What changed
At DevDay on September 29, 2026, OpenAI introduced Decisions API in limited preview. Developers define questions with finite pre-defined answers, provide context as text or images, and receive answers intended for direct software use. OpenAI names content classification, request routing and selecting an agent's next action as example workloads. The API uses GPT-6 Luna and OpenAI says a broad release is planned in the coming days.
Why it matters
This is not merely another structured-output option. OpenAI is exposing a separate API surface around the idea that many production AI calls are bounded decisions rather than conversations. That is the same software layer recently targeted by Jev, CLM-8B and GLiNER2.5-Decide. A frontier API provider adopting the pattern makes it easier for builders to compare decision-specific calls against general LLM generation on latency, cost, calibration and operational simplicity.
The contract is finite answers, not generated prose
Developers supply context and a known answer set instead of asking a model to generate and then parse free-form text. OpenAI explicitly positions the interface for classification, routing and agent-action selection, where the application already knows the legal outcomes.
Luna becomes more than a cheap chat model
The first Decisions API implementation focuses GPT-6 Luna on bounded questions. That gives OpenAI a way to reuse its inexpensive model tier behind a task-specific interface while applications consume decisions rather than conversational output.
The category is getting crowded quickly
BTN has already tracked Jev's typed probabilistic API and external Vercel adoption, open CLM-8B, and the much smaller GLiNER2.5-Decide. OpenAI's entry does not make those systems equivalent, but it strengthens the case that decision-specific inference is becoming a distinct production layer rather than a single startup's API design.
The important evidence is still missing
OpenAI has not yet published enough detail in the DevDay recap to compare calibration, latency, per-decision economics or exact response semantics against Jev and other decision models. Limited-preview behavior may also change before broad release.