The AI arena is free today

Open Superagent

Llama 3.1 405B Instruct vs Step-3.5-Flash

Step-3.5-Flash leads the LLM Stats Score 37.2 to 14.7. Step-3.5-Flash is 5.1x cheaper per token.

Meta · StepFun · Updated for 2026

Which is better?

Step-3.5-Flash leads the overall LLM Stats Score 37.2 to 14.7, ranking #68 overall.

On price, Step-3.5-Flash is roughly 5.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Llama 3.1 405B Instruct also accepts a larger context window (128,000 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Llama 3.1 405B Instruct

  • you process long inputs — it offers a 128,000 token context window

Choose Step-3.5-Flash

  • overall performance matters — it scores 37.2 and ranks #68 on LLM Stats
  • your work emphasizes reasoning — it leads those capability indexes
  • cost matters — it's about 5.1x cheaper per token
  • you want the most recent training data — it shipped Feb 2026

At a glance

The differences that matter most.

Llama 3.1 405B Instruct
Meta
Step-3.5-Flash
StepFun
Core performance indexes
LLM Stats Score
14.7
#232
37.2
#68
Reasoning
13.8
#232
37.2
#69
Coding
11.5
#153
20.5
#95
Cost, coverage & limits
Benchmark wins
—
—
Input price
$0.89 / M
$0.10 / M
Output price
$0.89 / M
$0.40 / M
Context window
128,000
65,536

Capability indexes

Additional strengths measured across groups of related public benchmarks

2 shared
Index
Llama 3.1 405B Instruct
Step-3.5-Flash
Math
19.3#168
33.9#50
Tool use
30.8#14
13.3#96
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

18 reported for Llama 3.1 405B Instruct · 7 for Step-3.5-Flash

No common benchmarks found

Llama 3.1 405B Instruct and Step-3.5-Flashdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Step-3.5-Flash costs less

For input processing, Llama 3.1 405B Instruct ($0.89/1M tokens) is 8.9x more expensive than Step-3.5-Flash ($0.10/1M tokens).

For output processing, Llama 3.1 405B Instruct ($0.89/1M tokens) is 2.2x more expensive than Step-3.5-Flash ($0.40/1M tokens).

In conclusion, Llama 3.1 405B Instruct is more expensive than Step-3.5-Flash.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Sun Sep 13 2026 • llm-stats.com
Meta
Llama 3.1 405B Instruct
Input tokens$0.89
Output tokens$0.89
Best providerLambda
StepFun
Step-3.5-Flash
Input tokens$0.10
Output tokens$0.40
Best providerStepFun
Notice missing or incorrect data?Start an Issue→

Model Size

Parameter count comparison

209.0B diff

Llama 3.1 405B Instruct has 209.0B more parameters than Step-3.5-Flash, making it 106.6% larger.

Meta
Llama 3.1 405B Instruct
405.0Bparameters
StepFun
Step-3.5-Flash
196.0Bparameters
405.0B
Llama 3.1 405B Instruct
196.0B
Step-3.5-Flash

Context Window

Maximum input and output token capacity

Llama 3.1 405B Instruct accepts 128,000 input tokens compared to Step-3.5-Flash's 65,536 tokens. Llama 3.1 405B Instruct can generate longer responses up to 128,000 tokens, while Step-3.5-Flash is limited to 8,192 tokens.

Meta
Llama 3.1 405B Instruct
Input128,000 tokens
Output128,000 tokens
StepFun
Step-3.5-Flash
Input65,536 tokens
Output8,192 tokens
Sun Sep 13 2026 • llm-stats.com

License

Usage and distribution terms

Llama 3.1 405B Instruct is licensed under Llama 3.1 Community License, while Step-3.5-Flash uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

Llama 3.1 405B Instruct

Llama 3.1 Community License

Open weights

Step-3.5-Flash

Apache 2.0

Open weights

Release Timeline

When each model was launched

Llama 3.1 405B Instruct was released on 2024-07-23, while Step-3.5-Flash was released on 2026-02-02.

Step-3.5-Flash is 19 months newer than Llama 3.1 405B Instruct.

Llama 3.1 405B Instruct

Jul 23, 2024

2.1 years ago

Step-3.5-Flash

Feb 2, 2026

7 months ago

1.5yr newer

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Llama 3.1 405B Instruct is available from Lambda, DeepInfra, Fireworks, Bedrock, Together, Hyperbolic, Google, Replicate. Step-3.5-Flash is available from StepFun.

Llama 3.1 405B Instruct

lambda logo
Lambda
Input Price:Input: $0.89/1MOutput Price:Output: $0.89/1M
deepinfra logo
Deepinfra
Input Price:Input: $1.79/1MOutput Price:Output: $1.79/1M
fireworks logo
Fireworks
Input Price:Input: $3.00/1MOutput Price:Output: $3.00/1M
bedrock logo
AWS Bedrock
Input Price:Input: $3.00/1MOutput Price:Output: $3.00/1M
together logo
Together
Input Price:Input: $3.50/1MOutput Price:Output: $3.50/1M
hyperbolic logo
Hyperbolic
Input Price:Input: $4.00/1MOutput Price:Output: $4.00/1M
google logo
Google
Input Price:Input: $5.00/1MOutput Price:Output: $16.00/1M
replicate logo
Replicate
Input Price:Input: $9.50/1MOutput Price:Output: $9.50/1M

Step-3.5-Flash

stepfun logo
StepFun
Input Price:Input: $0.10/1MOutput Price:Output: $0.40/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Llama 3.1 405B Instruct and Step-3.5-Flash side-by-side, then vote on the output you prefer.

Llama 3.1 405B Instruct
✓ Preferred
Step-3.5-Flash
Open in Playground

FAQ

Common questions about Llama 3.1 405B Instruct vs Step-3.5-Flash.

Which is better, Llama 3.1 405B Instruct or Step-3.5-Flash?

Step-3.5-Flash leads the LLM Stats Score 37.2 to 14.7. Llama 3.1 405B Instruct is made by Meta and Step-3.5-Flash is made by StepFun. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Llama 3.1 405B Instruct compare to Step-3.5-Flash in benchmarks?

Llama 3.1 405B Instruct scores ARC-C: 96.9%, GSM8k: 96.8%, API-Bank: 92.0%, Multilingual MGSM (CoT): 91.6%, HumanEval: 89.0%. Step-3.5-Flash scores AIME 2025: 97.3%, Tau-bench: 88.2%, LiveCodeBench v6: 86.4%, IMO-AnswerBench: 85.4%, SWE-Bench Verified: 74.4%.

Is Llama 3.1 405B Instruct cheaper than Step-3.5-Flash?

Step-3.5-Flash is 8.9x cheaper for input tokens. Llama 3.1 405B Instruct costs $0.89/M input and $0.89/M output via lambda. Step-3.5-Flash costs $0.10/M input and $0.40/M output via stepfun.

What are the context window sizes for Llama 3.1 405B Instruct and Step-3.5-Flash?

Llama 3.1 405B Instruct supports 128K tokens and Step-3.5-Flash supports 66K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Llama 3.1 405B Instruct and Step-3.5-Flash?

Key differences include LLM Stats Score (14.7 vs 37.2), context window (128K vs 66K), input pricing ($0.89 vs $0.10/M), licensing (Llama 3.1 Community License vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Llama 3.1 405B Instruct and Step-3.5-Flash?

Llama 3.1 405B Instruct is developed by Meta and Step-3.5-Flash is developed by StepFun.

Related comparisons