diff --git a/moli-benchmark/README.md b/moli-benchmark/README.md
index 28d54f3df0..7d39647285 100644
--- a/moli-benchmark/README.md
+++ b/moli-benchmark/README.md
@@ -130,7 +130,7 @@ them. The runner waits for load, fonts, two animation frames, and removal of
 `crashtest` with zero subtests. An outstanding wait remains a timeout, and a
 renderer crash is reported even when the browser process stays alive.
 
-Run testdriver input cases explicitly with `--mode cdp`.
+Explicit cases that reference `testdriver.js` use CDP in `--mode auto`.
 The CDP runner delivers trusted keyboard and mouse/pen input on an independent
 connection, so input can finish while a harness probe awaits a JavaScript
 promise. It supports `click`, ASCII and WebDriver special keys in `send_keys`,
diff --git a/moli-benchmark/moli_benchmark/wpt_cross/__main__.py b/moli-benchmark/moli_benchmark/wpt_cross/__main__.py
index 90d3e86f20..2ba4d7c55f 100644
--- a/moli-benchmark/moli_benchmark/wpt_cross/__main__.py
+++ b/moli-benchmark/moli_benchmark/wpt_cross/__main__.py
@@ -28,6 +28,7 @@ import time
 from collections import Counter
 from pathlib import Path
 from typing import Any
+from urllib.parse import urlsplit
 
 from .case_set import (
     ANY_JS_GLOBAL_CHOICES,
@@ -57,6 +58,22 @@ from ..config import clear_current_proxy_env
 REPO_CASE_LIST_DIR = Path(__file__).resolve().parents[2] / "wpt-cross-current"
 WPT_CROSS_CASE_TIMEOUT_SECONDS = 120.0
 WPT_CROSS_PARALLELISM = 50
+
+
+def _case_references_testdriver(wpt_root: Path, case: WptCase) -> bool:
+    path = urlsplit(case.case_path).path.lstrip("/")
+    for suffix, source_suffix in ((".any.html", ".any.js"), (".window.html", ".window.js")):
+        if path.endswith(suffix):
+            path = path.removesuffix(suffix) + source_suffix
+            break
+    source = (wpt_root / path).resolve()
+    try:
+        source.relative_to(wpt_root.resolve())
+        return b"/resources/testdriver" in source.read_bytes()
+    except (OSError, ValueError):
+        return False
+
+
 WPT_CROSS_PROFILES = (
     "default",
     "layout-testharness",
@@ -664,7 +681,13 @@ def main(argv: list[str] | None = None) -> int:
     if has_crashtests and args.mode == "cli":
         print("error: crashtests require CDP mode to observe readiness and crashes", file=sys.stderr)
         return 4
-    requires_cdp = fixed_layout_viewport or has_crashtests
+    native_input_required = args.mode != "cdp" and any(
+        _case_references_testdriver(args.wpt_root, case) for case in cases
+    )
+    if native_input_required and args.mode == "cli":
+        print("error: testdriver cases require CDP mode for native input", file=sys.stderr)
+        return 4
+    requires_cdp = fixed_layout_viewport or has_crashtests or native_input_required
     if fixed_layout_viewport and args.mode == "cli":
         print(
             "error: layout profiles and reftests require CDP mode for fixed viewport screenshots",
diff --git a/moli-benchmark/tests/test_wpt_native_input.py b/moli-benchmark/tests/test_wpt_native_input.py
index 10b2793827..3dbbd0c496 100644
--- a/moli-benchmark/tests/test_wpt_native_input.py
+++ b/moli-benchmark/tests/test_wpt_native_input.py
@@ -9,6 +9,7 @@ from types import SimpleNamespace
 from unittest.mock import AsyncMock
 
 from moli_benchmark.raw_cdp import RawCdpConnectionClosed
+from moli_benchmark.wpt_cross.__main__ import _case_references_testdriver
 from moli_benchmark.wpt_cross.case_set import WptCase
 from moli_benchmark.wpt_cross.native_input import NativeInput, Pointer, key_description
 
@@ -173,6 +174,17 @@ class NativeInputTests(unittest.IsolatedAsyncioTestCase):
 
 
 class NativeInputSelectionTests(unittest.TestCase):
+    def test_testdriver_detection_in_html_and_generated_variants(self):
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            (root / "input.html").write_text('<script src="/resources/testdriver.js"></script>')
+            (root / "keys.any.js").write_text('// META: script=/resources/testdriver.js\n')
+            (root / "plain.html").write_text('<script src="/resources/testharness.js"></script>')
+            self.assertTrue(_case_references_testdriver(root, WptCase("input.html?variant")))
+            self.assertTrue(_case_references_testdriver(root, WptCase("keys.any.html?variant")))
+            self.assertFalse(_case_references_testdriver(root, WptCase("plain.html")))
+            self.assertFalse(_case_references_testdriver(root, WptCase("../input.html")))
+
     def test_special_keys_preserve_physical_location(self):
         self.assertEqual((key_description("\ue007").code, key_description("\ue007").location), ("NumpadEnter", 3))
         self.assertEqual((key_description("\ue050").code, key_description("\ue050").location), ("ShiftRight", 2))