Claude Opus 5.5 vs GPT-5.6 Terra
Claude Opus 5.5 leads overall, B- to D. GPT-5.6 Terra is about 1.3x cheaper per task. By suite, Claude Opus 5.5 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 5.5
Claude Opus 5.5 leads overall, B- to D. By suite: Claude Opus 5.5 takes real-world issues, C+ to D+ (73% vs 50% capability); Claude Opus 5.5 takes spec planning, C+ to D+ (73% vs 53% capability); Claude Opus 5.5 takes vibe coding, B+ to F (90% vs 34% 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-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 5.5 is faster on real-world issues: a median task takes 1m 17s 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 5.5: real-world issues C- to C+, vibe coding B to B+; 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 5.5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 73% | 50% | +23% (Claude Opus 5.5 leads) |
| Median task time | 1m 17s | 2m 18s | 1m 1s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.015 / task | $0.021 / task | $0.006 / task lower (Claude Opus 5.5 leads) |
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-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 5.5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 73% | 53% | +19% (Claude Opus 5.5 leads) |
| Median task time | 4m 17s | 2m 37s | 1m 40s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.057 / task | $0.011 / task | $0.046 / task lower (GPT-5.6 Terra 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-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 5.5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 90% | 34% | +55% (Claude Opus 5.5 leads) |
| Median task time | 2m 44s | 2m 47s | 3s faster (Claude Opus 5.5 leads) |
| Approx. task cost | $0.007 / task | $0.028 / task | $0.021 / 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-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 5.5 or GPT-5.6 Terra?
Claude Opus 5.5 clears higher: tier 4 of 5 versus tier 2 for GPT-5.6 Terra 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-5.6 Terra?
Claude Opus 5.5 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 5.5 and GPT-5.6 Terra 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 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).