GPT-5.6 Luna vs GPT-6 Sol
GPT-6 Sol leads overall, D+ to D. By suite, GPT-5.6 Luna takes real-world issues (D to D-) and GPT-6 Sol takes spec planning (C to C-). Take GPT-5.6 Luna anyway when you want the side that is ahead 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 Sol vs GPT-5.6 Luna
GPT-6 Sol leads overall, D+ to D. By suite: GPT-5.6 Luna takes real-world issues, D to D- (45% vs 38% capability); GPT-6 Sol takes spec planning, C to C- (64% vs 57% capability); GPT-6 Sol takes vibe coding, D+ to F (51% vs 25% capability). GPT-5.6 Luna used <1% of ChatGPT Pro 5x's weekly limit per pass, at most $0.012 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). GPT-6 Sol is faster on real-world issues: a median task takes 2m 44s against 3m 7s. Both finished every task on it. Reasons to pick GPT-5.6 Luna anyway: it leads on real-world issues (D to D-).
Changed since W38: GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F.
| Dimension | GPT-5.6 Luna | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 45% | 38% | +7% (GPT-5.6 Luna leads) |
| Median task time | 3m 7s | 2m 44s | 23s faster (GPT-6 Sol leads) |
| Approx. task cost | <$0.015 / task | $0.012 / task | $0.003 / task lower (GPT-6 Sol leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x 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 Luna | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 57% | 64% | +7% (GPT-6 Sol leads) |
| Median task time | 3m 25s | 2m 23s | 1m 3s 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 Luna: 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 Luna | GPT-6 Sol | Advantage |
|---|---|---|---|
| Capability | 25% | 51% | +26% (GPT-6 Sol leads) |
| Median task time | 3m 40s | 3m 4s | 36s 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 Luna: 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 Luna or GPT-6 Sol?
Both clear tier 1 of 5, but GPT-5.6 Luna scores higher on capability: 45% versus 38% 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 Luna or GPT-6 Sol?
GPT-5.6 Luna used <1% of ChatGPT Pro 5x's weekly limit per pass, at most $0.012 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).
What do GPT-5.6 Luna and GPT-6 Sol cost a month?
GPT-5.6 Luna 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).