Claude Opus 5 vs GPT-5.6 Luna
Claude Opus 5 was superseded by Claude Opus 5.5. GPT-5.6 Luna was superseded by GPT-6 Luna. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
Claude Opus 5 leads overall, C to D. GPT-5.6 Luna is the cheaper side per task (at most $0.012). By suite, Claude Opus 5 takes real-world issues (C- to D) and spec planning (C to C-). Take GPT-5.6 Luna anyway when you want the side that is cheaper per task.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
Claude Opus 5 leads overall, C to D. By suite: Claude Opus 5 takes real-world issues, C- to D (57% vs 45% capability); Claude Opus 5 takes spec planning, C to C- (66% vs 57% capability); Claude Opus 5 takes vibe coding, C+ to F (72% vs 25% capability). Claude Opus 5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 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. Per task, GPT-5.6 Luna costs at most $0.012 against Claude Opus 5's $0.024, so GPT-5.6 Luna is the cheaper side. Claude Opus 5 is faster on real-world issues: a median task takes 1m 56s against 3m 7s. Both finished every task on it. Reasons to pick GPT-5.6 Luna anyway: it is cheaper per task (at most $0.012 vs $0.024).
Changed since the previous graded week: Claude Opus 5: real-world issues usage 3% to 1% of the weekly limit; GPT-5.6 Luna: spec planning D+ to C-, vibe coding C- to F.
| Dimension | Claude Opus 5 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 57% | 45% | +12% (Claude Opus 5 leads) |
| Median task time | 1m 56s | 3m 7s | 1m 11s faster (Claude Opus 5 leads) |
| Approx. task cost | $0.015 / task | <$0.015 / task | Even |
Claude Opus 5: 21.0% of Claude Max 5x (21.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 13.8 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 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 66% | 57% | +9% (Claude Opus 5 leads) |
| Median task time | 2m 9s | 3m 25s | 1m 17s faster (Claude Opus 5 leads) |
| Approx. task cost | $0.057 / task | <$0.057 / task | Even |
Claude Opus 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-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 | GPT-5.6 Luna | Advantage |
|---|---|---|---|
| Capability | 72% | 25% | +46% (Claude Opus 5 leads) |
| Median task time | 2m 51s | 3m 40s | 49s faster (Claude Opus 5 leads) |
| Approx. task cost | $0.011 / task | <$0.230 / task | $0.219 / task lower (Claude Opus 5 leads) |
Claude Opus 5: 1.6% of Claude Max 5x (1.6% / 5h) per good solve. Its weekly limit holds about 13.8 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 or GPT-5.6 Luna?
Claude Opus 5 clears higher: tier 2 of 5 versus tier 1 for GPT-5.6 Luna on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-21.
Which is cheaper per task, Claude Opus 5 or GPT-5.6 Luna?
Claude Opus 5 used 2% of Claude Max 5x's weekly limit per pass, $0.024 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. Per task, GPT-5.6 Luna costs at most $0.012 against Claude Opus 5's $0.024, so GPT-5.6 Luna is the cheaper side.
What do Claude Opus 5 and GPT-5.6 Luna cost a month?
Claude Opus 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).