diff --git a/instrumentation/opentelemetry-instrumentation-genai-openai/src/opentelemetry/instrumentation/genai/openai/patch.py b/instrumentation/opentelemetry-instrumentation-genai-openai/src/opentelemetry/instrumentation/genai/openai/patch.py
index 3782ca61c..9c5eb1afc 100644
--- a/instrumentation/opentelemetry-instrumentation-genai-openai/src/opentelemetry/instrumentation/genai/openai/patch.py
+++ b/instrumentation/opentelemetry-instrumentation-genai-openai/src/opentelemetry/instrumentation/genai/openai/patch.py
@@ -63,6 +63,22 @@ def chat_completions_create_v_new(
     capture_content = handler.should_capture_content()
 
     def traced_method(wrapped, instance, args, kwargs):
+        # Materialize generator/map-backed messages/tools before they are
+        # consumed by either instrumentation or the SDK (fixes #825).
+        messages_raw = kwargs.get("messages")
+        if messages_raw is not None and not isinstance(messages_raw, (list, tuple)):
+            try:
+                messages_raw = list(messages_raw)
+            except TypeError:
+                pass
+            kwargs = {**kwargs, "messages": messages_raw}
+        tools_raw = kwargs.get("tools")
+        if tools_raw is not None and not isinstance(tools_raw, (list, tuple)):
+            try:
+                tools_raw = list(tools_raw)
+            except TypeError:
+                pass
+            kwargs = {**kwargs, "tools": tools_raw}
         chat_invocation = create_chat_invocation(
             handler, kwargs, instance, capture_content=capture_content
         )
@@ -94,6 +110,22 @@ def async_chat_completions_create_v_new(
     capture_content = handler.should_capture_content()
 
     async def traced_method(wrapped, instance, args, kwargs):
+        # Materialize generator/map-backed messages/tools before they are
+        # consumed by either instrumentation or the SDK (fixes #825).
+        messages_raw = kwargs.get("messages")
+        if messages_raw is not None and not isinstance(messages_raw, (list, tuple)):
+            try:
+                messages_raw = list(messages_raw)
+            except TypeError:
+                pass
+            kwargs = {**kwargs, "messages": messages_raw}
+        tools_raw = kwargs.get("tools")
+        if tools_raw is not None and not isinstance(tools_raw, (list, tuple)):
+            try:
+                tools_raw = list(tools_raw)
+            except TypeError:
+                pass
+            kwargs = {**kwargs, "tools": tools_raw}
         chat_invocation = create_chat_invocation(
             handler, kwargs, instance, capture_content=capture_content
         )
diff --git a/instrumentation/opentelemetry-instrumentation-genai-openai/tests/test_issue_825_regression.py b/instrumentation/opentelemetry-instrumentation-genai-openai/tests/test_issue_825_regression.py
new file mode 100644
index 000000000..ff87e9549
--- /dev/null
+++ b/instrumentation/opentelemetry-instrumentation-genai-openai/tests/test_issue_825_regression.py
@@ -0,0 +1,61 @@
+"""Regression test for issue #825: instrumented wrapper materializes generators."""
+import os
+os.environ.setdefault("OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT", "SPAN_ONLY")
+
+from unittest.mock import MagicMock, AsyncMock, patch
+
+# Import the instrumented wrappers (production code unchanged)
+from opentelemetry.instrumentation.genai.openai.patch import (
+    chat_completions_create_v_new,
+    async_chat_completions_create_v_new,
+)
+
+def test_sync_wrapper_materializes_generator_messages():
+    mock_create = MagicMock(return_value={"choices": []})
+    handler = MagicMock()
+    handler.should_capture_content.return_value = False
+    wrapper = chat_completions_create_v_new(handler)
+    generator = (msg for msg in [{"role":"user","content":"hi"}])
+    wrapper(mock_create, None, [], {"messages": generator})
+    call_kwargs = mock_create.call_args.kwargs
+    assert isinstance(call_kwargs["messages"], list)
+    assert call_kwargs["messages"] == [{"role":"user","content":"hi"}]
+
+def test_sync_wrapper_materializes_generator_tools():
+    mock_create = MagicMock(return_value={"choices": []})
+    handler = MagicMock()
+    handler.should_capture_content.return_value = False
+    wrapper = chat_completions_create_v_new(handler)
+    generator = (t for t in [{"type":"function","function":{"name":"f"}}])
+    wrapper(mock_create, None, [], {"messages": [{"role":"user","content":"hi"}], "tools": generator})
+    call_kwargs = mock_create.call_args.kwargs
+    assert isinstance(call_kwargs["tools"], list)
+    assert call_kwargs["tools"] == [{"type":"function","function":{"name":"f"}}]
+
+def test_async_wrapper_materializes_generator_messages():
+    import asyncio
+    mock_create = AsyncMock(return_value={"choices": []})
+    handler = MagicMock()
+    handler.should_capture_content.return_value = False
+    wrapper = async_chat_completions_create_v_new(handler)
+    async def run():
+        generator = (msg for msg in [{"role":"user","content":"hi"}])
+        await wrapper(mock_create, None, [], {"messages": generator})
+    asyncio.run(run())
+    call_kwargs = mock_create.call_args.kwargs
+    assert isinstance(call_kwargs["messages"], list)
+    assert call_kwargs["messages"] == [{"role":"user","content":"hi"}]
+
+def test_async_wrapper_materializes_generator_tools():
+    import asyncio
+    mock_create = AsyncMock(return_value={"choices": []})
+    handler = MagicMock()
+    handler.should_capture_content.return_value = False
+    wrapper = async_chat_completions_create_v_new(handler)
+    async def run():
+        generator = (t for t in [{"type":"function","function":{"name":"f"}}])
+        await wrapper(mock_create, None, [], {"messages": [{"role":"user","content":"hi"}], "tools": generator})
+    asyncio.run(run())
+    call_kwargs = mock_create.call_args.kwargs
+    assert isinstance(call_kwargs["tools"], list)
+    assert call_kwargs["tools"] == [{"type":"function","function":{"name":"f"}}]