Gemini 3.8 Flash vs GPT-5.6 Luna
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.
| Dimension | Gemini 3.8 Flash | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 53% | 42% | +12% (Gemini 3.8 Flash leads) |
| Median task time | 4m 14s | 1m 53s | 2m 21s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.063 / task | $0.003 / task | $0.059 / task lower (GPT-5.6 Luna leads) |
Gemini 3.8 Flash: 20.4% of Google AI Pro (122.4% / 5h, 20.4% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: 1.0% of ChatGPT Plus (5.0% / 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 | Gemini 3.8 Flash | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 39% | 58% | +19% (GPT-5.6 Luna leads) |
| Median task time | 2m 39s | 2m 19s | 20s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.022 / task | not measured | - |
Gemini 3.8 Flash: 1.9% of Google AI Pro (11.7% / 5h, 1.9% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: 0.0% of ChatGPT Plus (1.0% / 5h) 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 | Gemini 3.8 Flash | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 52% | 42% | +10% (Gemini 3.8 Flash leads) |
| Median task time | 7m 7s | 3m 5s | 4m 2s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.046 / task | $0.003 / task | $0.043 / task lower (GPT-5.6 Luna leads) |
Gemini 3.8 Flash: 1.0% of Google AI Pro (6.0% / 5h, 1.0% / 1w) per good solve. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Luna: 0.1% of ChatGPT Plus (0.4% / 5h, 0.1% / 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, Gemini 3.8 Flash or GPT-5.6 Luna?
Gemini 3.8 Flash 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 2026-09-02.