Claude Opus 5.5 vs GPT-6 Luna
Claude Opus 5.5 leads overall, C+ to D. GPT-6 Luna is about 5.0x cheaper per task. By suite, Claude Opus 5.5 takes real-world issues (C- to D+) and spec planning (C+ to C-). Take GPT-6 Luna anyway when you want the side that is cheaper per task and 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, C+ to D. By suite: Claude Opus 5.5 takes real-world issues, C- to D+ (60% vs 50% capability); Claude Opus 5.5 takes spec planning, C+ to C- (69% vs 61% capability); Claude Opus 5.5 takes vibe coding, B to F (85% vs 33% capability). Claude Opus 5.5 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 18s. Both finished every task on it. Reasons to pick GPT-6 Luna anyway: it is cheaper per task ($0.002 vs $0.012) and it is faster on real-world issues (1m 0s vs 2m 18s median).
| Dimension | Claude Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 60% | 50% | +10% (Claude Opus 5.5 leads) |
| Median task time | 2m 18s | 1m 0s | 1m 18s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.015 / task | $0.003 / task | $0.012 / task lower (GPT-6 Luna leads) |
Claude Opus 5.5: 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 Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 69% | 61% | +8% (Claude Opus 5.5 leads) |
| Median task time | 3m 45s | 1m 8s | 2m 37s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.010 / task | <$0.011 / task | $0.001 / task lower (Claude Opus 5.5 leads) |
Claude Opus 5.5: 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 Opus 5.5 | GPT-6 Luna | Advantage |
|---|---|---|---|
| Capability | 85% | 33% | +52% (Claude Opus 5.5 leads) |
| Median task time | 2m 27s | 1m 37s | 50s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.046 / task | not measured | - |
Claude Opus 5.5: 0.8% of Claude Max 5x (0.8% / 5h, 0.2% / 1w) 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 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 2026-09-23.
Which is cheaper per task, Claude Opus 5.5 or GPT-6 Luna?
Claude Opus 5.5 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 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).