Claude Sonnet 5 vs GPT-6 Luna
Claude Sonnet 5 is no longer on the leaderboard. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
Both grade D overall. By suite, GPT-6 Luna takes real-world issues (C- to D+) and 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: GPT-6 Luna vs Claude Sonnet 5
Both grade D overall. By suite: GPT-6 Luna takes real-world issues, C- to D+ (57% vs 53% capability); GPT-6 Luna takes spec planning, D+ to D (55% vs 44% capability); vibe coding is even at F (31% vs 31% capability). Claude Sonnet 5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 per task at the listed price. 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). GPT-6 Luna is faster on real-world issues: a median task takes 1m 4s against 3m 35s. Both finished every task on it.
Changed since W39: Claude Sonnet 5: vibe coding D+ to F; GPT-6 Luna: real-world issues D+ to C-, spec planning C- to D+.
| Dimension | Claude Sonnet 5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 53% | 57% | +3% (GPT-6 Luna leads) |
| Median task time | 3m 35s | 1m 4s | 2m 31s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.015 / task | not measured | - |
Claude Sonnet 5: 12.0% of Claude Max 5x (12.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. 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. 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 | 44% | 55% | +11% (GPT-6 Luna leads) |
| Median task time | 5m 12s | 1m 20s | 3m 52s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.057 / task | <$0.011 / task | $0.046 / task lower (GPT-6 Luna leads) |
Claude Sonnet 5: 5.0% of Claude Max 5x (5.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 13.8 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 | 31% | 31% | Even |
| Median task time | 4m 31s | 1m 24s | 3m 7s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.007 / task | <$0.046 / task | $0.039 / task lower (Claude Sonnet 5 leads) |
Claude Sonnet 5: 1.0% of Claude Max 5x (1.0% / 5h) per good solve. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. 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. 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?
Claude Sonnet 5 clears higher: tier 3 of 5 versus tier 2 for GPT-6 Luna on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, Claude Sonnet 5 or GPT-6 Luna?
Claude Sonnet 5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 per task at the listed price. 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).
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).