GPT-6 Luna vs Kimi K3 256K
Kimi K3 256K leads overall, D+ to D. By suite, real-world issues is even at C- and Kimi K3 256K takes spec planning (C- to D+). Take GPT-6 Luna anyway when you want the side that is faster 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: Kimi K3 256K vs GPT-6 Luna
Kimi K3 256K leads overall, D+ to D. By suite: real-world issues is even at C- (57% vs 60% capability); Kimi K3 256K takes spec planning, C- to D+ (56% vs 55% capability); vibe coding is even at F (31% vs 34% capability). GPT-6 Luna used <1% of ChatGPT Plus's weekly limit per pass; at the ~$100 tier the board defaults to that is an estimated ~<0.2% of ChatGPT Pro 5x's weekly limit (est). Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price. GPT-6 Luna is faster on real-world issues: a median task takes 1m 4s against 3m 31s. Both finished every task on it. Reasons to pick GPT-6 Luna anyway: it is faster on real-world issues (1m 4s vs 3m 31s median).
Changed since W39: GPT-6 Luna: real-world issues D+ to C-, spec planning 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-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 57% | 60% | +3% (Kimi K3 256K leads) |
| Median task time | 1m 4s | 3m 31s | 2m 27s faster (GPT-6 Luna leads) |
| Approx. task cost | not measured | $0.126 / task | - |
GPT-6 Luna: under 1% of ChatGPT Plus (2.0% / 5h) per run. Its weekly limit holds about 6 of the week's 33.6 5h windows. 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-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 55% | 56% | +1% (Kimi K3 256K leads) |
| Median task time | 1m 20s | 5m 26s | 4m 6s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.011 / task | $0.224 / task | $0.213 / 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: 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-6 Luna | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 31% | 34% | +3% (Kimi K3 256K leads) |
| Median task time | 1m 24s | 7m 33s | 6m 9s faster (GPT-6 Luna leads) |
| Approx. task cost | <$0.046 / task | $0.233 / task | $0.187 / task lower (GPT-6 Luna leads) |
GPT-6 Luna: under 1% of ChatGPT Plus per good solve. Its weekly limit holds about 6 of the week's 33.6 5h windows. 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-6 Luna or Kimi K3 256K?
Kimi K3 256K clears higher: tier 4 of 5 versus tier 2 for GPT-6 Luna on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-27.
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; at the ~$100 tier the board defaults to that is an estimated ~<0.2% of ChatGPT Pro 5x's weekly limit (est). Kimi K3 256K used 31% of Kimi Allegretto's weekly limit per pass, $0.146 per task at the listed price.
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).