GLM 5.3 Flash vs GPT-5.5 Instant
GLM 5.3 Flash 
GPT-5.5 Instant Verdict
- GLM 5.3 Flash and GPT-5.5 Instant are level on quality (61.1 vs 60.5).
- GLM 5.3 Flash is stronger in coding, human preference, long context, multimodal, reasoning.
- GPT-5.5 Instant is stronger in agents & tools, composite, knowledge, instruction following, maths.
- GLM 5.3 Flash is 95× cheaper ($0.119 vs $11.25 per 1M blended).
- GPT-5.5 Instant streams 1.4× faster (129 vs 90 tokens per second).
| Metric | GLM 5.3 Flash | GPT-5.5 Instant |
|---|---|---|
| BenchLeader Index | 61.1 | 60.5 |
| Agents & tools score | 52.1 | 70.7 |
| Coding score | 64.3 | 61.1 |
| Composite score | 61.7 | 62.9 |
| Human preference score | 67.6 | 67.5 |
| Knowledge score | 67.7 | 69.4 |
| Long context score | 66.6 | 61.4 |
| Multimodal score | 65.5 | 59.7 |
| Reasoning score | 67.5 | 62.6 |
| Instruction following score | – | 69.8 |
| Maths score | – | 42.5 |
| Blended price $/M | $0.119 | $11.25 |
| Output speed | 90 tok/s | 129 tok/s |
| Time to first answer | 24.9 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 | 46.1% | 48.6% |
| Epoch Capabilities Index | 151.4 | 142.5 |
| LMArena Text | 1474 | 1474 |
| LMArena Hard Prompts | 1496 | 1491 |
| LMArena Coding | 1534 | 1514 |
| LMArena WebDev | 1605 | – |
| LMArena Vision | 1296 | 1251 |
| LMArena Agent | 2 | – |
| 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% | – |
| AA Intelligence Index | 41.9 | 26.8 |
| IFBench | – | 71.5% |
| AA-LCR | 80.0% | 70.0% |
| AA-Omniscience | 7.5 | 11.2 |
| Terminal-Bench Hard | – | 42.4% |
| GPQA Diamond (AA) | 91.2% | 84.7% |
| Humanity's Last Exam (AA) | 39.9% | 21.6% |
| SciCode (AA) | 51.6% | 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.
GLM 5.3 Flash vs GPT-5.5 Instant: questions
- Is GLM 5.3 Flash better than GPT-5.5 Instant?
- GLM 5.3 Flash and GPT-5.5 Instant are level on quality (61.1 vs 60.5). The BenchLeader Index combines every independent quality benchmark; GLM 5.3 Flash is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GLM 5.3 Flash better than GPT-5.5 Instant for coding?
- GLM 5.3 Flash scores higher in coding (64 vs 61 on the category index, where 50 is average).
- Is GLM 5.3 Flash better than GPT-5.5 Instant for agentic tasks?
- GPT-5.5 Instant scores higher in agentic tasks (71 vs 52 on the category index, where 50 is average).
- Which is cheaper, GLM 5.3 Flash or GPT-5.5 Instant?
- GLM 5.3 Flash is cheaper: $0.119 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, GLM 5.3 Flash or GPT-5.5 Instant?
- GPT-5.5 Instant streams faster: 129 against 90 output tokens per second.
- Which has the larger context window?
- GLM 5.3 Flash accepts more context: 1M against 400k tokens.