diff --git a/agentmain.py b/agentmain.py
index f0dc9600c..b2d8a555c 100644
--- a/agentmain.py
+++ b/agentmain.py
@@ -216,7 +216,14 @@ def run(self):
     parser.add_argument('--nolog', action='store_true')
     parser.add_argument('--no-user-tools', action='store_true')
     args, _unknown = parser.parse_known_args()
-    _extra_args = dict(zip([k.lstrip('-') for k in _unknown[::2]], _unknown[1::2])) if _unknown else {}
+    reflect_enabled = args.reflect is not None
+    if args.reflect == '':
+        parser.error("--reflect requires a non-empty script path")
+    if _unknown and not reflect_enabled:
+        parser.error(f"unrecognized arguments: {' '.join(_unknown)}")
+    if reflect_enabled and (len(_unknown) % 2 or any(len(k) <= 2 or not k.startswith('--') or k.startswith('---') for k in _unknown[::2]) or any(v.startswith('--') for v in _unknown[1::2])):
+        parser.error("reflect extra arguments must be --key value pairs")
+    _extra_args = dict(zip([k[2:] for k in _unknown[::2]], _unknown[1::2])) if _unknown else {}
 
     if (args.func or args.task) and not args.nobg:
         import subprocess, platform
diff --git a/tests/test_agentmain_cli_args.py b/tests/test_agentmain_cli_args.py
new file mode 100644
index 000000000..0d9c9541c
--- /dev/null
+++ b/tests/test_agentmain_cli_args.py
@@ -0,0 +1,84 @@
+import os
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+AGENTMAIN = ROOT / "agentmain.py"
+_RUNNER = (
+    "import runpy, sys\n"
+    "target = sys.argv[1]\n"
+    "sys.argv = [target, *sys.argv[2:]]\n"
+    "runpy.run_path(target, run_name='__main__')\n"
+)
+
+
+def run_agentmain(*args):
+    with tempfile.TemporaryDirectory() as tmp:
+        state = Path(tmp)
+        (state / "mykey.py").write_text("", encoding="utf-8")
+        plugins = state / "plugins"
+        plugins.mkdir()
+        (plugins / "__init__.py").write_text("", encoding="utf-8")
+        (plugins / "hooks.py").write_text(
+            "def trigger(event, ctx): return ctx\n"
+            "def discover_and_load(plugin_dir=None): return None\n",
+            encoding="utf-8",
+        )
+        env = os.environ.copy()
+        env["GA_LANG"] = "en"
+        env["PYTHONNOUSERSITE"] = "1"
+        env["PYTHONPATH"] = os.pathsep.join((str(state), str(ROOT)))
+        return subprocess.run(
+            [sys.executable, "-c", _RUNNER, str(AGENTMAIN), *args],
+            cwd=state,
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,
+            timeout=20,
+            env=env,
+        )
+
+
+class AgentMainCliArgumentTests(unittest.TestCase):
+    def test_unknown_args_without_reflect_fail_fast(self):
+        result = run_agentmain("--goal", "dummy-goal.json")
+        self.assertEqual(result.returncode, 2)
+        self.assertIn("unrecognized arguments: --goal dummy-goal.json", result.stderr)
+        self.assertNotIn("EOFError", result.stderr)
+
+    def test_reflect_extras_require_complete_key_value_pairs(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            script = Path(tmp) / "reflect_exit.py"
+            script.write_text("def check(): return '/exit'\n", encoding="utf-8")
+            for extras in (("--name",), ("--name", "--other"), ("---name", "hive-master")):
+                with self.subTest(extras=extras):
+                    result = run_agentmain("--reflect", str(script), *extras)
+                    self.assertEqual(result.returncode, 2)
+                    self.assertIn("reflect extra arguments must be --key value pairs", result.stderr)
+
+    def test_reflect_rejects_empty_script_path_explicitly(self):
+        result = run_agentmain("--reflect", "", "--name", "hive-master")
+        self.assertEqual(result.returncode, 2)
+        self.assertIn("--reflect requires a non-empty script path", result.stderr)
+
+    def test_reflect_key_value_extras_remain_supported(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            script = Path(tmp) / "reflect_exit.py"
+            script.write_text(
+                "def init(args): print('INIT_NAME=' + str(args.get('name')))\n"
+                "def check(): return '/exit'\n",
+                encoding="utf-8",
+            )
+            result = run_agentmain("--reflect", str(script), "--name", "hive-master")
+        self.assertEqual(result.returncode, 0, result.stderr)
+        self.assertIn("INIT_NAME=hive-master", result.stdout)
+        self.assertIn("[Reflect] loaded", result.stdout)
+
+
+if __name__ == "__main__":
+    unittest.main()