GPT-5.6 Luna vs GPT-5.6 Sol
GPT-5.6 Luna was superseded by GPT-6 Luna. GPT-5.6 Sol was superseded by GPT-6.1 Sol.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 Luna is the cheaper side per task (at most $0.012). By suite, GPT-5.6 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-5.6 Sol vs GPT-5.6 Luna
GPT-5.6 Sol leads overall, C- to D. By suite: GPT-5.6 Sol takes real-world issues, C- to D (60% vs 45% capability); GPT-5.6 Sol takes spec planning, C+ to C- (68% vs 57% capability); GPT-5.6 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-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Per task, GPT-5.6 Luna costs at most $0.012 against GPT-5.6 Sol's $0.036, 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 13s. Both finished every task on it. Reasons to pick GPT-5.6 Luna anyway: it is cheaper per task (at most $0.012 vs $0.036) and it is faster on real-world issues (3m 7s vs 3m 13s median).
Changed since W38: GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F; GPT-5.6 Sol: vibe coding C- to D+.
| Dimension | GPT-5.6 Luna | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 45% | 60% | +15% (GPT-5.6 Sol leads) |
| Median task time | 3m 7s | 3m 13s | 6s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.015 / task | $0.031 / task | $0.015 / task lower (GPT-5.6 Luna leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. GPT-5.6 Sol: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Luna | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 57% | 68% | +12% (GPT-5.6 Sol leads) |
| Median task time | 3m 25s | 6m 0s | 2m 34s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.057 / task | $0.057 / task | Even |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. GPT-5.6 Sol: 1.0% of ChatGPT Pro 5x (1.0% / 1w) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-5.6 Luna | GPT-5.6 Sol | Advantage |
|---|---|---|---|
| Capability | 25% | 51% | +26% (GPT-5.6 Sol leads) |
| Median task time | 3m 40s | 3m 56s | 16s faster (GPT-5.6 Luna leads) |
| Approx. task cost | <$0.230 / task | $0.092 / task | $0.138 / task lower (GPT-5.6 Sol leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per good solve. GPT-5.6 Sol: 0.4% of ChatGPT Pro 5x (0.4% / 1w) per good solve. 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-5.6 Sol?
GPT-5.6 Sol clears higher: tier 4 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-5.6 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-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Per task, GPT-5.6 Luna costs at most $0.012 against GPT-5.6 Sol's $0.036, so GPT-5.6 Luna is the cheaper side.
What do GPT-5.6 Luna and GPT-5.6 Sol cost a month?
GPT-5.6 Luna runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-5.6 Sol runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05).