Claude Sonnet 5 vs GPT-5.5
Pricing, benchmarks, and use case comparison
Verdict
Our pick: Claude Sonnet 5Pick Claude Sonnet 5 for cheaper, faster agentic coding with a strong terminal-agent record; pick GPT-5.5 for OpenAI's GA frontier default with a confirmed 1.05M context and top SWE-bench Verified.
Specs comparison
| Claude Sonnet 5 | GPT-5.5 | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Type | Closed source | Closed source |
| Context window | ✓1M | 1,050,000 tokens (128,000 max output) |
| Input / 1M tokens | ✓$3.00 | $5.00 |
| Output / 1M tokens | $15.00 | $30.00 |
| Release date | 2026-06 | 2026-04 |
Benchmarks
| Benchmark | Claude Sonnet 5 | GPT-5.5 |
|---|---|---|
| SWE-bench Verified | ✓~85.2% | 82.6% |
| Terminal-Bench 2.1 | 80.4% | - |
| SWE-bench Pro | ✓63.2% | 58.6% |
| OSWorld-Verified | 81.2% | - |
Scores sourced from official provider release posts and independent benchmark aggregators.
Capability and benchmarks
GPT-5.5 leads on classic software-engineering benchmarks: 82.6% SWE-bench Verified and 58.6% SWE-bench Pro. Sonnet 5 reports ~85.2% SWE-bench Verified (secondary sources) and a higher 63.2% SWE-bench Pro, plus 80.4% Terminal-Bench 2.1 and 81.2% OSWorld-Verified. On capability scores they are close (Sonnet coding 92 / reasoning 90 vs GPT-5.5 coding 93 / reasoning 92), so this comes down to price and context more than raw ability.
Price and context
Sonnet 5 is materially cheaper: $3/$15 standard ($2/$10 introductory through Aug 31, 2026) against GPT-5.5's $5/$30. GPT-5.5 offers a slightly larger, fully confirmed context (1,050,000 tokens vs Sonnet's 1M) but adds a surcharge above 272K input tokens (2x input, 1.5x output). Both are multimodal for text and image. Sonnet 5 is also faster (capability speed 82 vs 62), though its new tokenizer emits ~30% more tokens per text.
Which to pick
- Pick Sonnet 5 for cost-sensitive, high-volume agent loops, strong terminal-agent and computer-use work, and lower output pricing.
- Pick GPT-5.5 if you want OpenAI's recommended GA default, the top SWE-bench Verified figure, and tight integration with ChatGPT and the Responses API, and you can absorb the higher output cost.
Which should you choose?
Choose Claude Sonnet 5 if...
- →You want frontier-adjacent agentic coding but need better cost-efficiency than Opus
- →You are running high-volume agent loops and want strong reasoning per dollar
- →You are already on Sonnet 4.6 and want a same-price capability upgrade
- →You need a 1M context window with fast latency
Choose GPT-5.5 if...
- →Complex professional coding, data analysis, and multi-tool agentic workflows
- →Long-document or large-codebase tasks needing a 1M+ context window
- →You want OpenAI's recommended default frontier model for new projects