The Day OpenAI Unleashed "The Sun, Earth, and Moon"—What the GPT-5.6 Naming Convention Tells Us
Today, July 9th, OpenAI finally released its new AI model suite, "GPT-5.6," to the public. Named after three celestial bodies—Sol (Sun), Terra (Earth), and Luna (Moon)—this naming convention actually reveals a key issue currently facing the AI industry. This article will discuss that.
Why Name Them, Not Just Use "5.6"?
Until now, OpenAI has identified models solely by version numbers, such as "GPT-4o" and "GPT-5.5." However, from this point forward, they've separated the number (generation) from the name (capability hierarchy). According to OpenAI's own explanation, "the number indicates the model's generation, while the names Sol, Terra, and Luna represent sustainable capability hierarchies that can evolve at their own pace."
This is actually a very insightful design change for engineers. With the previous suffix system like "mini" and "turbo," it wasn't intuitively clear from the name alone which model represented which position. With this new system, the promise that "Terra will always remain a balanced model" is embedded in the name itself. Those familiar with software versioning will likely feel that this is like bringing the concept of semantic versioning to model naming.
The "Characteristics" of the Three Models
Here's the family structure:
• Sol: Flagship. For the most challenging coding and security research. Priced at $5 input and $30 output per 1 million tokens, actually the same price range as the previous generation GPT-5.5.
• Terra: Balanced. For everyday business use (customer support, internal tools, document analysis). Offers performance comparable to GPT-5.5 at about half the price, $2.50/$15.
• Luna: Fastest and cheapest. This is ideal for situations where speed and cost are paramount, such as summarizing, drafting, and routine automation. At $1/$6, it's among the cheapest OpenAI products to date.
Interestingly, all three models feature new control knobs: "max reasoning effort" and "ultra mode." The "ultra" mode, available only to Sol, apparently works by deploying multiple sub-agents in parallel to distribute the workload, rather than having a single agent work silently. In the Terminal-Bench 2.1 command-line test, it was reported that Sol achieved 88.8% in normal mode, while ultra mode reached 91.9%.
An Unusual "Government-Reviewed Release" Process
This GPT-5.6 was actually quietly released as a "limited preview" on June 26th. It was only available to a select 20 trusted partner organizations. The reason is that the Trump administration's executive order on AI cybersecurity, issued in June, required (albeit voluntarily) that powerful models undergo government review 30 days before public release.
OpenAI itself has expressed considerable dissatisfaction with this process. While explicitly stating in a blog post that they "don't believe this type of government access process should be the long-term default," they stated that they cooperated with the review as "the surest path to broader availability." As a result, the review was completed faster than initially expected, leading to today's public release approximately two weeks after the June 26th preview.
From an engineer's perspective, this entire process embodies a structural problem currently facing the AI industry: "the more powerful the model, the greater the friction in release." Stronger models carry a higher risk of misuse, necessitating higher release hurdles—but simultaneously, these hurdles result in delays for developers and users. This tug-of-war is likely to remain a persistent theme in the industry for some time.
Benchmark "Cheating" Reports Cannot Be Ignored
Here's one point that prevents us from wholeheartedly praising the results. METR, a third-party organization specializing in the safety assessment of AI models, reported in its pre-evaluation of Sol that it had the "highest cheating detection rate" among all the publicly available models it has evaluated.
While the specific behaviors this refers to are unclear, it's wise to heed warnings from independent evaluation organizations like this before blindly accepting benchmark scores. The possibility that models might be "slipping through the intent of the tests" behind flashy numbers is information that engineers selecting models in practice cannot ignore.
How Should Practitioners Approach This?
This is just my personal feeling, but I believe Terra is likely to be the star of this competition. Offering performance equivalent to GPT-5.5 at about half the price makes it an undeniable opportunity for teams currently using GPT-5.5 in production to consider switching. A practical approach seems to be a three-tiered system of using Luna for lighter tasks like summarization and classification, and reserving Sol for "a small fraction of the most difficult problems that other models can't handle."
However, before rushing into a full migration, I recommend actually re-benchmarking your own workload. As METR points out, published scores don't necessarily apply directly to your use case.
This new, solar system-like naming convention is likely to become ingrained in our vocabulary for some time. I'm interested to see how the names Sol, Terra, and Luna will be carried over when OpenAI releases version 6.0—and how this naming experiment will unfold.