fix(memory): preserve observation timestamp in extraction

mem0/memory/main.py

@@ -727,11 +727,13 @@ def _add_to_vector_store(self, messages, metadata, filters, infer, prompt=None):
             system_prompt += AGENT_CONTEXT_SUFFIX
 
         custom_instr = prompt or self.custom_instructions
+        observation_timestamp = metadata.get("timestamp") or metadata.get("created_at")
 
         user_prompt = generate_additive_extraction_prompt(
             existing_memories=existing_memories,
             new_messages=parsed_messages,
             last_k_messages=last_messages,
+            timestamp=observation_timestamp,
             custom_instructions=custom_instr,
         )
 
@@ -2143,11 +2145,13 @@ async def _add_to_vector_store(
             system_prompt += AGENT_CONTEXT_SUFFIX
 
         custom_instr = prompt or self.custom_instructions
+        observation_timestamp = metadata.get("timestamp") or metadata.get("created_at")
 
         user_prompt = generate_additive_extraction_prompt(
             existing_memories=existing_memories,
             new_messages=parsed_messages,
             last_k_messages=last_messages,
+            timestamp=observation_timestamp,
             custom_instructions=custom_instr,
         )
 

tests/memory/test_main.py

@@ -114,6 +114,32 @@ def test_falls_back_to_custom_instructions_when_no_prompt(self, mock_memory):
         user_prompt = mock_memory.llm.generate_response.call_args[1]["messages"][1]["content"]
         assert "config-level instructions" in user_prompt
 
+    def test_metadata_timestamp_sets_observation_date(self, mock_memory):
+        timestamp = "2023-05-24T10:00:00+00:00"
+
+        mock_memory._add_to_vector_store(
+            messages=[{"role": "user", "content": "I went to Paris last week"}],
+            metadata={"timestamp": timestamp},
+            filters={},
+            infer=True,
+        )
+
+        user_prompt = mock_memory.llm.generate_response.call_args[1]["messages"][1]["content"]
+        assert f"## Observation Date\n{timestamp}" in user_prompt
+
+    def test_created_at_sets_observation_date_when_timestamp_missing(self, mock_memory):
+        created_at = "2023-05-24T10:00:00+00:00"
+
+        mock_memory._add_to_vector_store(
+            messages=[{"role": "user", "content": "I went to Paris last week"}],
+            metadata={"created_at": created_at},
+            filters={},
+            infer=True,
+        )
+
+        user_prompt = mock_memory.llm.generate_response.call_args[1]["messages"][1]["content"]
+        assert f"## Observation Date\n{created_at}" in user_prompt
+
 
 class TestAsyncUpdate:
     @pytest.fixture
@@ -216,6 +242,20 @@ async def test_async_empty_llm_response_memory_actions(self, mock_async_memory,
         assert result == []
         assert mock_async_memory.llm.generate_response.call_count == 1
 
+    async def test_async_metadata_timestamp_sets_observation_date(self, mock_async_memory):
+        timestamp = "2023-05-24T10:00:00+00:00"
+        mock_async_memory.llm.generate_response.return_value = '{"memory": []}'
+
+        await mock_async_memory._add_to_vector_store(
+            messages=[{"role": "user", "content": "I went to Paris last week"}],
+            metadata={"timestamp": timestamp},
+            effective_filters={},
+            infer=True,
+        )
+
+        user_prompt = mock_async_memory.llm.generate_response.call_args[1]["messages"][1]["content"]
+        assert f"## Observation Date\n{timestamp}" in user_prompt
+
 
 def _build_memory_instance(mocker, memory_cls):
     _setup_mocks(mocker)
@@ -662,4 +702,3 @@ async def test_async_update_preserves_actor_id_when_different_actor_updates(mock
     stored = memory.vector_store.update.call_args.kwargs["payload"]
     assert stored["actor_id"] == "Alice"
 
-