Gemini 3.1 Pro vs GPT-5.6 Luna
GPT-5.6 Luna was superseded by GPT-6 Luna.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-5.6 Luna leads overall, D to F. GPT-5.6 Luna is the cheaper side per task (at most $0.012). By suite, Gemini 3.1 Pro takes real-world issues (D+ to D) and GPT-5.6 Luna takes spec planning (C- to F). Take Gemini 3.1 Pro 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-5.6 Luna vs Gemini 3.1 Pro
GPT-5.6 Luna leads overall, D to F. By suite: Gemini 3.1 Pro takes real-world issues, D+ to D (53% vs 45% capability); GPT-5.6 Luna takes spec planning, C- to F (57% vs 21% capability); vibe coding is even at F (27% vs 25% capability). Gemini 3.1 Pro used 15.9% of Google AI Pro's weekly limit per pass, $0.038 per task at the listed price. 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. Per task, GPT-5.6 Luna costs at most $0.012 against Gemini 3.1 Pro's $0.038, 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 4m 53s. Both finished every task on it. Reasons to pick Gemini 3.1 Pro anyway: it leads on real-world issues (D+ to D).
Changed since the previous graded week: Gemini 3.1 Pro: real-world issues usage 9.8% to 14.8% of the weekly limit, spec planning usage 0.9% to 1.1% of the weekly limit, vibe coding usage 1.0% to 0.7% of the weekly limit; GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F.
| Dimension | Gemini 3.1 Pro | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 53% | 45% | +8% (Gemini 3.1 Pro leads) |
| Median task time | 4m 53s | 3m 7s | 1m 46s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.045 / task | <$0.015 / task | $0.030 / task lower (GPT-5.6 Luna leads) |
Gemini 3.1 Pro: 14.8% of Google AI Pro (88.9% / 5h, 14.8% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Gemini 3.1 Pro | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 21% | 57% | +36% (GPT-5.6 Luna leads) |
| Median task time | 1m 46s | 3m 25s | 1m 40s faster (Gemini 3.1 Pro leads) |
| Approx. task cost | $0.013 / task | <$0.057 / task | $0.045 / task lower (Gemini 3.1 Pro leads) |
Gemini 3.1 Pro: 1.1% of Google AI Pro (6.5% / 5h, 1.1% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Gemini 3.1 Pro | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 27% | 25% | +2% (Gemini 3.1 Pro leads) |
| Median task time | 4m 38s | 3m 40s | 57s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.034 / task | <$0.230 / task | $0.196 / task lower (Gemini 3.1 Pro leads) |
Gemini 3.1 Pro: 0.7% of Google AI Pro (4.4% / 5h, 0.7% / 1w) per good solve. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: under 1% of ChatGPT Pro 5x 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, Gemini 3.1 Pro or GPT-5.6 Luna?
Gemini 3.1 Pro clears higher: tier 3 of 5 versus tier 1 for GPT-5.6 Luna on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, Gemini 3.1 Pro or GPT-5.6 Luna?
Gemini 3.1 Pro used 15.9% of Google AI Pro's weekly limit per pass, $0.038 per task at the listed price. 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. Per task, GPT-5.6 Luna costs at most $0.012 against Gemini 3.1 Pro's $0.038, so GPT-5.6 Luna is the cheaper side.