feat: support custom system prompt from CLI

main.py

@@ -11,6 +11,8 @@
     PHONE_AGENT_API_KEY: API key for model authentication (default: EMPTY)
     PHONE_AGENT_MAX_STEPS: Maximum steps per task (default: 100)
     PHONE_AGENT_DEVICE_ID: ADB device ID for multi-device setups
+    PHONE_AGENT_SYSTEM_PROMPT: Override system prompt text
+    PHONE_AGENT_SYSTEM_PROMPT_FILE: Path to UTF-8 system prompt file
 """
 
 import argparse
@@ -368,6 +370,9 @@ def parse_args() -> argparse.Namespace:
     # Use API key for authentication
     python main.py --apikey sk-xxxxx
 
+    # Use a custom system prompt
+    python main.py --system-prompt-file ./prompt.txt "Open the Android launcher"
+
     # Run with specific device
     python main.py --device-id emulator-5554
 
@@ -430,6 +435,20 @@ def parse_args() -> argparse.Namespace:
         help="Maximum steps per task",
     )
 
+    parser.add_argument(
+        "--system-prompt",
+        type=str,
+        default=os.getenv("PHONE_AGENT_SYSTEM_PROMPT"),
+        help="Override system prompt text",
+    )
+
+    parser.add_argument(
+        "--system-prompt-file",
+        type=str,
+        default=os.getenv("PHONE_AGENT_SYSTEM_PROMPT_FILE"),
+        help="Path to a UTF-8 file containing the system prompt override",
+    )
+
     # Device options
     parser.add_argument(
         "--device-id",
@@ -524,6 +543,22 @@ def parse_args() -> argparse.Namespace:
     return parser.parse_args()
 
 
+def resolve_system_prompt(
+    system_prompt: str | None, system_prompt_file: str | None
+) -> str | None:
+    """Resolve an optional system prompt override from text or a UTF-8 file."""
+    if system_prompt and system_prompt_file:
+        raise ValueError(
+            "--system-prompt and --system-prompt-file cannot be used together"
+        )
+
+    if system_prompt_file:
+        with open(system_prompt_file, encoding="utf-8") as f:
+            return f.read()
+
+    return system_prompt
+
+
 def handle_ios_device_commands(args) -> bool:
     """
     Handle iOS device-related commands.
@@ -684,6 +719,13 @@ def handle_device_commands(args) -> bool:
 def main():
     """Main entry point."""
     args = parse_args()
+    try:
+        system_prompt = resolve_system_prompt(
+            args.system_prompt, args.system_prompt_file
+        )
+    except (OSError, ValueError) as e:
+        print(f"Error: {e}", file=sys.stderr)
+        sys.exit(1)
 
     # Set device type globally based on args
     if args.device_type == "adb":
@@ -760,6 +802,7 @@ def main():
             device_id=args.device_id,
             verbose=not args.quiet,
             lang=args.lang,
+            system_prompt=system_prompt,
         )
 
         agent = IOSPhoneAgent(
@@ -773,6 +816,7 @@ def main():
             device_id=args.device_id,
             verbose=not args.quiet,
             lang=args.lang,
+            system_prompt=system_prompt,
         )
 
         agent = PhoneAgent(

tests/test_system_prompt_cli.py

@@ -0,0 +1,81 @@
+import sys
+from argparse import Namespace
+
+import pytest
+
+import main
+
+
+def test_parse_args_accepts_inline_system_prompt(monkeypatch):
+    monkeypatch.setattr(
+        sys,
+        "argv",
+        ["main.py", "--system-prompt", "Use short Android launcher labels."],
+    )
+
+    args = main.parse_args()
+
+    assert args.system_prompt == "Use short Android launcher labels."
+    assert args.system_prompt_file is None
+
+
+def test_resolve_system_prompt_reads_file(tmp_path):
+    prompt_file = tmp_path / "prompt.txt"
+    prompt_file.write_text("Report each launcher step to the user.", encoding="utf-8")
+
+    system_prompt = main.resolve_system_prompt(None, str(prompt_file))
+
+    assert system_prompt == "Report each launcher step to the user."
+
+
+def test_resolve_system_prompt_rejects_inline_and_file(tmp_path):
+    prompt_file = tmp_path / "prompt.txt"
+    prompt_file.write_text("file prompt", encoding="utf-8")
+
+    with pytest.raises(ValueError, match="--system-prompt"):
+        main.resolve_system_prompt("inline prompt", str(prompt_file))
+
+
+@pytest.mark.parametrize("device_type", ["adb", "ios"])
+def test_main_passes_custom_system_prompt_to_agent_config(monkeypatch, device_type):
+    captured = {}
+    args = Namespace(
+        apikey="EMPTY",
+        base_url="http://localhost:8000/v1",
+        device_id=None,
+        device_type=device_type,
+        lang="en",
+        list_apps=False,
+        max_steps=3,
+        model="autoglm-phone-9b",
+        quiet=True,
+        system_prompt="Only use short launcher labels.",
+        system_prompt_file=None,
+        task="Open the launcher",
+        wda_url="http://localhost:8100",
+    )
+
+    class FakeAgent:
+        def __init__(self, model_config, agent_config):
+            captured["agent_config"] = agent_config
+
+        def run(self, task):
+            return "ok"
+
+    class FakeDeviceFactory:
+        def list_devices(self):
+            return []
+
+    monkeypatch.setattr(main, "parse_args", lambda: args)
+    monkeypatch.setattr(main, "handle_device_commands", lambda _args: False)
+    monkeypatch.setattr(main, "check_system_requirements", lambda *_, **__: True)
+    monkeypatch.setattr(main, "check_model_api", lambda *_, **__: True)
+    monkeypatch.setattr(main, "set_device_type", lambda _device_type: None)
+    monkeypatch.setattr(main, "get_device_factory", lambda: FakeDeviceFactory())
+    monkeypatch.setattr(main, "list_ios_devices", lambda: [])
+    monkeypatch.setattr(main, "PhoneAgent", FakeAgent)
+    monkeypatch.setattr(main, "IOSPhoneAgent", FakeAgent)
+
+    main.main()
+
+    assert captured["agent_config"].system_prompt == "Only use short launcher labels."