opentelemetry: add span event for instructions (#1529)

Author: Kludex

pydantic_ai_slim/pydantic_ai/models/instrumented.py

@@ -261,9 +261,11 @@ def event_to_dict(event: Event) -> dict[str, Any]:
     @staticmethod
     def messages_to_otel_events(messages: list[ModelMessage]) -> list[Event]:
         events: list[Event] = []
+        last_model_request: ModelRequest | None = None
         for message_index, message in enumerate(messages):
             message_events: list[Event] = []
             if isinstance(message, ModelRequest):
+                last_model_request = message
                 for part in message.parts:
                     if hasattr(part, 'otel_event'):
                         message_events.append(part.otel_event())
@@ -275,6 +277,10 @@ def messages_to_otel_events(messages: list[ModelMessage]) -> list[Event]:
                     **(event.attributes or {}),
                 }
             events.extend(message_events)
+        if last_model_request and last_model_request.instructions:
+            events.insert(
+                0, Event('gen_ai.system.message', body={'content': last_model_request.instructions, 'role': 'system'})
+            )
         for event in events:
             event.body = InstrumentedModel.serialize_any(event.body)
         return events

tests/models/test_instrumented.py

@@ -692,3 +692,47 @@ def __repr__(self):
             'event.name': 'gen_ai.tool.message',
         },
     ]
+
+
+def test_messages_to_otel_events_instructions():
+    messages = [
+        ModelRequest(instructions='instructions', parts=[UserPromptPart('user_prompt')]),
+        ModelResponse(parts=[TextPart('text1')]),
+    ]
+    assert [
+        InstrumentedModel.event_to_dict(e) for e in InstrumentedModel.messages_to_otel_events(messages)
+    ] == snapshot(
+        [
+            {'content': 'instructions', 'role': 'system', 'event.name': 'gen_ai.system.message'},
+            {'content': 'user_prompt', 'role': 'user', 'gen_ai.message.index': 0, 'event.name': 'gen_ai.user.message'},
+            {
+                'role': 'assistant',
+                'content': 'text1',
+                'gen_ai.message.index': 1,
+                'event.name': 'gen_ai.assistant.message',
+            },
+        ]
+    )
+
+
+def test_messages_to_otel_events_instructions_multiple_messages():
+    messages = [
+        ModelRequest(instructions='instructions', parts=[UserPromptPart('user_prompt')]),
+        ModelResponse(parts=[TextPart('text1')]),
+        ModelRequest(instructions='instructions2', parts=[UserPromptPart('user_prompt2')]),
+    ]
+    assert [
+        InstrumentedModel.event_to_dict(e) for e in InstrumentedModel.messages_to_otel_events(messages)
+    ] == snapshot(
+        [
+            {'content': 'instructions2', 'role': 'system', 'event.name': 'gen_ai.system.message'},
+            {'content': 'user_prompt', 'role': 'user', 'gen_ai.message.index': 0, 'event.name': 'gen_ai.user.message'},
+            {
+                'role': 'assistant',
+                'content': 'text1',
+                'gen_ai.message.index': 1,
+                'event.name': 'gen_ai.assistant.message',
+            },
+            {'content': 'user_prompt2', 'role': 'user', 'gen_ai.message.index': 2, 'event.name': 'gen_ai.user.message'},
+        ]
+    )