Kimi K3 vs Claude Opus 5.5
Claude Opus 5.5 scores higher on 3 of the 3 benchmarks both models publish. The widest gap is on Humanity's Last Exam, where Claude Opus 5.5 leads by 20.9 points. Kimi K3 has open weights, so unlike Claude Opus 5.5 you can run it on your own GPU or deploy it on OpenLLM Buddy with no per-token fees.
Kimi K3Moonshot AI · OpenLLM Buddy catalog90.6compositeClaude Opus 5.5Anthropic · Closed API98.4compositeShared benchmarks
Raw published scores; the higher score on each row is highlighted. LMArena Elo is a human-preference vote and is not counted as a win.
- Humanity's Last Exam43.564.4
HLE-Full, no tools, max effortHumanity's Last Exam, no tools; max effort
- Humanity's Last Exam (with tools)56.067.7
HLE-Full, with tools, max effortHumanity's Last Exam, with tools (web search/fetch, code execution); max effort
- MMMU-Pro81.687.7
MMMU-Pro, no toolsMMMU-Pro (not original MMMU); AA independent run (Max, Default Fallback)
- LMArena Text Elo · not counted14881509
LMArena text overall, 'Kimi K3 (Max)', ±4, as of 2026-10-27LMArena Text, Overall; snapshot Oct 27, 2026; Claude Opus 5.5 (High); +/-7
Should you pick Kimi K3 or Claude Opus 5.5?
Pick Kimi K3 if…
- You need to self-host: keep prompts and data on your own GPU, avoid per-token fees, or fine-tune the weights.
- You want it running in minutes on a dedicated GPU through OpenLLM Buddy, in an uncensored build.
Pick Claude Opus 5.5 if…
- You care most about Humanity's Last Exam, Humanity's Last Exam (with tools), MMMU-Pro, where it scores at least 2 points higher.
- You want a managed API and would rather not run or pay for GPUs yourself.
- People prefer its answers in blind chats: LMArena Elo 1509 against 1488.
- You need fast responses: about 96 tokens per second through APIs, against 66.
Hardware and cost to run
Kimi K3
Even at 4-bit it needs about 1.9 TB (Multiple nodes (over 1.1 TB)), well beyond a home workstation, so most people run it on rented multi-GPU servers. Full BF16 precision needs about 6.4 TB (Multiple nodes (over 1.1 TB)).
On OpenLLM Buddy: Kimi-K3-Uncensored-GGUF runs on 8× H100 80GB as a GGUF quantized build, with an OpenAI-compatible API and no per-token fees. Prices start at $422 USD for 11 hours.
Deploy Kimi K3Claude Opus 5.5
Claude Opus 5.5 is only available through Anthropic's API, so it cannot be self-hosted; it costs $4 per million input tokens and $20 per million output tokens.
Category profile
Category index uses every test each model reports, not only the shared ones.
Specs side by side
| Kimi K3 | Claude Opus 5.5 | |
|---|---|---|
| Lab | Moonshot AI | Anthropic |
| Weights | Open | API only |
| Released | 2026-07-27 | 2026-09-22 |
| Parameters | 2.8T total, 104B active (MoE) | — |
| Context | 1M | 1M |
| License | Kimi K3 License (custom) | — |
| 4-bit memory | 1.9 TB · Multiple nodes (over 1.1 TB) | — |
| API price | $3.00 in / $15.00 out per 1M tokens | $4.00 in / $20.00 out per 1M tokens |
| API speed | 66 tok/s | 96 tok/s |
Related comparisons
Sources
| Model | Test | Score | Setting | Source |
|---|---|---|---|---|
| Kimi K3 | Humanity's Last Exam | 43.5 | HLE-Full, no tools, max effort | Kimi K3 model card (Hugging Face) |
| Claude Opus 5.5 | Humanity's Last Exam | 64.4 | Humanity's Last Exam, no tools; max effort | Anthropic Claude Opus 5.5 System Card (Table 8.1.A) |
| Kimi K3 | Humanity's Last Exam (with tools) | 56.0 | HLE-Full, with tools, max effort | Kimi K3 model card (Hugging Face) |
| Claude Opus 5.5 | Humanity's Last Exam (with tools) | 67.7 | Humanity's Last Exam, with tools (web search/fetch, code execution); max effort | Anthropic Claude Opus 5.5 System Card (Table 8.1.A); also in launch post |
| Kimi K3 | MMMU-Pro | 81.6 | MMMU-Pro, no tools | Kimi K3 model card (Hugging Face) |
| Claude Opus 5.5 | MMMU-Pro | 87.7 | MMMU-Pro (not original MMMU); AA independent run (Max, Default Fallback) | Artificial Analysis |
| Kimi K3 | LMArena Text Elo | 1488 | LMArena text overall, 'Kimi K3 (Max)', ±4, as of 2026-10-27 | Arena (LMArena) text leaderboard |
| Claude Opus 5.5 | LMArena Text Elo | 1509 | LMArena Text, Overall; snapshot Oct 27, 2026; Claude Opus 5.5 (High); +/-7 | LMArena (arena.ai) Text leaderboard |
Scores are published results from model cards, lab reports, and public leaderboards, each linked to its source. Settings such as thinking mode or test version differ between sources and are shown next to each score. OpenLLM Buddy catalog models are uncensored fine-tunes; their scores are those of the official base model. Data collected 2026-10-30. How the index works