GPT-5.6 Terra vs GPT-6 Sol
Both grade D+ overall. GPT-6 Sol is about 2.0x cheaper per task. By suite, GPT-5.6 Terra takes real-world issues (D+ to D-) and spec planning is even at C. Both agents run the same private suite cut headless through their own tools, each on its own subscription.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
Both grade D+ overall. By suite: GPT-5.6 Terra takes real-world issues, D+ to D- (50% vs 38% capability); spec planning is even at C (68% vs 64% capability); GPT-6 Sol takes vibe coding, D+ to F (51% vs 34% capability). GPT-5.6 Terra used 2% of ChatGPT Pro 5x's weekly limit per pass, $0.024 per task at the listed price. GPT-6 Sol used 5% of ChatGPT Plus's weekly limit per pass, $0.012 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1% of ChatGPT Pro 5x's weekly limit (est, about $0.012 per task). Per task, GPT-6 Sol is about 2.0x cheaper ($0.012 vs $0.024). GPT-6 Sol is faster on real-world issues: a median task takes 2m 44s against 3m 29s. Both finished every task on it.
Changed since W38: GPT-5.6 Terra: real-world issues usage 1% to 2% of the weekly limit, spec planning C- to C, vibe coding D- to F.
| Dimension | GPT-5.6 Terra | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 50% | 38% | +12% (GPT-5.6 Terra leads) |
| Median task time | 3m 29s | 2m 44s | 45s faster (GPT-6 Sol leads) |
| Approx. task cost | $0.031 / task | $0.012 / task | $0.018 / task lower (GPT-6 Sol leads) |
GPT-5.6 Terra: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. GPT-6 Sol: 4.0% of ChatGPT Plus (37.0% / 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 Sol | Advantage |
|---|---|---|---|
| Capability | 68% | 64% | +4% (GPT-5.6 Terra leads) |
| Median task time | 5m 34s | 2m 23s | 3m 11s faster (GPT-6 Sol leads) |
| Approx. task cost | <$0.057 / task | $0.011 / task | $0.046 / task lower (GPT-6 Sol leads) |
GPT-5.6 Terra: under 1% of ChatGPT Pro 5x per run. GPT-6 Sol: 1.0% of ChatGPT Plus (8.0% / 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 Terra | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 34% | 51% | +17% (GPT-6 Sol leads) |
| Median task time | 5m 32s | 3m 4s | 2m 28s faster (GPT-6 Sol leads) |
| Approx. task cost | <$0.230 / task | $0.018 / task | $0.212 / task lower (GPT-6 Sol leads) |
GPT-5.6 Terra: under 1% of ChatGPT Pro 5x per good solve. GPT-6 Sol: 0.4% of ChatGPT Plus (2.4% / 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 2026-09-21.
Which is cheaper per task, GPT-5.6 Terra or GPT-6 Sol?
GPT-5.6 Terra used 2% of ChatGPT Pro 5x's weekly limit per pass, $0.024 per task at the listed price. GPT-6 Sol used 5% of ChatGPT Plus's weekly limit per pass, $0.012 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1% of ChatGPT Pro 5x's weekly limit (est, about $0.012 per task). Per task, GPT-6 Sol is about 2.0x cheaper ($0.012 vs $0.024).
What do GPT-5.6 Terra and GPT-6 Sol cost a month?
GPT-5.6 Terra runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-6 Sol runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).