GPT-5.6 Sol vs Kimi K3 256K
GPT-5.6 Sol was superseded by GPT-6.1 Sol.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-5.6 Sol leads overall, C- to D+. GPT-5.6 Sol is about 4.0x cheaper per task. By suite, real-world issues is even at C- and GPT-5.6 Sol takes spec planning (C+ to C-). The data gives no reason to pick Kimi K3 256K over GPT-5.6 Sol this week.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: Kimi K3 256K vs GPT-5.6 Sol
GPT-5.6 Sol leads overall, C- to D+. By suite: real-world issues is even at C- (60% vs 60% capability); GPT-5.6 Sol takes spec planning, C+ to C- (68% vs 56% capability); GPT-5.6 Sol takes vibe coding, D+ to F (51% vs 34% capability). GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price. Per task, GPT-5.6 Sol is about 4.0x cheaper ($0.036 vs $0.146). GPT-5.6 Sol is faster on real-world issues: a median task takes 3m 13s against 3m 31s. Both finished every task on it. The data gives no reason to pick Kimi K3 256K over GPT-5.6 Sol this week.
Changed since the previous graded week: GPT-5.6 Sol: vibe coding C- to D+; Kimi K3 256K: real-world issues usage 23% to 21% of the weekly limit, spec planning D+ to C-, spec planning usage 11% to 10% of the weekly limit, vibe coding usage 3% to 2.6% of the weekly limit.
| Dimension | GPT-5.6 Sol | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 60% | 60% | Even |
| Median task time | 3m 13s | 3m 31s | 18s faster (GPT-5.6 Sol leads) |
| Approx. task cost | $0.031 / task | $0.126 / task | $0.095 / task lower (GPT-5.6 Sol leads) |
GPT-5.6 Sol: 2.0% of ChatGPT Pro 5x (2.0% / 1w) per run. Kimi K3 256K: 104.0% of Kimi Allegretto (104.0% / 5h, 21.0% / 1w) per run. Its weekly limit holds about 5 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 | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 68% | 56% | +12% (GPT-5.6 Sol leads) |
| Median task time | 6m 0s | 5m 26s | 34s faster (Kimi K3 256K leads) |
| Approx. task cost | $0.057 / task | $0.224 / task | $0.167 / task lower (GPT-5.6 Sol leads) |
GPT-5.6 Sol: 1.0% of ChatGPT Pro 5x (1.0% / 1w) per run. Kimi K3 256K: 52.0% of Kimi Allegretto (52.0% / 5h, 10.0% / 1w) per run. Its weekly limit holds about 5 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 | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 51% | 34% | +17% (GPT-5.6 Sol leads) |
| Median task time | 3m 56s | 7m 33s | 3m 36s faster (GPT-5.6 Sol leads) |
| Approx. task cost | $0.092 / task | $0.233 / task | $0.141 / task lower (GPT-5.6 Sol leads) |
GPT-5.6 Sol: 0.4% of ChatGPT Pro 5x (0.4% / 1w) per good solve. Kimi K3 256K: 13.2% of Kimi Allegretto (13.2% / 5h, 2.6% / 1w) per good solve. Its weekly limit holds about 5 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 Kimi K3 256K?
They are even on our ladder: both clear tier 4 of 5 at 60% capability 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 Kimi K3 256K?
GPT-5.6 Sol used 3% of ChatGPT Pro 5x's weekly limit per pass, $0.036 per task at the listed price. Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price. Per task, GPT-5.6 Sol is about 4.0x cheaper ($0.036 vs $0.146).
What do GPT-5.6 Sol and Kimi K3 256K cost a month?
GPT-5.6 Sol runs on ChatGPT Pro 5x at $100/month (public price as of 2026-09-05). Kimi K3 256K runs on Kimi Allegretto at $39/month (public price as of 2026-07-20).