Claude Sonnet 4.5 vs Claude 3.5 Sonnet (Thinking)
Compare Claude Sonnet 4.5 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 4.5 | Claude 3.5 Sonnet (Thinking) |
|---|---|---|
| Category | Frontier | Reasoning |
| Parameters | ~600B | ~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 4.5 when:
- ✓ Code generation
- ✓ Structured output
- ✓ Automation
Strong coding, Better instruction following, Reliable
Choose Claude 3.5 Sonnet (Thinking) when:
- ✓ Complex analysis
- ✓ Multi-step logic
- ✓ Verification tasks
Transparent thinking, Strong reasoning, Self-correction
Verdict: Claude Sonnet 4.5 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 4.5 is faster at ~350ms. Claude Sonnet 4.5 excels at Code generation 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 4.5 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 4.5 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 4.5 (Frontier) is optimized for: Code generation, Structured output, Automation. 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 4.5
response_a = client.chat.completions.create(
model="claude-sonnet-4-5",
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 4.5 or Claude 3.5 Sonnet (Thinking)?
Claude Sonnet 4.5 (Frontier, ~600B) offers Strong coding. Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) offers Transparent thinking. Choose Claude Sonnet 4.5 for Code generation or Claude 3.5 Sonnet (Thinking) for Complex analysis.
How much does Claude Sonnet 4.5 cost vs Claude 3.5 Sonnet (Thinking)?
Claude Sonnet 4.5: $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 4.5 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.