Short answer (July 2026): OpenAI released the GPT-5.6 family on July 9, 2026, with three tiers. GPT-5.6 Sol ($5/$30 per 1M tokens) is the flagship for complex coding and agentic work; GPT-5.6 Terra ($2.50/$15) is the balanced default for everyday tasks; GPT-5.6 Luna ($1/$6) is the fastest and cheapest for high-volume workloads. Pick by workload, not by hype.
- Best for complex coding & agents: GPT-5.6 Sol
- Best everyday default: GPT-5.6 Terra
- Best value at high volume: GPT-5.6 Luna
GPT-5.6 at a glance
| Model | Best for | API price (per 1M in/out) | Context window | Watch-out |
|---|---|---|---|---|
| GPT-5.6 Sol | Agentic coding, deep reasoning | $5 / $30 | 1.05M tokens, 128K output | Trails Claude on SWE-bench Pro |
| GPT-5.6 Terra | Everyday chat & work tasks | $2.50 / $15 | Not yet published | Only tier free users get |
| GPT-5.6 Luna | High-volume, latency-sensitive apps | $1 / $6 | Not yet published | Weakest at long multi-step reasoning |
How we compared
We compared the three GPT-5.6 tiers on published API pricing, context window, benchmark results (Terminal-Bench 2.1, SWE-bench Pro), and ChatGPT plan availability. All figures are current as of July 10, 2026, one day after launch, and sourced from OpenAI's announcement and independent benchmark coverage linked at the end.
GPT-5.6 Sol
Sol is the flagship. It ships with a 1,050,000-token context window and 128K max output, and OpenAI positions it as state-of-the-art across coding, knowledge work, cybersecurity, and science — at a notably lower price than previous frontier tiers ($5/$30 per 1M tokens).
On agentic benchmarks it delivers: 88.8% on Terminal-Bench 2.1 (91.9% in Ultra mode), ahead of Claude Mythos 5 (88.0%) and Claude Fable 5 (83.4%). The pitch is performance per dollar: frontier results with fewer tokens spent.
The honest caveat: on SWE-bench Pro, which measures multi-file software engineering, early reporting puts Sol at 64.6% versus 80.3% for Claude Mythos 5. If repo-scale refactoring is your daily driver, test both before switching.
GPT-5.6 Terra
Terra is the balanced middle tier at half Sol's price ($2.50/$15 per 1M tokens). It's the model most people will actually touch: it's the only GPT-5.6 tier available to Free and Go users in ChatGPT Work and Codex.
Terra is the sensible default for everyday work — drafting, summarizing, routine coding — where flagship reasoning is overkill. Its weakness is simply that it isn't Sol: for long agentic chains or hard debugging, the flagship is worth the premium.
GPT-5.6 Luna
Luna is the speed-and-cost tier at $1/$6 per 1M tokens — 5x cheaper than Sol on input. If you're running classification, extraction, chat at scale, or anything latency-sensitive, Luna is the pick.
The trade-off is depth: Luna is the weakest of the three at long multi-step reasoning, so keep it on well-scoped tasks and route the hard ones up-tier.
Ultra mode and ChatGPT Work
Two launch extras matter for the comparison. Ultra mode coordinates multiple agents across parallel workstreams to finish complex tasks faster — it's what lifts Sol from 88.8% to 91.9% on Terminal-Bench 2.1. It's available to Pro and Enterprise plans in the new ChatGPT Work agent (web, mobile, desktop), and to Plus and above in Codex.
Also on the calendar: GPT-5.4 retires on July 23, 2026, while GPT-5.5 models stay available. If you're still pinned to 5.4 in production, this is your migration window.
Which GPT-5.6 model should you choose?
- Agentic coding, terminal work, long autonomous tasks → Sol (Ultra mode if your plan has it)
- Everyday assistant work, drafts, summaries, routine code → Terra
- High-volume API calls, classification, chatbots at scale → Luna
- On the Free or Go plan → Terra is your only GPT-5.6 option
- Repo-scale multi-file refactoring → benchmark Sol against Claude first; SWE-bench Pro says it's not a lock
Frequently asked questions
What is the difference between GPT-5.6 Sol, Terra, and Luna?
Sol is OpenAI's flagship GPT-5.6 model for maximum capability, Terra is the balanced mid-tier for everyday work, and Luna is the fastest and most cost-efficient tier. They share the GPT-5.6 generation but differ in depth of reasoning, speed, and price.
How much does GPT-5.6 cost?
Via the API, GPT-5.6 Sol costs $5 input / $30 output per 1M tokens, Terra costs $2.50/$15, and Luna costs $1/$6. In ChatGPT, Free and Go users get Terra, while Plus, Pro, Business, and Enterprise plans can choose all three tiers.
Is GPT-5.6 Sol better than Claude for coding?
It depends on the task. Sol leads on Terminal-Bench 2.1 (88.8%, or 91.9% in Ultra mode, versus 88.0% for Claude Mythos 5), but trails on SWE-bench Pro multi-file engineering (64.6% versus 80.3%). Agentic terminal work favors Sol; large multi-file refactors still favor Claude.
What is GPT-5.6 Ultra mode?
Ultra is OpenAI's highest-capability setting: it coordinates multiple agents across parallel workstreams to complete complex tasks faster. It's available in ChatGPT Work for Pro and Enterprise plans, and in Codex for Plus plans and above.
What happens to GPT-5.4 and GPT-5.5?
OpenAI retires GPT-5.4 on July 23, 2026, two weeks after the GPT-5.6 launch. GPT-5.5 models remain available for now.
Bottom line
GPT-5.6 isn't one model, it's a routing decision: Sol for hard problems, Terra for daily work, Luna for volume. The real story is price — frontier-class output at $5/$30 resets the performance-per-dollar bar, even if Claude keeps the multi-file engineering crown for now.
Which tier are you moving to — and is anyone actually leaving GPT-5.5? Tell us in the comments.
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