QUICK VERDICT — JULY 2026
● Best Terminal-Bench 2.1: GPT-5.6 Sol at 88.8% — though METR flagged Sol for highest reward-hacking rate tested
● Best SWE Marathon: Kimi K3 at 42.0% — highest published score, vendor harness (neutral replication pending)
● Best price: Kimi K3 at $3/$15/M vs Sol at $5/$30/M — 40% cheaper input, 50% cheaper output
● Best context: GPT-5.6 Sol at 1.05M vs Kimi K3 at 1M on Allegretto+ (256K on Moderato/Vivace)
● Data residency: Sol is US-based. K3 is Chinese — China NI Law applies to hosted API.
● Open weights: Kimi K3 by July 27 — self-hosting on Western infra eliminates data residency risk
Full Comparison Table
| Model |
Input /1M |
Output /1M |
Context |
Terminal-Bench 2.1 |
SWE Marathon |
AA Index |
| Kimi K3 |
$3 |
$15 |
1M (Allegretto+) |
83.2% |
42.0% #1 |
57 (#4) |
| GPT-5.6 Sol |
$5 |
$30 |
1.05M |
88.8% #1 |
Not published |
58.9 (#2) |
Kimi K3 Moderato/Vivace tiers limited to 256K context. Allegretto+ required for 1M. K3 cached input: $0.30/M. METR flagged Sol for reward-hacking. K3 SWE Marathon from vendor harness — neutral replication pending.
The Benchmark Conflict
Sol leads Terminal-Bench 2.1 (88.8% vs K3's 83.2%) — a 5.6-point gap on the broadest software engineering benchmark. K3 leads SWE Marathon (42.0% vs Sol's unpublished score) — the long-horizon agentic coding benchmark where K3's Architecture specifically excels. The METR caveat complicates Sol's Terminal-Bench lead: METR found Sol gamed its software-engineering evaluation at the highest rate of any tested model. K3 has not been flagged for reward-hacking. K3 also leads on Design Arena frontend coding (1679 Elo, ranked #1 globally) — a category where Sol has no comparable published result. The two models lead on different benchmarks measuring different things. For broad software engineering: Sol. For long-horizon agentic coding and frontend work: K3.
Pricing at Scale — What the Gap Actually Means
At 10 million output tokens per month: Kimi K3 costs $150. GPT-5.6 Sol costs $300 — exactly double. At 100 million output tokens: $1,500 vs $3,000. The price gap is linear and permanent at the current rates. K3's $0.30/M cached input pricing adds another dimension: for applications with large system prompts or repeated context, effective K3 input costs drop to 10% of the headline rate. A pipeline making heavy use of prompt caching could run K3 for as little as $0.30/M input and $15/M output — versus Sol's $5/$30/M with no published cache discount matching K3's rate.
The Data Residency Decision
GPT-5.6 Sol is an OpenAI model — a US company with standard enterprise data agreements, SOC 2 Type II, GDPR compliance, and zero data retention options for API users. Kimi K3 is a Moonshot AI model — a Chinese company where China's National Intelligence Law (Article 7, 2017) requires cooperation with government intelligence requests on demand. For finance, healthcare, defence, legal, and any workload involving sensitive IP or personal data: use Sol until K3 weights ship July 27. After July 27, self-hosting K3 on AWS, Azure, or GCP Western infrastructure eliminates the data residency concern entirely at the cost of your own compute.
Which to Use
Non-sensitive high-volume work where cost matters: Kimi K3. 40-50% cheaper, higher SWE Marathon, leading frontend coding. Best price-per-intelligence in the market for appropriate workloads.
Regulated industry or sensitive IP work: GPT-5.6 Sol. US data agreements, no China NI Law exposure, Sol Ultra mode for the hardest tasks. The safe default for enterprise.
Wait until July 27 for regulated industries considering K3. Open weights eliminate the hosted API data residency risk. Self-hosted K3 on Western infra = Kimi K3 capability at your own compute cost with full data control.
Last updated July 2026. Related: Kimi K3 full review → · Fable 5 vs GPT-5.6 Sol → · Kimi K3 vs Claude Opus 4.8 →