feat(models): add pinned backend manifests and offline verification

scripts/fetch-model.py

@@ -1,7 +1,6 @@
 #!/usr/bin/env python3
 """Explicit setup only: fetch the pinned ~178 MB Redux weights; never used by runtime."""
 import argparse
-import hashlib
 import os
 from pathlib import Path
 import sys
@@ -9,14 +8,7 @@ import tempfile
 import urllib.request
 
 sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "python"))
-from frameyap.model_files import FILES, REVISION
-
-
-def matches(path, size, digest):
-    if not path.is_file() or path.is_symlink() or path.stat().st_size != size:
-        return False
-    with path.open("rb") as stream:
-        return hashlib.file_digest(stream, "sha256").hexdigest() == digest
+from frameyap.model_files import check_file, check_model, load_backends
 
 
 def main():
@@ -26,30 +18,38 @@ def main():
     dest = args.destination.expanduser().absolute()
     if dest.is_symlink():
         parser.error("destination must not be a symlink")
+    backend = load_backends()["redux"]
     dest.mkdir(mode=0o700, parents=True, exist_ok=True)
-    for name, (size, digest) in FILES.items():
-        target = dest / name
-        if matches(target, size, digest):
+    for item in backend.files:
+        target = dest / item.path
+        reason, _ = check_file(dest, item)
+        if reason is None:
             continue
-        if target.exists() or target.is_symlink():
-            parser.error(f"existing mismatched file: {target}; move it aside explicitly")
-        url = f"https://huggingface.co/moondream/parakeet-redux/resolve/{REVISION}/{name}"
+        if reason != "missing_files":
+            parser.error(f"existing mismatched or unsafe file: {target}; move it aside explicitly")
+        # This explicit Redux-only tool does not implement a generic model downloader.
+        url = f"{backend.source}/resolve/{backend.revision}/{item.path}"
         fd, temp = tempfile.mkstemp(prefix=".download-", dir=dest)
         try:
             with os.fdopen(fd, "wb") as output, urllib.request.urlopen(url, timeout=60) as source:
                 total = 0
                 while chunk := source.read(1024 * 1024):
                     total += len(chunk)
-                    if total > size:
+                    if total > item.size:
                         raise ValueError("download exceeded pinned size")
                     output.write(chunk)
-            if not matches(Path(temp), size, digest):
-                raise ValueError(f"pinned SHA-256/size mismatch: {name}")
+            if check_file(dest, item)[0] != "missing_files":
+                parser.error(f"destination changed during download: {target}")
+            # Check the temporary file using the same pinned verifier before install.
+            if check_file(dest, type(item)(Path(temp).name, item.size, item.sha256))[0] is not None:
+                raise ValueError(f"pinned SHA-256/size mismatch: {item.path}")
             os.replace(temp, target)
         finally:
             Path(temp).unlink(missing_ok=True)
-    print(f"Pinned Redux {REVISION} verified in {dest}")
-    print("Model attribution: moondream/parakeet-redux, CC-BY-4.0; see downloaded README.md.")
+    if check_model(backend, dest)["state"] != "installed_verified":
+        raise ValueError("pinned model verification failed")
+    print(f"Pinned Redux {backend.revision} verified in {dest}")
+    print(f"Model attribution: {backend.attribution} License: {backend.license_id}.")
 
 
 if __name__ == "__main__":