July 31, 2026 · 7 min read

DeepSeek V4 Flash vs V4 Pro: Which One and When

DeepSeek's V4 family splits into two very different animals: Flash (284B MoE, 13B active), which got its big 0731 release today, and Pro (1.6T MoE, 49B active), the reasoning heavyweight still in preview on the API. Same 1M context, same MIT open weights policy, very different jobs. Here is the practical breakdown.

Spec Sheet

V4 Flash (0731)V4 Pro (Preview)
Total parameters284B1.6T
Active per token13B49B
Context1M in / 384K out1M in / 384K out
API price / M tokens$0.14 in, $0.28 out$0.435 in, $0.87 out
Responses API / CodexYes, native (0731)No
Open weightsMIT, on HFMIT, on HF
4 bit GGUF size~155 GB~900 GB (server only)
Runs at homeYes, 192 GB memory classNo

The Plot Twist: Flash Beats Pro at Agent Work

Until this morning the story was simple: Pro is the smart one, Flash is the cheap one. The 0731 re post training broke that. On Terminal Bench 2.1, Flash 0731 posts 82.7; on DeepSWE it jumped from 7.3 to 54.4; and across several code and agent benchmarks it now outscores the V4 Pro Preview, a model activating nearly four times the parameters per token. DeepSeek trained the small model into a specialist and, for agent loop workloads, the specialist wins.

Pro keeps the crown where breadth and depth dominate: hard math, long proofs, dense multi document reasoning. The 1.6T expert pool is not decoration; on deep reasoning evals Pro Preview remains ahead, and a future Pro release trained with the same agent recipe would presumably retake the lead. But that model is not here today, and Flash 0731 is.

Cost in Practice

The sticker gap says 3.1x on output, but agent reality widens it: agent loops burn output tokens (Flash's cheap side) and resend context (where cache hits cost fractions of a cent on both). A day of heavy agent work that costs single digit dollars on Flash lands in the tens on Pro. On flat plans the gap disappears from your bill: LU Labs carries both models in the Hosted Pro plan at 49€/mo against one quota, which makes switching per task free, in the way that produces the honest comparison: use both, notice which one you stop switching away from.

The Local Angle

This one is not close. Flash fits in 155 GB at 4 bit and runs on a 192 GB Mac Studio or big RAM workstation at interactive speeds (full math in the hardware post, setup in the local guide). Pro at 4 bit approaches 900 GB and wants a multi GPU node (details in the Pro guide). If owning the model matters to you, the family decision is already made, and the community agrees: the abliterated Flash build is the most downloaded uncensored model of 2026.

Verdict by Workload

WorkloadPick
Coding agents, terminal work, repo tasksFlash 0731, it benchmarks ahead and speaks Responses API
Everyday chat and writingFlash, the quality gap does not justify 3x
Hard math, proofs, research grade reasoningPro
Very long document analysis at full 1M contextPro (hosted; nobody runs 1M locally)
Running on your own hardwareFlash, by forfeit

Try both sides of the family: Flash on your GPU, Pro in the cloud, one interface.

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