Fix SAM symlink crash and make prefetch-models.sh resilient per-step

download_sam_model.py crashed with an uncaught PermissionError when
data/models/ is root-owned (common after a prior Docker run) and a
non-root host user tries to recreate the convenience sam_model.pth
symlink — observed in the wild, and it aborted the whole prefetch run
before U2Net/BEN2/BiRefNet-HR were ever attempted. Worse, the same
unguarded symlink call sat inside the post-download try/except, so a
successful download could get deleted just because the symlink step
failed afterward. Wrapped symlink creation in a shared helper that
warns and continues instead of raising — the real model file already
satisfies entrypoint.sh's checks regardless of the symlink.

prefetch-models.sh now treats SAM, U2Net, and the HuggingFace models as
independent steps (one failing no longer aborts the rest) and prints a
summary of which steps failed, so a single run gives full diagnostic
signal instead of stopping at the first error.

prefetch-models.sh

@@ -12,9 +12,11 @@
 #   ./prefetch-models.sh --sdxl    # also prefetch SDXL base + inpaint (~13GB)
 #
 # Safe to re-run: every download here skips files that already exist
-# (HuggingFace Hub) or are already present (SAM/U2Net).
+# (HuggingFace Hub) or are already present (SAM/U2Net). Each model is
+# independent — one failing (e.g. no network reachable at all) doesn't
+# block the others from being attempted.
 
-set -euo pipefail
+set -uo pipefail
 
 cd "$(dirname "$0")"
 
@@ -36,26 +38,29 @@ if [ "${1:-}" = "--sdxl" ]; then
     PREFETCH_SDXL=1
 fi
 
+FAILED=()
+
 echo "=================================================="
 echo "  Prefetching AI models (host-side, no Docker)"
 echo "=================================================="
 
 echo ""
 echo "── SAM (Smart Select) ───────────────────────────────"
-python3 scripts/download_sam_model.py vit_b
+python3 scripts/download_sam_model.py vit_b || FAILED+=("SAM")
 
 echo ""
 echo "── U2Net (Remove Background fallback) ──────────────"
-python3 scripts/download_u2net_model.py u2net
+python3 scripts/download_u2net_model.py u2net || FAILED+=("U2Net")
 
 echo ""
 echo "── HuggingFace Hub models (BEN2, BiRefNet-HR) ───────"
 
 if ! python3 -c "import huggingface_hub" &>/dev/null; then
     echo "Installing huggingface_hub (lightweight — no torch/GPU needed for this step)..."
-    python3 -m pip install --quiet --user "huggingface_hub>=0.23.0"
+    python3 -m pip install --quiet --user "huggingface_hub>=0.23.0" || FAILED+=("huggingface_hub install")
 fi
 
+if python3 -c "import huggingface_hub" &>/dev/null; then
     # HF_HOME must match what the container resolves by default: the bind mount
     # maps ./data/hf_cache -> /root/.cache/huggingface, and the container never
     # sets HF_HOME explicitly, so it defaults to ~/.cache/huggingface there.
@@ -65,7 +70,7 @@ fi
     # same way, rather than us hardcoding it and risking a mismatch.
     export HF_HOME="$(pwd)/data/hf_cache"
 
-PREFETCH_SDXL="$PREFETCH_SDXL" python3 - << 'PYEOF'
+    PREFETCH_SDXL="$PREFETCH_SDXL" python3 - << 'PYEOF' || FAILED+=("HuggingFace models")
 import os
 from huggingface_hub import snapshot_download
 
@@ -81,12 +86,23 @@ for repo_id in repos:
     snapshot_download(repo_id=repo_id, ignore_patterns=["*.msgpack", "flax_*", "tf_*"])
     print(f"  done: {repo_id}")
 PYEOF
+else
+    echo "⚠ Skipping BEN2/BiRefNet-HR — huggingface_hub unavailable (install failed above)"
+    FAILED+=("HuggingFace models")
+fi
 
 echo ""
 echo "=================================================="
+if [ ${#FAILED[@]} -eq 0 ]; then
     echo "  Done. Models cached under ./data/models and ./data/hf_cache"
     if [ "$PREFETCH_SDXL" != "1" ]; then
         echo "  (SDXL not included — re-run with --sdxl to also prefetch txt2img/inpaint, ~13GB)"
     fi
     echo "  Start the app:  ./bring-up-local-gpu.sh"
+else
+    echo "  Finished with failures: ${FAILED[*]}"
+    echo "  If ALL of the above failed, this host can't reach the internet right now"
+    echo "  (check: curl -v https://github.com) — that's a host/network issue, not Docker."
+    echo "  If only some failed, re-run this script to retry just those."
+fi
 echo "=================================================="

scripts/download_sam_model.py

@@ -40,6 +40,20 @@ SAM_MODELS = {
     }
 }
 
+def create_symlink(symlink_path: Path, target_name: str):
+    """Best-effort convenience symlink. Never raises — a missing/stale
+    symlink is harmless (callers also check the real filename directly),
+    but data/models/ is often root-owned from a prior Docker run, which
+    makes unlink/symlink_to fail with PermissionError for other users."""
+    try:
+        if symlink_path.exists() or symlink_path.is_symlink():
+            symlink_path.unlink()
+        symlink_path.symlink_to(target_name)
+        print(f"Symlink created: {symlink_path} -> {target_name}")
+    except OSError as e:
+        print(f"(skipping symlink: {e})")
+
+
 def download_with_progress(url: str, dest_path: Path):
     """Download file with progress indicator"""
     print(f"Downloading to: {dest_path}")
@@ -88,12 +102,7 @@ def main():
         print(f"\nModel already exists at: {dest_path}")
         print("To re-download, delete the file first.")
 
-        # Create symlink for easy access
-        symlink_path = models_dir / 'sam_model.pth'
-        if symlink_path.exists() or symlink_path.is_symlink():
-            symlink_path.unlink()
-        symlink_path.symlink_to(dest_path.name)
-        print(f"Symlink created: {symlink_path} -> {dest_path.name}")
+        create_symlink(models_dir / 'sam_model.pth', dest_path.name)
         return
 
     print(f"\nDownloading SAM {model_type.upper()} ({model_info['size']})...")
@@ -103,17 +112,13 @@ def main():
     try:
         download_with_progress(model_info['url'], dest_path)
 
-        # Create symlink for easy access
         symlink_path = models_dir / 'sam_model.pth'
-        if symlink_path.exists() or symlink_path.is_symlink():
-            symlink_path.unlink()
-        symlink_path.symlink_to(dest_path.name)
+        create_symlink(symlink_path, dest_path.name)
 
         print()
         print("=" * 60)
         print("SUCCESS!")
         print(f"Model saved to: {dest_path}")
-        print(f"Symlink: {symlink_path}")
         print("=" * 60)
 
     except Exception as e: