GPT-5.6 Sol vs GPT-5.6 Terra
GPT-5.6 Sol was superseded by GPT-6.1 Sol.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-5.6 Sol leads overall, C- to D. GPT-5.6 Terra is about 1.9x cheaper per task. By suite, GPT-5.6 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 cheaper per task and 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-5.6 Terra vs GPT-5.6 Sol
GPT-5.6 Sol leads overall, C- to D. By suite: GPT-5.6 Sol takes real-world issues, C- to D+ (60% vs 50% capability); GPT-5.6 Sol takes spec planning, C+ to D+ (68% vs 53% capability); GPT-5.6 Sol takes vibe coding, D+ to F (51% vs 34% capability). GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. 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). Per task, GPT-5.6 Terra is about 1.9x cheaper ($0.019 vs $0.036). GPT-5.6 Terra is faster on real-world issues: a median task takes 2m 18s against 3m 13s. Both finished every task on it. Reasons to pick GPT-5.6 Terra anyway: it is cheaper per task ($0.019 vs $0.036) and it is faster on real-world issues (2m 18s vs 3m 13s median).
Changed since the previous graded week: GPT-5.6 Sol: vibe coding C- to D+; 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.
| Dimension | GPT-5.6 Sol | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 60% | 50% | +10% (GPT-5.6 Sol leads) |
| Median task time | 3m 13s | 2m 18s | 55s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.031 / task | $0.021 / task | $0.009 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Sol: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. 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. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Sol | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 68% | 53% | +15% (GPT-5.6 Sol leads) |
| Median task time | 6m 0s | 2m 37s | 3m 22s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.057 / task | $0.011 / task | $0.046 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Sol: 1.0% of ChatGPT Pro 5x (1.0% / 1w) per run. 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. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Sol | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 51% | 34% | +17% (GPT-5.6 Sol leads) |
| Median task time | 3m 56s | 2m 47s | 1m 9s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.092 / task | $0.028 / task | $0.064 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Sol: 0.4% of ChatGPT Pro 5x (0.4% / 1w) per good solve. 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. 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 Sol or GPT-5.6 Terra?
GPT-5.6 Sol clears higher: tier 4 of 5 versus tier 2 for GPT-5.6 Terra on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-21.
Which is cheaper per task, GPT-5.6 Sol or GPT-5.6 Terra?
GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. 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). Per task, GPT-5.6 Terra is about 1.9x cheaper ($0.019 vs $0.036).
What do GPT-5.6 Sol and GPT-5.6 Terra cost a month?
GPT-5.6 Sol runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-5.6 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).