GPT-5.6 Luna vs GPT-6.1 Sol
GPT-5.6 Luna was superseded by GPT-6 Luna. 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-6.1 Sol leads overall, C to D. GPT-5.6 Luna is the cheaper side per task (at most $0.012). By suite, GPT-6.1 Sol takes real-world issues (C- to D) and spec planning (C+ to C-). Take GPT-5.6 Luna 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-6.1 Sol vs GPT-5.6 Luna
GPT-6.1 Sol leads overall, C to D. By suite: GPT-6.1 Sol takes real-world issues, C- to D (57% vs 45% capability); GPT-6.1 Sol takes spec planning, C+ to C- (73% vs 57% capability); GPT-6.1 Sol takes vibe coding, C+ to F (72% 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-6.1 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-5.6 Luna costs at most $0.012 against GPT-6.1 Sol's $0.015, so GPT-5.6 Luna is the cheaper side. GPT-5.6 Luna is faster on real-world issues: a median task takes 3m 7s against 3m 26s. Both finished every task on it. Reasons to pick GPT-5.6 Luna anyway: it is cheaper per task (at most $0.012 vs $0.015) and it is faster on real-world issues (3m 7s vs 3m 26s median).
Changed since W38: GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F; GPT-6.1 Sol has one graded week under this version (W40).
| Dimension | GPT-5.6 Luna | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 45% | 57% | +12% (GPT-6.1 Sol leads) |
| Median task time | 3m 7s | 3m 26s | 19s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.015 / task | $0.012 / task | $0.003 / task lower (GPT-6.1 Sol leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. 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 Luna | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 57% | 73% | +17% (GPT-6.1 Sol leads) |
| Median task time | 3m 25s | 6m 22s | 2m 57s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.057 / task | $0.023 / task | $0.034 / task lower (GPT-6.1 Sol leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. 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 Luna | GPT-6.1 Sol | Advantage |
|---|---|---|---|
| Capability | 25% | 72% | +46% (GPT-6.1 Sol leads) |
| Median task time | 3m 40s | 4m 55s | 1m 14s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.230 / task | $0.018 / task | $0.212 / task lower (GPT-6.1 Sol leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per good solve. 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 Luna or GPT-6.1 Sol?
GPT-6.1 Sol clears higher: tier 2 of 5 versus tier 1 for GPT-5.6 Luna 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-6.1 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-6.1 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-5.6 Luna costs at most $0.012 against GPT-6.1 Sol's $0.015, so GPT-5.6 Luna is the cheaper side.
What do GPT-5.6 Luna and GPT-6.1 Sol cost a month?
GPT-5.6 Luna runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-6.1 Sol runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).