Overview
GPT-5.6 Luna is the cost-optimized model in OpenAI's GPT-5.6 series, announced on June 26, 2026 alongside the flagship Sol and the mid-tier Terra. OpenAI positions Luna as its fast, affordable option in the GPT-5.6 family, aimed at high-volume background tasks, batch processing, embedded applications, classification, and simple agent steps.
Luna accepts text and image input and is priced at OpenAI's lowest headline rate in the GPT-5.6 tier — $1 per 1M input tokens and $6 per 1M output tokens. In the GPT-5.6 naming system, the number identifies the generation and the tier names — Sol, Terra, Luna — identify durable capability tiers that can advance on their own cadence.
Access at launch is restricted: in coordination with the U.S. government, OpenAI began with a limited preview to around 20 vetted partner organizations through the API and Codex, with general availability across ChatGPT, Codex, and the API planned in the following weeks.
| Released | 2026-06-26 |
|---|---|
| License | Proprietary |
| Weights | API only |
| Modalities | Text, Vision |
| Status | Preview |
Benchmarks
- Terminal-Bench 2.182.5%
Scores on a 0–100 scale (25-point gridlines); higher is better. Each benchmark links to its published source.
Pricing
| Input | $1.00 / 1M tokens |
|---|---|
| Output | $6.00 / 1M tokens |
Strengths
- OpenAI's lowest headline pricing in the GPT-5.6 family, $1/$6 per 1M tokens
- Reasoning-model architecture with text and image input
- Designed for high-volume background, batch, and embedded workloads
- Ships with the GPT-5.6 series safety stack for production deployments
Best for
- Reach for it for high-volume batch processing, classification, and embedded application work.
- Reach for it for simple agent steps where cost per call matters more than reasoning depth.
- Reach for it when a workload's economics require the lowest GPT-5.6 per-token rate.
How to access
| Provider | Model ID |
|---|---|
| OpenAI API ↗ | — |
GPT (Flagship / Thinking) — every version
The full lineage of the GPT (Flagship / Thinking) line, newest first. Every version has its own page — click any to compare specs, benchmarks and pricing.
| Version | Released | Context | License |
|---|---|---|---|
| GPT-5.6 Sol | 2026-06-26 | — | Proprietary |
| GPT-5.6 Terra | 2026-06-26 | — | Proprietary |
| GPT-5.6 Luna | 2026-06-26 | — | Proprietary |
| GPT-5.5current | 2026-04-23 | 1.05M | Proprietary |
| GPT-5.4 | 2026-03-05 | — | Proprietary |
| GPT-5.2 | 2025-12-11 | — | Proprietary |
| GPT-5.1 | 2025-11-12 | — | Proprietary |
| GPT-5 | 2025-08-07 | — | Proprietary |
| GPT-4o | 2024-05-13 | — | Proprietary |
FAQ
When was GPT-5.6 Luna released?
OpenAI announced GPT-5.6 Luna on June 26, 2026 as a limited preview, alongside GPT-5.6 Sol and GPT-5.6 Terra. Initial access was restricted to roughly 20 vetted partner organizations via the API and Codex, with broader rollout planned in the following weeks.
How much does GPT-5.6 Luna cost?
GPT-5.6 Luna is priced at $1.00 per 1M input tokens and $6.00 per 1M output tokens — OpenAI's lowest headline rate in the GPT-5.6 series, targeting cost-sensitive, high-volume workloads.
How does GPT-5.6 Luna compare to Sol and Terra?
On Terminal-Bench 2.1, OpenAI reports Luna at 82.5%, versus 88.8% for Sol (91.9% in ultra mode) and 84.3% for Terra. Luna sits at the smallest, most affordable end of the GPT-5.6 series and is aimed at high-volume batch, classification, and embedded work rather than the hardest reasoning problems.
What is GPT-5.6 Luna best for?
OpenAI positions Luna as the cost-optimized tier for high-volume background tasks, batch processing, embedded applications, classification, and simple agent steps — workloads where cost per call is the primary constraint.