diff --git a/tools/lib/filereader.py b/tools/lib/filereader.py
index ee9ee294bb..f5418be81a 100644
--- a/tools/lib/filereader.py
+++ b/tools/lib/filereader.py
@@ -1,4 +1,5 @@
 import os
+import io
 import posixpath
 import socket
 from functools import cache
@@ -41,9 +42,17 @@ def file_exists(fn):
     return URLFile(fn).get_length_online() != -1
   return os.path.exists(fn)
 
+class DiskFile(io.BufferedReader):
+  def get_multi_range(self, ranges: list[tuple[int, int]]) -> list[bytes]:
+    parts = []
+    for r in ranges:
+      self.seek(r[0])
+      parts.append(self.read(r[1] - r[0]))
+    return parts
 
-def FileReader(fn, debug=False):
+def FileReader(fn):
   fn = resolve_name(fn)
   if fn.startswith(("http://", "https://")):
-    return URLFile(fn, debug=debug)
-  return open(fn, "rb")
+    return URLFile(fn)
+  else:
+    return DiskFile(open(fn, "rb"))
diff --git a/tools/lib/url_file.py b/tools/lib/url_file.py
index 2bf3ba8209..01c6c5dc47 100644
--- a/tools/lib/url_file.py
+++ b/tools/lib/url_file.py
@@ -1,13 +1,11 @@
+import re
 import logging
 import os
 import socket
-import time
 from hashlib import sha256
 from urllib3 import PoolManager, Retry
 from urllib3.response import BaseHTTPResponse
 from urllib3.util import Timeout
-from urllib3.exceptions import MaxRetryError
-
 
 from openpilot.common.utils import atomic_write
 from openpilot.system.hardware.hw import Paths
@@ -42,12 +40,11 @@ class URLFile:
       URLFile._pool_manager = PoolManager(num_pools=10, maxsize=100, socket_options=socket_options, retries=retries)
     return URLFile._pool_manager
 
-  def __init__(self, url: str, timeout: int = 10, debug: bool = False, cache: bool | None = None):
+  def __init__(self, url: str, timeout: int = 10, cache: bool | None = None):
     self._url = url
     self._timeout = Timeout(connect=timeout, read=timeout)
     self._pos = 0
     self._length: int | None = None
-    self._debug = debug
     #  True by default, false if FILEREADER_CACHE is defined, but can be overwritten by the cache input
     self._force_download = not int(os.environ.get("FILEREADER_CACHE", "0"))
     if cache is not None:
@@ -63,10 +60,7 @@ class URLFile:
     pass
 
   def _request(self, method: str, url: str, headers: dict[str, str] | None = None) -> BaseHTTPResponse:
-    try:
-      return URLFile.pool_manager().request(method, url, timeout=self._timeout, headers=headers)
-    except MaxRetryError as e:
-      raise URLFileException(f"Failed to {method} {url}: {e}") from e
+    return URLFile.pool_manager().request(method, url, timeout=self._timeout, headers=headers)
 
   def get_length_online(self) -> int:
     response = self._request('HEAD', self._url)
@@ -125,39 +119,45 @@ class URLFile:
         return response
 
   def read_aux(self, ll: int | None = None) -> bytes:
-    download_range = False
-    headers = {}
-    if self._pos != 0 or ll is not None:
-      if ll is None:
-        end = self.get_length() - 1
-      else:
-        end = min(self._pos + ll, self.get_length()) - 1
-      if self._pos >= end:
-        return b""
-      headers['Range'] = f"bytes={self._pos}-{end}"
-      download_range = True
+    if ll is None:
+      length = self.get_length()
+      if length == -1:
+        raise URLFileException(f"Remote file is empty or doesn't exist: {self._url}")
+      end = length
+    else:
+      end = self._pos + ll
+    data = self.get_multi_range([(self._pos, end)])
+    self._pos += len(data[0])
+    return data[0]
 
-    if self._debug:
-      t1 = time.monotonic()
+  def get_multi_range(self, ranges: list[tuple[int, int]]) -> list[bytes]:
+    # HTTP range requests are inclusive
+    assert all(e > s for s, e in ranges), "Range end must be greater than start"
+    rs = [f"{s}-{e-1}" for s, e in ranges if e > s]
 
-    response = self._request('GET', self._url, headers=headers)
-    ret = response.data
+    r = self._request("GET", self._url, headers={"Range": "bytes=" + ",".join(rs)})
+    if r.status not in [200, 206]:
+      raise URLFileException(f"Expected 206 or 200 response {r.status} ({self._url})")
 
-    if self._debug:
-      t2 = time.monotonic()
-      if t2 - t1 > 0.1:
-        print(f"get {self._url} {headers!r} {t2 - t1:.3f} slow")
+    ctype = (r.headers.get("content-type") or "").lower()
+    if "multipart/byteranges" not in ctype:
+      return [r.data,]
 
-    response_code = response.status
-    if response_code == 416:  # Requested Range Not Satisfiable
-      raise URLFileException(f"Error, range out of bounds {response_code} {headers} ({self._url}): {repr(ret)[:500]}")
-    if download_range and response_code != 206:  # Partial Content
-      raise URLFileException(f"Error, requested range but got unexpected response {response_code} {headers} ({self._url}): {repr(ret)[:500]}")
-    if (not download_range) and response_code != 200:  # OK
-      raise URLFileException(f"Error {response_code} {headers} ({self._url}): {repr(ret)[:500]}")
+    m = re.search(r'boundary="?([^";]+)"?', ctype)
+    if not m:
+      raise URLFileException(f"Missing multipart boundary ({self._url})")
+    boundary = m.group(1).encode()
 
-    self._pos += len(ret)
-    return ret
+    parts = []
+    for chunk in r.data.split(b"--" + boundary):
+      if b"\r\n\r\n" not in chunk:
+        continue
+      payload = chunk.split(b"\r\n\r\n", 1)[1].rstrip(b"\r\n")
+      if payload and payload != b"--":
+        parts.append(payload)
+    if len(parts) != len(ranges):
+      raise URLFileException(f"Expected {len(ranges)} parts, got {len(parts)} ({self._url})")
+    return parts
 
   def seek(self, pos: int) -> None:
     self._pos = pos