OpenAI adds phase parameter to GPT-5.4 for commentary and final answers

• OpenAI has documented a new phase field for GPT-5.4 responses, splitting assistant messages into in-progress commentary and terminal final_answer states so agents can surface status updates without treating them as the turn’s final output phase docs.
• The integration detail is operational, not cosmetic: OpenAI’s phase docs says builders should pass those phase-tagged assistant messages back on subsequent turns, preserving the conversation state the model emitted.
• GPT-5.4 also appears to support mid-run steering: in a demo thread, a user message changes the model’s reasoning trajectory while it is still working, which points to a more stateful orchestration loop than a single monolithic completion.
• Broader GPT-5.4 rollout details in OpenAI’s Help Center page show the model is being positioned as the heavier reasoning tier inside ChatGPT, with separate handling for Thinking and higher-end usage tiers.

OpenAI’s new GPT-5.4 integration note shows assistant outputs can now carry a phase value that distinguishes “preamble / still working” from the terminal answer. The example in the developer thread returns one assistant message with phase: "commentary" and a later one with phase: "final_answer", giving agent builders a clean way to stream progress text such as “Checking the news now...” before the actual result lands.

The important implementation detail is state replay. In the same thread, OpenAI says that if you are building your own agent, “it’s important” to pass that parameter back on subsequent turns, and the linked integration notes show a follow-up request that reuses the prior assistant output before sending a new user instruction. That implies phase is part of the model-visible conversation record, not just UI metadata.

The new phase field fits a broader GPT-5.4 pattern: the model can expose more of its in-flight work without collapsing everything into a single final blob. In Daniel Mac’s demo, GPT-5.4 accepts a new user message that changes its reasoning path mid-task, which he describes as “a brand new AI model capability.” His theory of a “stateful orchestration loop” is still interpretation, but the observed behavior matches OpenAI’s decision to formalize non-final assistant messages.

That matters for agent UX and control surfaces. A system can now show commentary updates while tools are running, keep those messages structurally distinct from the answer, and continue the thread with the same phased messages preserved. OpenAI’s ChatGPT model doc also separates GPT-5.4 Thinking from faster modes and notes model-specific limits, reinforcing that GPT-5.4 is being exposed as a longer-horizon reasoning path rather than just another stateless chat variant.