Overview
GPT-5.6 is a flagship model series from OpenAI, first unveiled on **2026/6/26** and fully rolled out globally on **2026/7/10** after completing U.S. government security review. It represents OpenAI's strategic counterattack following **Anthropic's valuation surpassing OpenAI for the first time** (Anthropic $965 billion vs OpenAI $852 billion). The three tiers are: **Sol** (flagship) / **Terra** (balanced, for high-load tasks) / **Luna** (lightweight reasoning) — named after "Sun, Earth, Moon" replacing the previous Mini/Pro numeric designations.
**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 instead **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, faster Terra and Luna—have been rated as **High Risk** in both "cybersecurity" and "biological/chemical" domains. Previously, this rating was typically only applied to flagship models. OpenAI invested **over 700,000 A100-equivalent GPU hours** in automated red team testing, equipped with the strongest tiered security protections to date.
**Synchronized actions on 7/10**: OpenAI simultaneously 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. Also launched was the **Prompt Cache** mechanism, significantly reducing enterprise-level repetitive call costs.
Core capability upgrades along two lines: (1) **Terminal-Bench 2.1 achieved 91.9%, ranking first globally**—Sol surpassed all current models in long-horizon terminal tasks; (2) **Agent-level native operations**—coding/cross-platform GUI operations/tool invocation in one stop. OpenAI emphasizes that Sol "**is better at helping defenders discover and fix vulnerabilities, rather than autonomously executing a complete attack chain**."
Pricing is the highlight: **Sol is only $5/M input + $30/M output per million tokens**—**about half the price of Claude Fable 5 ($10/$50)** . OpenAI directly targets Fable 5 with "capability parity + price halving" (and Fable 5 is still under export controls). This is a rapid iteration just over two months after GPT-5.5 (released 2026/4/23), and also OpenAI's first flagship release after filing for IPO—valuation and product rhythm are deeply intertwined.
Key Features
- Sol/Terra/Luna Three-Tier Matrix: Flagship Sol (top-tier Agent) / Balanced Terra (high-load tasks) / Lightweight Luna (low-cost reasoning), covering all scenarios
- Terminal-Bench 2.1 Global First: Sol on terminal long-horizon tasks: 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 Half of Fable 5: $5/M input + $30/M output, about half of Claude Fable 5 ($10/$50), compounded by Fable 5 availability issues under regulation
- White House Regulatory "Safety Lock": Limited preview as requested by the U.S. government, 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 + biological/chemical domains—indirectly confirming their strong capabilities
- 700K GPU Hours Red Team Testing: Invested over 700,000 A100-equivalent GPU hours in automated red team testing, equipped with the strongest tiered security protections to date
- Defensive Agent Positioning: OpenAI explicitly states Sol "is better at helping defenders discover and fix vulnerabilities, rather than autonomously executing a complete attack chain"
- Developer Price on Par with GPT-5.5: Standard version price matches GPT-5.5, but with cross-generational capability upgrades, maximizing cost-effectiveness
Use Cases
- Long-horizon programming / terminal Agent tasks (Terminal-Bench 2.1 SOTA)
- Enterprise-level pilot during trusted partner preview phase (invitation list)
- Developers affected by Fable 5 export control/regulatory unavailability and cost-sensitive
- ChatGPT Pro heavy users for subsequent upgrade (Sol release cadence TBD)
- Government/critical infrastructure scenarios requiring highest security review and red team verification
- Codex / Workspace Agents pipeline upgrade
Pros
- Terminal-Bench 2.1 achieves 91.9% global first
- Sol price only half of Claude Fable 5, extremely cost-effective
- Three-tier version covers all scenarios from affordable to top-tier
- Natural hedge against Fable 5 export control risks
- 700K GPU hours red team + tiered security is the highest current security level
- OpenAI's flagship release on the eve of IPO, promising iteration cadence
Pricing
**Sol (Flagship)**: $5 / $30 per million tokens, about half of Claude Fable 5 ($10/$50). **Terra (Balanced)**: $2.50 / $15 per million tokens, 2x cheaper than GPT-5.5. **Luna (Lightweight)**: $1 / $6 per million tokens, OpenAI's cheapest flagship series model currently. **ChatGPT Subscription**: Not fully open yet, only preview for trusted partners; Plus/Pro/Team/Enterprise rollout cadence controlled by OpenAI. **Codex / Workspace Agents**: Priority access for invited partners.
Summary
GPT-5.6 is OpenAI's **strategic counterattack** during the "Anthropic valuation surpassing + Fable 5 export control window"—**Sol tops Terminal-Bench 2.1 (91.9%) + price half of Fable 5 + Sol/Terra/Luna three-tier matrix** brings it back to the lead in long-horizon programming Agents. Note: Due to U.S. government regulatory requirements, **currently only open for preview to "trusted partners"** , regular users and most developers won't have access in the short term. If you work on long-horizon programming / terminal Agents / complex multi-step tasks, GPT-5.6 Sol is one of the strongest options; if you do daily conversation/writing, GPT-5.5 Instant is still sufficient; if you are heavily tied to the Claude ecosystem (Claude Code, etc.), you can wait for Fable 5's unblocking and Anthropic's counter product.
Version History
- GPT-5.6 Sol / Terra / Luna (2026-06-26): Sol achieves 91.9% global first on Terminal-Bench 2.1; price half of Fable 5 ($5/$30); limited preview to 'trusted partners' as requested by U.S. government; full series rated high risk in both cybersecurity + biochemical domains for the first time
- GPT-5.5 Instant (2026-06 mid): Hallucination rate reduced by 52% compared to GPT-5.5, serving as ChatGPT's default conversation model
- GPT-5.5 (2026-04-23): New generation flagship, the first from-scratch retrained base model since GPT-4.5, positioned as 'a new kind of intelligence for real work'
- GPT-5 / 5.5 Instant (2025-2026 early): GPT-5 flagship debut; Instant readability update; gradual retirement of older models