GPT-5.6 Terra vs GPT-6.1 Sol
GPT-6.1 Sol leads overall, C to D. GPT-6.1 Sol is about 1.3x cheaper per task. By suite, GPT-6.1 Sol takes real-world issues (C- to D+) and spec planning (C+ to D+). Take GPT-5.6 Terra anyway when you want the side that is faster on real-world issues.Measured
Each agent graded on the same private suites, running headless through its own tools. Advantages are oriented so a win is a win, whichever way the metric runs.
Verdict: GPT-6.1 Sol vs GPT-5.6 Terra
GPT-6.1 Sol leads overall, C to D. By suite: GPT-6.1 Sol takes real-world issues, C- to D+ (57% vs 50% capability); GPT-6.1 Sol takes spec planning, C+ to D+ (73% vs 53% capability); GPT-6.1 Sol takes vibe coding, C+ to F (72% vs 34% capability). GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). GPT-6.1 Sol used 6% of ChatGPT Plus's weekly limit per pass, $0.015 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.2% of ChatGPT Pro 5x's weekly limit (est, about $0.015 per task). Per task, GPT-6.1 Sol is about 1.3x cheaper ($0.015 vs $0.019). GPT-5.6 Terra is faster on real-world issues: a median task takes 2m 18s against 3m 26s. Both finished every task on it. Reasons to pick GPT-5.6 Terra anyway: it is faster on real-world issues (2m 18s vs 3m 26s median).
Changed since W36: GPT-5.6 Terra: real-world issues D to D+, real-world issues usage 9.2% to 7% of the weekly limit, spec planning C- to D+, spec planning usage 2.0% to 1% of the weekly limit, vibe coding F to D, vibe coding usage 0.5% to 0.6% of the weekly limit; GPT-6.1 Sol has one graded week under this version (W40).
| Dimension | GPT-5.6 Terra | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 50% | 57% | +7% (GPT-6.1 Sol leads) |
| Median task time | 2m 18s | 3m 26s | 1m 8s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.021 / task | $0.012 / task | $0.009 / task lower (GPT-6.1 Sol leads) |
GPT-5.6 Terra: 7.0% of ChatGPT Plus (46.0% / 5h, 7.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. GPT-6.1 Sol: 4.0% of ChatGPT Plus (28.0% / 5h, 4.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Terra | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 53% | 73% | +20% (GPT-6.1 Sol leads) |
| Median task time | 2m 37s | 6m 22s | 3m 45s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.011 / task | $0.023 / task | $0.011 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Terra: 1.0% of ChatGPT Plus (10.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. GPT-6.1 Sol: 2.0% of ChatGPT Plus (9.0% / 5h, 2.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Terra | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 34% | 72% | +37% (GPT-6.1 Sol leads) |
| Median task time | 2m 47s | 4m 55s | 2m 7s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.028 / task | $0.018 / task | $0.009 / task lower (GPT-6.1 Sol leads) |
GPT-5.6 Terra: 0.6% of ChatGPT Plus (3.0% / 5h, 0.6% / 1w) per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. GPT-6.1 Sol: 0.4% of ChatGPT Plus (2.2% / 5h, 0.4% / 1w) per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. Each figure is a share of that agent's own plan, so there is no delta to draw.
Grades and deltas are comparable only within a suite version. See methodology.
Frequently asked questions
Which is better for coding, GPT-5.6 Terra or GPT-6.1 Sol?
Both clear tier 2 of 5, but GPT-6.1 Sol scores higher on capability: 57% versus 50% on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, GPT-5.6 Terra or GPT-6.1 Sol?
GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). GPT-6.1 Sol used 6% of ChatGPT Plus's weekly limit per pass, $0.015 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.2% of ChatGPT Pro 5x's weekly limit (est, about $0.015 per task). Per task, GPT-6.1 Sol is about 1.3x cheaper ($0.015 vs $0.019).
What do GPT-5.6 Terra and GPT-6.1 Sol cost a month?
GPT-5.6 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20). GPT-6.1 Sol runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).