diff --git a/litellm/llms/bedrock/files/transformation.py b/litellm/llms/bedrock/files/transformation.py
index edd86960542..694447bca26 100644
--- a/litellm/llms/bedrock/files/transformation.py
+++ b/litellm/llms/bedrock/files/transformation.py
@@ -600,12 +600,11 @@ class BedrockFilesConfig(BaseAWSLLM, BaseFilesConfig):
             ## 1. If jsonl, check if there's a model name
             file_content: Final = self._get_content_from_openai_file(extracted_file_data_content)
 
-            # Split into lines and parse each line as JSON. A file that is not JSONL gets the generic name below; the
-            # upload's own conversion is what rejects a malformed batch file.
-            with suppress(json.JSONDecodeError):
-                openai_jsonl_content: Final = [json.loads(line) for line in file_content.splitlines() if line.strip()]
-                if len(openai_jsonl_content) > 0:
-                    return self._get_s3_object_name_from_batch_jsonl(openai_jsonl_content)
+            # Reject a malformed line here rather than falling back: the upload only converts (and so re-checks) files
+            # whose MIME type is on the batch allowlist, so for any other MIME type this is the only check.
+            openai_jsonl_content: Final = _parse_batch_jsonl(file_content)
+            if len(openai_jsonl_content) > 0:
+                return self._get_s3_object_name_from_batch_jsonl(openai_jsonl_content)
 
         ## 2. If not jsonl, store under a server-generated managed object name
         filename: Final = extracted_file_data.get("filename")
diff --git a/tests/unit/llms/bedrock/files/test_bedrock_files_transformation.py b/tests/unit/llms/bedrock/files/test_bedrock_files_transformation.py
index 503c3724cae..b5d22ca5d61 100644
--- a/tests/unit/llms/bedrock/files/test_bedrock_files_transformation.py
+++ b/tests/unit/llms/bedrock/files/test_bedrock_files_transformation.py
@@ -4387,10 +4387,25 @@ class TestMalformedBatchJsonl:
         assert exc_info.value.status_code == 400
         assert "line 3" in exc_info.value.message
 
-    def test_object_name_inference_still_falls_back_for_a_non_json_file(self):
-        from litellm.llms.bedrock.files.transformation import BedrockFilesConfig
+    @pytest.mark.parametrize("content_type", ["application/jsonl", "application/x-jsonl"])
+    def test_create_file_rejects_a_malformed_line_before_uploading(self, content_type: str):
+        """application/x-jsonl is not on the batch MIME allowlist, so the upload skips conversion for it; the line
+        check must still run so the broken file is rejected instead of landing in S3 unchanged."""
+        from litellm.llms.bedrock.common_utils import BedrockError
 
-        object_name = BedrockFilesConfig().get_object_name(
-            {"content": b"just some text, not jsonl", "filename": "notes.txt"}, purpose="batch"
-        )
-        assert object_name.endswith("notes.txt")
+        with respx.mock as router:
+            any_request: Final = router.route()
+            with pytest.raises(BedrockError) as exc_info:
+                litellm.create_file(
+                    file=("batch.jsonl", _MALFORMED_BATCH_JSONL, content_type),
+                    purpose="batch",
+                    custom_llm_provider="bedrock",
+                    model="bedrock/amazon.nova-pro-v1:0",
+                    s3_bucket_name="litellm-batch-bucket",
+                    aws_region_name="us-west-2",
+                    aws_access_key_id="test-key-id",
+                    aws_secret_access_key="test-secret",
+                )
+        assert exc_info.value.status_code == 400
+        assert "line 3" in exc_info.value.message
+        assert not any_request.called