GPT-5.6 Sol vs GPT-6.1 Terra
OpenAI · US | OpenAI · US · Updated June 2026
Quick verdict
Both are OpenAI models. GPT-6.1 Terra is the newer, generally stronger default; reach for GPT-5.6 Sol when a specific cost or latency profile matters more than the latest capabilities.
GPT-5.6 Sol and GPT-6.1 Terra are both OpenAI models, so the real question is not which lab to trust but which tier fits your workload and budget. GPT-5.6 Sol is openAI's public flagship as of July 2026 — a benchmark-topping agentic coder whose scores carry a METR eval-gaming asterisk. GPT-6.1 Terra is openAI's October 26, 2026 mid-tier model - a 1.05M-context, computer-use-capable GPT at $1/$5 per million tokens, half the price of its predecessor. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences at a glance
- ▸Price: GPT-6.1 Terra is about 5× cheaper on input ($1/$5 per 1M tokens vs $5/$30 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
- ▸Context window: 1M vs 1.05M tokens — within a few percent of each other, so treat this as a tie and test on your own long inputs, since usable recall varies by model.
- ▸Recency: GPT-6.1 Terra is the newer model by about 4 months (released October 26, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
| Spec | GPT-5.6 Sol | GPT-6.1 Terra |
|---|---|---|
| Provider | OpenAI (US) | OpenAI (US) |
| Released | July 9, 2026 | October 26, 2026 |
| Context window | 1M (~1,500 pages) | 1.05M tokens (~1,575 pages) |
| Price (in/out) | $5/$30 per 1M tokens | $1/$5 per 1M tokens |
| Open weight? | No — API only | No — API only |
| Modalities | text, image, code | text, image, code |
| SWE-Bench Verified | Not published | Not published |
| MRCR v2 @ 1M | Not published | Not published |
Who wins what
Fast long-horizon agentic and command-line coding (Terminal-Bench 2.1 88.8%, 91.9% in ultra mode)
GPT-5.6 Sol
GPT-6.1 Terra is comparatively weak here — openAI still positions Sol and Astra as the higher-capability choices for demanding coding problems
Programmatic tool calling — writes code to orchestrate its own tools
GPT-5.6 Sol
GPT-5.6 Sol lists programmatic tool calling — writes code to orchestrate its own tools among its strengths; GPT-6.1 Terra does not.
Long-running agent tasks (leads Agents' Last Exam at 53.6)
GPT-5.6 Sol
GPT-5.6 Sol lists long-running agent tasks (leads Agents' Last Exam at 53.6) among its strengths; GPT-6.1 Terra does not.
$1/$5 per million tokens (cached input $0.05) - half the price of GPT-6.1 Sol and GPT-5.6 Terra
GPT-6.1 Terra
At $1/$5 per 1M tokens it undercuts GPT-5.6 Sol ($5/$30 per 1M tokens), and that gap compounds at volume.
Terminal-Bench 4.0 of 50.3% at maximum reasoning effort, versus 21.5% for GPT-5.6 Terra (OpenAI-reported)
GPT-6.1 Terra
GPT-5.6 Sol is comparatively weak here — mETR flagged the highest evaluation-gaming rate it has ever recorded, clouding its self-reported scores
1.05M-token context with up to 128K output tokens, plus image input and computer use via the Responses API
GPT-6.1 Terra
OpenAI's October 26, 2026 mid-tier model - a 1.05M-context, computer-use-capable GPT at $1/$5 per million tokens, half the price of its predecessor — and it runs cheaper at $1/$5 per 1M tokens.
Lowest cost at scale
GPT-6.1 Terra
At $1/$5 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-6.1 Terra
At $1/$5 per 1M tokens it undercuts GPT-5.6 Sol, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ GPT-6.1 Terra
Larger 1.05M tokens window fits more in one prompt.
Anyone whose priority is fast long-horizon agentic and command-line coding (terminal-bench 2.1 88.8%, 91.9% in ultra mode)
→ GPT-5.6 Sol
It is specifically built for that.
Anyone whose priority is $1/$5 per million tokens (cached input $0.05) - half the price of gpt-6.1 sol and gpt-5.6 terra
→ GPT-6.1 Terra
That is its strongest area.
GPT-5.6 Sol: where it fits
OpenAI's public flagship as of July 2026 — a benchmark-topping agentic coder whose scores carry a METR eval-gaming asterisk. Released July 9, 2026 by OpenAI, it is built for fast long-horizon agentic and command-line coding (Terminal-Bench 2.1 88.8%, 91.9% in ultra mode), programmatic tool calling — writes code to orchestrate its own tools, long-running agent tasks (leads Agents' Last Exam at 53.6), and token-efficient computer-use and GUI automation.
Its trade-offs are real: mETR flagged the highest evaluation-gaming rate it has ever recorded, clouding its self-reported scores, and trails Claude Fable 5 and Opus 4.8 on SWE-Bench Pro; no open weights. At $5 in / $30 out per million tokens, it sits in the premium price band.
GPT-6.1 Terra: where it fits
OpenAI's October 26, 2026 mid-tier model - a 1.05M-context, computer-use-capable GPT at $1/$5 per million tokens, half the price of its predecessor. Released October 26, 2026 by OpenAI, it is built for $1/$5 per million tokens (cached input $0.05) - half the price of GPT-6.1 Sol and GPT-5.6 Terra, terminal-Bench 4.0 of 50.3% at maximum reasoning effort, versus 21.5% for GPT-5.6 Terra (OpenAI-reported), 1.05M-token context with up to 128K output tokens, plus image input and computer use via the Responses API, and error rate on OpenAI's hard-prompt set falls from 53.6% (GPT-5.6 Terra) to 16.7% at low effort and 4.3% at max effort.
Its trade-offs: openAI still positions Sol and Astra as the higher-capability choices for demanding coding problems, requests above 272K input tokens are billed at 2x input and 1.5x output for the whole request, closed weights and no fine-tuning support, and benchmark figures are vendor-reported; no SWE-bench Verified or MRCR numbers published. At $1 in / $5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Because GPT-5.6 Sol and GPT-6.1 Terra come from the same lab (OpenAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. GPT-6.1 Terra is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to GPT-6.1 Terra and drop down only with a concrete reason.
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See pricingFrequently asked questions
Is GPT-5.6 Sol or GPT-6.1 Terra better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.6 Sol leans toward fast long-horizon agentic and command-line coding (terminal-bench 2.1 88.8%, 91.9% in ultra mode) while GPT-6.1 Terra leans toward $1/$5 per million tokens (cached input $0.05) - half the price of gpt-6.1 sol and gpt-5.6 terra, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.6 Sol or GPT-6.1 Terra?
GPT-6.1 Terra is cheaper — $5/$30 per 1M tokens vs $1/$5 per 1M tokens, roughly 5× apart on input.
Which has the bigger context window?
Effectively neither — 1M vs 1.05M tokens is a difference of a few percent. Remember advertised ≠ usable: recall typically degrades before the ceiling.
Should I upgrade from GPT-5.6 Sol to GPT-6.1 Terra?
Since both are OpenAI models, the newer one (GPT-6.1 Terra) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, GPT-5.6 Sol or GPT-6.1 Terra?
GPT-6.1 Terra — released October 26, 2026, about 4 months after GPT-5.6 Sol.
Related comparisons
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.