diff --git a/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_fsspec_upload/fsspec_hook.py b/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_fsspec_upload/fsspec_hook.py
index 319b5252cb..60481f65ff 100644
--- a/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_fsspec_upload/fsspec_hook.py
+++ b/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_fsspec_upload/fsspec_hook.py
@@ -19,6 +19,7 @@
 import logging
 import posixpath
 import threading
+from base64 import b64encode
 from concurrent.futures import Future, ThreadPoolExecutor
 from dataclasses import asdict, dataclass
 from functools import partial
@@ -151,7 +152,12 @@ def _do_upload(
         path: str, json_encodeable: Callable[[], JsonEncodeable]
     ) -> None:
         with fsspec_open(path, "w") as file:
-            json.dump(json_encodeable(), file, separators=(",", ":"))
+            json.dump(
+                json_encodeable(),
+                file,
+                separators=(",", ":"),
+                cls=Base64JsonEncoder,
+            )
 
     def upload(
         self,
@@ -206,3 +212,10 @@ def to_dict(
     def shutdown(self) -> None:
         # TODO: support timeout
         self._executor.shutdown()
+
+
+class Base64JsonEncoder(json.JSONEncoder):
+    def default(self, o: Any) -> Any:
+        if isinstance(o, bytes):
+            return b64encode(o).decode()
+        return super().default(o)
diff --git a/util/opentelemetry-util-genai/tests/test_fsspec_upload.py b/util/opentelemetry-util-genai/tests/test_fsspec_upload.py
index 670a3b9342..4e6f2470dc 100644
--- a/util/opentelemetry-util-genai/tests/test_fsspec_upload.py
+++ b/util/opentelemetry-util-genai/tests/test_fsspec_upload.py
@@ -14,7 +14,6 @@
 
 
 # pylint: disable=import-outside-toplevel,no-name-in-module
-
 import importlib
 import logging
 import sys
@@ -200,26 +199,31 @@ def test_upload(self):
 
 
 class TestFsspecUploadHookIntegration(TestBase):
+    def setUp(self):
+        super().setUp()
+        self.hook = FsspecUploadHook(base_path=BASE_PATH)
+
+    def tearDown(self):
+        super().tearDown()
+        self.hook.shutdown()
+
     def assert_fsspec_equal(self, path: str, value: str) -> None:
         with fsspec.open(path, "r") as file:
             self.assertEqual(file.read(), value)
 
     def test_upload_completions(self):
-        hook = FsspecUploadHook(
-            base_path=BASE_PATH,
-        )
         tracer = self.tracer_provider.get_tracer(__name__)
         log_record = LogRecord()
 
         with tracer.start_as_current_span("chat mymodel") as span:
-            hook.upload(
+            self.hook.upload(
                 inputs=FAKE_INPUTS,
                 outputs=FAKE_OUTPUTS,
                 system_instruction=FAKE_SYSTEM_INSTRUCTION,
                 span=span,
                 log_record=log_record,
             )
-        hook.shutdown()
+        self.hook.shutdown()
 
         finished_spans = self.get_finished_spans()
         self.assertEqual(len(finished_spans), 1)
@@ -250,25 +254,39 @@ def test_upload_completions(self):
             '[{"content":"You are a helpful assistant.","type":"text"}]',
         )
 
-    @staticmethod
-    def upload_with_log(log_record: LogRecord):
-        hook = FsspecUploadHook(
-            base_path=BASE_PATH,
-        )
-
-        hook.upload(
+    def test_stamps_empty_log(self):
+        log_record = LogRecord()
+        self.hook.upload(
             inputs=FAKE_INPUTS,
             outputs=FAKE_OUTPUTS,
             system_instruction=FAKE_SYSTEM_INSTRUCTION,
             log_record=log_record,
         )
-        hook.shutdown()
-
-    def test_stamps_empty_log(self):
-        log_record = LogRecord()
-        self.upload_with_log(log_record)
 
         # stamp on both body and attributes
         self.assertIn("gen_ai.input.messages_ref", log_record.attributes)
         self.assertIn("gen_ai.output.messages_ref", log_record.attributes)
         self.assertIn("gen_ai.system_instructions_ref", log_record.attributes)
+
+    def test_upload_bytes(self) -> None:
+        log_record = LogRecord()
+        self.hook.upload(
+            inputs=[
+                types.InputMessage(
+                    role="user",
+                    parts=[
+                        types.Text(content="What is the capital of France?"),
+                        {"type": "generic_bytes", "bytes": b"hello"},
+                    ],
+                )
+            ],
+            outputs=FAKE_OUTPUTS,
+            system_instruction=FAKE_SYSTEM_INSTRUCTION,
+            log_record=log_record,
+        )
+        self.hook.shutdown()
+
+        self.assert_fsspec_equal(
+            log_record.attributes["gen_ai.input.messages_ref"],
+            '[{"role":"user","parts":[{"content":"What is the capital of France?","type":"text"},{"type":"generic_bytes","bytes":"aGVsbG8="}]}]',
+        )