feat: load checkpoints from Hugging Face

pyproject.toml

@@ -11,6 +11,7 @@ dependencies = [
   "click>=8.1.7",
   "deepmerge>=2.0",
   "hydra-core>=1.3.2",
+  "huggingface-hub>=0.32.0",
   "librosa>=0.10.1",
   "lightning[extra]==2.5.0",
   "loguru>=0.7.3",

src/batdetect2/api_v2.py

@@ -653,7 +653,7 @@ class BatDetect2API:
     @classmethod
     def from_checkpoint(
         cls,
-        path: data.PathLike,
+        path: data.PathLike | str,
         audio_config: AudioConfig | None = None,
         train_config: TrainingConfig | None = None,
         evaluation_config: EvaluationConfig | None = None,

src/batdetect2/cli/evaluate.py

@@ -12,14 +12,8 @@ DEFAULT_OUTPUT_DIR = Path("outputs") / "evaluation"
 
 
 @cli.command(name="evaluate", short_help="Evaluate a model checkpoint.")
-@click.argument("model_path", type=click.Path(exists=True))
+@click.argument("model_path", type=str)
 @click.argument("test_dataset", type=click.Path(exists=True))
-@click.option(
-    "--targets",
-    "targets_config",
-    type=click.Path(exists=True),
-    help="Path to targets config file.",
-)
 @click.option(
     "--audio-config",
     type=click.Path(exists=True),
@@ -80,10 +74,9 @@ DEFAULT_OUTPUT_DIR = Path("outputs") / "evaluation"
     default=0,
 )
 def evaluate_command(
-    model_path: Path,
+    model_path: str,
     test_dataset: Path,
     base_dir: Path,
-    targets_config: Path | None,
     audio_config: Path | None,
     evaluation_config: Path | None,
     inference_config: Path | None,

src/batdetect2/cli/finetune.py

@@ -17,8 +17,8 @@ __all__ = ["finetune_command"]
     "--model",
     "model_path",
     required=True,
-    type=click.Path(exists=True),
-    help="Path to a checkpoint to fine-tune from.",
+    type=str,
+    help="Path to a checkpoint or a Hugging Face URI to fine-tune from.",
 )
 @click.option(
     "--targets",
@@ -106,7 +106,7 @@ __all__ = ["finetune_command"]
 )
 def finetune_command(
     train_dataset: Path,
-    model_path: Path,
+    model_path: str,
     targets_config: Path,
     val_dataset: Path | None = None,
     ckpt_dir: Path | None = None,

src/batdetect2/cli/inference.py

@@ -102,7 +102,7 @@ def common_predict_options(func):
 
 
 def _build_api(
-    model_path: Path,
+    model_path: str,
     audio_config: Path | None,
     inference_config: Path | None,
     outputs_config: Path | None,
@@ -144,7 +144,7 @@ def _build_api(
 
 
 def _run_prediction(
-    model_path: Path,
+    model_path: str,
     audio_files: list[Path],
     output_path: Path,
     audio_config: Path | None,
@@ -195,12 +195,12 @@ def _run_prediction(
     name="directory",
     short_help="Predict on audio files in a directory.",
 )
-@click.argument("model_path", type=click.Path(exists=True))
+@click.argument("model_path", type=str)
 @click.argument("audio_dir", type=click.Path(exists=True))
 @click.argument("output_path", type=click.Path())
 @common_predict_options
 def predict_directory_command(
-    model_path: Path,
+    model_path: str,
     audio_dir: Path,
     output_path: Path,
     audio_config: Path | None,
@@ -239,12 +239,12 @@ def predict_directory_command(
     name="file_list",
     short_help="Predict on paths listed in a text file.",
 )
-@click.argument("model_path", type=click.Path(exists=True))
+@click.argument("model_path", type=str)
 @click.argument("file_list", type=click.Path(exists=True))
 @click.argument("output_path", type=click.Path())
 @common_predict_options
 def predict_file_list_command(
-    model_path: Path,
+    model_path: str,
     file_list: Path,
     output_path: Path,
     audio_config: Path | None,
@@ -287,12 +287,12 @@ def predict_file_list_command(
     name="dataset",
     short_help="Predict on recordings from a dataset config.",
 )
-@click.argument("model_path", type=click.Path(exists=True))
+@click.argument("model_path", type=str)
 @click.argument("dataset_path", type=click.Path(exists=True))
 @click.argument("output_path", type=click.Path())
 @common_predict_options
 def predict_dataset_command(
-    model_path: Path,
+    model_path: str,
     dataset_path: Path,
     output_path: Path,
     audio_config: Path | None,

