DeepSeek V4.1 Flash Opens Limited Internal Beta with New Architecture and Native Multimodality

Starting September 8, multiple sources reported that DeepSeek quietly opened a limited internal beta for V4.1 Flash, a "middle version" with model ID deepseek-v4.1-flash-expires-on-0910, the slug indicating expiry on September 10. Key upgrades include a brand-new architecture and native multimodality, with the official line claiming stronger capability, faster speed, and lower cost. Calling conventions, billing, and concurrency rules are now largely clear, developer benchmarks have emerged, and the model has appeared on Hugging Face, though an official public announcement and full evaluations remain pending.

Confirmed

• Jiqizhixin reported that DeepSeek officially announced the internal test of the V4.1 Flash middle version; APPSO, Zhidongxi and other outlets confirmed the same.
• Usage: keep baseurl unchanged and set the model name to an ID beginning with deepseek-v4.1-flash-expires-on-09 (e.g., deepseek-v4.1-flash-expires-on-0910), where the date marks expiry.
• According to vista8's relay of an official WeChat group notice, billing matches V4 Flash with max 20 concurrent requests per account; teortaxesTex's leaked info points to the same concurrency limit and a vision-capable build (V4-Flash-Vision [Intermediate]).
• On pricing, MiaAIlab (relayed by MicahBerkley) described the price as extremely aggressive: roughly 58 million tokens per US dollar, available for about 2 days.
• Third-party account LuminaBench spotted the intermediate build being tested via API; tokenbender suggested it precedes the official release.
• On September 10, Kevin Kern tested the preview endpoint, measuring 300 tok/s and heavily parallelizing subagents; he noted the preview endpoint does not yet accept vision input. Zhidongxi reported output speeds up to 507 tokens/s.
• On September 10, Reddit users found a deepseek-ai/DeepSeek-V4.1-Flash model page on Hugging Face, suggesting a quiet official upload; specs unconfirmed.

Unconfirmed

• The news initially spread via bloggers such as op7418 and AGI Hunt from a DeepSeek WeChat group, unverified at the time; Jiqizhixin later framed it as officially announced, but a formal public announcement and full capability details are still pending.
• @NFTChen (relayed by solyarisoftware) claimed V4.1 Flash would be officially released around September 10 Beijing time, with V4 Pro requests routed at Flash pricing; not confirmed by DeepSeek.
• The preview endpoint's lack of vision input sits in tension with the "native multimodality" claim; whether the formal release adds vision remains to be seen.
• teortaxesTex relayed community banter hoping it can at least beat GLM 5.3 Flash outside of vision—opinion only, no benchmark basis.

Why it matters

• This is DeepSeek's first reported use of an "expires-on" middle-version limited beta with explicit billing and concurrency rules plus aggressive pricing, signaling a product cadence of rapid iteration through real developer workloads before formal release.
• Native multimodality marks a major upgrade to DeepSeek's flagship line; with 300 tok/s measured, an appearance on Hugging Face, and the community benchmarking it against GLM 5.3 Flash, the formal release's multimodal capabilities deserve close attention.

