DeepSeek V4 Flash vs Qwen3.5-397B-A17B

Name: DeepSeek V4 Flash
Author: DeepSeek

DeepSeek V4 Flash (2026) and Qwen3.5-397B-A17B (2026) are frontier-tier reasoning models from DeepSeek and Alibaba. DeepSeek V4 Flash ships a 1m-token context window, while Qwen3.5-397B-A17B ships a 262k-token context window. On MMLU PRO, Qwen3.5-397B-A17B leads by 1.4 pts. On pricing, DeepSeek V4 Flash ranges from $0.22 to $0.44/1M input tokens by tier; Qwen3.5-397B-A17B costs $0.39/1M input tokens. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

DeepSeek V4 Flash is safer overall; choose Qwen3.5-397B-A17B when vision-heavy evaluation matters.

Decision scorecard

Local evidence first

Signal	DeepSeek V4 Flash	Qwen3.5-397B-A17B	How to read it
Best for	reasoning-heavy apps, tool-calling agents, and long-context analysis	reasoning-heavy apps, multimodal apps, and tool-calling agents	Use-case synthesis from product type, capability flags, context, and provider data.
Decision fit	Coding, RAG, and Agents	Coding, RAG, and Agents	Primary workload tags from local decision data.
Context window	1m	262k	Higher is better when prompts, retrieval chunks, or transcripts are large.
Cheapest output	$0.12/1M tokens	$2.34/1M tokens	Cheapest tracked provider route; verify your exact region and tier.
Provider routes	5 tracked	4 tracked	Broader coverage can reduce vendor lock-in and fallback risk.
Shared benchmarks	6 shared	MMLU PRO leader	Visible benchmark lead is 1.4 points on MMLU PRO.

Decision tradeoffs

Choose DeepSeek V4 Flash when...

DeepSeek V4 Flash holds a shared-benchmark lead on SWE-bench Verified, ahead by 2.8 points.
DeepSeek V4 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
DeepSeek V4 Flash has the lower cheapest tracked output price at $0.12/1M tokens.
DeepSeek V4 Flash has broader tracked provider coverage for fallback and route flexibility.
Local decision data tags DeepSeek V4 Flash for Coding, RAG, and Agents.

Choose Qwen3.5-397B-A17B when...

Qwen3.5-397B-A17B holds a shared-benchmark lead on MMLU PRO, ahead by 1.4 points.
Qwen3.5-397B-A17B uniquely exposes Vision and Multimodal in local model data.
Local decision data tags Qwen3.5-397B-A17B for Coding, RAG, and Agents.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate DeepSeek V4 Flash

Requests / monthInput tokens / requestOutput tokens / request

DeepSeek V4 Flash

$76.26

Cheapest tracked route/tier: OpenRouter

Qwen3.5-397B-A17B

$897

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $821. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

DeepSeek V4 Flash -> Qwen3.5-397B-A17B

Provider overlap exists on OpenRouter and Novita AI; start route-level A/B tests there.
Qwen3.5-397B-A17B is $2.22/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Qwen3.5-397B-A17B adds Vision and Multimodal in local capability data.

Qwen3.5-397B-A17B -> DeepSeek V4 Flash

Provider overlap exists on OpenRouter and Novita AI; start route-level A/B tests there.
DeepSeek V4 Flash is $2.22/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
Check replacement coverage for Vision and Multimodal before moving production traffic.

Specs

Specification	DeepSeek V4 Flash DeepSeek	Qwen3.5-397B-A17B Alibaba
Released	2026-04-24	2026-02-16
Context window	1m	262k
Parameters	284B	397B
Architecture	Mixture of Experts	Mixture of Experts
License	MITOSI-approved	Apache 2.0OSI-approved
Openness	Open source	Open source
Weights	Available	Available
Code	Unknown	Unknown
Commercial use	Commercial use: permitted	Commercial use: permitted
Knowledge cutoff	-	-

Pricing and availability

Pricing attribute	DeepSeek V4 Flash	Qwen3.5-397B-A17B
Input price	Off-peak $0.22/1M tokens All UTC hours outside DeepSeek's peak windows. Cache-hit input: $0.007 per 1M tokens; cache-miss input: $0.22 per 1M; output: $0.66 per 1M. Peak $0.44/1M tokens 01:00-04:00 and 06:00-10:00 UTC. Cache-hit input: $0.014 per 1M tokens; cache-miss input: $0.44 per 1M; output: $1.32 per 1M.	$0.39/1M tokens
Output price	Off-peak $0.66/1M tokens All UTC hours outside DeepSeek's peak windows. Cache-hit input: $0.007 per 1M tokens; cache-miss input: $0.22 per 1M; output: $0.66 per 1M. Peak $1.32/1M tokens 01:00-04:00 and 06:00-10:00 UTC. Cache-hit input: $0.014 per 1M tokens; cache-miss input: $0.44 per 1M; output: $1.32 per 1M.	$2.34/1M tokens
Providers	DeepSeek Platform OpenRouter Microsoft Foundry Vercel AI Gateway Novita AI	OpenRouter Together AI Alibaba Cloud PAI-EAS Novita AI

Capabilities

Capability	DeepSeek V4 Flash	Qwen3.5-397B-A17B
Vision	No	Yes
Multimodal	No	Yes
Reasoning	Yes	Yes
JSON / Tool use	Yes	Yes
Structured outputs	Yes	Yes
Code execution	No	No
IDE integration	No	No
Computer use	No	No
Parallel agents	No	No

Benchmarks

Benchmark	DeepSeek V4 Flash	Qwen3.5-397B-A17B
MMLU PRO	86.4	87.8
SWE-bench Verified	79.0	76.2
Google-Proof Q&A	88.1	89.3
LiveCodeBench	91.6	83.6
Humanity's Last Exam	34.8	28.7
Terminal-Bench 2.0	56.9	52.5

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Last reviewed: 2026-07-03. Data sourced from public model cards and provider documentation.

Both models

DeepSeek V4 Flash Qwen3.5-397B-A17B