src/batdetect2/cli/train.py

@@ -18,10 +18,10 @@ __all__ = ["train_command"]
 @click.option(
     "--model",
     "model_path",
-    type=click.Path(exists=True),
+    type=str,
     help=(
-        "Path to a checkpoint to continue training from. If omitted, "
-        "training starts from a fresh model config."
+        "Path to a checkpoint or a Hugging Face URI to continue training "
+        "from. If omitted, training starts from a fresh model config."
     ),
 )
 @click.option(
@@ -118,7 +118,7 @@ __all__ = ["train_command"]
 def train_command(
     train_dataset: Path,
     val_dataset: Path | None = None,
-    model_path: Path | None = None,
+    model_path: str | None = None,
     ckpt_dir: Path | None = None,
     log_dir: Path | None = None,
     base_dir: Path | None = None,

src/batdetect2/train/__init__.py

@@ -1,4 +1,7 @@
-from batdetect2.train.checkpoints import DEFAULT_CHECKPOINT_DIR
+from batdetect2.train.checkpoints import (
+    DEFAULT_CHECKPOINT_DIR,
+    resolve_checkpoint_path,
+)
 from batdetect2.train.config import TrainingConfig
 from batdetect2.train.lightning import (
     TrainingModule,
@@ -26,5 +29,6 @@ __all__ = [
     "TrainingModule",
     "build_trainer",
     "load_model_from_checkpoint",
+    "resolve_checkpoint_path",
     "run_train",
 ]

src/batdetect2/train/checkpoints.py

@@ -1,13 +1,16 @@
 from pathlib import Path
 from typing import Literal
 
+from huggingface_hub import hf_hub_download
 from lightning.pytorch.callbacks import Callback, ModelCheckpoint
+from soundevent.data import PathLike
 
 from batdetect2.core import BaseConfig
 
 __all__ = [
     "CheckpointConfig",
     "build_checkpoint_callback",
+    "resolve_checkpoint_path",
 ]
 
 DEFAULT_CHECKPOINT_DIR: Path = Path("outputs") / "checkpoints"
@@ -53,3 +56,51 @@ def build_checkpoint_callback(
         save_last=config.save_last,
         every_n_epochs=config.every_n_epochs,
     )
+
+
+def resolve_checkpoint_path(path: PathLike | str) -> Path:
+    """Resolve a local path or Hugging Face checkpoint URI.
+
+    Parameters
+    ----------
+    path : PathLike | str
+        Local checkpoint path or a Hugging Face URI of the form
+        ``hf://owner/repo/path/to/checkpoint.ckpt``.
+
+    Returns
+    -------
+    Path
+        Resolved local filesystem path to the checkpoint.
+    """
+    if isinstance(path, str) and path.startswith("hf://"):
+        repo_id, filename = _parse_huggingface_uri(path)
+        return Path(hf_hub_download(repo_id=repo_id, filename=filename))
+
+    if not isinstance(path, Path):
+        path = Path(path)
+
+    if not path.exists():
+        raise FileNotFoundError(f"Checkpoint not found: {path}")
+
+    return path
+
+
+def _parse_huggingface_uri(uri: str) -> tuple[str, str]:
+    prefix = "hf://"
+    if not uri.startswith(prefix):
+        raise ValueError(
+            "Hugging Face checkpoint URIs must start with 'hf://'."
+        )
+
+    without_prefix = uri.removeprefix(prefix).strip("/")
+    parts = without_prefix.split("/")
+
+    if len(parts) < 3:
+        raise ValueError(
+            "Hugging Face checkpoint URIs must be in the form "
+            "'hf://owner/repo/path/to/checkpoint.ckpt'."
+        )
+
+    repo_id = "/".join(parts[:2])
+    filename = "/".join(parts[2:])
+    return repo_id, filename

