Gemini 3.8 Flash vs GPT-5.6 Terra
Gemini 3.8 Flash leads overall, C- to D. GPT-5.6 Terra is about 3.0x cheaper per task. By suite, Gemini 3.8 Flash takes real-world issues (C- to D+) and spec planning is even at D+. Take GPT-5.6 Terra 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 Terra vs Gemini 3.8 Flash
Gemini 3.8 Flash leads overall, C- to D. By suite: Gemini 3.8 Flash takes real-world issues, C- to D+ (60% vs 50% capability); spec planning is even at D+ (50% vs 53% capability); Gemini 3.8 Flash takes vibe coding, C- to F (56% vs 34% capability). Gemini 3.8 Flash used 23.7% of Google AI Pro's weekly limit per pass, $0.057 per task at the listed price. GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). Per task, GPT-5.6 Terra is about 3.0x cheaper ($0.019 vs $0.057). GPT-5.6 Terra is faster on real-world issues: a median task takes 2m 18s against 5m 21s. Both finished every task on it. Reasons to pick GPT-5.6 Terra anyway: it is cheaper per task ($0.019 vs $0.057) and it is faster on real-world issues (2m 18s vs 5m 21s median).
Changed since the previous graded week: Gemini 3.8 Flash: real-world issues F to C-, real-world issues usage 18.0% to 21.9% of the weekly limit, spec planning usage 2.0% to 1.8% of the weekly limit, vibe coding D+ to C-, vibe coding usage 1.2% to 1.1% of the weekly limit; GPT-5.6 Terra: real-world issues D to D+, real-world issues usage 9.2% to 7% of the weekly limit, spec planning C- to D+, spec planning usage 2.0% to 1% of the weekly limit, vibe coding F to D, vibe coding usage 0.5% to 0.6% of the weekly limit.
| Dimension | Gemini 3.8 Flash | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 60% | 50% | +10% (Gemini 3.8 Flash leads) |
| Median task time | 5m 21s | 2m 18s | 3m 3s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.067 / task | $0.021 / task | $0.046 / task lower (GPT-5.6 Terra leads) |
Gemini 3.8 Flash: 21.9% of Google AI Pro (131.3% / 5h, 21.9% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Terra: 7.0% of ChatGPT Plus (46.0% / 5h, 7.0% / 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 Terra | Advantage |
|---|---|---|---|
| Capability | 50% | 53% | +3% (GPT-5.6 Terra leads) |
| Median task time | 3m 0s | 2m 37s | 23s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.021 / task | $0.011 / task | $0.010 / task lower (GPT-5.6 Terra leads) |
Gemini 3.8 Flash: 1.8% of Google AI Pro (11.0% / 5h, 1.8% / 1w) per run. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Terra: 1.0% of ChatGPT Plus (10.0% / 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 Terra | Advantage |
|---|---|---|---|
| Capability | 56% | 34% | +22% (Gemini 3.8 Flash leads) |
| Median task time | 7m 51s | 2m 47s | 5m 4s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.048 / task | $0.028 / task | $0.021 / task lower (GPT-5.6 Terra leads) |
Gemini 3.8 Flash: 1.1% of Google AI Pro (6.3% / 5h, 1.1% / 1w) per good solve. Its weekly limit holds 6 of the week's 33.6 5h windows. GPT-5.6 Terra: 0.6% of ChatGPT Plus (3.0% / 5h, 0.6% / 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 Terra?
Gemini 3.8 Flash clears higher: tier 4 of 5 versus tier 2 for GPT-5.6 Terra on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-27.
Which is cheaper per task, Gemini 3.8 Flash or GPT-5.6 Terra?
Gemini 3.8 Flash used 23.7% of Google AI Pro's weekly limit per pass, $0.057 per task at the listed price. GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). Per task, GPT-5.6 Terra is about 3.0x cheaper ($0.019 vs $0.057).