GPT-5.6 Terra vs GPT-6 Sol
GPT-6 Sol was superseded by GPT-6.1 Sol. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
GPT-6 Sol leads overall, C- to D. The two cost about the same per task. By suite, GPT-6 Sol takes real-world issues (C- to D+) and spec planning (C- to D+). The data gives no reason to pick GPT-5.6 Terra over GPT-6 Sol this week.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 Sol vs GPT-5.6 Terra
GPT-6 Sol leads overall, C- to D. By suite: GPT-6 Sol takes real-world issues, C- to D+ (55% vs 50% capability); GPT-6 Sol takes spec planning, C- to D+ (60% vs 53% capability); GPT-6 Sol takes vibe coding, C- to F (61% 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 Sol used 7% of ChatGPT Plus's weekly limit per pass, $0.017 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.4% of ChatGPT Pro 5x's weekly limit (est, about $0.017 per task). Per task the two cost about the same ($0.019 vs $0.017). GPT-6 Sol is faster on real-world issues: a median task takes 1m 41s against 2m 18s. Both finished every task on it. The data gives no reason to pick GPT-5.6 Terra over GPT-6 Sol this week.
Changed since the previous graded week: 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 Sol: real-world issues D- to C-, real-world issues usage 4% to 5% of the weekly limit, spec planning C to C-, spec planning usage 1% to 2% of the weekly limit, vibe coding D+ to C-.
| Dimension | GPT-5.6 Terra | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 50% | 55% | +5% (GPT-6 Sol leads) |
| Median task time | 2m 18s | 1m 41s | 37s faster (GPT-6 Sol leads) |
| Approx. task cost | $0.021 / task | $0.015 / task | $0.006 / task lower (GPT-6 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 Sol: 5.0% of ChatGPT Plus (35.0% / 5h, 5.0% / 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 Sol | Advantage |
|---|---|---|---|
| Capability | 53% | 60% | +7% (GPT-6 Sol leads) |
| Median task time | 2m 37s | 2m 58s | 20s 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 Sol: 2.0% of ChatGPT Plus (10.0% / 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 Sol | Advantage |
|---|---|---|---|
| Capability | 34% | 61% | +27% (GPT-6 Sol leads) |
| Median task time | 2m 47s | 2m 44s | 3s faster (GPT-6 Sol leads) |
| Approx. task cost | $0.028 / task | $0.018 / task | $0.009 / task lower (GPT-6 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 Sol: 0.4% of ChatGPT Plus (1.8% / 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 Sol?
GPT-5.6 Terra clears higher: tier 2 of 5 versus tier 1 for GPT-6 Sol 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 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 Sol used 7% of ChatGPT Plus's weekly limit per pass, $0.017 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.4% of ChatGPT Pro 5x's weekly limit (est, about $0.017 per task). Per task the two cost about the same ($0.019 vs $0.017).
What do GPT-5.6 Terra and GPT-6 Sol cost a month?
GPT-5.6 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20). GPT-6 Sol runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).