DeepSeek V4 Flash vs Llama 3.1 405B Instruct

Name: DeepSeek V4 Flash
Author: DeepSeek

DeepSeek V4 Flash (2026) and Llama 3.1 405B Instruct (2024) are frontier reasoning models from DeepSeek and AI at Meta. DeepSeek V4 Flash ships a 1m-token context window, while Llama 3.1 405B Instruct ships a 128k-token context window. On Massive Multitask Language Understanding, DeepSeek V4 Flash leads by 0.1 pts. 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 fits 8x more tokens; pick it for long-context work and Llama 3.1 405B Instruct for tighter calls.

Decision scorecard

Local evidence first

Signal	DeepSeek V4 Flash	Llama 3.1 405B Instruct	How to read it
Best for	reasoning-heavy apps, tool-calling agents, and long-context analysis	provider-routed production	Use-case synthesis from product type, capability flags, context, and provider data.
Decision fit	Coding, RAG, and Agents	RAG, Long context, and Classification	Primary workload tags from local decision data.
Context window	1m	128k	Higher is better when prompts, retrieval chunks, or transcripts are large.
Cheapest output	$0.12/1M tokens	$2.40/1M tokens	Cheapest tracked provider route; verify your exact region and tier.
Provider routes	5 tracked	11 tracked	Broader coverage can reduce vendor lock-in and fallback risk.
Shared benchmarks	Massive Multitask Language Understanding leader	1 shared	Visible benchmark lead is 0.1 points on Massive Multitask Language Understanding.

Decision tradeoffs

Choose DeepSeek V4 Flash when...

DeepSeek V4 Flash holds a shared-benchmark lead on Massive Multitask Language Understanding, ahead by 0.1 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 uniquely exposes Reasoning and JSON / Tool use in local model data.
Local decision data tags DeepSeek V4 Flash for Coding, RAG, and Agents.

Choose Llama 3.1 405B Instruct when...

Llama 3.1 405B Instruct has broader tracked provider coverage for fallback and route flexibility.
Local decision data tags Llama 3.1 405B Instruct for RAG, Long context, and Classification.

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

Llama 3.1 405B Instruct

$2,520

Cheapest tracked route/tier: AWS Bedrock

Estimated monthly gap: $2,444. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

DeepSeek V4 Flash -> Llama 3.1 405B Instruct

Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
Llama 3.1 405B Instruct is $2.28/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Check replacement coverage for Reasoning and JSON / Tool use before moving production traffic.

Llama 3.1 405B Instruct -> DeepSeek V4 Flash

Provider overlap exists on Microsoft Foundry; start route-level A/B tests there.
DeepSeek V4 Flash is $2.28/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
DeepSeek V4 Flash adds Reasoning and JSON / Tool use in local capability data.

Specs

Specification	DeepSeek V4 Flash DeepSeek	Llama 3.1 405B Instruct AI at Meta
Released	2026-04-24	2024-07-23
Context window	1m	128k
Parameters	284B	405B
Architecture	Mixture of Experts	Decoder Only
License	MITOSI-approved	Llama 3 Community
Openness	Open source	Open weights
Weights	Available	Available
Code	Unknown	Unknown
Commercial use	Commercial use: permitted	Commercial use: conditional
Knowledge cutoff	-	2023-12

Pricing and availability

Pricing attribute	DeepSeek V4 Flash	Llama 3.1 405B Instruct
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.	$2.40/1M 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.	$2.40/1M tokens
Providers	DeepSeek Platform OpenRouter Microsoft Foundry Vercel AI Gateway Novita AI	OctoAI API (Deprecated)Together AI Fireworks AI IBM watsonx Scale AI GenAI Platform NVIDIA NIM

Capabilities

Capability	DeepSeek V4 Flash	Llama 3.1 405B Instruct
Vision	No	No
Multimodal	No	No
Reasoning	Yes	No
JSON / Tool use	Yes	No
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	Llama 3.1 405B Instruct
Massive Multitask Language Understanding	88.7	88.6

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Last reviewed: 2026-07-11. Data sourced from public model cards and provider documentation.

Both models

DeepSeek V4 Flash Llama 3.1 405B Instruct