GPT-5.6 Terra vs Kimi K3 256K
Kimi K3 256K leads overall, D+ to D. GPT-5.6 Terra is about 7.6x cheaper per task. By suite, Kimi K3 256K takes real-world issues (C- to D+) and spec planning (C- to D+). Take GPT-5.6 Terra anyway when you want the side that is cheaper per task and 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-5.6 Terra
Kimi K3 256K leads overall, D+ to D. By suite: Kimi K3 256K takes real-world issues, C- to D+ (60% vs 50% capability); Kimi K3 256K takes spec planning, C- to D+ (56% vs 53% capability); vibe coding is even at F (34% vs 34% capability). GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). 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 Terra is about 7.6x cheaper ($0.019 vs $0.146). GPT-5.6 Terra is faster on real-world issues: a median task takes 2m 18s against 3m 31s. Both finished every task on it. Reasons to pick GPT-5.6 Terra anyway: it is cheaper per task ($0.019 vs $0.146) and it is faster on real-world issues (2m 18s vs 3m 31s median).
Changed since the previous graded week: GPT-5.6 Terra: real-world issues D to D+, real-world issues usage 9.2% to 7% of the weekly limit, spec planning C- to D+, spec planning usage 2.0% to 1% of the weekly limit, vibe coding F to D, vibe coding usage 0.5% to 0.6% of the weekly limit; 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 Terra | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 50% | 60% | +10% (Kimi K3 256K leads) |
| Median task time | 2m 18s | 3m 31s | 1m 14s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.021 / task | $0.126 / task | $0.104 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Terra: 7.0% of ChatGPT Plus (46.0% / 5h, 7.0% / 1w) 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-5.6 Terra | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 53% | 56% | +3% (Kimi K3 256K leads) |
| Median task time | 2m 37s | 5m 26s | 2m 49s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.011 / task | $0.224 / task | $0.213 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Terra: 1.0% of ChatGPT Plus (10.0% / 5h, 1.0% / 1w) 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-5.6 Terra | Kimi K3 256K | Advantage |
|---|---|---|---|
| Capability | 34% | 34% | Even |
| Median task time | 2m 47s | 7m 33s | 4m 45s faster (GPT-5.6 Terra leads) |
| Approx. task cost | $0.028 / task | $0.233 / task | $0.206 / task lower (GPT-5.6 Terra leads) |
GPT-5.6 Terra: 0.6% of ChatGPT Plus (3.0% / 5h, 0.6% / 1w) 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-5.6 Terra or Kimi K3 256K?
Kimi K3 256K clears higher: tier 4 of 5 versus tier 2 for GPT-5.6 Terra on real-world@v3, our private suite of real-world coding problems. Latest measurement 2026-09-28.
Which is cheaper per task, GPT-5.6 Terra or Kimi K3 256K?
GPT-5.6 Terra used 8% of ChatGPT Plus's weekly limit per pass, $0.019 per task at the listed price; at the ~$100 tier the board defaults to that is an estimated ~1.6% of ChatGPT Pro 5x's weekly limit (est, about $0.019 per task). 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 Terra is about 7.6x cheaper ($0.019 vs $0.146).
What do GPT-5.6 Terra and Kimi K3 256K cost a month?
GPT-5.6 Terra 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).