Fix: lazy imports for ZeroGPU compatibility

app.py

@@ -10,12 +10,9 @@ try:
 except ImportError:
     ON_ZEROGPU = False
 
-from pipeline import ensure_model, generate_chart
+from pipeline import generate_chart
 from visualizer import build_visualizer_html
 
-# Pre-load model on CPU at startup
-ensure_model()
-
 PLACEHOLDER_HTML = """
 <div style="font-family: system-ui, sans-serif; background: #111; border-radius: 12px;
     padding: 60px 20px; text-align: center; color: #666; max-width: 900px; margin: 0 auto;">

midmid/beat_tracker.py

@@ -3,7 +3,6 @@
 from dataclasses import dataclass
 
 import numpy as np
-from beat_this.inference import File2Beats
 
 
 @dataclass
@@ -15,6 +14,7 @@ class BeatData:
 
 def track_beats(audio_path: str, device: str = "cuda") -> BeatData:
     """Run beat and downbeat tracking on an audio file."""
+    from beat_this.inference import File2Beats
     processor = File2Beats(checkpoint_path="final0", device=device)
     beats, downbeats = processor(audio_path)
 

pipeline.py

@@ -15,16 +15,7 @@ from pathlib import Path
 import numpy as np
 import torch
 
-from midmid.beat_tracker import track_beats
-from midmid.tempo_map import derive_tempo_map, get_median_bpm, estimate_time_signature
-from midmid.offset import calculate_offset
-from midmid.sections import detect_sections
-from midmid.constraints import enforce_constraints
 from midmid.datatypes import ChartData, NoteEvent
-from midmid.inference import load_model_from_hub, predict_notes, move_models_to_device
-from midmid.midi_writer import write_midi
-from midmid.audio_prep import prepare_audio
-from midmid.ini_writer import write_ini
 
 RESOLUTION = 192
 MODEL_REPO = "markury/midmid3-19m-0326"
@@ -37,6 +28,7 @@ def ensure_model():
     """Pre-load model on CPU (called at app startup)."""
     global _chart_model
     if _chart_model is None:
+        from midmid.inference import load_model_from_hub
         print("Loading chart model from HF Hub...")
         _chart_model = load_model_from_hub(MODEL_REPO, device="cpu")
         print("Chart model loaded.")
@@ -70,6 +62,16 @@ def generate_chart(
     Returns:
         (zip_path, chart_json) where chart_json has the data for the visualizer.
     """
+    from midmid.beat_tracker import track_beats
+    from midmid.tempo_map import derive_tempo_map, get_median_bpm, estimate_time_signature
+    from midmid.offset import calculate_offset
+    from midmid.sections import detect_sections
+    from midmid.constraints import enforce_constraints
+    from midmid.inference import predict_notes, move_models_to_device
+    from midmid.midi_writer import write_midi
+    from midmid.audio_prep import prepare_audio
+    from midmid.ini_writer import write_ini
+
     device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
     model = ensure_model()
     model.to(device)