Claude Opus 5 vs GPT-5.6 Terra
Claude Opus 5 was superseded by Claude Opus 5.5. 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 Terra is about 1.3x cheaper per task. By suite, Claude Opus 5 takes real-world issues (C- to D+) and spec planning (C to D+). Take GPT-5.6 Terra 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 Terra 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 50% capability); Claude Opus 5 takes spec planning, C to D+ (66% vs 53% capability); Claude Opus 5 takes vibe coding, C+ to F (72% vs 34% 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 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). Per task, GPT-5.6 Terra is about 1.3x cheaper ($0.019 vs $0.024). Claude Opus 5 is faster on real-world issues: a median task takes 1m 56s against 2m 18s. Both finished every task on it. Reasons to pick GPT-5.6 Terra anyway: it is cheaper per task ($0.019 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 Terra: real-world issues D to D+, real-world issues usage 9.2% to 7% of the weekly limit, spec planning C- to D+, spec planning usage 2.0% to 1% of the weekly limit, vibe coding F to D, vibe coding usage 0.5% to 0.6% of the weekly limit.
| Dimension | Claude Opus 5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 57% | 50% | +7% (Claude Opus 5 leads) |
| Median task time | 1m 56s | 2m 18s | 22s faster (Claude Opus 5 leads) |
| Approx. task cost | $0.015 / task | $0.021 / task | $0.006 / task lower (Claude Opus 5 leads) |
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 Terra: 7.0% of ChatGPT Plus (46.0% / 5h, 7.0% / 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 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 66% | 53% | +12% (Claude Opus 5 leads) |
| Median task time | 2m 9s | 2m 37s | 29s faster (Claude Opus 5 leads) |
| Approx. task cost | $0.057 / task | $0.011 / task | $0.046 / task lower (GPT-5.6 Terra leads) |
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 Terra: 1.0% of ChatGPT Plus (10.0% / 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 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 72% | 34% | +37% (Claude Opus 5 leads) |
| Median task time | 2m 51s | 2m 47s | 4s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.011 / task | $0.028 / task | $0.017 / 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 Terra: 0.6% of ChatGPT Plus (3.0% / 5h, 0.6% / 1w) 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 or GPT-5.6 Terra?
Both clear tier 2 of 5, but Claude Opus 5 scores higher on capability: 57% versus 50% 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 Terra?
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 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). Per task, GPT-5.6 Terra is about 1.3x cheaper ($0.019 vs $0.024).
What do Claude Opus 5 and GPT-5.6 Terra cost a month?
Claude Opus 5 runs on Claude Max 5x at $100/month (public price as of 2026-07-27). GPT-5.6 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).