diff --git a/README.md b/README.md
index c406c88c..71754a35 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,7 @@ Browse sibling episode files and the active mpv queue in one overlay modal. Open
 
 ## Requirements
 
-Only **mpv** and Anki+AnkiConnect is required. Everything else is optional but enhances the experience
+Only **mpv** and Anki+AnkiConnect are required. Everything else is optional but enhances the experience.
 
 | Dependency           | Status      | What it does                             |
 | -------------------- | ----------- | ---------------------------------------- |
diff --git a/launcher/commands/playback-command.test.ts b/launcher/commands/playback-command.test.ts
index c3634464..f85f5cae 100644
--- a/launcher/commands/playback-command.test.ts
+++ b/launcher/commands/playback-command.test.ts
@@ -151,6 +151,7 @@ test('plugin auto-start playback leaves app lifetime to managed-playback owner',
     ...context.args,
     target: '/tmp/movie.mkv',
     targetKind: 'file',
+    useTexthooker: true,
   };
   context.pluginRuntimeConfig = {
     socketPath: '/tmp/subminer.sock',
@@ -213,6 +214,7 @@ test('plugin auto-start playback attaches a warm background app through the laun
     ...context.args,
     target: '/tmp/movie.mkv',
     targetKind: 'file',
+    useTexthooker: true,
   };
   context.pluginRuntimeConfig = {
     socketPath: '/tmp/subminer.sock',
@@ -268,3 +270,47 @@ test('plugin auto-start playback attaches a warm background app through the laun
     false,
   );
 });
+
+test('plugin auto-start attach mode omits texthooker flag when CLI texthooker is disabled', async () => {
+  const context = createContext();
+  context.args = {
+    ...context.args,
+    target: '/tmp/movie.mkv',
+    targetKind: 'file',
+  };
+  context.pluginRuntimeConfig = {
+    socketPath: '/tmp/subminer.sock',
+    binaryPath: '',
+    backend: 'auto',
+    autoStart: true,
+    autoStartVisibleOverlay: true,
+    autoStartPauseUntilReady: true,
+    texthookerEnabled: true,
+    aniskipEnabled: true,
+    aniskipButtonKey: 'TAB',
+  };
+  const calls: string[] = [];
+
+  await runPlaybackCommandWithDeps(context, {
+    ensurePlaybackSetupReady: async () => {},
+    chooseTarget: async () => ({ target: context.args.target, kind: 'file' }),
+    checkDependencies: () => {},
+    registerCleanup: () => {},
+    startMpv: async () => {
+      calls.push('startMpv');
+    },
+    waitForUnixSocketReady: async () => true,
+    startOverlay: async (_appPath, _args, _socketPath, extraAppArgs = []) => {
+      calls.push(`startOverlay:${extraAppArgs.join(' ')}`);
+    },
+    launchAppCommandDetached: () => {},
+    log: () => {},
+    cleanupPlaybackSession: async () => {},
+    getMpvProc: () => null,
+    isAppControlServerAvailable: async () => true,
+  } as Parameters<typeof runPlaybackCommandWithDeps>[1] & {
+    isAppControlServerAvailable: () => Promise<boolean>;
+  });
+
+  assert.deepEqual(calls, ['startMpv', 'startOverlay:--show-visible-overlay']);
+});
diff --git a/launcher/commands/playback-command.ts b/launcher/commands/playback-command.ts
index 86d8a9b3..5aeb62f0 100644
--- a/launcher/commands/playback-command.ts
+++ b/launcher/commands/playback-command.ts
@@ -282,7 +282,9 @@ export async function runPlaybackCommandWithDeps(
             pluginRuntimeConfig.autoStartVisibleOverlay
               ? '--show-visible-overlay'
               : '--hide-visible-overlay',
-            ...(pluginRuntimeConfig.texthookerEnabled ? ['--texthooker'] : []),
+            ...(args.useTexthooker && effectivePluginRuntimeConfig.texthookerEnabled
+              ? ['--texthooker']
+              : []),
           ]
         : [];
     await deps.startOverlay(appPath, args, mpvSocketPath, extraAppArgs);
diff --git a/launcher/mpv.test.ts b/launcher/mpv.test.ts
index 0b2beda7..86d8920c 100644
--- a/launcher/mpv.test.ts
+++ b/launcher/mpv.test.ts
@@ -767,7 +767,10 @@ test('startOverlay attaches through the running app control socket without spawn
     let buffer = '';
     socket.on('data', (chunk) => {
       buffer += chunk.toString('utf8');
-      const line = buffer.split(/\r?\n/, 1)[0];
+      const newlineMatch = buffer.match(/\r?\n/);
+      if (!newlineMatch || newlineMatch.index === undefined) return;
+      const line = buffer.slice(0, newlineMatch.index).trim();
+      buffer = buffer.slice(newlineMatch.index + newlineMatch[0].length);
       if (!line) return;
       const payload = JSON.parse(line) as { argv?: unknown };
       if (Array.isArray(payload.argv)) {
@@ -823,6 +826,59 @@ test('startOverlay attaches through the running app control socket without spawn
   }
 });
 
