.ts
+++ b/bin.ts
@@ -69,6 +69,44 @@ import { uploadSourcemapsCommand } from './src/commands/upload-sourcemaps';
 import { skillCommand } from './src/commands/skill';
 import { cliCommand } from './src/commands/cli';
 import { recoverOrphanedSettingsBackups } from './src/lib/agent/claude-settings';
+import { releaseTerminal } from './src/ui/tui/terminal';
+import { runCleanups } from './src/utils/wizard-abort';
+import { logToFile, getLogFilePath } from './src/utils/debug';
+
+// Last-resort net for any error no local handler caught. A TUI command may
+// already own the alt screen, so leave it, print a readable line, and exit —
+// otherwise the user is stranded on a blank screen with the real error lost in
+// the discarded alt buffer. Node already terminates on these events; this only
+// makes the exit clean.
+function handleFatal(err: unknown): void {
+  // Preserve the full stack in the wizard log first, as the runner's fatal
+  // path does — the readable line below carries only err.message, and the
+  // crash this net exists to catch ("Cannot read properties of undefined
+  // (reading 'S')") names no module without its stack. logToFile needs no
+  // init and never throws, so it is safe this early and inside the handler.
+  logToFile('[bin] FATAL:', err);
+  releaseTerminal();
+  const message = err instanceof Error ? err.message : String(err);
+  // eslint-disable-next-line no-console
+  console.error(
+    `\n\x1b[1;91m✖ The PostHog wizard crashed: ${message}\x1b[0m\n` +
+      `Full logs: ${getLogFilePath()}\n`,
+  );
+  emitWizardError({ code: ErrorCodes.InternalUnhandled, message });
+  // Run registered cleanups before exiting, same as wizardAbort() and the
+  // runner catch/signal paths — a fatal event otherwise skips them, leaving
+  // state a cleanup owns unrestored (e.g. the backed-up .claude/settings.json
+  // that backupAndFixClaudeSettings deletes and registers a restore for).
+  runCleanups();
+  process.exit(1);
+}
+// Skip under test: the CLI suites import bin.ts and mock process.exit to throw,
+// so a global handler would turn every mocked exit into a worker crash. Prod
+// builds inline NODE_ENV as 'production', so the net is always live for users.
+if (process.env.NODE_ENV !== 'test') {
+  process.on('unhandledRejection', handleFatal);
+  process.on('uncaughtException', handleFatal);
+}
 
