GPT-5.6 Sol vs GPT-6 Astra
GPT-5.6 Sol was superseded by GPT-6.1 Sol. The grades below are the last ones measured, so read them as history rather than as this week's board. See the current roster.
GPT-6 Astra leads overall, C to C-. GPT-5.6 Sol is about 1.5x cheaper per task. By suite, GPT-5.6 Sol takes real-world issues (C- to D) and spec planning is even at C+. Take GPT-5.6 Sol anyway when you want the side that is cheaper per task 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 GPT-5.6 Sol
GPT-6 Astra leads overall, C to C-. By suite: GPT-5.6 Sol takes real-world issues, C- to D (60% vs 43% capability); spec planning is even at C+ (68% vs 74% capability); GPT-6 Astra takes vibe coding, C+ to D+ (74% vs 51% capability). GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 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, GPT-5.6 Sol is about 1.5x cheaper ($0.036 vs $0.053). GPT-6 Astra is faster on real-world issues: a median task takes 2m 13s against 3m 13s. Both finished every task on it. Reasons to pick GPT-5.6 Sol anyway: it is cheaper per task ($0.036 vs $0.053) and it leads on real-world issues (C- to D).
Changed since W38: GPT-5.6 Sol: vibe coding C- to D+; GPT-6 Astra has one graded week under this version (W40).
| Dimension | GPT-5.6 Sol | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 60% | 43% | +17% (GPT-5.6 Sol leads) |
| Median task time | 3m 13s | 2m 13s | 1m 0s faster (GPT-6 Astra leads) |
| Approx. task cost | $0.031 / task | $0.052 / task | $0.021 / task lower (GPT-5.6 Sol leads) |
GPT-5.6 Sol: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. 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 | GPT-5.6 Sol | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 68% | 74% | +6% (GPT-6 Astra leads) |
| Median task time | 6m 0s | 3m 5s | 2m 54s faster (GPT-6 Astra leads) |
| Approx. task cost | $0.057 / task | $0.057 / task | Even |
GPT-5.6 Sol: 1.0% of ChatGPT Pro 5x (1.0% / 1w) per run. 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 | GPT-5.6 Sol | GPT-6 Astra | Advantage |
|---|---|---|---|
| Capability | 51% | 74% | +23% (GPT-6 Astra leads) |
| Median task time | 3m 56s | 2m 40s | 1m 16s faster (GPT-6 Astra leads) |
| Approx. task cost | $0.092 / task | $0.046 / task | $0.046 / task lower (GPT-6 Astra leads) |
GPT-5.6 Sol: 0.4% of ChatGPT Pro 5x (0.4% / 1w) per good solve. 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, GPT-5.6 Sol or GPT-6 Astra?
GPT-5.6 Sol 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 2026-09-21.
Which is cheaper per task, GPT-5.6 Sol or GPT-6 Astra?
GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 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, GPT-5.6 Sol is about 1.5x cheaper ($0.036 vs $0.053).
What do GPT-5.6 Sol and GPT-6 Astra cost a month?
GPT-5.6 Sol runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). GPT-6 Astra runs on ChatGPT Plus at $20/month (public price as of 2026-07-20).