DeepSeek-V4.1-Flash (API model: deepseek-flash): released 2026-09-10, 552B-parameter MoE with a Causal Encoder-Decoder architecture (only 8B active parameters for input, 16B for output), 1M-token context, MIT-licensed. Peak pricing: input $0.30 / output $1.20 per 1M tokens (off-peak halved) — cheaper than the predecessor V4-Flash. Terminal-Bench 4.0 jumps from 7.0 to 31.2, DeepSWE v1.1 (74.2) ties Claude Opus 5 (74.0). KV cache compressed to 890 bytes/token (1/4 of the predecessor, 437x less than DeepSeek-V1). DeepSeek announced that starting Sept 14, all traffic to its own V4-Pro flagship will be routed to this Flash model and billed at Flash rates.
DeepSeek-V4.1-Flash (`deepseek-flash`) is a 552B MoE with 8B prefill and 16B decode active parameters, a 1M-token context window, and 384K maximum output. It is MIT-licensed, priced at $0.30 input and $1.20 output per million peak-hour tokens, and brings CED, CSA2, and FP4 KV-cache compression to agent workloads.
DeepSeek-V4-Flash-Vision-Exp: 284B total / 13B active-parameter MoE, 1M context, 384K max output; priced identically to plain V4-Flash (Input $0.44 / Output $1.32 at peak, half that off-peak); wins 6 of 7 text-agent benchmarks against its own predecessor (DeepSWE hits 59.3, edging past Opus-4.8's 58.0); multimodal-agent scores close in on Opus-4.8 (trails by 2.9 on ApexBench, actually leads on ZeroBench); each image is capped at 384 tokens / roughly 800×800 resolution, trading fine detail for near-zero cost
DeepSeek used MLA and MoE innovations to drive inference costs to an industry low. V4 Flash activates only 13B parameters while approaching frontier-model quality and ranks first by OpenRouter usage. This guide traces V1 through V4, the R1 reasoning branch, and how to choose each version.