GPT-5.5 or Claude Sonnet 5?
Choose GPT-5.5 when existing gpt-5.5 production workflows and migration baselines is the closer match. Choose Claude Sonnet 5 when production coding and agents where speed and quality both matter matters more. Test both on the same real tasks before moving a production workflow.
Existing GPT-5.5 production workflows and migration baselines
Production coding and agents where speed and quality both matter
GPT-5.5
Earlier flagship model for coding and complex professional work.
Official specification ↗Claude Sonnet 5
Anthropic's fast workhorse model balancing intelligence, speed and price.
Official specification ↗Side-by-side comparison
| Category | GPT-5.5 | Claude Sonnet 5 |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Type | Model · Reasoning model | Model · Balanced reasoning model |
| Pricing summary | $5 input, $0.50 cached input and $30 output per 1M tokens | $2 input, $0.20 cache read and $10 output per 1M tokens |
| Input price | $5 / 1M tokens | $2 / 1M tokens |
| Cached input | $0.50 / 1M tokens | $0.20 / 1M tokens |
| Output price | $30 / 1M tokens | $10 / 1M tokens |
| Context window | 1.05M tokens | 1M tokens |
| Maximum output | 128K tokens | 128K tokens |
| Knowledge cutoff | December 1, 2025 | January 2026 |
| Reasoning | none, low, medium, high, xhigh | Adaptive; high default effort |
| Relative speed | Moderate | Fast |
| Input modalities | Text and image | Text and image |
| Output modalities | Text | Text |
| Tools and integrations | Functions, web search, file search, computer use and supported Responses API tools | Claude API tool use, computer use and agent workflows |
| API / access | v1/responses, v1/chat/completions and v1/batch | Claude Messages API |
| Best fit | Existing GPT-5.5 production workflows and migration baselines | Production coding and agents where speed and quality both matter |
| Company | OpenAI | Anthropic |
| Product category | Model · Reasoning model | Model · Balanced reasoning model |
| Current pricing note | $5 input, $0.50 cached input and $30 output per 1M tokens | $2 input, $0.20 cache read and $10 output per 1M tokens |
| Best suited to | Existing GPT-5.5 production workflows and migration baselines | Production coding and agents where speed and quality both matter |
| Key capabilities | 1.05M context; 128K maximum output; Vision input; Responses API tools | Agentic coding; Adaptive thinking; 1M context; Fast production work |
| Last verified | 2026-09-08 | 2026-09-08 |
| Official product source | https://developers.openai.com/api/docs/models/gpt-5.5 | https://platform.claude.com/docs/en/models/sonnet-5/overview |
How we reached this verdict
We looked at the things that affect everyday use: what each product can do, how its plans are structured, where it fits into your existing workflow, and what the provider currently documents. Benchmark results are useful context, but they are not a universal winner score because test settings and tools vary.
Common questions
GPT-5.5 or Claude Sonnet 5: which should I choose?
Choose GPT-5.5 for existing gpt-5.5 production workflows and migration baselines. Choose Claude Sonnet 5 for production coding and agents where speed and quality both matter. Validate the decision with your own prompts and total task cost.
Is GPT-5.5 cheaper than Claude Sonnet 5?
Pricing units can differ. GPT-5.5: $5 input, $0.50 cached input and $30 output per 1M tokens. Claude Sonnet 5: $2 input, $0.20 cache read and $10 output per 1M tokens. Check tool charges, plan limits, caching and long-context rules before comparing totals.
Which is better for coding and agent work?
Capability depends on the selected product surface, tools and harness. GPT-5.5 is positioned for existing gpt-5.5 production workflows and migration baselines; Claude Sonnet 5 is positioned for production coding and agents where speed and quality both matter. Run the same repository task on both.
How do their context windows compare?
GPT-5.5 lists 1.05M tokens; Claude Sonnet 5 lists 1M tokens. A larger limit does not by itself guarantee better retrieval or lower cost.
Official sources
Use these provider pages to confirm current features, pricing and availability.
AI tools change quickly. We checked this page on 2026-09-08. Before you subscribe, confirm the latest price, regional availability and usage limits on the provider website.