Redundant id property for phase type messages is causing added latency for OpenAI models #4783
Description
Tracking cleanup for Responses API prompt round-tripping.
Problem:
Assistant messages that participate in phase-based Responses API round-tripping are carrying a redundant standalone output message id in addition to the phase metadata. This creates avoidable payload overhead and additional processing for OpenAI model requests.
Desired behavior:
- Attach the response output message id only for assistant messages that have phase metadata.
- Store that id alongside the phase metadata rather than as a separate prompt payload.
- Send non-phase assistant history back as plain assistant input messages.
- Preserve phased assistant history as Responses API output messages with stable ids.
Acceptance criteria:
- Non-phase assistant messages do not include a response output message id in outgoing prompt history.
- Phased assistant messages retain the output message id only through phase metadata.
- OpenAI Responses API request construction and round-tripping tests cover this behavior.
- Existing compile/test validation remains clean.