Claude Opus 5.5 vs GPT-6 Luna
Claude Opus 5.5 leads overall, B- to D. By suite, Claude Opus 5.5 takes real-world issues (C+ to C-) and spec planning (C+ to D+). Take GPT-6 Luna anyway when you want the side that is faster on real-world issues.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 Opus 5.5
Claude Opus 5.5 leads overall, B- to D. By suite: Claude Opus 5.5 takes real-world issues, C+ to C- (73% vs 57% capability); Claude Opus 5.5 takes spec planning, C+ to D+ (73% vs 55% capability); Claude Opus 5.5 takes vibe coding, B+ to F (90% vs 31% capability). Claude Opus 5.5 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 1m 17s. Both finished every task on it. Reasons to pick GPT-6 Luna anyway: it is faster on real-world issues (1m 4s vs 1m 17s median).
Changed since W39: Claude Opus 5.5: real-world issues C- to C+, vibe coding B to B+; GPT-6 Luna: real-world issues D+ to C-, spec planning C- to D+.
| Dimension | Claude Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 73% | 57% | +17% (Claude Opus 5.5 leads) |
| Median task time | 1m 17s | 1m 4s | 12s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.015 / task | not measured | - |
Claude Opus 5.5: 11.0% of Claude Max 5x (11.0% / 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 Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 73% | 55% | +18% (Claude Opus 5.5 leads) |
| Median task time | 4m 17s | 1m 20s | 2m 57s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.057 / task | <$0.011 / task | $0.046 / task lower (GPT-6 Luna leads) |
Claude Opus 5.5: 6.0% of Claude Max 5x (6.0% / 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 Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 90% | 31% | +59% (Claude Opus 5.5 leads) |
| Median task time | 2m 44s | 1m 24s | 1m 21s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.007 / task | <$0.046 / task | $0.039 / task lower (Claude Opus 5.5 leads) |
Claude Opus 5.5: 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 Opus 5.5 or GPT-6 Luna?
Claude Opus 5.5 clears higher: tier 4 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 Opus 5.5 or GPT-6 Luna?
Claude Opus 5.5 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 Opus 5.5 and GPT-6 Luna cost a month?
Claude Opus 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). GPT-6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).