GPT-5.6 Luna vs GPT-6 Luna
Both grade D overall. By suite, GPT-6 Luna takes real-world issues (D+ to D) and spec planning is even at C-. Both agents run the same private suite cut headless through their own tools, each on its own subscription. The grades are re-measured every week, and each cost figure is read off the provider's own usage meter.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 Luna vs GPT-5.6 Luna
Both grade D overall. By suite: GPT-6 Luna takes real-world issues, D+ to D (50% vs 45% capability); spec planning is even at C- (57% vs 61% capability); vibe coding is even at F (25% vs 33% 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 Luna used 1% of ChatGPT Plus's weekly limit per pass, $0.002 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~0.2% of ChatGPT Pro 5x's weekly limit (est, about $0.002 per task). GPT-6 Luna is faster on real-world issues: a median task takes 1m 0s against 3m 7s. Both finished every task on it.
Changed since W38: GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F.
| Dimension | GPT-5.6 Luna | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 45% | 50% | +5% (GPT-6 Luna leads) |
| Median task time | 3m 7s | 1m 0s | 2m 7s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.015 / task | $0.003 / task | $0.012 / task lower (GPT-6 Luna leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. GPT-6 Luna: 1.0% of ChatGPT Plus (1.0% / 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 | GPT-5.6 Luna | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 57% | 61% | +4% (GPT-6 Luna leads) |
| Median task time | 3m 25s | 1m 8s | 2m 18s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.057 / task | <$0.011 / task | $0.046 / task lower (GPT-6 Luna leads) |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per run. GPT-6 Luna: under 1% of ChatGPT Plus 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 Luna | Advantage |
|---|---|---|---|
| Capability | 25% | 33% | +8% (GPT-6 Luna leads) |
| Median task time | 3m 40s | 1m 37s | 2m 3s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.230 / task | not measured | - |
GPT-5.6 Luna: under 1% of ChatGPT Pro 5x per good solve. GPT-6 Luna: under 1% of ChatGPT Plus (0.4% / 5h) 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 Luna?
GPT-6 Luna 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 Luna?
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 Luna used 1% of ChatGPT Plus's weekly limit per pass, $0.002 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~0.2% of ChatGPT Pro 5x's weekly limit (est, about $0.002 per task).
What do GPT-5.6 Luna and GPT-6 Luna cost a month?
GPT-5.6 Luna runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).