fix(openai): fix content normalization in openai backend history adapter (#1064)

* fix(llm): preserve null content on OpenAI tool-call turns

OpenAI-compatible providers can return assistant tool-call messages with
content=null. Coercing that to "" before history replay breaks providers
that bind opaque reasoning state to the exact assistant message shape.

Keep null only when the normalized response has tool calls; tool-less
null still becomes "", and content_override stays authoritative.

Fixes #1061

* test(live_llm): cover OpenAI null content tool-call replay

Add a live multi-turn tool replay that asserts provider content=null stays
null through normalize + OpenAIHistoryAdapter and that the continuation
still answers. Mark gpt_4/gpt_5 families as supports_tool_replay.

* docs(llm): note content_override None sentinel semantics

None means no override, not force-null content. Addresses review on #1064.
This commit is contained in:
Aakash Kattelu 2026-08-26 12:14:32 -04:00 committed by GitHub
parent 370232e139
commit dea2917fa9
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7 changed files with 314 additions and 7 deletions

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@ -441,10 +441,19 @@ class OpenAIBackend:
)
cache_creation, cache_read = extract_openai_cache_tokens(usage)
# content_override=None means no override, not "force content to None"
if content_override is not None:
content: Any = content_override
elif message.content is not None:
content = message.content
elif tool_calls:
# Preserve null content on tool-call turns for history replay
content = None
else:
content = ""
return CompletionResult(
content=content_override
if content_override is not None
else (message.content or ""),
content=content,
input_tokens=usage.prompt_tokens if usage else 0,
output_tokens=usage.completion_tokens if usage else 0,
cache_creation_input_tokens=cache_creation,

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@ -63,8 +63,8 @@ export OPENROUTER_API_KEY="sk-or-v1-..."
Coverage by provider:
- Anthropic: structured output path, prompt caching metrics, thinking blocks, multi-turn tool replay
- OpenAI GPT-4 class: structured outputs, prompt caching
- OpenAI GPT-5 class (incl. gpt-5.x point-releases): structured outputs, prompt caching, `reasoning_effort`, `max_completion_tokens` routing
- OpenAI GPT-4 class: structured outputs, prompt caching, multi-turn tool replay (null `content` preserved)
- OpenAI GPT-5 class (incl. gpt-5.x point-releases): structured outputs, prompt caching, `reasoning_effort`, `max_completion_tokens` routing, multi-turn tool replay (null `content` preserved)
- OpenAI transport → OpenRouter non-reasoning models (e.g. `inception/mercury-2`): non-chat / diffusion architectures must stay on `max_tokens`, no `reasoning_effort`, tool-calling parameter-schema compatibility is the canary for exotic OR-served providers
- Gemini 2.5/3.0 classes: structured outputs, cached-content reuse, thought signatures, multi-turn tool replay
- Gemini 3.1 class: thinking and tool replay coverage by default; structured-output/caching coverage should only be added once Google documents support for that path

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@ -58,6 +58,7 @@ MODEL_FAMILIES: tuple[LiveModelFamily, ...] = (
default_models=("gpt-4.1",),
supports_structured_output=True,
supports_caching=True,
supports_tool_replay=True,
docs_url="https://platform.openai.com/docs/models/gpt-4.1",
),
LiveModelFamily(
@ -68,6 +69,7 @@ MODEL_FAMILIES: tuple[LiveModelFamily, ...] = (
supports_structured_output=True,
supports_caching=True,
supports_reasoning=True,
supports_tool_replay=True,
docs_url="https://platform.openai.com/docs/models/gpt-5",
),
# OpenAI-compatible transport → OpenRouter-served non-reasoning models.

