Llama 3.1 405B vs Claude 3.5 Sonnet (Thinking)

Compare Llama 3.1 405B and Claude 3.5 Sonnet (Thinking): 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 Llama 3.1 405B Claude 3.5 Sonnet (Thinking)
CategoryOpen SourceReasoning
Parameters405B~500B
Context Window128K200K
Input Price$0.08/1M tokens$0.03/1M tokens
Output Price$0.14/1M tokens$0.15/1M tokens
Latency~600ms~600ms

Choose Llama 3.1 405B when:

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

Largest open model, Highest open-source quality

Choose Claude 3.5 Sonnet (Thinking) when:

  • ✓ Complex analysis
  • ✓ Multi-step logic
  • ✓ Verification tasks
Key Strengths:

Transparent thinking, Strong reasoning, Self-correction

Verdict: Llama 3.1 405B vs Claude 3.5 Sonnet (Thinking)

For cost efficiency, Claude 3.5 Sonnet (Thinking) wins at $0.03/1M input tokens. For speed, Claude 3.5 Sonnet (Thinking) is faster at ~600ms. Llama 3.1 405B excels at Premium tasks while Claude 3.5 Sonnet (Thinking) is better for Complex analysis. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

Llama 3.1 405B costs $0.08/1M input tokens and $0.14/1M output tokens. Claude 3.5 Sonnet (Thinking) costs $0.03 input and $0.15 output. Claude 3.5 Sonnet (Thinking) is 2.7x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

Llama 3.1 405B has a 128K context window with ~600ms latency. Claude 3.5 Sonnet (Thinking) offers 200K context at ~600ms. Claude 3.5 Sonnet (Thinking) has the larger context window.

Best For

Llama 3.1 405B (Open Source) is optimized for: Premium tasks, Research, Fine-tuning base. Claude 3.5 Sonnet (Thinking) (Reasoning) works best for: Complex analysis, Multi-step logic, Verification tasks.

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

# Use Claude 3.5 Sonnet (Thinking)
response_b = client.chat.completions.create(
    model="claude-3-5-sonnet-thinking",
    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, Llama 3.1 405B or Claude 3.5 Sonnet (Thinking)?

Llama 3.1 405B (Open Source, 405B) offers Largest open model. Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) offers Transparent thinking. Choose Llama 3.1 405B for Premium tasks or Claude 3.5 Sonnet (Thinking) for Complex analysis.

How much does Llama 3.1 405B cost vs Claude 3.5 Sonnet (Thinking)?

Llama 3.1 405B: $0.08/1M input, $0.14/1M output. Claude 3.5 Sonnet (Thinking): $0.03/1M input, $0.15/1M 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 Llama 3.1 405B and Claude 3.5 Sonnet (Thinking) 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.