GLM-5.3-Flash vs GPT-5.5 Pro
GLM-5.3-Flash 
GPT-5.5 Pro Verdict
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 63.9.
- GLM-5.3-Flash is stronger in agents & tools, coding, composite, human preference, knowledge, long context, multimodal.
- GPT-5.5 Pro (xhigh) is stronger in maths, reasoning.
- GLM-5.3-Flash is 567× cheaper ($0.119 vs $67.50 per 1M blended).
- GLM-5.3-Flash streams 24.5× faster (98 vs 4 tokens per second).
| Metric | GLM-5.3-Flash | GPT-5.5 Pro (xhigh) |
|---|---|---|
| BenchLeader Index | 63.9 | 67.1 |
| Agents & tools score | 68.0 | – |
| Coding score | 64.0 | – |
| Composite score | 61.7 | – |
| Human preference score | 67.6 | – |
| Knowledge score | 67.8 | – |
| Long context score | 66.5 | – |
| Maths score | 71.0 | 74.5 |
| Multimodal score | 65.3 | – |
| Reasoning score | 70.3 | 80.1 |
| Blended price $/M | $0.119 | $67.50 |
| Output speed | 98 tok/s | 4 tok/s |
| Time to first answer | 22.9 s | 3.5 s |
| Context window | 1M | 1.1M |
| FrontierMath Tiers 1–3 | – | 87.7% |
| FrontierMath Tier 4 | – | 78.0% |
| SciCode | 46.1% | – |
| Epoch Capabilities Index | 151.4 | – |
| LMArena Text | 1475 | – |
| LMArena Hard Prompts | 1498 | – |
| LMArena Coding | 1525 | – |
| LMArena WebDev | 1607 | – |
| LMArena Vision | 1299 | – |
| LMArena Agent | 1.1 | – |
| LiveBench | 71.6% | – |
| LiveBench Reasoning | 77.6% | – |
| LiveBench Coding | 79.0% | – |
| LiveBench Agentic Coding | 56.8% | – |
| LiveBench Mathematics | 81.2% | – |
| LiveBench Data Analysis | 76.4% | – |
| LiveBench Language | 77.3% | – |
| LiveBench Instruction Following | 52.8% | – |
| AA Intelligence Index | 41.9 | – |
| AA-LCR | 80.0% | – |
| AA-Omniscience | 7.5 | – |
| GPQA Diamond (AA) | 91.2% | – |
| Humanity's Last Exam (AA) | 39.9% | – |
| SciCode (AA) | 51.6% | – |
| ARC-AGI-1 | – | 95.0% |
| ARC-AGI-2 | – | 84.2% |
| CritPt | 15.4% | 30.6% |
| GDPval (AA) | 57.8% | – |
| τ²-Bench Banking (AA) | 47.2% | – |
| LMArena Maths | 1513 | – |
| LMArena Creative Writing | 1435 | – |
| LMArena Instruction Following | 1471 | – |
| LMArena Multi-turn | 1475 | – |
| LMArena Longer Queries | 1476 | – |
| LMCA | – | 53.9% |
| DTBench | – | 96.0% |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
GLM-5.3-Flash vs GPT-5.5 Pro: questions
- Is GLM-5.3-Flash better than GPT-5.5 Pro?
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 63.9. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 Pro (xhigh) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, GLM-5.3-Flash or GPT-5.5 Pro?
- GLM-5.3-Flash is cheaper: $0.119 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, GLM-5.3-Flash or GPT-5.5 Pro?
- GLM-5.3-Flash streams faster: 98 against 4 output tokens per second.
- Which has the larger context window?
- GPT-5.5 Pro accepts more context: 1.1M against 1M tokens.