Kimi K3 vs GPT-5.6 Sol
Open-source flagship vs closed-source flagship
On Terminal-Bench 2.1 (AA terms): Sol 89.5, K3 88.3 — the largest open-weights model ever is just 1.2 points behind the closed-source flagship. The price gap is an order of magnitude.
Key points
TB 2.1 (AA terms)
K3 88.3 vs Sol 89.5 — a 1.2-point gap. Under vals.ai's unified harness: 80.90 / 85.77.
K3 parameter count
The largest open-weights model ever: Stable LatentMoE, 896 experts with 16 active per token.
K3 official API price
Per million tokens input/output (cache hit $0.30). Sol's official price is $5/$30.
Context windows
K3 natively 1M; Sol 400K. K3 wins long-context scenarios.
Where each model sits
Kimi K3 (launched at WAIC 07-16, weights open-sourced 07-27) is Moonshot's flagship reasoning model: 2.8T MoE, 1M context, mandatory reasoning (low/high/max tiers, default max). GPT-5.6 Sol is the flagship tier of OpenAI's 5.6 series: closed-source, 400K, Codex's default high-end model. One is the ceiling of open weights; the other is the benchmark of closed APIs.
Open source gets this close for the first time
Since launch, K3 has been neck-and-neck with closed flagships on multiple boards: it ties GLM-5.3 for the open-source lead on the Artificial Analysis Intelligence Index (~60 vs the closed flagship Sol's 61), and it became the first open model to top the frontend Code Arena at 1679 Elo. Requests surged within 11 days of the weights going open, and Moonshot briefly paused consumer subscription expansion.
Timeline
Kimi K3 launches at WAIC: 2.8T, the largest open-weights model ever.
K3 weights go open and requests surge; the same period sees Sol's 5.6 series cut prices (Luna -80%).
K3 ties GLM-5.3 for the AA open-source lead; on TB 2.1, K3's 88.3 stays close behind Sol's 89.5.
Confirmed vs watch out
Confirmed
Both models' parameters, context, official pricing and leaderboard positions are backed by official pages or re-checkable leaderboards; both have real call volume on QCode.
Watch out
K3's reasoning can't be turned off, so simple tasks naturally burn more tokens; Sol can run without reasoning. When comparing prices, convert by your task type — don't just read the unit-price table.
Pick by scenario
Pick Kimi K3
You want open weights (self-hostable), ultra-long context (1M), or budget-sensitive heavy-reasoning tasks. Official API: $3/$15.
Pick GPT-5.6 Sol
You want the Codex ecosystem, adjustable reasoning tiers, Fast mode (2.5x), or an existing OpenAI toolchain. $5/$30.
How to verify yourself
Run the same batch of real tasks on both: note that K3 defaults to max reasoning (more tokens but a higher first-pass rate), while Sol lets you tune effort per task. Convert by 'first-pass rate × total token cost' — that is your real unit price.
On QCode
Both kimi-k3 and gpt-5.6-sol are on sale (with real calls in the last 30 days). Same key, official price times the service rate; given K3's mandatory-reasoning token profile, run a small real batch before committing.
FAQ
Which is stronger, Kimi K3 or GPT-5.6 Sol?
On TB 2.1 (AA terms): Sol 89.5 vs K3 88.3 — a 1.2-point gap, the closest an open model has ever come. Numbers differ across leaderboards, so fix one board before comparing.
Is K3 open-source?
Yes — the weights went open on 2026-07-27 (2.8T, the largest ever). Self-hosting needs serious GPU memory; for most people the API is the realistic route.
How big is the price gap?
Official API: K3 at $3/$15 ($0.30 on cache hit), Sol at $5/$30. But K3's mandatory reasoning inflates token usage — convert by task type before comparing.
How big are the context windows?
K3: 1M tokens. Sol: 400K. K3 wins for long repos and long documents.
Can K3's reasoning be turned off?
No — only low / high / max tiers, default max. It's expensive for simple Q&A; route chore work to cheaper models.
Can I call both on QCode?
Both are on sale, switchable with the same key. Catalog prices follow the live /models listing.
Sources
Moonshot's official launch (07-16) and open-weights release (07-27), Artificial Analysis Intelligence Index, vals.ai TB2.1 snapshot (08-22), The Batch (08-21), QCode /models (08-22).
Open or closed — run both, then decide
K3 and Sol are testable on QCode with one key; do the math on real tasks.
Related reading
Kimi K3 guide
Calling, reasoning tiers and pricing details.
Sol vs Terra vs Luna
Choosing inside the 5.6 series.
K3 vs Opus 5
Another open-vs-closed flagship pairing.
Not affiliated with Moonshot / OpenAI. Leaderboard numbers are a 2026-08 snapshot.