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@ -2,10 +2,13 @@ from __future__ import annotations
import pytest
from src.llm.history_adapters import OpenAIHistoryAdapter
from src.llm.request_builder import execute_completion
from .conftest import (
StructuredLiveResponse,
execute_local_tool,
favorite_prime_tools,
make_backend,
make_large_system_prompt,
require_provider_key,
@ -30,6 +33,11 @@ _JSON_OBJECT_SPECS = tuple(
for spec in get_live_model_specs(provider="openai")
if spec.family == "openai_json_object"
)
_TOOL_REPLAY_SPECS = tuple(
spec
for spec in get_live_model_specs(provider="openai")
if spec.supports_tool_replay
)
@pytest.mark.asyncio
@ -194,3 +202,83 @@ async def test_live_openai_json_object_structured_output(
assert parse_calls == []
assert create_calls, "expected a chat.completions.create call"
assert create_calls[0]["kwargs"]["response_format"] == {"type": "json_object"}
@pytest.mark.asyncio
@pytest.mark.parametrize("model_spec", _TOOL_REPLAY_SPECS, ids=lambda spec: spec.id)
async def test_live_openai_tool_replay_preserves_null_content(
model_spec: LiveModelSpec,
) -> None:
"""Tool-call turns with provider content=null must stay null through
normalize + history replay, and the continuation must still succeed."""
require_provider_key(model_spec)
# Leave reasoning_effort unset: gpt-5.4 rejects function tools with any
# explicit reasoning_effort other than 'none' on /v1/chat/completions.
backend, config = make_backend(model_spec)
tools = favorite_prime_tools()
adapter = OpenAIHistoryAdapter()
initial_messages = [
{
"role": "user",
"content": (
"Before answering, call the get_favorite_prime tool exactly once. "
"Do not answer with plain text on this turn. "
"After you receive the tool result, answer in one sentence that "
"includes the number and the word 'prime'."
),
}
]
first = await execute_completion(
backend,
config,
messages=initial_messages,
max_tokens=1024,
tools=tools,
tool_choice="required",
)
assert first.tool_calls, "OpenAI should issue a tool call in the first turn"
raw_message = first.raw_response.choices[0].message
raw_content = raw_message.content
if raw_content is None:
assert first.content is None
else:
assert first.content == raw_content
assistant_message = adapter.format_assistant_tool_message(first)
assert assistant_message["content"] is (
first.content if isinstance(first.content, str) else None
)
if raw_content is None:
assert assistant_message["content"] is None
tool_call = first.tool_calls[0]
tool_result = execute_local_tool(tool_call.name, tool_call.input)
replay_messages = initial_messages + [
assistant_message,
*adapter.format_tool_results(
[
{
"tool_id": tool_call.id,
"tool_name": tool_call.name,
"result": tool_result,
}
]
),
]
second = await execute_completion(
backend,
config,
messages=replay_messages,
max_tokens=1024,
tools=tools,
tool_choice="auto",
)
assert not second.tool_calls, "continuation should answer without another tool call"
assert isinstance(second.content, str)
assert "13" in second.content
assert "prime" in second.content.lower()

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@ -1138,12 +1138,114 @@ async def test_openai_backend_structured_with_tools_uses_create_not_parse() -> N
assert "strict" not in call["tools"][0]["function"]
def _tool_call_message(
*,
content: str | None,
reasoning_details: list[Any] | None = None,
) -> SimpleNamespace:
return SimpleNamespace(
content=content,
tool_calls=[
SimpleNamespace(
id="call_probe",
function=SimpleNamespace(
name="search",
arguments='{"query":"honcho"}',
),
)
],
reasoning_details=reasoning_details or [],
reasoning_content=None,
)
def _completion_response(
message: SimpleNamespace, finish_reason: str
) -> SimpleNamespace:
return SimpleNamespace(
choices=[SimpleNamespace(finish_reason=finish_reason, message=message)],
usage=SimpleNamespace(
prompt_tokens=10,
completion_tokens=5,
prompt_tokens_details=None,
),
)
def test_openai_normalize_preserves_null_content_on_tool_call_turns() -> None:
reasoning_details = [
{
"type": "reasoning.encrypted",
"data": "opaque",
"format": "openai-responses-v1",
"id": "binding",
"index": 0,
}
]
response = _completion_response(
_tool_call_message(content=None, reasoning_details=reasoning_details),
"tool_calls",
)
result = OpenAIBackend(Mock())._normalize_response( # pyright: ignore[reportPrivateUsage]
response
)
assert result.content is None
assert result.tool_calls[0].id == "call_probe"
assert result.tool_calls[0].name == "search"
assert result.tool_calls[0].input == {"query": "honcho"}
assert result.reasoning_details == reasoning_details
def test_openai_normalize_coerces_null_content_without_tool_calls() -> None:
message = SimpleNamespace(
content=None,
tool_calls=[],
reasoning_details=[],
reasoning_content=None,
)
response = _completion_response(message, "stop")
result = OpenAIBackend(Mock())._normalize_response( # pyright: ignore[reportPrivateUsage]
response
)
assert result.content == ""
def test_openai_normalize_keeps_empty_string_content_on_tool_call_turns() -> None:
response = _completion_response(
_tool_call_message(content=""),
"tool_calls",
)
result = OpenAIBackend(Mock())._normalize_response( # pyright: ignore[reportPrivateUsage]
response
)
assert result.content == ""
def test_openai_normalize_content_override_is_authoritative() -> None:
response = _completion_response(
_tool_call_message(content=None),
"tool_calls",
)
result = OpenAIBackend(Mock())._normalize_response( # pyright: ignore[reportPrivateUsage]
response, content_override="override"
)
assert result.content == "override"
@pytest.mark.asyncio
async def test_openai_backend_structured_with_tools_skips_parsing_tool_call_turn() -> (
None
):
"""A tool-call turn under tools + response_format must not attempt JSON
parsing (its content is empty and _parse_or_repair raises on that)."""
parsing (provider content is null and _parse_or_repair raises on that)."""
client = Mock()
client.chat.completions.create = AsyncMock(
return_value=SimpleNamespace(
@ -1183,7 +1285,7 @@ async def test_openai_backend_structured_with_tools_skips_parsing_tool_call_turn
response_format=_StructuredResponse,
)
assert result.content == "" # raw empty text, not a parsed model
assert result.content is None # provider null, not a parsed model
assert result.tool_calls[0].name == "search"
assert result.tool_calls[0].input == {"query": "honcho"}

