Claude 3.5 Sonnet (Thinking) vs o3 Pro
Compare Claude 3.5 Sonnet (Thinking) and o3 Pro: 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 3.5 Sonnet (Thinking) | o3 Pro |
|---|---|---|
| Category | Reasoning | Reasoning |
| Parameters | ~500B | ~1T |
| Context Window | 200K | 200K |
| Input Price | $0.03/1M tokens | $0.15/1M tokens |
| Output Price | $0.15/1M tokens | $0.60/1M tokens |
| Latency | ~600ms | ~5000ms |
Choose Claude 3.5 Sonnet (Thinking) when:
- ✓ Complex analysis
- ✓ Multi-step logic
- ✓ Verification tasks
Transparent thinking, Strong reasoning, Self-correction
Choose o3 Pro when:
- ✓ Research-grade reasoning
- ✓ Mathematical proofs
- ✓ Hardest problems
Deepest reasoning, Best for hard problems, Highest accuracy
Verdict: Claude 3.5 Sonnet (Thinking) vs o3 Pro
For cost efficiency, Claude 3.5 Sonnet (Thinking) wins at $0.03/1M input tokens. For speed, o3 Pro is faster at ~5000ms. Claude 3.5 Sonnet (Thinking) excels at Complex analysis while o3 Pro is better for Research-grade reasoning. 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 3.5 Sonnet (Thinking) costs $0.03/1M input tokens and $0.15/1M output tokens. o3 Pro costs $0.15 input and $0.60 output. Claude 3.5 Sonnet (Thinking) is 5.0x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.
Performance & Context
Claude 3.5 Sonnet (Thinking) has a 200K context window with ~600ms latency. o3 Pro offers 200K context at ~5000ms. Both have identical context windows.
Best For
Claude 3.5 Sonnet (Thinking) (Reasoning) is optimized for: Complex analysis, Multi-step logic, Verification tasks. o3 Pro (Reasoning) works best for: Research-grade reasoning, Mathematical proofs, Hardest problems.
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 3.5 Sonnet (Thinking)
response_a = client.chat.completions.create(
model="claude-3-5-sonnet-thinking",
messages=[{"role": "user", "content": "Your question here"}]
)
# Use o3 Pro
response_b = client.chat.completions.create(
model="o3-pro",
messages=[{"role": "user", "content": "Your question here"}]
)Frequently Asked Questions
Which is better, Claude 3.5 Sonnet (Thinking) or o3 Pro?
Claude 3.5 Sonnet (Thinking) (Reasoning, ~500B) offers Transparent thinking. o3 Pro (Reasoning, ~1T) offers Deepest reasoning. Choose Claude 3.5 Sonnet (Thinking) for Complex analysis or o3 Pro for Research-grade reasoning.
How much does Claude 3.5 Sonnet (Thinking) cost vs o3 Pro?
Claude 3.5 Sonnet (Thinking): $0.03/1M input, $0.15/1M output. o3 Pro: $0.15/1M input, $0.60/1M 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 3.5 Sonnet (Thinking) and o3 Pro 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.