TL;DR

OpenAI shipped the August update of GPT-5.6 Sol and Luna today. Three changes matter: Plus and Pro users get a user-facing reasoning-effort slider, Luna is now available to Free-tier users, and the older GPT-5.5 Instant is fully retired. The same-day system card classifies the new Sol and Luna as High capability in both Cybersecurity and Biological & Chemical domains — but still below the Critical threshold. (OpenAI Deployment Safety, OpenAI blog)

What actually changed

Per the official Deployment Safety Hub description:

  • Free and Go users get a new default model for everyday chats. This is the first time the Luna tier has been opened up to free users.
  • Plus and Pro users get the updated GPT-5.6 Sol. The most visible UX change is a new reasoning-effort slider that lets users decide how much compute ChatGPT spends on each response.
  • Codex and ChatGPT Work are not moving to the August model yet. They stay on the July release — OpenAI explicitly distinguishes the "August release" from the "July release" in the system card to keep enterprise environments stable.
  • The old GPT-5.5 Instant has been retired across the board, which means the Free tier's default model is indirectly upgraded.

The interesting shift: OpenAI is making "reasoning depth" a user-visible knob rather than just an API parameter (). In product terms, that is OpenAI moving the trade-off between "deep thinking" and "fast answer" from the developer to the end user.

What the safety card actually says

The August system card contains concrete numbers worth pulling out:

  1. Capability classification. Both August Sol and Luna are classified as High capability in Cybersecurity and Biological & Chemical domains, but below Critical. The same safeguards from the July release apply — no new mitigations were added.
  2. Cyber range combined pass rate. Sol (August) reaches 83.3%, Luna (August) reaches 61.5%, while the July Sol and GPT-5.5 Thinking sat at 92.3%. The August Sol is actually a slight regression in scenarios like EDR Evasion, Leaked Token, and Binary Exploitation.
  3. Internal Capture The Flag. Sol hits 97.06% — saturating the eval set. On a single capability axis (find-and-exploit), the August Sol is near the ceiling of this evaluation.
  4. CVE-Bench (real-world web vulnerabilities). Sol is above the High threshold; Luna is below. That gap inside a single model family is a clean empirical "flagship vs mid-tier" split.
  5. U18 evaluations. OpenAI introduced dedicated under-18 evaluations covering self-harm, eating disorders, age-restricted goods, and sexual content. Sol and Luna score 0.808 / 0.810 on Eating Disorders, 0.865 / 0.857 on Age-restricted goods — visible improvement over the GPT-5.5 Instant June update.

OpenAI's own framing: the updated models are better at finding and fixing vulnerabilities than at reliably executing end-to-end attacks against hardened targets. That is why access is opened up for defenders, with targeted safeguards and monitoring rather than new restrictions.

Why this update matters

OpenAI usually downplays these "small" updates, but the August release has structural shifts worth tracking:

  • Product layer. Making reasoning-effort a user-visible slider is OpenAI's first admission that "depth of thought" is a productizable commodity. Anything that builds "deep reasoning" into the brand — from Cursor to Perplexity to Manus-style agents — will now be compared against this slider.
  • Capability layer. Sol nearly saturates the internal CTF eval (97%) and clears the CVE-Bench High threshold, while Luna is below the same threshold. A single model name (GPT-5.6) now hides a real capability cliff. Developers building agents need to pick Sol or Luna explicitly based on this gap, not based on the name.
  • Safety layer. Cyber and Bio/Chem are explicitly flagged as High under OpenAI's Preparedness Framework, which is the tier where mitigations exist but continuous monitoring is required. They are not at Critical (the threshold defined as "find and develop functional zero-days in hardened systems without human intervention"), so no extra access controls have been triggered yet.
  • Enterprise layer. Codex and ChatGPT Work stayed on July. That detail is easy to miss but matters for enterprise SLAs: OpenAI is quietly splitting the to-B stability track from the to-C capability track within the same model family.

So what

The real signal of this August update is not parameter size or benchmark deltas. It is OpenAI turning — an API parameter that has been quietly important since o1 — into a UI slider that any ChatGPT user can grab.

The downstream consequences worth watching:

  1. Every consumer AI assistant will add a reasoning-effort knob in the next six months, simply because OpenAI has set the anchor. Products without one will feel "less flexible" by default.
  2. The capability gap inside one model name is now official. Sol and Luna land on opposite sides of the same High-cyber threshold. The lesson: agent builders should pick by capability tier, not by model name.
  3. Cyber capability is approaching saturation. Sol already at 97% on internal CTF and above High on CVE-Bench means the next step toward the Preparedness Framework's Critical definition is genuinely close. This is the single most important threshold to track in OpenAI's next two system cards.
  4. Enterprise vs consumer version splitting is becoming the norm. Codex/Work on July, ChatGPT on August — that pattern will spread. Integrators should expect "same model name, different behavior" to be the default assumption.

In OpenAI's vocabulary, "update" no longer means "step up one tier". It means "split the previous tier into two versions and place each on a different user surface." Once that cadence sticks, the product, safety, and business layers all get reshaped at the same time. (OpenAI Deployment Safety, OpenAI blog)