src/batdetect2/train/lightning.py

@@ -6,6 +6,7 @@ from soundevent.data import PathLike
 from batdetect2.models import Model, ModelConfig, build_model
 from batdetect2.models.types import ModelOutput
 from batdetect2.targets import TargetConfig
+from batdetect2.train.checkpoints import resolve_checkpoint_path
 from batdetect2.train.config import TrainingConfig
 from batdetect2.train.losses import build_loss
 from batdetect2.train.optimizers import build_optimizer
@@ -130,7 +131,7 @@ class StoredConfig:
 
 
 def load_model_from_checkpoint(
-    path: PathLike,
+    path: PathLike | str,
 ) -> tuple[Model, StoredConfig]:
     """Load a model and its configuration from a Lightning checkpoint.
 
@@ -146,7 +147,8 @@ def load_model_from_checkpoint(
         The restored ``Model`` instance and the ``ModelConfig`` that
         describes its architecture, preprocessing, and postprocessing.
     """
-    module = TrainingModule.load_from_checkpoint(path)  # type: ignore
+    resolved_path = resolve_checkpoint_path(path)
+    module = TrainingModule.load_from_checkpoint(resolved_path)
     training_config = TrainingConfig.model_validate(module.train_config)
     model_config = ModelConfig.model_validate(module.model_config)
     targets_config = TargetConfig.model_validate(module.targets_config)

tests/test_train/test_checkpoints.py

@@ -4,6 +4,7 @@ import pytest
 from soundevent import data
 
 from batdetect2.train import TrainingConfig, run_train
+from batdetect2.train.checkpoints import resolve_checkpoint_path
 
 pytestmark = pytest.mark.slow
 
@@ -92,3 +93,44 @@ def test_train_controls_which_checkpoints_are_kept(
     assert last_checkpoints
     assert len(best_checkpoints) == 1
     assert "epoch" in best_checkpoints[0].name
+
+
+def test_resolve_checkpoint_path_returns_local_path_unchanged(
+    tmp_path: Path,
+) -> None:
+    local_path = tmp_path / "model.ckpt"
+    local_path.write_bytes(b"checkpoint")
+
+    assert resolve_checkpoint_path(local_path) == local_path
+    assert resolve_checkpoint_path(str(local_path)) == local_path
+
+
+def test_resolve_checkpoint_path_downloads_huggingface_checkpoint(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    expected_path = tmp_path / "downloaded.ckpt"
+
+    def fake_hf_hub_download(repo_id: str, filename: str) -> str:
+        assert repo_id == "owner/repo"
+        assert filename == "weights/model.ckpt"
+        return str(expected_path)
+
+    monkeypatch.setattr(
+        "batdetect2.train.checkpoints.hf_hub_download",
+        fake_hf_hub_download,
+    )
+
+    resolved = resolve_checkpoint_path("hf://owner/repo/weights/model.ckpt")
+
+    assert resolved == expected_path
+
+
+def test_resolve_checkpoint_path_rejects_incomplete_huggingface_uri() -> None:
+    with pytest.raises(ValueError, match="hf://owner/repo/path/to"):
+        resolve_checkpoint_path("hf://owner/repo")
+
+
+def test_resolve_checkpoint_path_rejects_missing_local_path() -> None:
+    with pytest.raises(FileNotFoundError, match="Checkpoint not found"):
+        resolve_checkpoint_path("missing.ckpt")