DeepSeek debuts DeepSeek-V4.1-Flash, its smallest model built on its new Causal Encoder-Decoder architecture, with 552B backbone parameters and 1M-token context

Chinese artificial intelligence startup DeepSeek on Thursday launched DeepSeek-V4.1-Flash, which the company said is the smallest model …

Reuters 2026-09-11

Context & Ripple Effects

DeepSeek's V4 line has been expanding across capability tiers: April coverage contrasted V4 Pro and V4 Flash on parameter scale, context length and token pricing, while August brought a multimodal V4 Flash experiment. V4-Pro also established DeepSeek's willingness to compete on price against Kimi K3.

V4.1-Flash moves that Flash tier onto the Causal Encoder-Decoder design while retaining a 1M-token context window. DeepSeek says the architecture reduces the KV-cache memory and storage required for agent workloads; that matters as the company has said demand and agent complexity are straining its backend systems.

First-order effects

Developers using DeepSeek gain a 1M-context model in the new architecture family, with native visual understanding cited by DeepSeek.
DeepSeek can position V4.1-Flash as a more infrastructure-efficient successor to its prior Flash offering: the company says its KV cache uses one-quarter the HBM and one-eighth the SSD storage of the previous generation.

Second-order effects

DeepSeek's own lower-priced V4-Pro launch puts pressure on rivals such as Kimi K3 to compete across both flagship capability and lower-cost agent serving, rather than on benchmark performance alone.
Lower cache requirements shift more of the economics of long-running agents toward model architecture and serving efficiency, making DeepSeek's planned backend overhaul more consequential to product delivery.

Third-order effects

If encoder-decoder-style designs preserve capability while reducing active inference and cache resources, frontier-model competition will increasingly be decided by the cost of serving agent contexts, not backbone parameter totals alone.
The V4 family points to a segmented model market in which the same vendor offers premium, multimodal and efficiency-oriented variants around a shared long-context platform.

The trend: AI-model vendors are differentiating long-context agent offerings through inference and memory efficiency alongside raw model scale.

