GPT-6 Luna vs Kimi K3 256K
Both grade D overall. GPT-6 Luna is about 66x cheaper per task. By suite, Kimi K3 256K takes real-world issues (C- to D+) and GPT-6 Luna takes spec planning (C- 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: Kimi K3 256K vs GPT-6 Luna
Both grade D overall. By suite: Kimi K3 256K takes real-world issues, C- to D+ (57% vs 50% capability); GPT-6 Luna takes spec planning, C- to D+ (61% vs 53% capability); vibe coding is even at F (33% vs 24% capability). GPT-6 Luna used 1% of ChatGPT Plus's weekly limit per pass, $0.002 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~0.2% of ChatGPT Pro 5x's weekly limit (est, about $0.002 per task). Kimi K3 256K used 34% of Kimi Allegretto's weekly limit per pass, $0.161 per task at the listed price. Per task, GPT-6 Luna is about 66x cheaper ($0.002 vs $0.161). GPT-6 Luna is faster on real-world issues: a median task takes 1m 0s against 4m 5s. Both finished every task on it.
Changed since W38: Kimi K3 256K: real-world issues usage 22% to 23% of the weekly limit, spec planning D to D+, spec planning usage 9% to 11% of the weekly limit, vibe coding D+ to C-, vibe coding usage 2.6% to 3% of the weekly limit.
| Dimension | GPT-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 50% | 57% | +7% (Kimi K3 256K leads) |
| Median task time | 1m 0s | 4m 5s | 3m 5s faster (GPT-6 Luna leads) |
| Approx. task cost | $0.003 / task | $0.138 / task | $0.134 / task lower (GPT-6 Luna leads) |
GPT-6 Luna: 1.0% of ChatGPT Plus (1.0% / 5h, 1.0% / 1w) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Kimi K3 256K: 115.0% of Kimi Allegretto (115.0% / 5h, 23.0% / 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-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 61% | 53% | +8% (GPT-6 Luna leads) |
| Median task time | 1m 8s | 5m 36s | 4m 28s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.011 / task | $0.247 / task | $0.235 / task lower (GPT-6 Luna leads) |
GPT-6 Luna: under 1% of ChatGPT Plus per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. Kimi K3 256K: 58.0% of Kimi Allegretto (58.0% / 5h, 11.0% / 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-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 33% | 24% | +9% (GPT-6 Luna leads) |
| Median task time | 1m 37s | 6m 33s | 4m 56s faster (GPT-6 Luna leads) |
| Approx. task cost | not measured | $0.269 / task | - |
GPT-6 Luna: under 1% of ChatGPT Plus (0.4% / 5h) per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. Kimi K3 256K: 14.0% of Kimi Allegretto (14.0% / 5h, 3.0% / 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-6 Luna or Kimi K3 256K?
Both clear tier 2 of 5, but Kimi K3 256K scores higher on capability: 57% versus 50% on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-23.
Which is cheaper per task, GPT-6 Luna or Kimi K3 256K?
GPT-6 Luna used 1% of ChatGPT Plus's weekly limit per pass, $0.002 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~0.2% of ChatGPT Pro 5x's weekly limit (est, about $0.002 per task). Kimi K3 256K used 34% of Kimi Allegretto's weekly limit per pass, $0.161 per task at the listed price. Per task, GPT-6 Luna is about 66x cheaper ($0.002 vs $0.161).
What do GPT-6 Luna and Kimi K3 256K cost a month?
GPT-6 Luna runs on ChatGPT Plus at $20/month (public price as of 2026-07-20). Kimi K3 256K runs on Kimi Allegretto at $39/month (public price as of 2026-07-20).