Llama 3.1 405B Instruct vs Phi-4 Mini Flash Reasoning

Name: Llama 3.1 405B Instruct
Author: AI at Meta

Llama 3.1 405B Instruct (2024) and Phi-4 Mini Flash Reasoning (2025) are frontier reasoning models from AI at Meta and Microsoft Research. Llama 3.1 405B Instruct ships a 128k-token context window, while Phi-4 Mini Flash Reasoning ships a 128k-token context window. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Phi-4 Mini Flash Reasoning is safer overall; choose Llama 3.1 405B Instruct when provider fit matters.

Decision scorecard

Local evidence first

Signal	Llama 3.1 405B Instruct	Phi-4 Mini Flash Reasoning	How to read it
Best for	provider-routed production	reasoning-heavy apps	Use-case synthesis from product type, capability flags, context, and provider data.
Decision fit	RAG, Long context, and Classification	Long context	Primary workload tags from local decision data.
Context window	128k	128k	Higher is better when prompts, retrieval chunks, or transcripts are large.
Cheapest output	$2.40/1M tokens	-	Cheapest tracked provider route; verify your exact region and tier.
Provider routes	11 tracked	1 tracked	Broader coverage can reduce vendor lock-in and fallback risk.
Shared benchmarks	0 shared	0 shared	No shared benchmark scores are available for this pair yet.

Decision tradeoffs

Choose Llama 3.1 405B Instruct when...

Llama 3.1 405B Instruct has broader tracked provider coverage for fallback and route flexibility.
Llama 3.1 405B Instruct uniquely exposes Structured outputs in local model data.
Local decision data tags Llama 3.1 405B Instruct for RAG, Long context, and Classification.

Choose Phi-4 Mini Flash Reasoning when...

Phi-4 Mini Flash Reasoning uniquely exposes Reasoning in local model data.
Local decision data tags Phi-4 Mini Flash Reasoning for Long context.

Monthly cost at traffic

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

Requests / monthInput tokens / requestOutput tokens / request

Llama 3.1 405B Instruct

$2,520

Cheapest tracked route/tier: AWS Bedrock

Phi-4 Mini Flash Reasoning

Unavailable

No complete token price in local provider data

Cost delta unavailable until both models have sourced input and output token prices.

Switch friction

Llama 3.1 405B Instruct -> Phi-4 Mini Flash Reasoning

Provider overlap exists on NVIDIA NIM; start route-level A/B tests there.
Check replacement coverage for Structured outputs before moving production traffic.
Phi-4 Mini Flash Reasoning adds Reasoning in local capability data.

Phi-4 Mini Flash Reasoning -> Llama 3.1 405B Instruct

Provider overlap exists on NVIDIA NIM; start route-level A/B tests there.
Check replacement coverage for Reasoning before moving production traffic.
Llama 3.1 405B Instruct adds Structured outputs in local capability data.

Specs

Specification	Llama 3.1 405B Instruct AI at Meta	Phi-4 Mini Flash Reasoning Microsoft Research
Released	2024-07-23	2025-12-01
Context window	128k	128k
Parameters	405B	3.8B
Architecture	Decoder Only	Decoder Only
License	Llama 3 Community	MITOSI-approved
Openness	Open weights	Open source
Weights	Available	Unknown
Code	Unknown	Unknown
Commercial use	Commercial use: conditional	Commercial use: permitted
Knowledge cutoff	2023-12	2025-02

Pricing and availability

Pricing attribute	Llama 3.1 405B Instruct	Phi-4 Mini Flash Reasoning
Input price	$2.40/1M tokens	-
Output price	$2.40/1M tokens	-
Providers	OctoAI API (Deprecated)Together AI Fireworks AI IBM watsonx Scale AI GenAI Platform NVIDIA NIM	NVIDIA NIM

Capabilities

Capability	Llama 3.1 405B Instruct	Phi-4 Mini Flash Reasoning
Vision	No	No
Multimodal	No	No
Reasoning	No	Yes
JSON / Tool use	No	No
Structured outputs	Yes	No
Code execution	No	No
IDE integration	No	No
Computer use	No	No
Parallel agents	No	No

Benchmarks

No shared benchmark scores are currently available for this pair.

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Model pages

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

Both models

Llama 3.1 405B Instruct Phi-4 Mini Flash Reasoning