Claude Sonnet 4 vs Claude 3.5 Sonnet (Thinking)
Compare Claude Sonnet 4 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
| Feature | Claude Sonnet 4 | Claude 3.5 Sonnet (Thinking) |
|---|---|---|
| Category | Frontier | Reasoning |
| Parameters | ~500B | ~500B |
| Context Window | 200K | 200K |
| Input Price | $0.03/1M tokens | $0.03/1M tokens |
| Output Price | $0.15/1M tokens | $0.15/1M tokens |
| Latency | ~350ms | ~600ms |
Choose Claude Sonnet 4 when:
- ✓ General Q&A
- ✓ Content generation
- ✓ Temple chatbots
Excellent reasoning-per-dollar, 200K context, Strong multilingual
Choose Claude 3.5 Sonnet (Thinking) when:
- ✓ Complex analysis
- ✓ Multi-step logic
- ✓ Verification tasks
Transparent thinking, Strong reasoning, Self-correction
Verdict: Claude Sonnet 4 vs Claude 3.5 Sonnet (Thinking)
For cost efficiency, Claude 3.5 Sonnet (Thinking) wins at $0.03/1M input tokens. For speed, Claude Sonnet 4 is faster at ~350ms. Claude Sonnet 4 excels at General Q&A 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
Claude Sonnet 4 costs $0.03/1M input tokens and $0.15/1M output tokens. Claude 3.5 Sonnet (Thinking) costs $0.03 input and $0.15 output. Both models are similarly priced. XALEN offers batch processing at 50% discount on both models.
Performance & Context
Claude Sonnet 4 has a 200K context window with ~350ms latency. Claude 3.5 Sonnet (Thinking) offers 200K context at ~600ms. Both have identical context windows.
Best For
Claude Sonnet 4 (Frontier) is optimized for: General Q&A, Content generation, Temple chatbots. 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 Claude Sonnet 4
response_a = client.chat.completions.create(
model="claude-sonnet-4",
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"}]
)Frequently Asked Questions
Which is better, Claude Sonnet 4 or Claude 3.5 Sonnet (Thinking)?
Claude Sonnet 4 (Frontier, ~500B) offers Excellent reasoning-per-dollar. Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) offers Transparent thinking. Choose Claude Sonnet 4 for General Q&A or Claude 3.5 Sonnet (Thinking) for Complex analysis.
How much does Claude Sonnet 4 cost vs Claude 3.5 Sonnet (Thinking)?
Claude Sonnet 4: $0.03/1M input, $0.15/1M 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 Claude Sonnet 4 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.