GPT-5.6 Luna vs GPT-6 Astra
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 | GPT-5.6 Luna | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 42% | 57% | +15% (GPT-6 Astra leads) |
| Median task time | 1m 53s | 1m 56s | 3s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.003 / task | $0.046 / task | $0.043 / task lower (GPT-5.6 Luna leads) |
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. GPT-6 Astra: 3.0% of ChatGPT Pro $100 (3.0% / 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-6 Astra | Advantage |
|---|---|---|---|
| Capability | 58% | 74% | +16% (GPT-6 Astra leads) |
| Median task time | 2m 19s | 4m 0s | 1m 41s faster (GPT-5.6 Luna leads) |
| Approx. task cost | not measured | $0.057 / task | - |
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. GPT-6 Astra: 1.0% of ChatGPT Pro $100 (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-6 Astra | Advantage |
|---|---|---|---|
| Capability | 42% | 61% | +19% (GPT-6 Astra leads) |
| Median task time | 3m 5s | 2m 54s | 11s faster (GPT-6 Astra leads) |
| Approx. task cost | $0.003 / task | $0.046 / task | $0.043 / task lower (GPT-5.6 Luna leads) |
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. GPT-6 Astra: 0.2% of ChatGPT Pro $100 (0.2% / 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-6 Astra?
GPT-6 Astra 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 2026-09-01.
How much do GPT-5.6 Luna and GPT-6 Astra cost?
GPT-5.6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20). GPT-6 Astra runs on ChatGPT Pro $100 at $100/month (public price as of 2026-09-05).