diff --git a/autonomous-coding/autonomous_agent_demo.py b/autonomous-coding/autonomous_agent_demo.py
index 2cd3b5551..7c6d28ad6 100755
--- a/autonomous-coding/autonomous_agent_demo.py
+++ b/autonomous-coding/autonomous_agent_demo.py
@@ -59,7 +59,7 @@ def parse_args() -> argparse.Namespace:
         "--max-iterations",
         type=int,
         default=None,
-        help="Maximum number of agent iterations (default: unlimited)",
+        help="Positive maximum number of agent iterations (default: unlimited)",
     )
 
     parser.add_argument(
@@ -69,7 +69,10 @@ def parse_args() -> argparse.Namespace:
         help=f"Claude model to use (default: {DEFAULT_MODEL})",
     )
 
-    return parser.parse_args()
+    args = parser.parse_args()
+    if args.max_iterations is not None and args.max_iterations <= 0:
+        parser.error("--max-iterations must be a positive integer")
+    return args
 
 
 def main() -> None:
diff --git a/autonomous-coding/test_iteration_limit.py b/autonomous-coding/test_iteration_limit.py
new file mode 100644
index 000000000..45947fc77
--- /dev/null
+++ b/autonomous-coding/test_iteration_limit.py
@@ -0,0 +1,34 @@
+"""Check CLI iteration limits without starting an agent or calling an API."""
+
+import runpy
+import sys
+from pathlib import Path
+from types import ModuleType
+from unittest.mock import AsyncMock
+
+import pytest
+
+
+@pytest.mark.parametrize("limit", [None, "1", "3", "0", "-1", "-10"])
+def test_iteration_limit(monkeypatch, capsys, limit):
+    agent = ModuleType("agent")
+    runner = AsyncMock()
+    agent.run_autonomous_agent = runner
+    monkeypatch.setitem(sys.modules, "agent", agent)
+    monkeypatch.setenv("ANTHROPIC_API_KEY", "unused-test-key")
+    args = [] if limit is None else ["--max-iterations", limit]
+    monkeypatch.setattr(sys, "argv", ["autonomous_agent_demo.py", *args])
+    script = Path(__file__).with_name("autonomous_agent_demo.py")
+
+    if limit is not None and int(limit) <= 0:
+        with pytest.raises(SystemExit) as error:
+            runpy.run_path(str(script), run_name="__main__")
+        assert error.value.code == 2
+        assert "positive integer" in capsys.readouterr().err
+        runner.assert_not_called()
+    else:
+        runpy.run_path(str(script), run_name="__main__")
+        runner.assert_awaited_once()
+        assert runner.call_args.kwargs["max_iterations"] == (
+            None if limit is None else int(limit)
+        )