When building the `input` list for the OpenAI Responses API from prior
conversation turns, an assistant text-only turn was being serialized as:
{"role": "assistant",
"content": [{"type": "output_text", "text": "..."}]}
The openai-python SDK's EasyInputMessage shape uses a plain string for
this case, matching what a direct OpenAI Responses call would send. Use
the same shape so our history matches the SDK exactly, and add tests
covering both _build_responses_input and a two-turn response.reply()
flow.
The previous commit wired up encrypted_content round-trip but only
tested that the data flows through correctly on a single tool round-
trip. This adds a multi-turn cassette test that proves the full
interleaved-reasoning capability:
- Each turn produces fresh reasoning_tokens (not just the first)
- Every prior reasoning block is round-tripped on every subsequent
turn (the Nth turn echoes >= N-1 reasoning items)
- ReasoningParts persisted on the assistant messages carry the same
encrypted_content + id that gets sent back on the wire
The puzzle is shaped so the model can't parallelize tool calls -
each db_lookup result tells it the next key to use, forcing the
model to think between calls. The recorded 4-turn chain shows
reasoning_tokens of 45/98/196/17 across turns with reasoning items
accumulating in every outgoing input.
This is the GPT-5-class capability that Chat Completions can't
deliver because it discards reasoning between turns.
When the Responses API returns a reasoning item alongside function
calls, capture its opaque id + encrypted_content as provider_metadata
on the resulting ReasoningPart. _build_responses_input already echoed
that metadata back as a reasoning input item on the next turn - now
the output side actually populates it.
This preserves the model's hidden chain of thought across the tool
round-trip. Without it, GPT-5-class models silently lose ~3% on
SWE-bench (per OpenAI) when used with tools.
Adds a dedicated VCR test that asserts the encrypted_content captured
on the first turn appears verbatim in the second turn's outgoing
request body.
Adds Responses and AsyncResponses classes that drive the OpenAI
/v1/responses endpoint. The existing Chat / AsyncChat classes are
unchanged because other plugins import them.
gpt-5.5 (and gpt-5.5-2026-04-23) is now registered against Responses
by default. Pass `-o chat_completions 1` to fall back to the older
/v1/chat/completions code path.
This is feature parity with the Chat path (text, tools, streaming,
schema, reasoning_effort, verbosity, attachments, system prompts).
Interleaved reasoning across tool round-trips is not exercised yet -
encrypted reasoning items are accepted on the input side, but the
plugin doesn't yet stash them on outgoing ReasoningParts.
Simon Willison