2026-09-08 ~ 2026-09-10 · 18 related posts

Full story(18 episodes)→

• Episode 1: DeepSeek V4.1 Flash Opens Limited Internal Beta with New Architecture and Native Multimodality(2026-09-08, 18 posts)
• Episode 2: DeepSeek V4.1 Flash Tested: Blazing 350 Tokens/s but Still Experimental(2026-09-08, 2 posts)
• Episode 3: DeepSeek cuts V4-Flash API prices with new peak/off-peak billing from Sept 10(2026-09-08, 6 posts)
• Episode 4: DeepSeek V4.1 Flash Nears Frontier Models at a Fraction of the Cost, Independent Tests Show(2026-09-09, 15 posts)
• Episode 5: DeepSeek Releases Open-Source V4.1 Flash, Beating Its Own Flagship at a Fraction of the Cost(2026-09-09, 57 posts)
• Episode 6: DeepSeek V4.1 Flash Leaks: 552B Asymmetric MoE Claimed to Rival GPT-5.6 Sol(2026-09-10, 21 posts)
• Episode 7: DeepSeek V4.1 Flash Benchmark Results Leak, Sparking Community Discussion(2026-09-10, 2 posts)
• Episode 8: DeepSeek Shrinks Per-Token KV Cache 54x in Nine Months to Sub-KB Levels(2026-09-10, 6 posts)
• Episode 9: Leaked DeepSeek-V4.1-Flash Touted as New Open-Source King(2026-09-10, 3 posts)
• Episode 10: Bug Hunt Bench Ranks Frontier Coding Models on 105 Real Bugs(2026-09-10, 13 posts)
• Episode 11: DeepSeek V4.1 Flash Confirmed to Center on YOCO Architecture(2026-09-10, 7 posts)
• Episode 12: Leaked DeepSeek V4.1 Flash Tech Report Reveals KV Cache-Obsessed Flagship(2026-09-11, 44 posts)
• Episode 13: DeepSeek V4.1 Flash tops Vals open-source index at $0.30 per run(2026-09-11, 2 posts)
• Episode 14: DeepSeek launches V4.1-Flash: 552B backbone, 1M-token context(2026-09-11, 5 posts)
• Episode 15: DeepSeek V4.1 Flash scores 40 in AA index despite rising hallucinations(2026-09-11, 2 posts)
• Episode 16: Inside KV-Cache Sharing: How DeepSeek CED and GLM 5.2 Differ(2026-09-11, 4 posts)
• Episode 17: DeepSeek 4.1 Flash Shows Big Gains in Kernel Engineering and Cost(2026-09-11, 2 posts)
• Episode 18: SGLang delivers Day 0 support for DeepSeek V4.1 Flash, hitting 873 tok/s(2026-09-12, 2 posts)

• How to call DeepSeek V4.1 Flash beta: model name and rate limits revealed — 赛博禅心 · 2026-09-08
• Rumored DeepSeek V4.1 Flash surfaces, user hopes it beats GLM 5.3 Flash — teortaxesTex · 2026-09-08
• Rumor: DeepSeek V4.1 Flash released with stronger native multimodal — op7418 · 2026-09-08
• DeepSeek V4.1 Flash reportedly in private beta with new architecture and native multimodal support — vista8 · 2026-09-08
• DeepSeek spotted testing V4-Flash-Vision: new arch, native multimodal, same price — teortaxesTex · 2026-09-08
• DeepSeek V4.1 Flash beta goes live with new architecture, native multimodality, up to 507 tokens/s — 智东西 · 2026-09-08
• DeepSeek quietly tests V4.1 Flash API beta with new architecture and native multimodality — tokenbender · 2026-09-08
• DeepSeek Opens Limited-Time Beta of V4.1Flash: New Architecture, Native Multimodal, Expires Sept 10 — APPSO · 2026-09-08
• DeepSeek Flash 4.1 spotted testing via API with new architecture, release imminent — kimmonismus · 2026-09-08
• DeepSeek v4.1 Flash flash sale: 58M tokens for $1, available for 2 days only — MicahBerkley · 2026-09-09
• DeepSeek v4.1 flash preview spotted running at ~300 tok/s, vision still missing — kevinkern · 2026-09-10
• [source] DeepSeek v4.1 Flash preview spotted: ~300 tok/s, fires lots of subagents, no vision yet — kevinkern · 2026-09-10
• Rumor: DeepSeek V4.1 Flash to launch ~Sept 10, V4 Pro requests rerouted at Flash pricing — solyarisoftware · 2026-09-10
• DeepSeek-V4.1-Flash spotted on Hugging Face, unannounced — t4a8945 · 2026-09-10

4 near-duplicate retellings: AGI Hunt · jiqizhixin · aigclink · Nunki08