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Python: deduplicate MessagePack FileHistoryProvider writes #8224

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Merged
Eduard van Valkenburg (eavanvalkenburg) merged 1 commit into from
Sep 10, 2026
Merged

Python: deduplicate MessagePack FileHistoryProvider writes #8224

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6 changes: 5 additions & 1 deletion python/packages/core/agent_framework/_sessions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2335,8 +2335,12 @@ def _append_messages() -> None:
for message in new_messages:
file_handle.write(f"{self._serialize_json_message(message)}\n")
return
existing_messages = self._read_msgpack_messages(file_path) if file_path.exists() else []
new_messages = filter_new_messages(existing_messages, messages)
if not new_messages:
return
with file_path.open("ab") as file_handle:
for message in messages:
for message in new_messages:
serialized = _DEFAULT_MSGPACK_ENCODER.encode(message.to_dict())
file_handle.write(len(serialized).to_bytes(self._MSGPACK_RECORD_HEADER_BYTES, "big"))
file_handle.write(serialized)
Expand Down
50 changes: 42 additions & 8 deletions python/packages/core/tests/core/test_sessions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1636,6 +1636,28 @@ async def test_stores_and_loads_length_prefixed_msgpack(self, tmp_path: Path) ->
assert first_record_length > 0
assert raw[4 : 4 + first_record_length] == msgspec.msgpack.encode(messages[0].to_dict())

@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_save_messages_deduplicates_replayed_transcript(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
) -> None:
provider = FileHistoryProvider(tmp_path, serialization_format=serialization_format)
first_turn = [
Message(role="user", contents=["hello"]),
Message(role="assistant", contents=["hi there"]),
]
full_transcript = [
Message(role="user", contents=["hello"]),
Message(role="assistant", contents=["hi there"]),
Message(role="user", contents=["follow-up"]),
Message(role="assistant", contents=["reply"]),
]

await provider.save_messages("replayed-transcript", first_turn)
await provider.save_messages("replayed-transcript", full_transcript)

loaded = await provider.get_messages("replayed-transcript")
assert [message.text for message in loaded] == ["hello", "hi there", "follow-up", "reply"]

@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_round_trips_marked_refusal_text(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
Expand Down Expand Up @@ -1913,9 +1935,12 @@ def tracked_open(path: Path, *args: Any, **kwargs: Any) -> Any:
loaded = await provider.get_messages(session_id)
assert [message.text for message in loaded] == ["first", "second"]

async def test_save_messages_deduplicates_identical_messages(self, tmp_path: Path) -> None:
@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_save_messages_deduplicates_identical_messages(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
) -> None:
"""Test that FileHistoryProvider does not re-append already persisted messages."""
provider = FileHistoryProvider(tmp_path)
provider = FileHistoryProvider(tmp_path, serialization_format=serialization_format)

msg1 = Message(role="user", contents=["hello"])
msg2 = Message(role="assistant", contents=["hi there"])
Expand All @@ -1928,9 +1953,12 @@ async def test_save_messages_deduplicates_identical_messages(self, tmp_path: Pat
loaded = await provider.get_messages("s1")
assert len(loaded) == 2

async def test_save_messages_only_appends_new_messages(self, tmp_path: Path) -> None:
@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_save_messages_only_appends_new_messages(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
) -> None:
"""Test that FileHistoryProvider filters out old messages and only appends new ones"""
provider = FileHistoryProvider(tmp_path)
provider = FileHistoryProvider(tmp_path, serialization_format=serialization_format)

msg1 = Message(role="user", contents=["hello"])
msg2 = Message(role="assistant", contents=["hi there"])
Expand All @@ -1945,9 +1973,12 @@ async def test_save_messages_only_appends_new_messages(self, tmp_path: Path) ->
assert len(loaded) == 3
assert loaded[2].text == "how are you?"

async def test_save_messages_different_roles_same_text_not_deduplicated(self, tmp_path: Path) -> None:
@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_save_messages_different_roles_same_text_not_deduplicated(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
) -> None:
"""Test that messages with the same text but different roles are kept separate."""
provider = FileHistoryProvider(tmp_path)
provider = FileHistoryProvider(tmp_path, serialization_format=serialization_format)

msg1 = Message(role="user", contents=["ping"])
msg2 = Message(role="assistant", contents=["ping"])
Expand All @@ -1974,9 +2005,12 @@ async def test_deduplication_file_integrity(self, tmp_path: Path) -> None:
raw_lines = (await asyncio.to_thread(session_file.read_text, encoding="utf-8")).splitlines()
assert len(raw_lines) == 3

async def test_save_messages_preserves_duplicate_content(self, tmp_path: Path) -> None:
@pytest.mark.parametrize("serialization_format", ["json", "msgpack"])
async def test_save_messages_preserves_duplicate_content(
self, tmp_path: Path, serialization_format: Literal["json", "msgpack"]
) -> None:
"""Test that two identical user turns in the same batch are both persisted."""
provider = FileHistoryProvider(tmp_path)
provider = FileHistoryProvider(tmp_path, serialization_format=serialization_format)

yes_1 = Message(role="user", contents=["yes"])
yes_2 = Message(role="user", contents=["yes"])
Expand Down
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