Use independent HTTP range connections for ModelScope

mirror_worker.py

@@ -64,7 +64,7 @@ def commit_batch(target: HfApi, batch: list[tuple[str, Path]]) -> None:
 
 
 def direct_download(path: str, target: Path, size: int, expected_sha256: str | None) -> None:
-    """Download a ModelScope object via direct HTTP/2 range requests.
+    """Download a ModelScope object via direct concurrent HTTP range requests.
 
     This intentionally bypasses ModelScope's snapshot/cache/downloader stack.
     Ranges write directly into a preallocated temporary file, avoiding the
@@ -85,7 +85,11 @@ def direct_download(path: str, target: Path, size: int, expected_sha256: str | N
         timeout = httpx.Timeout(connect=30.0, read=120.0, write=120.0, pool=30.0)
         limits = httpx.Limits(max_connections=20, max_keepalive_connections=16)
         with httpx.Client(
-            http2=True,
+            # ModelScope's redirect endpoint intermittently resets HTTP/2
+            # multiplexed streams.  A pool of independent HTTP/1.1 ranges is
+            # faster in practice because failed streams do not take siblings
+            # down with the same connection.
+            http2=False,
             follow_redirects=True,
             timeout=timeout,
             limits=limits,