Claude Opus 5.5 vs GPT-5.6 Luna
Claude Opus 5.5 leads overall, C+ to D. By suite, Claude Opus 5.5 takes real-world issues (C- to D) and spec planning (C+ to C-). The data gives no reason to pick GPT-5.6 Luna over Claude Opus 5.5 this week.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-5.6 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 45% capability); Claude Opus 5.5 takes spec planning, C+ to C- (69% vs 57% capability); Claude Opus 5.5 takes vibe coding, B to F (85% vs 25% 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-5.6 Luna used <1% of ChatGPT Pro 5x's weekly limit per pass, at most $0.012 per task at the listed price. Claude Opus 5.5 is faster on real-world issues: a median task takes 2m 18s against 3m 7s. Both finished every task on it. The data gives no reason to pick GPT-5.6 Luna over Claude Opus 5.5 this week.
Changed since W38: GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F.
| Dimension | Claude Opus 5.5 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 60% | 45% | +15% (Claude Opus 5.5 leads) |
| Median task time | 2m 18s | 3m 7s | 49s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.015 / task | <$0.015 / task | Even |
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-5.6 Luna: under 1% of ChatGPT Pro 5x per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Opus 5.5 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 69% | 57% | +12% (Claude Opus 5.5 leads) |
| Median task time | 3m 45s | 3m 25s | 20s faster (GPT-5.6 Luna leads) |
| Approx. task cost | $0.010 / task | <$0.057 / task | $0.047 / 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-5.6 Luna: under 1% of ChatGPT Pro 5x per run. Each figure is a share of that agent's own plan, so there is no delta to draw.
| Dimension | Claude Opus 5.5 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 85% | 25% | +59% (Claude Opus 5.5 leads) |
| Median task time | 2m 27s | 3m 40s | 1m 13s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.046 / task | <$0.230 / task | $0.184 / task lower (Claude Opus 5.5 leads) |
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-5.6 Luna: under 1% of ChatGPT Pro 5x 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, Claude Opus 5.5 or GPT-5.6 Luna?
Claude Opus 5.5 clears higher: tier 4 of 5 versus tier 1 for GPT-5.6 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-5.6 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-5.6 Luna used <1% of ChatGPT Pro 5x's weekly limit per pass, at most $0.012 per task at the listed price.
What do Claude Opus 5.5 and GPT-5.6 Luna cost a month?
Claude Opus 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). GPT-5.6 Luna runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05).