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@ -113,3 +113,31 @@ def test_openai_history_adapter_omits_empty_thinking_content(
message = adapter.format_assistant_tool_message(result)
assert "reasoning_content" not in message
def test_openai_history_adapter_preserves_null_content_on_tool_call_turns() -> None:
adapter = OpenAIHistoryAdapter()
reasoning_details = [
{
"type": "reasoning.encrypted",
"data": "opaque",
"format": "openai-responses-v1",
"id": "binding",
"index": 0,
}
]
result = CompletionResult(
content=None,
reasoning_details=reasoning_details,
tool_calls=[
ToolCallResult(id="call_probe", name="search", input={"query": "honcho"})
],
)
message = adapter.format_assistant_tool_message(result)
assert message["content"] is None
assert message["reasoning_details"] == reasoning_details
assert message["tool_calls"][0]["id"] == "call_probe"
assert message["tool_calls"][0]["function"]["name"] == "search"
assert message["tool_calls"][0]["function"]["arguments"] == '{"query": "honcho"}'

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@ -102,3 +102,81 @@ async def test_tool_loop_replays_reasoning_content_on_continuation() -> None:
"tool_call_id": "call_1",
"content": "result",
}
@pytest.mark.asyncio
async def test_tool_loop_replays_null_assistant_content_on_continuation() -> None:
calls: list[list[dict[str, Any]]] = []
responses = iter(
[
HonchoLLMCallResponse(
content=None,
output_tokens=5,
finish_reasons=["tool_calls"],
tool_calls_made=[
{
"id": "call_1",
"name": "search",
"input": {"query": "honcho"},
}
],
reasoning_details=[
{
"type": "reasoning.encrypted",
"data": "opaque",
"format": "openai-responses-v1",
"id": "binding",
"index": 0,
}
],
),
HonchoLLMCallResponse(
content="done",
output_tokens=3,
finish_reasons=["stop"],
tool_calls_made=[],
),
]
)
async def fake_call(*_args: Any, **kwargs: Any) -> HonchoLLMCallResponse[Any]:
calls.append(deepcopy(kwargs["messages"]))
return next(responses)
async def execute_search(_name: str, _input: dict[str, Any]) -> str:
return "result"
with patch.object(tool_loop, "honcho_llm_call_inner", new=fake_call):
result = await execute_tool_loop(
prompt="hi",
max_tokens=64,
messages=[{"role": "user", "content": "hi"}],
tools=[
{
"name": "search",
"description": "Search",
"input_schema": {"type": "object"},
}
],
tool_choice="auto",
tool_executor=execute_search,
max_tool_iterations=5,
response_model=None,
json_mode=False,
temperature=None,
stop_seqs=None,
verbosity=None,
enable_retry=False,
retry_attempts=1,
max_input_tokens=None,
get_attempt_plan=_make_plan,
before_retry_callback=lambda _retry_state: None,
stream_final=False,
telemetry=None,
)
assert isinstance(result, HonchoLLMCallResponse)
assert len(calls) == 2
assert calls[1][1]["content"] is None
assert calls[1][1]["reasoning_details"][0]["data"] == "opaque"
assert calls[1][1]["tool_calls"][0]["function"]["name"] == "search"