+test('startOverlay falls back to legacy app startup when control command fails', async () => {
+  if (process.platform === 'win32') return;
+
+  const { dir, socketPath } = createTempSocketPath();
+  const controlSocketPath = path.join(dir, 'control.sock');
+  const appPath = path.join(dir, 'fake-subminer.sh');
+  const appInvocationsPath = path.join(dir, 'app-invocations.log');
+  const originalControlSocket = process.env.SUBMINER_APP_CONTROL_SOCKET;
+
+  fs.writeFileSync(
+    appPath,
+    [
+      '#!/bin/sh',
+      `printf '%s\\n' "$@" >> ${JSON.stringify(appInvocationsPath)}`,
+      'if [ "$1" = "--app-ping" ]; then exit 0; fi',
+      'exit 0',
+      '',
+    ].join('\n'),
+  );
+  fs.chmodSync(appPath, 0o755);
+
+  const controlServer = net.createServer((socket) => {
+    socket.on('data', () => {
+      socket.end(JSON.stringify({ ok: false, error: 'boom' }) + '\n');
+    });
+  });
+
+  try {
+    process.env.SUBMINER_APP_CONTROL_SOCKET = controlSocketPath;
+    await new Promise<void>((resolve, reject) => {
+      controlServer.once('error', reject);
+      controlServer.listen(controlSocketPath, resolve);
+    });
+
+    await startOverlay(appPath, makeArgs(), socketPath);
+
+    const invocationText = fs.readFileSync(appInvocationsPath, 'utf8');
+    assert.match(invocationText, /--app-ping/);
+    assert.match(invocationText, /--start/);
+  } finally {
+    if (originalControlSocket === undefined) {
+      delete process.env.SUBMINER_APP_CONTROL_SOCKET;
+    } else {
+      process.env.SUBMINER_APP_CONTROL_SOCKET = originalControlSocket;
+    }
+    await new Promise<void>((resolve) => controlServer.close(() => resolve()));
+    state.overlayProc = null;
+    state.overlayManagedByLauncher = false;
+    state.appPath = '';
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+});
+
 test('startOverlay keeps lifecycle ownership for its already-managed app', async () => {
   const { dir, socketPath } = createTempSocketPath();
   const appPath = path.join(dir, 'fake-subminer.sh');
diff --git a/launcher/mpv.ts b/launcher/mpv.ts
index ba95ea9f..a3a584eb 100644
--- a/launcher/mpv.ts
+++ b/launcher/mpv.ts
@@ -1058,7 +1058,6 @@ export async function startOverlay(
       clearOverlayManagedByLauncher();
       state.overlayProc = null;
     }
-    return;
   }
 
   const appAlreadyRunning = isAppAlreadyRunning(appPath, args.logLevel);
diff --git a/src/main.ts b/src/main.ts
index d77c3143..629600a8 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -3077,10 +3077,14 @@ const openFirstRunSetupWindowHandler = createOpenFirstRunSetupWindowHandler({
       return;
     }
     if (submission.action === 'open-config-settings') {
-      firstRunSetupMessage = openConfigSettingsWindow()
+      const opened = openConfigSettingsWindow();
+      firstRunSetupMessage = opened
         ? 'Opened SubMiner settings.'
         : 'SubMiner settings are unavailable.';
-      return { skipRender: true };
+      if (opened) {
+        return { skipRender: true };
+      }
+      return;
     }
     if (submission.action === 'refresh') {
       const snapshot = await firstRunSetupService.refreshStatus('Status refreshed.');
diff --git a/src/main/runtime/app-control-server.test.ts b/src/main/runtime/app-control-server.test.ts
index 41c899b8..cbe0581f 100644
--- a/src/main/runtime/app-control-server.test.ts
+++ b/src/main/runtime/app-control-server.test.ts
@@ -45,3 +45,31 @@ test('app control server dispatches argv requests and replies ok', async () => {
     fs.rmSync(dir, { recursive: true, force: true });
   }
 });
+
+test('app control server rejects requests larger than 64KB by UTF-8 byte length', async () => {
+  if (process.platform === 'win32') return;
+
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-control-test-'));
+  const socketPath = path.join(dir, 'control.sock');
+  const received: string[][] = [];
+  const server = startAppControlServer({
+    socketPath,
+    platform: 'linux',
+    handleArgv: (argv) => {
+      received.push(argv);
+    },
+  });
+
+  try {
+    await waitForSocketPath(socketPath);
+    const result = await sendAppControlCommand(Array.from({ length: 4 }, () => 'あ'.repeat(6000)), {
+      socketPath,
+    });
+
+    assert.deepEqual(result, { ok: false, error: 'App control request too large' });
+    assert.deepEqual(received, []);
+  } finally {
+    server.close();
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+});
diff --git a/src/main/runtime/app-control-server.ts b/src/main/runtime/app-control-server.ts
index ea45f189..5b11a7b3 100644
--- a/src/main/runtime/app-control-server.ts
+++ b/src/main/runtime/app-control-server.ts
@@ -44,12 +44,14 @@ export function startAppControlServer(options: AppControlServerOptions): AppCont
 
   const server = net.createServer((socket) => {
     let buffer = '';
+    let byteCount = 0;
     let handled = false;
 
     socket.on('data', (chunk) => {
       if (handled) return;
+      byteCount += chunk.length;
       buffer += chunk.toString('utf8');
-      if (buffer.length > 65536) {
+      if (byteCount > 65536) {
         handled = true;
         writeResponse(socket, { ok: false, error: 'App control request too large' });
         return;