diff --git a/litellm/files/utils.py b/litellm/files/utils.py
index 9639042caab..a0df7a89b0f 100644
--- a/litellm/files/utils.py
+++ b/litellm/files/utils.py
@@ -3,6 +3,22 @@ from typing import Optional
 from litellm.types.llms.openai import CreateFileRequest
 from litellm.types.utils import ExtractedFileData
 
+# MIME types a .jsonl batch upload is plausibly labeled with. Clients are
+# inconsistent (text/plain, application/json, octet-stream, ndjson, ...), so a
+# batch file must not silently bypass the streaming path just because of its
+# declared type. ``purpose == "batch"`` is the authoritative signal; non-JSONL
+# content still fails loudly when the rows are parsed.
+_BATCH_JSONL_CONTENT_TYPES = frozenset(
+    {
+        "application/jsonl",
+        "application/json",
+        "application/octet-stream",
+        "application/x-ndjson",
+        "application/x-jsonlines",
+        "text/plain",
+    }
+)
+
 
 class FilesAPIUtils:
     """
@@ -41,6 +57,7 @@ class FilesAPIUtils:
     @staticmethod
     def valid_content_type(content_type: Optional[str]) -> bool:
         """
-        Check if the content type is valid
+        Whether the upload's MIME type is one a batch JSONL file is plausibly
+        sent as (see ``_BATCH_JSONL_CONTENT_TYPES``).
         """
-        return content_type in set(["application/jsonl", "application/octet-stream"])
+        return content_type in _BATCH_JSONL_CONTENT_TYPES
diff --git a/litellm/llms/custom_httpx/llm_http_handler.py b/litellm/llms/custom_httpx/llm_http_handler.py
index d55a715c7d3..5fa92ec544e 100644
--- a/litellm/llms/custom_httpx/llm_http_handler.py
+++ b/litellm/llms/custom_httpx/llm_http_handler.py
@@ -1,3 +1,4 @@
+import asyncio
 import json
 import ssl
 from urllib.parse import parse_qs, urlencode, urlparse, urlunparse
@@ -3527,10 +3528,13 @@ class BaseLLMHTTPHandler:
     def _iter_resumable_chunks(
         byte_iter: Iterator[bytes], chunk_size: int
     ) -> Iterator[bytes]:
-        """Regroup a byte stream into ``chunk_size`` pieces followed by a final
-        piece of whatever remains (possibly empty). Every piece but the last is
-        exactly ``chunk_size`` bytes, so the caller can keep that a 256 KiB
-        multiple and never buffers more than one chunk.
+        """Regroup a byte stream into ``chunk_size`` pieces, yielding a final
+        partial piece only when it is non-empty. Every full piece is exactly
+        ``chunk_size`` bytes (kept a 256 KiB multiple for GCS) and never more than
+        one chunk is buffered. An exactly chunk-aligned stream yields only full
+        chunks, so the upload finalizes on its last data chunk instead of making
+        an extra empty request; a 0-byte stream yields nothing and the caller
+        finalizes with a single empty request.
         """
         buf = bytearray()
         for piece in byte_iter:
@@ -3538,7 +3542,8 @@ class BaseLLMHTTPHandler:
             while len(buf) >= chunk_size:
                 yield bytes(buf[:chunk_size])
                 del buf[:chunk_size]
-        yield bytes(buf)
+        if buf:
+            yield bytes(buf)
 
     @staticmethod
     def _resumable_content_range(offset: int, data_len: int, is_final: bool) -> str:
@@ -3676,7 +3681,15 @@ class BaseLLMHTTPHandler:
 
         offset = 0
         pending: Optional[bytes] = None
-        for chunk in self._iter_resumable_chunks(stream.iter_bytes(), chunk_size):
+        # Producing each chunk runs the synchronous per-row transform for that
+        # chunk's worth of rows. Pull it off the event loop thread so a large
+        # upload does not block other concurrent requests between PUTs.
+        chunk_iter = self._iter_resumable_chunks(stream.iter_bytes(), chunk_size)
+        done = object()
+        while True:
+            chunk = await asyncio.to_thread(next, chunk_iter, done)
+            if chunk is done:
+                break
             if pending is not None:
                 await self._asend_resumable_chunk(
                     httpx_client,
diff --git a/tests/test_litellm/llms/vertex_ai/files/test_vertex_ai_files_streaming.py b/tests/test_litellm/llms/vertex_ai/files/test_vertex_ai_files_streaming.py
index 9d9af82c605..cd556c48b6b 100644
--- a/tests/test_litellm/llms/vertex_ai/files/test_vertex_ai_files_streaming.py
+++ b/tests/test_litellm/llms/vertex_ai/files/test_vertex_ai_files_streaming.py
@@ -483,6 +483,25 @@ class TestResumableUploadUrl:
         assert "uploadType=resumable" in url
         assert "uploadType=media" not in url
 
