diff --git a/util/opentelemetry-util-genai/CHANGELOG.md b/util/opentelemetry-util-genai/CHANGELOG.md
index 7cef62c3dc..ee539d6b15 100644
--- a/util/opentelemetry-util-genai/CHANGELOG.md
+++ b/util/opentelemetry-util-genai/CHANGELOG.md
@@ -13,6 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3798](#3798))
 - Record content-type and use canonical paths in fsspec genai uploader
   ([https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3795](#3795))
+- Make inputs / outputs / system instructions optional params to `on_completion`,
+  ([https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3802](#3802)).
 
 ## Version 0.1b0 (2025-09-25)
 
diff --git a/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_upload/completion_hook.py b/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_upload/completion_hook.py
index ec175ab776..351b74cc3b 100644
--- a/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_upload/completion_hook.py
+++ b/util/opentelemetry-util-genai/src/opentelemetry/util/genai/_upload/completion_hook.py
@@ -60,9 +60,9 @@
 
 @dataclass
 class Completion:
-    inputs: list[types.InputMessage]
-    outputs: list[types.OutputMessage]
-    system_instruction: list[types.MessagePart]
+    inputs: list[types.InputMessage] | None
+    outputs: list[types.OutputMessage] | None
+    system_instruction: list[types.MessagePart] | None
 
 
 @dataclass
@@ -210,10 +210,13 @@ def on_completion(
         log_record: LogRecord | None = None,
         **kwargs: Any,
     ) -> None:
+        if not any([inputs, outputs, system_instruction]):
+            return
+        # An empty list will not be uploaded.
         completion = Completion(
-            inputs=inputs,
-            outputs=outputs,
-            system_instruction=system_instruction,
+            inputs=inputs or None,
+            outputs=outputs or None,
+            system_instruction=system_instruction or None,
         )
         # generate the paths to upload to
         ref_names = self._calculate_ref_path()
@@ -225,23 +228,36 @@ def to_dict(
         ) -> JsonEncodeable:
             return [asdict(dc) for dc in dataclass_list]
 
+        references = [
+            (ref_name, ref, ref_attr)
+            for ref_name, ref, ref_attr in [
+                (
+                    ref_names.inputs_ref,
+                    completion.inputs,
+                    GEN_AI_INPUT_MESSAGES_REF,
+                ),
+                (
+                    ref_names.outputs_ref,
+                    completion.outputs,
+                    GEN_AI_OUTPUT_MESSAGES_REF,
+                ),
+                (
+                    ref_names.system_instruction_ref,
+                    completion.system_instruction,
+                    GEN_AI_SYSTEM_INSTRUCTIONS_REF,
+                ),
+            ]
+            if ref
+        ]
         self._submit_all(
             {
-                # Use partial to defer as much as possible to the background threads
-                ref_names.inputs_ref: partial(to_dict, completion.inputs),
-                ref_names.outputs_ref: partial(to_dict, completion.outputs),
-                ref_names.system_instruction_ref: partial(
-                    to_dict, completion.system_instruction
-                ),
-            },
+                ref_name: partial(to_dict, ref)
+                for ref_name, ref, _ in references
+            }
         )
 
         # stamp the refs on telemetry
-        references = {
-            GEN_AI_INPUT_MESSAGES_REF: ref_names.inputs_ref,
-            GEN_AI_OUTPUT_MESSAGES_REF: ref_names.outputs_ref,
-            GEN_AI_SYSTEM_INSTRUCTIONS_REF: ref_names.system_instruction_ref,
-        }
+        references = {ref_attr: name for name, _, ref_attr in references}
         if span:
             span.set_attributes(references)
         if log_record:
diff --git a/util/opentelemetry-util-genai/tests/test_upload.py b/util/opentelemetry-util-genai/tests/test_upload.py
index 26e33467a7..ae43d3b4a7 100644
--- a/util/opentelemetry-util-genai/tests/test_upload.py
+++ b/util/opentelemetry-util-genai/tests/test_upload.py
@@ -162,6 +162,33 @@ def test_upload_then_shutdown(self):
             "should have uploaded 3 files",
         )
 
+    def test_upload_when_inputs_outputs_empty(self):
+        record = LogRecord()
+        self.hook.on_completion(
+            inputs=[],
+            outputs=[],
+            system_instruction=FAKE_SYSTEM_INSTRUCTION,
+            log_record=record,
+        )
+        # all items should be consumed
+        self.hook.shutdown()
+
+        self.assertEqual(
+            self.mock_fs.open.call_count,
+            1,
+            "should have uploaded 1 file",
+        )
+        assert record.attributes is not None
+        for ref_key in [
+            "gen_ai.input.messages_ref",
+            "gen_ai.output.messages_ref",
+            "gen_ai.system_instructions_ref",
+        ]:
+            if ref_key == "gen_ai.system_instructions_ref":
+                self.assertIn(ref_key, record.attributes)
+            else:
+                self.assertNotIn(ref_key, record.attributes)
+
     def test_upload_blocked(self):
         with self.block_upload():
             # fill the queue