Overview
GPT-5.6 is OpenAI's flagship model series that **debuted on 2026/6/26** and **was globally rolled out on 2026/7/10 after completing U.S. government security review**. It is OpenAI's strategic counterattack after **Anthropic's valuation surpassed OpenAI for the first time** (Anthropic 965 billion vs OpenAI 852 billion). Three tiers: **Sol** (flagship) / **Terra** (balanced, for high-load tasks) / **Luna** (lightweight inference) — named after "Sun, Earth, Moon" replacing the previous Mini/Pro numeric naming.
**This release has an unprecedented background**: Under U.S. government regulatory requirements, OpenAI did not immediately fully open GPT-5.6 on 6/26, but **first provided preview access to a small number of "trusted partners"**. After about two weeks of tiered security review and red team testing, it was opened to all users on 7/10. This is the first time in OpenAI's history that all models in a family — including the smaller and faster Terra and Luna — have been marked as **High Risk** in both "cybersecurity" and "bio/chemical" domains. Previously, this rating typically appeared only on flagship models. OpenAI invested **over 700,000 A100-equivalent GPU hours** in automated red team testing, equipped with the strongest layered security protection to date.
**7/10 simultaneous actions**: OpenAI also released **ChatGPT Work** (a native agent tool for enterprise collaboration) and integrated the **standalone Codex coding tool into the ChatGPT desktop client**, covering web / mobile / Windows / macOS across all terminals — forming a Chat / Work / Codex three-in-one entry point, directly competing with the Claude Code + Claude Enterprise combination. During the same period, **Prompt Cache** was launched, significantly reducing enterprise-level repeated call costs.
Core capability upgrades on two fronts: (1) **Terminal-Bench 2.1 scored 91.9%, ranking first globally** — Sol surpasses all current models in long-horizon terminal tasks; (2) **Agent-level native operations** — coding / cross-platform GUI operations / tool calling in one stop. OpenAI emphasized that Sol is "**better at helping defenders discover and fix vulnerabilities rather than autonomously executing full attack chains**".
**7/30 latest update**: OpenAI announced **significant price cuts for Terra and Luna**. Terra dropped from $2.50/$15 to **$1.25/$7.50**, and Luna from $1/$6 to **$0.50/$3**, a 50% reduction, further consolidating cost-performance advantages. Sol's price remains unchanged. This price cut is seen as continued pressure on Claude Fable 5 and may pave the way for larger-scale enterprise adoption.
Key Features
- Sol/Terra/Luna three-tier matrix: Flagship Sol (top-tier Agent) / balanced Terra (high-load tasks) / lightweight Luna (low-cost inference), covering all scenarios
- Terminal-Bench 2.1 global first: Sol on terminal long-horizon task benchmark: standard mode 88.8% (surpassing Claude Mythos 5's 88.0%), Ultra mode (sub-agent acceleration) reaches 91.9%, setting a new record among all current models
- Sol price only half of Fable 5: $5/M input + $30/M output, about half of Claude Fable 5 ($10/$50), compounded by Fable 5's regulatory availability issues
- White House regulatory 'safety lock': Limited preview at U.S. government request, only open to 'trusted partners', the strongest compliance layer in OpenAI's history
- Full series marked High Risk: First time even Terra/Luna are rated high risk in both cybersecurity and bio/chemical domains — indirectly confirming their capability strength
- 700K GPU hours red team testing: Invested over 700,000 A100-equivalent GPU hours in automated red teaming, equipped with the strongest layered security protection to date
- Defensive Agent positioning: OpenAI explicitly stated that Sol is 'better at helping defenders discover and fix vulnerabilities rather than autonomously executing full attack chains'
- Developer price on par with GPT-5.5: Standard version price matches GPT-5.5, but with cross-generational capability upgrades, maximizing cost-performance
Use Cases
- Long-horizon coding / terminal Agent tasks (Terminal-Bench 2.1 SOTA)
- Enterprise-level pilots during trusted partner preview phase (invitation list)
- Developers who cannot use Claude Fable 5 due to export controls / regulations and are cost-sensitive
- ChatGPT Pro heavy users for future upgrades (Sol availability timeline pending)
- Government / critical infrastructure scenarios requiring highest security review and red team validation
- Codex / Workspace Agents chain upgrades
Pros
- Terminal-Bench 2.1 scored 91.9%, global first
- Sol price only half of Claude Fable 5, extremely cost-effective
- Three tiers cover all scenarios from budget to top-tier
- Natural hedge against Fable 5 export control risks
- 700K GPU hours red team + layered security is the current highest security standard
- Flagship release on the eve of IPO, promising iteration pace
Pricing
**Sol (flagship)**: $5 / $30 per million tokens, about half of Claude Fable 5 ($10/$50). **Terra (balanced)**: $1.25 / $7.50 per million tokens (50% price cut on 7/30, originally $2.50/$15), 4x cheaper than GPT-5.5. **Luna (lightweight)**: $0.50 / $3 per million tokens (50% price cut on 7/30, originally $1/$6), OpenAI's cheapest flagship series model currently. **ChatGPT subscription**: Not fully open yet, only preview for trusted partners; Plus / Pro / Team / Enterprise availability timeline controlled by OpenAI. **Codex / Workspace Agents**: Priority access for invited partners.
Summary
The GPT-5.6 series is a flagship model released by OpenAI in June 2026 and fully rolled out in July after completing a security review. It includes three tiers—Sol, Terra, and Luna—targeting top-tier performance, high-load balanced tasks, and lightweight scenarios, respectively. The series achieved a global highest score of 91.9% in Terminal-Bench 2.1, with the Sol version offering more competitive pricing at equivalent capability, while also providing a relatively high level of security assurance through 700,000 GPU-hours of red team testing and a layered security mechanism. It suits developers and enterprises with clear requirements for performance, cost, or security compliance, and the three-tier configuration allows for on-demand selection. As a strategic product ahead of OpenAI's IPO, its subsequent iterations are worth watching.
Version History
- 官网已发布GPT-5.6 Sol（下一代模型）预览页面，评测仅提及GPT-5.6-Cyber网络安全专用模型，未覆盖So: The official website has released the preview page for GPT-5.6 Sol (next-generation model). The evaluation only mentions the GPT-5.6-Cyber cybersecurity-specific model and does not cover the new updates of the Sol version.
- OpenAI 推出 GPT-5.6-Cyber，面向授权漏洞研究的网络安全专用模型 (2026-08-10): OpenAI releases cybersecurity-specific model GPT-5.6-Cyber, available through Daybreak Red for authorized vulnerability research, vulnerability validation, and security testing. The model is designed to address the challenge of narrowing cyber defense windows, providing security researchers with a specialized tool.
- GPT-5.6 Sol更新+Luna免费默认 (2026-08-06): Sol准确性和一致性提升（错误率降~68%），Luna成免费默认模型并提供无限文本聊天和Think按钮；Luna输入降价80%、Terra降20%、Sol API加速；ChatGPT Work和Codex教育插件上线
- GPT-5.6 如何推进性价比前沿 (2026-07-30): OpenAI has introduced lower pricing for the Luna and Terra versions of GPT-5.6, using more efficient models to help enterprises deploy AI workflows at scale.