Discussion

@deepseek_ai @deepseek_ai on x
🚀 Introducing DeepSeek-V4.1-Flash: smarter, faster, more efficient. 🔹 Introducing the smallest model in our new architecture family, with native visual understanding. 🔹 Designed for greater capability, faster inference, higher throughput, and scaling to larger models. 1/6
@deepseek_ai @deepseek_ai on x
💾 Smaller KV cache. Bigger savings. Compared with the previous generation, V4.1-Flash's KV cache needs just: 🔹 1/4 the HBM 🔹 1/8 the SSD storage Cache-hit charges often account for a large share of agent costs. Compressing the cache cuts those costs significantly. 3/6
@chrisgpt Chris on x
DeepSeek V4.1 Flash just dropped! It's a 552B MoE model, but activates only 8B parameters for input and 16B for output. And it's beating models like GPT-5.6 Sol and Opus 5 on several agentic/coding benchmarks. CyberGym: 88.1 vs 84.5 GPT-5.6 Sol Automation-Bench: 54.8 vs 45.8 Deep…
@ns123abc Nik on x
Deepseek just dropped v4.1 flash, fully open weights it beats gpt 5.6 sol, opus 5 and every chinese model on coding and cybersecurity at ~86x cheaper cost per million tokens running at 420-507 tok/s = faster than gemini 3.8 flash “smallest model in our new architecture family” bt…
@deepseek_ai @deepseek_ai on x
🧠 Asymmetric architecture. More intelligence, less cost. 🔹 552B-parameter MoE. 🔹 New Causal Encoder-Decoder architecture: just 8B active parameters for input, 16B for output. 🔹 New pre-training methods + larger-scale RL post-training deliver benchmark results ahead of flagship mo…
@bindureddy Bindu Reddy on x
Absolutely Insane! DeepSeek V4.1 Flash has astounding benchmark numbers It powers our personal agents and is close to FREE 😲 Get AI to write email, research topics, and pretty much do all your work and pay nothing
@jenzhuscott Jen Zhu on x
WTF 😅🚀😳 “98% of Astra's score at 1.4% of cost” Cancel the fucking IPOs 😂
@thom_wolf Thomas Wolf on x
don't get distracted by all the hedging words in its name ("flash", minor version): seems like DeepSeek V4.1 Flash is a major update weights at: https://huggingface.co/... paper at: https://huggingface.co/...
@kimmonismus @kimmonismus on x
DeepSeek just released V4.1-Flash with a new architecture, six weeks after its July V4-Flash update. July's release improved post-training while keeping the architecture unchanged. (Same with GLM-5.3/Flash) V4.1 introduces a Causal Encoder-Decoder architecture with native visual …
@theahmadosman Ahmad on x
This new DeepSeek V4.1 Flash model will make GPUs prices go even higher ... way higher $40k RTX PRO 6000 incoming Bookmark this tweet
@victor207755822 Deli Chen on x
Just Try It !
@sudoingx @sudoingx on x
deepseek keeps punching above its weight man, this is insane. the new v4.1 flash is a 552B MoE with a new asymmetric trick, 8B active parameters on input, 16B on output, and look what that buys in the table. it beats their own v4 PRO on almost every agentic bench, terminal bench …
@rishdotblog Rishabh Srivastava on x
Wow. Cheaper than luna (atleast on a per token basis), with perf between terra and sol Thank you deepseek - the openness with which they're sharing their IP is incredible! Amazing to see the price-performance frontier improve so rapidly
@jun_song Jun Song on x
open-weight Flash model just mogged Opus-5 and GPT-5.6-Sol. This is insane.
@jenzhuscott Jen Zhu on x
Instead of getting anxious by brute compute agent swarm solving a math problem you've never heard of, or an unknown researcher's doom post... Friends, here is a small/mighty OSS model that gives you can customize while costs you nothing. No dooms day drama, no lecturing, no virtu…
@zainhas Zain on x
oh wow have not seen this before for any model... this complicates things > “DeepSeek-V4.1-Flash supports a continuously controllable reasoning effort from 1 to 100.” reasoning_effort = [1 to 100]
@deryatr_ Derya Unutmaz on x
A significant part of the psy-op for the doomsday fearmongering is to stop this!👇But they won't succeed! I'm so happy DeepSeek just switched on the lights on this dark day. V4.1 Flash looks incredible! Better than even GLM-5.3, which is already an amazing open-source model!
@eriskiiii Eris on x
holy fucking shit this thing is fast. 200 TPS from the official fucking endpoint.
@miaai_lab Mia on x
DeepSeek v4.1 Flash is the smallest model in their new architecture. It weights 510 GB total. Which means 342 GB larger, or 204% bigger than DeepSeek v4 Flash Vision Exp.
@theahmadosman Ahmad on x
You see this? This is why I told you all to go get yourselves some compute Models will continue to get better, more intelligent, capable, efficient, and smaller
@zizhpan Zizheng Pan on x
DeepSeek-V4.1-Flash is now publicly available on App, Web, and API. Our first flagship model with native multimodal support. Faster. More capable. Lower price. Open weights as usual.
@ivanfioravanti Ivan Fioravanti on x
Unbelievable intelligence compressed in a Flash model! Probably going big big big is not the right answer. Smaller, less expensive and more capable models is the real way.
@ypwang61 Yiping Wang on x
A future where AGI is accessible and affordable enough to be used correctly by anyone, anywhere.
@aravsrinivas Aravind Srinivas on x
Wow!
@testingcatalog @testingcatalog on x
DeepSeek V4.1 Flash is now available on Huggingface! > 552B parameters MoE model with a new Encoder-Decoder structure. > V4.1 Flash adopted a new pre-training method and underwent larger-scale reinforcement learning post-training. > The smallest model in DeepSeek new architecture…
@zephyr_z9 @zephyr_z9 on x
The whale strikes back!!!
@doubilitysteven Wen Liu on x
make “encoder-decoder” great again😉
@deepseek_ai @deepseek_ai on x
🌐 Supporting open source. Expanding deployment options. We'll work closely with the open-source community on V4.1-Flash inference support and explore more deployment options. Planning a large-scale deployment with 2,000 GPUs + a storage cluster? Let's talk. 🔹 Model: https://huggi…
@sheriyuo Xiuyu Li on x
DeepSeek V4.1 Flash, with its almost unreal RL results, has brought us back to an RL era that felt like it had disappeared. RL, rise again. BERT, rise again. https://huggingface.co/...
@whoareme33 Nick Mykhailyshyn on x
deepseek-v4.1-flash is insane! it found a 0day RCE in handlebars.js v4.7.9 in minutes for just $0.05 what's interesting is that deepseek-v4-pro-0813 needed multiple runs with the same prompt. flash found it consistently. security researchers, we're so cooked :)
Deedy Das Deedy Das on linkedin
DeepSeek might be the new king of open-source models. It obliterates GLM 5.3 and Kimi K3 on benchmarks while being 4x and 10x cheaper. …
@jessefelder.com Jesse Felder on bluesky
‘DeepSeek rolled out an AI model that charges as little as a fraction of a cent per million tokens, ramping up the pressure on rivals from Anthropic PBC to Z.AI Co.’ www.bloomberg.com/news/article... [image]
r/opencodeCLI r on reddit
deepseek-ai/DeepSeek-V4.1-Flash · Hugging Face LAUNCHED
r/LocalLLM r on reddit
DeepSeek-V4.1-Flash is out
r/LocalLLaMA r on reddit
deepseek-ai/DeepSeek-V4.1-Flash · Hugging Face

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