Claude Sonnet 5.5 vs GPT-6 Astra
GPT-6 Astra leads overall, C to C-. Claude Sonnet 5.5 is about 18x cheaper per task. By suite, Claude Sonnet 5.5 takes real-world issues (C- to D) and spec planning is even at C+. Take Claude Sonnet 5.5 anyway when you want the side that is cheaper per task, faster on real-world issues and ahead on real-world issues.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-6 Astra vs Claude Sonnet 5.5
GPT-6 Astra leads overall, C to C-. By suite: Claude Sonnet 5.5 takes real-world issues, C- to D (60% vs 43% capability); spec planning is even at C+ (74% vs 74% capability); GPT-6 Astra takes vibe coding, C+ to D+ (74% vs 48% capability). Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. GPT-6 Astra used 22% of ChatGPT Plus's weekly limit per pass, $0.053 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~4.4% of ChatGPT Pro 5x's weekly limit (est, about $0.053 per task). Per task, Claude Sonnet 5.5 is about 18x cheaper ($0.003 vs $0.053). Claude Sonnet 5.5 is faster on real-world issues: a median task takes 37s against 2m 13s. Both finished every task on it. Reasons to pick Claude Sonnet 5.5 anyway: it is cheaper per task ($0.003 vs $0.053), it is faster on real-world issues (37s vs 2m 13s median) and it leads on real-world issues (C- to D).
| Dimension | Claude Sonnet 5.5 | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 60% | 43% | +17% (Claude Sonnet 5.5 leads) |
| Median task time | 37s | 2m 13s | 1m 36s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.002 / task | $0.052 / task | $0.050 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6 Astra: 17.0% of ChatGPT Plus (112.0% / 5h, 17.0% / 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 5.5 | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 74% | 74% | +0% (Claude Sonnet 5.5 leads) |
| Median task time | 3m 25s | 3m 5s | 19s faster (GPT-6 Astra leads) |
| Approx. task cost | $0.007 / task | $0.057 / task | $0.051 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 4.0% of Claude Max 5x (4.0% / 5h) per run. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6 Astra: 5.0% of ChatGPT Plus (27.0% / 5h, 5.0% / 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 5.5 | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 48% | 74% | +26% (GPT-6 Astra leads) |
| Median task time | 56s | 2m 40s | 1m 44s faster (Claude Sonnet 5.5 leads) |
| Approx. task cost | $0.001 / task | $0.046 / task | $0.045 / task lower (Claude Sonnet 5.5 leads) |
Claude Sonnet 5.5: 0.2% of Claude Max 5x (0.2% / 5h) per good solve. Its weekly limit holds about 13.8 of the week's 33.6 5h windows. GPT-6 Astra: 1.0% of ChatGPT Plus (7.2% / 5h, 1.0% / 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 5.5 or GPT-6 Astra?
Claude Sonnet 5.5 clears higher: tier 4 of 5 versus tier 2 for GPT-6 Astra on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, Claude Sonnet 5.5 or GPT-6 Astra?
Claude Sonnet 5.5 used <1% of Claude Max 5x's weekly limit per pass, $0.003 per task at the listed price. GPT-6 Astra used 22% of ChatGPT Plus's weekly limit per pass, $0.053 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~4.4% of ChatGPT Pro 5x's weekly limit (est, about $0.053 per task). Per task, Claude Sonnet 5.5 is about 18x cheaper ($0.003 vs $0.053).
What do Claude Sonnet 5.5 and GPT-6 Astra cost a month?
Claude Sonnet 5.5 runs on Claude Max 5x at $100/month (public price as of 2026-07-20). GPT-6 Astra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).