GPT-5.6 Sol, Terra and Luna: What OpenAI Launched
OpenAI launched GPT-5.6 on June 26 as three tiers: Sol, Terra and Luna. Here are the confirmed prices, the benchmarks, and the government access catch.
By Capital & Compute
After weeks of leaks and a public spat with the federal government over timing, the GPT-5.6 launch finally arrived on June 26, 2026, and it was not one model. OpenAI previewed GPT-5.6 as a three-tier suite: Sol, the flagship; Terra, a mid tier; and Luna, a budget option. The whole suite went out in a US-government-gated limited preview to roughly 20 partners, the rollout the administration had asked for.
The three tiers and what they cost
The headline change is the split. Where GPT-5.5 was a single flagship rate, GPT-5.6 ships as a ladder. Sol is the heavy model for long-horizon coding, security and agentic work. Terra is positioned at GPT-5.5-level performance for half the cost, aimed at high-volume production. Luna is the fast, cheap option for routine tasks.
| Tier | Input / Mtok | Output / Mtok | Cached input / Mtok | Positioned for |
|---|---|---|---|---|
| Sol | $5.00 | $30.00 | $0.50 | Long-horizon coding, security |
| Terra | $2.50 | $15.00 | $0.25 | High-volume production work |
| Luna | $1.00 | $6.00 | $0.10 | Fast, routine, low-cost tasks |
The most quietly important number is Sol’s. At $5 / $30 it is priced at exactly GPT-5.5’s standard rate, the “hold the line” outcome that the pre-launch GPT-5.6 pricing analysis flagged as the base case. OpenAI did not charge more for the flagship. It added a cheaper tier instead. Against Anthropic, that lands hard: Sol is half the per-token price of Claude Fable 5 at $10 / $50.
| Tool | Cost per task | Multiple of baseline |
|---|---|---|
| GPT-5.6 Luna | $6.00 | - |
| GPT-5.6 Terra | $15.00 | - |
| GPT-5.6 Sol | $30.00 | - |
| Claude Fable 5 | $50.00 | - |
Two reasoning modes, and a Cerebras speed claim
Every tier ships with two reasoning modes. Max mode gives the model the most time to reason down a single deep chain, trading latency for accuracy. Ultra mode splits the work across parallel subagents that coordinate on one task. The benchmark gap between them is real: in OpenAI’s reported Terminal-Bench 2.1 numbers, Sol scores 88.76 percent in max mode and 91.91 percent in ultra, against GPT-5.5 at 83.4 percent.
OpenAI also said Sol will run on Cerebras wafer-scale hardware at up to 750 tokens per second starting in July. That sounds like a model breakthrough but is mostly a chip story: the same hardware has run smaller models far faster, and Sol is the slowest of them because it is the largest. The full breakdown is in GPT-5.6 Sol on Cerebras: 750 tokens per second. Speed changes what the model is usable for, not what it costs per token.
The catch: you probably cannot use it yet
The suite launched into a limited preview open only to about 20 partner organizations, through the API and Codex, at the direction of the US government. The arrangement followed a Trump-administration request to stagger the release on national security grounds, built on a June 2, 2026 executive order that invites federal vetting of frontier models before release.
That preview-only status is the asterisk on every other number here. The pricing is published and the benchmarks are reported, but for most teams GPT-5.6 is not yet something you can run. OpenAI said wider access is planned in the weeks after launch. The leak cycle that preceded all this, and how the prediction markets misread the timing, is covered in the GPT-5.6 preview leak post.
What to do with this now
If you are budgeting, the practical takeaway is that the GPT-5.6 flagship did not raise the headline rate, so plans anchored to GPT-5.5’s $5 / $30 still hold, and the new Terra and Luna tiers open cheaper routing for high-volume work. Drop the confirmed rates into the cost-per-task calculator to see what they mean for your own token counts, compare tiers head to head in the model comparison tool, and watch the AI model release tracker for the moment broader access opens.
Frequently asked questions
- What is GPT-5.6 Sol, Terra and Luna?
- GPT-5.6 is the OpenAI model suite launched June 26, 2026 in three tiers: Sol is the flagship for hard coding, security and agentic work; Terra is a mid tier at GPT-5.5-level performance for half the cost; and Luna is a fast, low-cost tier for routine tasks. All three offer max and ultra reasoning modes.
- How much does GPT-5.6 cost?
- Per million tokens: Sol is $5 input and $30 output, Terra is $2.50 and $15, and Luna is $1 and $6. Cached input bills 90 percent off on each tier ($0.50, $0.25 and $0.10). The flagship Sol matches GPT-5.5 pricing exactly.
- Is GPT-5.6 better than Claude Mythos 5?
- On the agentic-coding benchmark Terminal-Bench 2.1, OpenAI reports Sol ahead: 88.76 percent in max mode and 91.91 percent in ultra mode, against Claude Mythos 5 at 88 percent. OpenAI also reports matching Mythos 5 on cybersecurity benchmarks with roughly one-third fewer output tokens. Independent comparisons are still limited.
- Can I use GPT-5.6 right now?
- Only if you are one of about 20 government-approved partners. GPT-5.6 launched in a limited preview via the API and Codex at the direction of the US government, and OpenAI said wider public access is planned in the weeks after the June 26 launch.
Sources
- OpenAI. (2026). Previewing GPT-5.6 Sol: a next-generation model. Primary announcement; the June 26 2026 launch of Sol, Terra and Luna, tier pricing, reasoning modes, benchmarks, and limited-preview access. Verified 2026-06-27. openai.com/index/previewing-gpt-5-6-sol
- The Decoder. (2026). OpenAI’s GPT-5.6 Sol launches to rival Claude Mythos under government access rules it calls unsustainable. Secondary coverage; pricing, Cerebras speed, the unsustainable-access quote. Verified 2026-06-27. the-decoder.com
- MarkTechPost. (2026). OpenAI previews GPT-5.6 with Sol, Terra and Luna: tiered models, new reasoning modes, limited access. Secondary coverage; tier positioning, max and ultra modes, Terminal-Bench 2.1 figures. Verified 2026-06-27. marktechpost.com
- VentureBeat. (2026). OpenAI unveils GPT-5.6 Sol, Terra and Luna models, but only accessible to limited preview partners for now, per US Gov. Secondary coverage; limited-preview access to about 20 partners. Verified 2026-06-27. venturebeat.com