GPT-6 Luna vs Composer 2.5
Both grade D overall. By suite, real-world issues is even at C- and GPT-6 Luna takes spec planning (D+ to D). 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: Composer 2.5 vs GPT-6 Luna
Both grade D overall. By suite: real-world issues is even at C- (57% vs 57% capability); GPT-6 Luna takes spec planning, D+ to D (55% vs 48% capability); vibe coding is even at F (31% vs 23% capability). GPT-6 Luna used <1% of ChatGPT Plus's weekly limit per pass; at the ~$100 tier the board defaults to that is an estimated ~<0.2% of ChatGPT Pro 5x's weekly limit (est). Composer 2.5 used 2.0% of Cursor Pro's monthly limit per pass, $0.021 per task at the listed price. GPT-6 Luna is faster on real-world issues: a median task takes 1m 4s against 1m 34s. Both finished every task on it.
Changed since W39: GPT-6 Luna: real-world issues D+ to C-, spec planning C- to D+; Composer 2.5: real-world issues D+ to C-.
| Dimension | GPT-6 Luna | Composer 2.5 | Advantage |
|---|---|---|---|
| Capability | 57% | 57% | Even |
| Median task time | 1m 4s | 1m 34s | 30s faster (GPT-6 Luna leads) |
| Approx. task cost | not measured | $0.021 / task | - |
GPT-6 Luna: under 1% of ChatGPT Plus (2.0% / 5h) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Composer 2.5: 1.6% of Cursor Pro (1.6% / 1m) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-6 Luna | Composer 2.5 | Advantage |
|---|---|---|---|
| Capability | 55% | 48% | +7% (GPT-6 Luna leads) |
| Median task time | 1m 20s | 1m 8s | 13s faster (Composer 2.5 leads) |
| Approx. task cost | <$0.011 / task | $0.022 / task | $0.011 / task lower (GPT-6 Luna leads) |
GPT-6 Luna: under 1% of ChatGPT Plus per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Composer 2.5: 0.4% of Cursor Pro (0.4% / 1m) per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | GPT-6 Luna | Composer 2.5 | Advantage |
|---|---|---|---|
| Capability | 31% | 23% | +8% (GPT-6 Luna leads) |
| Median task time | 1m 24s | 1m 37s | 13s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.046 / task | $0.022 / task | $0.024 / task lower (Composer 2.5 leads) |
GPT-6 Luna: under 1% of ChatGPT Plus per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. Composer 2.5: 0.1% of Cursor Pro (0.1% / 1m) 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-6 Luna or Composer 2.5?
GPT-6 Luna clears higher: tier 2 of 5 versus tier 1 for Composer 2.5 on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-27.
Which is cheaper per task, GPT-6 Luna or Composer 2.5?
GPT-6 Luna used <1% of ChatGPT Plus's weekly limit per pass; at the ~$100 tier the board defaults to that is an estimated ~<0.2% of ChatGPT Pro 5x's weekly limit (est). Composer 2.5 used 2.0% of Cursor Pro's monthly limit per pass, $0.021 per task at the listed price.
What do GPT-6 Luna and Composer 2.5 cost a month?
GPT-6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20). Composer 2.5 runs on Cursor Pro at $20/month (public price as of 2026-07-20).