Claude Sonnet 5 vs GPT-6 Luna
Both grade D overall. GPT-6 Luna is about 5.0x cheaper per task. By suite, real-world issues is even at D+ and GPT-6 Luna takes spec planning (C- to D). Both agents run the same private suite cut headless through their own tools, each on its own subscription.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 Claude Sonnet 5
Both grade D overall. By suite: real-world issues is even at D+ (50% vs 50% capability); GPT-6 Luna takes spec planning, C- to D (61% vs 42% capability); Claude Sonnet 5 takes vibe coding, D+ to F (51% vs 33% capability). Claude Sonnet 5 used 1% of Claude Max 5x's weekly limit per pass, $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). Per task, GPT-6 Luna is about 5.0x cheaper ($0.002 vs $0.012). GPT-6 Luna is faster on real-world issues: a median task takes 1m 0s against 2m 55s. Both finished every task on it.
Changed since W32: Claude Sonnet 5: real-world issues F to D+.
| Dimension | Claude Sonnet 5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 50% | 50% | Even |
| Median task time | 2m 55s | 1m 0s | 1m 55s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.015 / task | $0.003 / task | $0.012 / task lower (GPT-6 Luna leads) |
Claude Sonnet 5: 16.0% of Claude Max 5x (16.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 14.6 of the week's 33.6 5h windows. 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 | Claude Sonnet 5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 42% | 61% | +19% (GPT-6 Luna leads) |
| Median task time | 4m 20s | 1m 8s | 3m 12s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.010 / task | <$0.011 / task | $0.001 / task lower (Claude Sonnet 5 leads) |
Claude Sonnet 5: 6.0% of Claude Max 5x (6.0% / 5h) per run. Its weekly limit holds about 14.6 of the week's 33.6 5h windows. 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 | Claude Sonnet 5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 51% | 33% | +18% (Claude Sonnet 5 leads) |
| Median task time | 4m 26s | 1m 37s | 2m 49s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.016 / task | not measured | - |
Claude Sonnet 5: 2.4% of Claude Max 5x (2.4% / 5h) per good solve. Its weekly limit holds about 14.6 of the week's 33.6 5h windows. 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, Claude Sonnet 5 or GPT-6 Luna?
They are even on our ladder: both clear tier 2 of 5 at 50% capability on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-21.
Which is cheaper per task, Claude Sonnet 5 or GPT-6 Luna?
Claude Sonnet 5 used 1% of Claude Max 5x's weekly limit per pass, $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). Per task, GPT-6 Luna is about 5.0x cheaper ($0.002 vs $0.012).
What do Claude Sonnet 5 and GPT-6 Luna cost a month?
Claude Sonnet 5 runs on Claude Max 5x at $100/month (public price as of 2026-07-20). GPT-6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).