Claude Sonnet 4.5 vs o3-pro
Claude Sonnet 4.5 (2025) and o3-pro (2025) are frontier-tier reasoning models from Anthropic and OpenAI. Claude Sonnet 4.5 ships a 200k-token context window, while o3-pro ships a 200k-token context window. On Google-Proof Q&A, o3-pro leads by 0.6 pts. On pricing, Claude Sonnet 4.5 ranges from $3 to $6/1M input tokens by tier; o3-pro costs $20/1M input tokens. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Claude Sonnet 4.5 is safer overall; choose o3-pro when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Claude Sonnet 4.5 | o3-pro |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200k | 200k |
| Cheapest output | $15/1M tokens | $80/1M tokens |
| Provider routes | 8 tracked | 3 tracked |
| Shared benchmarks | 1 rows | Google-Proof Q&A leader |
Decision tradeoffs
- Claude Sonnet 4.5 has the lower cheapest tracked output price at $15/1M tokens.
- Claude Sonnet 4.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.
- o3-pro holds a shared-benchmark lead on Google-Proof Q&A, ahead by 0.6 points.
- o3-pro uniquely exposes Code execution in local model data.
- Local decision data tags o3-pro for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Sonnet 4.5
$6,150
Cheapest tracked route/tier: Microsoft Foundry
o3-pro
$36,000
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $29,850. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- o3-pro is $65/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- o3-pro adds Code execution in local capability data.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- Claude Sonnet 4.5 is $65/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-09-29 | 2025-06-10 |
| Context window | 200k | 200k |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | 2025-12 | 2025-08 |
Pricing and availability
| Pricing attribute | Claude Sonnet 4.5 | o3-pro |
|---|---|---|
| Input price |
| $20/1M tokens |
| Output price |
| $80/1M tokens |
| Providers |
Capabilities
| Capability | Claude Sonnet 4.5 | o3-pro |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Sonnet 4.5 | o3-pro |
|---|---|---|
| Google-Proof Q&A | 83.4 | 84.0 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has Claude Sonnet 4.5 at 83.4 and o3-pro at 84, with o3-pro ahead by 0.6 points. The largest visible gap is 0.6 points on Google-Proof Q&A, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on code execution: o3-pro. Both models share vision, multimodal input, reasoning mode, and function calling, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Claude Sonnet 4.5 lists tiered pricing: 0-200,001t is $3/1M input and $15/1M output; 200,001t+ is $6/1M input and $22.50/1M output, while o3-pro lists $20/1M input and $80/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Claude Sonnet 4.5 lower by about $31.40 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 8 providers versus 3, so concentration risk also matters.
Choose Claude Sonnet 4.5 when vision-heavy evaluation, lower cheapest-tier input-token cost, and broader provider choice are central to the workload. Choose o3-pro when coding workflow support are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Claude Sonnet 4.5 or o3-pro?
Claude Sonnet 4.5 supports 200k tokens, while o3-pro supports 200k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Claude Sonnet 4.5 or o3-pro?
Claude Sonnet 4.5 lists tiered pricing: 0-200,001t is $3/1M input and $15/1M output; 200,001t+ is $6/1M input and $22.50/1M output. o3-pro lists $20/1M input and $80/1M output tokens on the cheapest tracked provider. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is Claude Sonnet 4.5 or o3-pro open source?
Claude Sonnet 4.5 is listed under Proprietary. o3-pro is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Claude Sonnet 4.5 or o3-pro?
Both Claude Sonnet 4.5 and o3-pro expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Claude Sonnet 4.5 or o3-pro?
Both Claude Sonnet 4.5 and o3-pro expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run Claude Sonnet 4.5 and o3-pro?
Claude Sonnet 4.5 is available on Microsoft Foundry, Anthropic, Snowflake Cortex, GCP Vertex AI, and AWS Bedrock. o3-pro is available on OpenRouter, OpenAI API, and Vercel AI Gateway. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-22. Data sourced from public model cards and provider documentation.