Claude Opus 5.5 vs Gemini 3.8 Flash
Claude Opus 5.5 
Gemini 3.8 Flash Verdict
- Claude Opus 5.5 (thinking) leads on quality: 70.7 vs 64.6.
- Claude Opus 5.5 (thinking) is stronger in composite, knowledge, long context, multimodal, reasoning.
- Gemini 3.8 Flash (medium) is stronger in agents & tools, coding.
- Gemini 3.8 Flash (medium) is 5.3× cheaper ($1.50 vs $8.00 per 1M blended).
- Gemini 3.8 Flash (medium) streams 1.6× faster (78 vs 48 tokens per second).
| Metric | Claude Opus 5.5 (thinking) | Gemini 3.8 Flash (medium) |
|---|---|---|
| BenchLeader Index | 70.7 | 64.6 |
| Composite score | 95.0 | 77.7 |
| Knowledge score | 85.0 | 76.7 |
| Long context score | 68.5 | 68.2 |
| Multimodal score | 71.9 | 68.3 |
| Reasoning score | 95.0 | 64.3 |
| Agents & tools score | – | 74.8 |
| Coding score | – | 60.1 |
| Blended price $/M | $8.00 | $1.50 |
| Output speed | 48 tok/s | 78 tok/s |
| Time to first answer | 4.2 s | 2.4 s |
| Context window | 1M | 1.0M |
| SciCode | – | 54.4% |
| FrontierCode | – | 41.2% |
| AA Intelligence Index | 57.6 | 39.8 |
| AA-LCR | 84.7% | 84.0% |
| MMMU-Pro | 87.7% | 84.2% |
| AA-Omniscience | 46.4 | 28.6 |
| GPQA Diamond (AA) | – | 93.5% |
| Humanity's Last Exam (AA) | 61.4% | 42.1% |
| SciCode (AA) | 66.9% | 55.1% |
| CritPt | 31.7% | 12.3% |
| GDPval (AA) | 67.3% | 45.4% |
| τ²-Bench Banking (AA) | – | 45.8% |
| DeepSWE | – | 71.0% |
| LMCA | – | 52.9% |
| DTBench | – | 94.9% |
| CursorBench | – | 37.3% |
| GDP.pdf | – | 23.4% |
| Terminal-Bench 4.0 (AA) | 59.6% | 19.7% |
| Terminal-Bench 2.1 (AA) | – | 83.9% |
| AutomationBench | 69.5% | – |
| GDP.pdf | 26.2% | – |
| Harvey LAB | 91.2% | – |
| AA-Omniscience: accuracy | 66.2% | 53.0% |
| AA-Omniscience: non-hallucination | 41.4% | 48.1% |
| AA-Briefcase | 1822 | – |
Data as of 2026-09-22. Best configuration of each model; every score links to its source on the model pages.
Claude Opus 5.5 vs Gemini 3.8 Flash: questions
- Is Claude Opus 5.5 better than Gemini 3.8 Flash?
- Claude Opus 5.5 (thinking) leads on quality: 70.7 vs 64.6. The BenchLeader Index combines every independent quality benchmark; Claude Opus 5.5 (thinking) is ahead overall as of 2026-09-22, but check the category scores for your use.
- Which is cheaper, Claude Opus 5.5 or Gemini 3.8 Flash?
- Gemini 3.8 Flash is cheaper: $1.50 against $8.00 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Opus 5.5 or Gemini 3.8 Flash?
- Gemini 3.8 Flash streams faster: 78 against 48 output tokens per second.
- Which has the larger context window?
- Gemini 3.8 Flash accepts more context: 1.0M against 1M tokens.