Claude Sonnet 5 vs GPT-5.6 Terra
Claude Sonnet 5 is no longer on the leaderboard. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
Both grade D overall. GPT-5.6 Terra is about 1.3x cheaper per task. By suite, real-world issues is even at D+ and GPT-5.6 Terra takes spec planning (D+ to D). Both agents run the same private suite cut headless through their own tools, each on its own subscription.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 Sonnet 5
Both grade D overall. By suite: real-world issues is even at D+ (53% vs 50% capability); GPT-5.6 Terra takes spec planning, D+ to D (53% vs 44% capability); vibe coding is even at F (31% vs 34% capability). Claude Sonnet 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). GPT-5.6 Terra is faster on real-world issues: a median task takes 2m 18s against 3m 35s. Both finished every task on it.
Changed since the previous graded week: Claude Sonnet 5: vibe coding D+ to F; 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 Sonnet 5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 53% | 50% | +3% (Claude Sonnet 5 leads) |
| Median task time | 3m 35s | 2m 18s | 1m 18s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.015 / task | $0.021 / task | $0.006 / task lower (Claude Sonnet 5 leads) |
Claude Sonnet 5: 12.0% of Claude Max 5x (12.0% / 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 Sonnet 5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 44% | 53% | +10% (GPT-5.6 Terra leads) |
| Median task time | 5m 12s | 2m 37s | 2m 34s 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 Sonnet 5: 5.0% of Claude Max 5x (5.0% / 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 Sonnet 5 | GPT-5.6 Terra | Advantage |
|---|---|---|---|
| Capability | 31% | 34% | +3% (GPT-5.6 Terra leads) |
| Median task time | 4m 31s | 2m 47s | 1m 44s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.007 / task | $0.028 / task | $0.021 / task lower (Claude Sonnet 5 leads) |
Claude Sonnet 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 Sonnet 5 or GPT-5.6 Terra?
Claude Sonnet 5 clears higher: tier 3 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 Sonnet 5 or GPT-5.6 Terra?
Claude Sonnet 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 Sonnet 5 and GPT-5.6 Terra cost a month?
Claude Sonnet 5 runs on Claude Max 5x at $100/month (public price as of 2026-07-20). GPT-5.6 Terra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).