diff --git a/backend/tests/AGENTS.md b/backend/tests/AGENTS.md
index fe2a274616..a956a4cd2b 100644
--- a/backend/tests/AGENTS.md
+++ b/backend/tests/AGENTS.md
@@ -18,6 +18,12 @@ ownership and capture cleanup. Retain the real XLSX conversion coverage.
 
 Backend tests must preserve the runtime invariants they exercise without changing production execution topology.
 
+`test_doctor_script.py` runs a copied doctor from a temporary checkout with an
+empty-model config. Drop inherited `DEER_FLOW_*`, `PYTHONPATH` and `PYTHONHOME`
+from child processes; cover help, invalid flags, normal reporting and an
+unrelated parent config that stays untouched. Keep argument parsing at the CLI
+entry point so in-process `doctor.main()` callers do not consume pytest's argv.
+
 `test_run_terminal_protocol.py` exercises authoritative `run.terminal`
 evidence through real Worker finalization. Keep final commit authority,
 producer drain, singleton confirmation, and Seal boundaries observable. Release all storage/producer gates before bounded cleanup,
diff --git a/backend/tests/test_doctor_script.py b/backend/tests/test_doctor_script.py
new file mode 100644
index 0000000000..ba0c6b38c3
--- /dev/null
+++ b/backend/tests/test_doctor_script.py
@@ -0,0 +1,96 @@
+"""CLI contract for scripts/doctor.py, exercised in a disposable checkout."""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+
+
+@pytest.fixture
+def doctor_checkout(tmp_path: Path) -> Path:
+    checkout = tmp_path / "checkout"
+    scripts_dir = checkout / "scripts"
+    scripts_dir.mkdir(parents=True)
+    (checkout / "frontend").mkdir()
+    shutil.copyfile(REPO_ROOT / "scripts" / "doctor.py", scripts_dir / "doctor.py")
+    (checkout / "config.yaml").write_text("config_version: 5\nmodels: []\n", encoding="utf-8")
+    return checkout
+
+
+def _run_doctor(checkout: Path, *args: str) -> subprocess.CompletedProcess[str]:
+    env = {name: value for name, value in os.environ.items() if not name.startswith("DEER_FLOW_") and name not in {"PYTHONPATH", "PYTHONHOME"}}
+    return subprocess.run(
+        [sys.executable, str(checkout / "scripts" / "doctor.py"), *args],
+        cwd=checkout,
+        env=env,
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        errors="replace",
+        check=False,
+        timeout=30,
+    )
+
+
+def test_help_prints_usage_without_running_diagnostics(doctor_checkout: Path):
+    result = _run_doctor(doctor_checkout, "--help")
+
+    assert result.returncode == 0, result.stderr
+    assert "usage:" in result.stdout
+    assert "Status:" not in result.stdout
+    assert "System Requirements" not in result.stdout
+
+
+def test_unknown_flag_exits_2_with_usage_error(doctor_checkout: Path):
+    result = _run_doctor(doctor_checkout, "--verbos")
+
+    assert result.returncode == 2
+    assert "unrecognized arguments: --verbos" in result.stderr
+    assert "Status:" not in result.stdout
+    assert "System Requirements" not in result.stdout
+
+
+def test_no_arguments_still_runs_the_diagnostics(doctor_checkout: Path):
+    result = _run_doctor(doctor_checkout)
+
+    # Missing host tools or an incomplete fixture config may produce failures;
+    # either exit code must still come with the normal diagnostic report.
+    assert result.returncode in (0, 1), result.stderr
+    assert "Status:" in result.stdout
+    assert "System Requirements" in result.stdout
+
+
+def test_no_arguments_ignores_inherited_runtime_configuration(doctor_checkout: Path, tmp_path: Path, monkeypatch):
+    external_root = tmp_path / "external project"
+    external_root.mkdir()
+    external_config = external_root / "config.yaml"
+    config_bytes = b"config_version: 5\nmodels:\n  - name: inherited-model\n"
+    external_config.write_bytes(config_bytes)
+    external_env = external_root / ".env"
+    env_bytes = b"# unrelated developer environment\n"
+    external_env.write_bytes(env_bytes)
+    external_home = tmp_path / "external home"
+    for name, value in {
+        "DEER_FLOW_CONFIG_PATH": external_config,
+        "DEER_FLOW_PROJECT_ROOT": external_root,
+        "DEER_FLOW_ENV_FILE": external_env,
+        "DEER_FLOW_HOME": external_home,
+    }.items():
+        monkeypatch.setenv(name, str(value))
+
+    result = _run_doctor(doctor_checkout)
+
+    assert result.returncode in (0, 1), result.stderr
+    assert "Status:" in result.stdout
+    assert "no models found" in result.stdout
+    assert "1 model(s)" not in result.stdout
+    assert external_config.read_bytes() == config_bytes
+    assert external_env.read_bytes() == env_bytes
+    assert not external_home.exists()
diff --git a/scripts/doctor.py b/scripts/doctor.py
index cb16cd98af..95e2001ad1 100644
--- a/scripts/doctor.py
+++ b/scripts/doctor.py
@@ -11,6 +11,7 @@ Exit codes:
 
 from __future__ import annotations
 
+import argparse
 import json
 import os
 import shutil
@@ -979,4 +980,11 @@ def main() -> int:
 
 
 if __name__ == "__main__":
+    # Parsed here rather than inside main(): the unit tests call main() in-process
+    # under pytest, whose argv must not reach argparse.
+    parser = argparse.ArgumentParser(
+        prog="python scripts/doctor.py",
+        description=("DeerFlow Health Check (make doctor): checks system requirements, configuration, LLM provider, and optional components, then prints an actionable report."),
+    )
+    parser.parse_args()
     sys.exit(main())