DeepSeek V4.1 Flash 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 Terminal-Bench 4.0, where Claude Opus 5.5 leads by 35.2 points. DeepSeek V4.1 Flash 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.
DeepSeek V4.1 FlashDeepSeek · OpenLLM Buddy catalog79.8compositeClaude 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 Exam36.864.4
Pass@1, no tools, max effort (text-only subset: 39.1)Humanity's Last Exam, no tools; max effort
- Humanity's Last Exam (with tools)63.967.7
Pass@1, with tools, max effortHumanity's Last Exam, with tools (web search/fetch, code execution); max effort
- Terminal-Bench 4.031.266.4
Terminal-Bench 4.0, Pass@1, max effortTerminal-Bench 4.0; xhigh effort (66.36% in text, safeguards enabled)
- LMArena Text Elo · not counted14761509
LMArena text overall, 'DeepSeek-V4.1-Flash-20260910 (Max)', ±6, as of 2026-10-27LMArena Text, Overall; snapshot Oct 27, 2026; Claude Opus 5.5 (High); +/-7
Should you pick DeepSeek V4.1 Flash or Claude Opus 5.5?
Pick DeepSeek V4.1 Flash if…
- You need to self-host: keep prompts and data on your own GPU, avoid per-token fees, or fine-tune the weights.
- You need fast responses: about 217 tokens per second through APIs, against 96.
- Cost matters: $1.20 per million output tokens against $20.00.
- 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), Terminal-Bench 4.0, 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 1476.
Hardware and cost to run
DeepSeek V4.1 Flash
Even at 4-bit it needs about 381 GB (4× H200 (564 GB)), well beyond a home workstation, so most people run it on rented multi-GPU servers. Full BF16 precision needs about 1.3 TB (Multiple nodes (over 1.1 TB)).
On OpenLLM Buddy: DeepSeek-V4.1-Flash-UNCENSORED-FP8 runs on 4× H200 141GB as an FP8 build, with an OpenAI-compatible API and no per-token fees. Prices start at $280 USD for 11 hours.
Deploy DeepSeek V4.1 FlashClaude 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
| DeepSeek V4.1 Flash | Claude Opus 5.5 | |
|---|---|---|
| Lab | DeepSeek | Anthropic |
| Weights | Open | API only |
| Released | 2026-09-10 | 2026-09-22 |
| Parameters | 552B total, 16B active (MoE) | — |
| Context | 1M | 1M |
| License | MIT | — |
| 4-bit memory | 381 GB · 4× H200 (564 GB) | — |
| API price | $0.300 in / $1.20 out per 1M tokens | $4.00 in / $20.00 out per 1M tokens |
| API speed | 217 tok/s | 96 tok/s |
Related comparisons
- DeepSeek V4.1 Flash vs DeepSeek V4 Pro
- DeepSeek V4.1 Flash vs GPT-6 Astra
- DeepSeek V4.1 Flash vs Gemini 3.8 Flash
DeepSeek V4.1 Flash vs MiMo V2.6 Pro- GLM 5.3 Flash vs DeepSeek V4.1 Flash
- Qwen3.8 27B vs DeepSeek V4.1 Flash
- Gemma 4 31B vs DeepSeek V4.1 Flash
- Kimi K3 vs Claude Opus 5.5
- GLM 5.3 vs Claude Opus 5.5
Sources
| Model | Test | Score | Setting | Source |
|---|---|---|---|---|
| DeepSeek V4.1 Flash | Humanity's Last Exam | 36.8 | Pass@1, no tools, max effort (text-only subset: 39.1) | DeepSeek-V4.1-Flash 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) |
| DeepSeek V4.1 Flash | Humanity's Last Exam (with tools) | 63.9 | Pass@1, with tools, max effort | DeepSeek-V4.1-Flash 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 |
| DeepSeek V4.1 Flash | Terminal-Bench 4.0 | 31.2 | Terminal-Bench 4.0, Pass@1, max effort | DeepSeek-V4.1-Flash model card (Hugging Face) |
| Claude Opus 5.5 | Terminal-Bench 4.0 | 66.4 | Terminal-Bench 4.0; xhigh effort (66.36% in text, safeguards enabled) | Anthropic Claude Opus 5.5 System Card (Table 8.1.A / sec 8.5) |
| DeepSeek V4.1 Flash | LMArena Text Elo | 1476 | LMArena text overall, 'DeepSeek-V4.1-Flash-20260910 (Max)', ±6, 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