MakeHardwareStation() always triggers GitHub model download even with manually patched package_map

[UnderJollyRogers]

Issue Description:

When using manipulation.station.MakeHardwareStation() with a custom Parser and a patched package_map to point to local model resources (e.g., inside a virtual environment), Drake still attempts to download model files from GitHub.

I am working in a virtual environment where I pre-installed all required models under:

$VIRTUAL_ENV/share/drake_models/

In order to avoid online fetching, I use a parser_preload_callback:

def prefinalize(parser):
    package_map = parser.package_map()
    if package_map.Contains("drake_models"):
        package_map.Remove("drake_models")
    package_map.Add("drake_models", models_dir)


station = builder.AddSystem(MakeHardwareStation(
    scenario,
    parser_preload_callback=prefinalize
))

Despite this setup, Drake still attempts to fetch packages online when calling MakeHardwareStation().

Workaround

I was able to bypass the issue by not using MakeHardwareStation() and instead building the plant manually. This method gives me full control over the Parser and package_map, avoiding the unwanted GitHub downloads:

venv = os.environ.get("VIRTUAL_ENV")
if not venv:
    raise RuntimeError("No VIRTUAL_ENV found. Activate your venv first.")

models_dir = os.path.join(venv, "share", "drake_models")
allegro_pkg_dir = os.path.join(models_dir, "allegro_hand_description")
allegro_urdf = os.path.join(allegro_pkg_dir, "urdf", "allegro_hand_description_left.urdf")

if not os.path.exists(allegro_urdf):
    raise FileNotFoundError(f"Can't find Allegro URDF at: {allegro_urdf}")

builder = DiagramBuilder()
plant, scene_graph = AddMultibodyPlantSceneGraph(builder, time_step=0.0)
meshcat = StartMeshcat()
MeshcatVisualizer.AddToBuilder(builder, scene_graph, meshcat)

parser = Parser(plant)
pm = parser.package_map()

# Forcefully remove and remap the 'drake_models' package to local
if pm.Contains("drake_models"):
    pm.Remove("drake_models")
pm.Add("drake_models", models_dir)

# Also add the sub-package if needed
if not pm.Contains("allegro_hand_description"):
    pm.Add("allegro_hand_description", allegro_pkg_dir)

instances = parser.AddModels(allegro_urdf)
plant.Finalize()

This manual setup works as expected and respects the local model paths. However, a similar result is currently not possible using MakeHardwareStation() due to its internal handling of model loading.