Claude Sonnet 5 vs GPT-5.5 Instant
Claude Sonnet 5 
GPT-5.5 Instant Verdict
- Claude Sonnet 5 (high) and GPT-5.5 Instant are level on quality (61.4 vs 60.5).
- Claude Sonnet 5 (high) is stronger in coding, composite, long context, multimodal, reasoning.
- GPT-5.5 Instant is stronger in agents & tools, human preference, knowledge, instruction following, maths.
- Claude Sonnet 5 (high) is 2.8× cheaper ($4.00 vs $11.25 per 1M blended).
- GPT-5.5 Instant streams 2.2× faster (129 vs 60 tokens per second).
| Metric | Claude Sonnet 5 (high) | GPT-5.5 Instant |
|---|---|---|
| BenchLeader Index | 61.4 | 60.5 |
| Agents & tools score | 61.8 | 70.7 |
| Coding score | 61.6 | 61.1 |
| Composite score | 69.5 | 62.9 |
| Human preference score | 66.2 | 67.5 |
| Knowledge score | 62.4 | 69.4 |
| Long context score | 64.8 | 61.4 |
| Multimodal score | 63.1 | 59.7 |
| Reasoning score | 66.8 | 62.6 |
| Instruction following score | – | 69.8 |
| Maths score | – | 42.5 |
| Blended price $/M | $4.00 | $11.25 |
| Output speed | 60 tok/s | 129 tok/s |
| Time to first answer | 10.0 s | 16.8 s |
| Context window | 1M | 400k |
| GPQA Diamond | – | 82.5% |
| FrontierMath Tiers 1–3 | – | 26.3% |
| FrontierMath Tier 4 | – | 2.4% |
| OTIS Mock AIME | – | 68.1% |
| SciCode | 48.6% | 48.6% |
| WeirdML | 68.8% | – |
| Epoch Capabilities Index | – | 142.5 |
| LMArena Text | 1462 | 1474 |
| LMArena Hard Prompts | 1490 | 1491 |
| LMArena Coding | 1521 | 1514 |
| LMArena WebDev | 1538 | – |
| LMArena Vision | 1278 | 1251 |
| LMArena Agent | 6.3 | – |
| AA Intelligence Index | 32.0 | 26.8 |
| IFBench | – | 71.5% |
| AA-LCR | 76.7% | 70.0% |
| AA-Omniscience | -3.7 | 11.2 |
| Terminal-Bench Hard | – | 42.4% |
| GPQA Diamond (AA) | – | 84.7% |
| Humanity's Last Exam (AA) | 35.7% | 21.6% |
| SciCode (AA) | 54.3% | 52.5% |
| τ²-Bench Telecom (AA) | – | 49.4% |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
Claude Sonnet 5 vs GPT-5.5 Instant: questions
- Is Claude Sonnet 5 better than GPT-5.5 Instant?
- Claude Sonnet 5 (high) and GPT-5.5 Instant are level on quality (61.4 vs 60.5). The BenchLeader Index combines every independent quality benchmark; Claude Sonnet 5 (high) is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is Claude Sonnet 5 better than GPT-5.5 Instant for coding?
- Claude Sonnet 5 scores higher in coding (62 vs 61 on the category index, where 50 is average).
- Is Claude Sonnet 5 better than GPT-5.5 Instant for agentic tasks?
- GPT-5.5 Instant scores higher in agentic tasks (71 vs 62 on the category index, where 50 is average).
- Which is cheaper, Claude Sonnet 5 or GPT-5.5 Instant?
- Claude Sonnet 5 is cheaper: $4.00 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Sonnet 5 or GPT-5.5 Instant?
- GPT-5.5 Instant streams faster: 129 against 60 output tokens per second.
- Which has the larger context window?
- Claude Sonnet 5 accepts more context: 1M against 400k tokens.