+    def test_batch_text_plain_uses_resumable_upload_type(self):
+        # Clients often label a .jsonl batch upload as text/plain; it must still
+        # take the streaming/resumable path, not the buffered media path.
+        cfg = VertexAIFilesConfig()
+        request: CreateFileRequest = {
+            "file": ("batch.jsonl", _make_openai_jsonl_bytes(3), "text/plain"),
+            "purpose": "batch",
+        }
+        url = cfg.get_complete_file_url(
+            api_base=None,
+            api_key=None,
+            model="",
+            optional_params={},
+            litellm_params={"gcs_bucket_name": "test-bucket"},
+            data=request,
+        )
+        assert "uploadType=resumable" in url
+        assert "uploadType=media" not in url
+
     def test_binary_upload_stays_simple_media(self):
         cfg = VertexAIFilesConfig()
         request: CreateFileRequest = {
@@ -539,9 +558,16 @@ class TestResumableChunking:
         pieces = list(BaseLLMHTTPHandler._iter_resumable_chunks(iter([b"x" * 10]), 4))
         assert pieces == [b"xxxx", b"xxxx", b"xx"]
 
-    def test_exact_multiple_yields_trailing_empty_for_finalize(self):
+    def test_exact_multiple_yields_no_trailing_empty(self):
+        # An exactly chunk-aligned stream yields only full chunks; the upload
+        # finalizes on the last data chunk instead of an extra empty request.
         pieces = list(BaseLLMHTTPHandler._iter_resumable_chunks(iter([b"x" * 8]), 4))
-        assert pieces == [b"xxxx", b"xxxx", b""]
+        assert pieces == [b"xxxx", b"xxxx"]
+
+    def test_empty_stream_yields_nothing(self):
+        # A 0-byte stream yields no chunks; the caller finalizes with one empty
+        # request (bytes */0).
+        assert list(BaseLLMHTTPHandler._iter_resumable_chunks(iter([]), 4)) == []
 
     def test_default_chunk_size_is_256kib_multiple(self):
         assert BaseLLMHTTPHandler._RESUMABLE_CHUNK_SIZE % (256 * 1024) == 0
@@ -640,11 +666,13 @@ class TestResumableUploadProtocol:
         assert bytes(state["received"]) == expected
         assert response.object == "file"
 
-    async def test_exact_multiple_finalizes_with_empty_chunk(self):
-        # Build a body that is an exact multiple of the chunk size so the stream
-        # ends on a chunk boundary; the upload must still finalize (bytes */TOTAL).
+    async def test_exact_multiple_finalizes_on_last_data_chunk(self):
+        # A body that is an exact multiple of the chunk size finalizes on its
+        # last data chunk (bytes (TOTAL-chunk)-(TOTAL-1)/TOTAL), with no extra
+        # empty finalize request.
         chunk_size = 256
-        stream = _FixedBytesStream(b"a" * (chunk_size * 3))
+        total = chunk_size * 3
+        stream = _FixedBytesStream(b"a" * total)
         config = {"body_stream": stream, "chunk_size": chunk_size}
         session_url = "https://storage.googleapis.com/upload/sess?upload_id=SID"
         mock, state = _gcs_resumable_mock(session_url)
@@ -657,8 +685,9 @@ class TestResumableUploadProtocol:
             timeout=None,
         )
 
-        assert state["ranges"][-1] == f"bytes */{chunk_size * 3}"
-        assert bytes(state["received"]) == b"a" * (chunk_size * 3)
+        assert state["ranges"][-1] == f"bytes {total - chunk_size}-{total - 1}/{total}"
+        assert "*" not in state["ranges"][-1]
+        assert bytes(state["received"]) == b"a" * total
         assert response.status_code == 200
 
     async def test_failed_chunk_raises(self):