Claude Sonnet 4.5 vs Llama 3.1 405B

Compare Claude Sonnet 4.5 and Llama 3.1 405B: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.

Updated 2026-05-21 · By Abhishek Raj · Our methodology

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Feature Claude Sonnet 4.5 Llama 3.1 405B
CategoryFrontierOpen Source
Parameters~600B405B
Context Window200K128K
Input Price$0.03/1M tokens$0.08/1M tokens
Output Price$0.15/1M tokens$0.14/1M tokens
Latency~350ms~600ms

Choose Claude Sonnet 4.5 when:

  • ✓ Code generation
  • ✓ Structured output
  • ✓ Automation
Key Strengths:

Strong coding, Better instruction following, Reliable

Choose Llama 3.1 405B when:

  • ✓ Premium tasks
  • ✓ Research
  • ✓ Fine-tuning base
Key Strengths:

Largest open model, Highest open-source quality

Verdict: Claude Sonnet 4.5 vs Llama 3.1 405B

For cost efficiency, Claude Sonnet 4.5 wins at $0.03/1M input tokens. For speed, Claude Sonnet 4.5 is faster at ~350ms. Claude Sonnet 4.5 excels at Code generation while Llama 3.1 405B is better for Premium tasks. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

Claude Sonnet 4.5 costs $0.03/1M input tokens and $0.15/1M output tokens. Llama 3.1 405B costs $0.08 input and $0.14 output. Claude Sonnet 4.5 is 2.7x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

Claude Sonnet 4.5 has a 200K context window with ~350ms latency. Llama 3.1 405B offers 128K context at ~600ms. Claude Sonnet 4.5 has the larger context window.

Best For

Claude Sonnet 4.5 (Frontier) is optimized for: Code generation, Structured output, Automation. Llama 3.1 405B (Open Source) works best for: Premium tasks, Research, Fine-tuning base.

Try Both on XALEN

Both models are available through XALEN's OpenAI-compatible API. Switch between them by changing the model parameter:

from xalen import XALEN

client = XALEN(api_key="xln_test_YOUR_KEY")

# Use Claude Sonnet 4.5
response_a = client.chat.completions.create(
    model="claude-sonnet-4-5",
    messages=[{"role": "user", "content": "Your question here"}]
)

# Use Llama 3.1 405B
response_b = client.chat.completions.create(
    model="llama-3-1-405b",
    messages=[{"role": "user", "content": "Your question here"}]
)

Start Building with XALEN

200+ AI models. One API. Pay-as-you-go.

Get API Key Try in Playground

Frequently Asked Questions

Which is better, Claude Sonnet 4.5 or Llama 3.1 405B?

Claude Sonnet 4.5 (Frontier, ~600B) offers Strong coding. Llama 3.1 405B (Open Source, 405B) offers Largest open model. Choose Claude Sonnet 4.5 for Code generation or Llama 3.1 405B for Premium tasks.

How much does Claude Sonnet 4.5 cost vs Llama 3.1 405B?

Claude Sonnet 4.5: $0.03/1M input, $0.15/1M output. Llama 3.1 405B: $0.08/1M input, $0.14/1M output. Both available on XALEN with batch processing at 50% discount.

Can I use both models on XALEN?

Yes. XALEN provides 200+ models through a single OpenAI-compatible API. Switch between Claude Sonnet 4.5 and Llama 3.1 405B by changing the model parameter. No code changes needed.

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Last updated: 2026-05-21. Pricing and specifications may change. Check pricing page for latest rates.