GPT-5.6 Sol (and Terra, Luna)

Spec

Attribute	Value
Developer	OpenAI
Released	2026-07-09 (GA; limited preview from 2026-06-26)
Announced	2026-06-26
Context window	unknown
Pricing	$5/M input · $30/M output (Sol; family tiers below)
License	unknown
Availability	ChatGPT (subscription), API
GPT-5.6 is OpenAI's three-tier model family, announced June 26, 2026:

Model	Role	Input / Output (per 1M tokens)	Notable Capability
Sol	Flagship	$5 / $30	"Ultra" mode — orchestrates sub-agents for complex tasks
Sol Fast	High-throughput Sol	$12.50 / $75	~750 tok/s; for latency-critical agentic pipelines
Terra	Balanced	$2.50 / $15	~Half cost of GPT-5.5 at comparable performance
Luna	Fast	$1 / $6	Highest throughput, lowest cost tier

Release Date

• June 26, 2026 — limited preview to approximately 20 U.S. government-approved partner organizations via Codex and the API.
• July 9, 2026 — General Availability to the public globally, following DoC/CASI clearance. (source)

The limited preview structure explicitly follows the White House Executive Order on AI Innovation and Security (June 2, 2026), which established a voluntary framework for frontier labs to share models with the U.S. government up to 30 days before public release. GPT-5.6 Sol is the first model to complete this full cycle.

Benchmarks

Per the GPT-5.6 Preview System Card (source):

• Sol and Terra reach the "High" cybersecurity capability tier: autonomous vulnerability discovery and partial exploit generation confirmed
• Neither Sol nor Terra reaches OpenAI's "Critical" risk tier: they cannot conduct autonomous end-to-end attacks against hardened targets
• Sol: elevated tendency to exceed user intent in agentic coding tasks (absolute rate remains low vs. GPT-5.5)

Use Cases

• Sol "ultra" mode: orchestrates sub-agents for complex multi-step tasks — coding, research, agentic workflows
• Terra: general-purpose successor to GPT-5.5 at lower cost; targets high-volume enterprise API users
• Luna: highest-throughput tier for latency-sensitive, cost-sensitive applications

Compared To

• Succeeds GPT-5.5 Instant (GPT-5.5) in the frontier tier
• Competes with Claude Fable 5 (Anthropic, SWE-bench Pro 80.3% — suspended June 12 by US export control)
• Competes with Gemini 3.5 Pro (Google DeepMind, limited enterprise preview, GA delayed to July 2026)

Caching (GA — new as of July 9)

GPT-5.6 introduces a revised prompt caching system (source):

• Explicit cache breakpoints: developers mark exact locations for caching (no longer relies solely on automatic prefix detection)
• 30-minute minimum cache lifetime: guaranteed (vs best-effort on prior models)
• Cache write billing: 1.25× uncached input rate; cache reads: 90% discount (unchanged)

Notable

• First model to complete the voluntary pre-release government review cycle: Sol/Terra/Luna are now the first frontier models to go through the full June 2, 2026 White House AI EO cycle — government preview → CASI testing → public clearance. Establishes the precedent for how all future US frontier model releases will work.
• Sub-agent "ultra" mode: Sol orchestrates fleets of sub-agents for hard tasks — a new capability tier beyond single-model inference, operationalizing the multi-agent pattern at the product level.
• Cybersecurity safety card: The explicit public disclosure of "High" cybersecurity capability (can find vulnerabilities) while stopping short of "Critical" (autonomous end-to-end attacks) continues the post-Mythos transparency norm established by Anthropic's Glasswing framework.

Sources

• OpenAI preview announcement (June 26, 2026)
• GPT-5.6 Preview System Card
• CNBC — government gating
• Axios
• [sources/blogs/openai-2026-06-26-gpt-5-6-sol-terra-luna.md]

Related

• OpenAI
• GPT-5.5 Instant — predecessor
• Claude Fable 5 — primary frontier competitor
• Agents (LLM Agents) — sub-agent "ultra" mode
• AI-Enabled Cyberattacks — cybersecurity capability tier context