 // Heal any .claude/settings backup a previous interrupted run left orphaned,
 // before anything else reads Claude settings — conflict detection, OAuth, and
diff --git a/package.json b/package.json
index 2772dd02..e173ad42 100644
--- a/package.json
+++ b/package.json
@@ -45,7 +45,7 @@
     "fflate": "^0.8.3",
     "fuse.js": "^7.5.0",
     "glob": "9.3.5",
-    "ink": "^6.8.0",
+    "ink": "6.8.0",
     "inquirer": "^6.2.0",
     "jiti": "^2.7.0",
     "jsonc-parser": "^3.3.1",
@@ -55,7 +55,8 @@
     "opn": "^5.4.0",
     "pi-mcp-adapter": "~2.15.0",
     "posthog-node": "^5.45.2",
-    "react": "^19.2.4",
+    "react": "19.2.4",
+    "react-reconciler": "0.33.0",
     "read-env": "^1.3.0",
     "recast": "^0.23.3",
     "semver": "^7.5.3",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index e0fab155..435f0b1b 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -48,7 +48,7 @@ importers:
         specifier: 9.3.5
         version: 9.3.5
       ink:
-        specifier: ^6.8.0
+        specifier: 6.8.0
         version: 6.8.0(@types/react@19.2.14)(react@19.2.4)
       inquirer:
         specifier: ^6.2.0
@@ -78,8 +78,11 @@ importers:
         specifier: ^5.45.2
         version: 5.45.2
       react:
-        specifier: ^19.2.4
+        specifier: 19.2.4
         version: 19.2.4
+      react-reconciler:
+        specifier: 0.33.0
+        version: 0.33.0(react@19.2.4)
       read-env:
         specifier: ^1.3.0
         version: 1.3.0
diff --git a/src/ui/tui/__tests__/start-tui.test.ts b/src/ui/tui/__tests__/start-tui.test.ts
new file mode 100644
index 00000000..d6121150
--- /dev/null
+++ b/src/ui/tui/__tests__/start-tui.test.ts
@@ -0,0 +1,55 @@
+import { startTUI } from '@ui/tui/start-tui';
+import { Program } from '@ui/tui/store';
+
+// render() is the throw site: Ink's reconciler blows up on a react /
+// react-reconciler version mismatch. Force that here.
+const renderThrows = new Error(
+  "Cannot read properties of undefined (reading 'S')",
+);
+vi.mock('ink', async (importOriginal) => ({
+  ...(await importOriginal<typeof import('ink')>()),
+  render: () => {
+    throw renderThrows;
+  },
+}));
+vi.mock('../../../utils/analytics.js', () => ({
+  analytics: {
+    wizardCapture: vi.fn(),
+    setTag: vi.fn(),
+    shutdown: vi.fn().mockResolvedValue(undefined),
+  },
+}));
+vi.mock('../../../utils/debug.js', () => ({
+  logToFile: vi.fn(),
+}));
+
+const LEAVE_ALT_SCREEN = '\x1b[?1049l';
+const ENTER_ALT_SCREEN = '\x1b[?1049h';
+
+describe('startTUI', () => {
+  it('leaves the alt screen before a render() crash propagates', () => {
+    const chunks: string[] = [];
+    const originalWrite = process.stdout.write;
+    process.stdout.write = ((chunk: unknown) => {
+      chunks.push(String(chunk));
+      return true;
+    }) as typeof process.stdout.write;
+
+    try {
+      expect(() => startTUI('1.0.0', Program.PostHogIntegration)).toThrow(
+        renderThrows,
+      );
+    } finally {
+      process.stdout.write = originalWrite;
+    }
+
+    const output = chunks.join('');
+    // The alt screen was entered, then left — so the caller's error message
+    // lands in the restored main buffer instead of a discarded one.
+    expect(output).toContain(ENTER_ALT_SCREEN);
+    expect(output).toContain(LEAVE_ALT_SCREEN);
+    expect(output.lastIndexOf(LEAVE_ALT_SCREEN)).toBeGreaterThan(
+      output.indexOf(ENTER_ALT_SCREEN),
+    );
+  });
+});
diff --git a/src/ui/tui/start-tui.ts b/src/ui/tui/start-tui.ts
index f7b10a8f..c1af9f58 100644
--- a/src/ui/tui/start-tui.ts
+++ b/src/ui/tui/start-tui.ts
@@ -35,9 +35,20 @@ export function startTUI(
   const inkUI = new InkUI(store);
   setUI(inkUI);
 
-  const { unmount: inkUnmount, waitUntilExit } = render(
-    createElement(App, { store }),
-  );
+  // render() throws synchronously when Ink's reconciler cannot drive the
+  // resolved React — the signature of a react / react-reconciler version
+  // mismatch. enterDarkTerminal() already switched to the alt screen, so leave
+  // it before the error propagates. Without this the caller prints its message
+  // into the alt buffer, which the terminal discards on exit, and the user is
+  // left on a blank screen with no message.
+  let rendered: ReturnType<typeof render>;
+  try {
+    rendered = render(createElement(App, { store }));
+  } catch (err) {
+    releaseTerminal();
+    throw err;
+  }
+  const { unmount: inkUnmount, waitUntilExit } = rendered;
 
   analytics.setTag('program_id', program);
   // The launch marker — the first event of every TUI run, captured under