Claude Sonnet 4.6 vs GPT-5.5
2026 - Pricing, benchmarks, and use case comparison
Quick take
- •GPT-5.5 is open-weights - free to self-host with no API costs. Claude Sonnet 4.6 requires paid API access.
- •Claude Sonnet 4.6 has a 200K context window - 2x larger than GPT-5.5's 128K. Better for long documents and large codebases.
Specs comparison
| Claude Sonnet 4.6 | GPT-5.5 | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Type | Closed source | Closed source |
| Context window | ✓200K | 128K |
| Input / 1M tokens | $3.00 | ✓Free (self-host) |
| Output / 1M tokens | $15.00 | Free (self-host) |
| Release date | 2025-07 | 2026-04 |
Benchmarks
| Benchmark | Claude Sonnet 4.6 | GPT-5.5 |
|---|---|---|
| SWE-bench Verified | ~49% | - |
| MMLU | ~88% | - |
| HumanEval | ~93% | - |
Scores sourced from official provider release posts.
Strengths
Claude Sonnet 4.6
- ✓Strong coding and debugging across most languages
- ✓Excellent at following multi-step instructions
- ✓200K context handles entire codebases
- ✓Fast enough for interactive use cases
- ✓Solid function calling and structured output
GPT-5.5
- ✓Improved instruction following over GPT-4o
- ✓Stronger long-context coherence
- ✓Better output consistency for agentic pipelines
- ✓GPT-5.5 Pro tier for reliability-critical workloads
- ✓Easier migration path than jumping from GPT-4o to GPT-5
Which should you choose?
Choose Claude Sonnet 4.6 if you need...
- →Production API integrations
- →Coding assistants and IDEs
- →Document analysis
- →Agentic workflows
Choose GPT-5.5 if you need...
- →Production API integrations migrating from GPT-4o
- →Agentic workflows needing consistent structured output
- →Long-context document tasks
- →Teams deferring full GPT-5 migration costs