GLM 5.3 Flash vs GPT-5.3-Codex
GLM 5.3 Flash 
GPT-5.3-Codex Verdict
- GPT-5.3-Codex leads on quality: 62.5 vs 61.1.
- GLM 5.3 Flash is stronger in coding, human preference, multimodal, reasoning.
- GPT-5.3-Codex is stronger in agents & tools, composite, knowledge, long context, instruction following.
- GLM 5.3 Flash is 40× cheaper ($0.119 vs $4.81 per 1M blended).
- GPT-5.3-Codex streams 1.4× faster (121 vs 90 tokens per second).
| Metric | GLM 5.3 Flash | GPT-5.3-Codex |
|---|---|---|
| BenchLeader Index | 61.1 | 62.5 |
| Agents & tools score | 52.1 | 62.7 |
| Coding score | 64.3 | 54.8 |
| Composite score | 61.7 | 70.1 |
| Human preference score | 67.6 | – |
| Knowledge score | 67.7 | 69.3 |
| Long context score | 66.6 | 68.3 |
| Multimodal score | 65.5 | 63.0 |
| Reasoning score | 67.5 | – |
| Instruction following score | – | 73.2 |
| Blended price $/M | $0.119 | $4.81 |
| Output speed | 90 tok/s | 121 tok/s |
| Time to first answer | 24.9 s | 58.2 s |
| Context window | 1M | 400k |
| Terminal-Bench | – | 78.4% |
| SciCode | 46.1% | – |
| WeirdML | – | 79.3% |
| APEX-Agents | – | 31.8% |
| Epoch Capabilities Index | 151.4 | 156.6 |
| LMArena Text | 1474 | – |
| LMArena Hard Prompts | 1496 | – |
| LMArena Coding | 1534 | – |
| LMArena WebDev | 1605 | 1409 |
| LMArena Vision | 1296 | – |
| 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 | 32.5 |
| IFBench | – | 75.4% |
| AA-LCR | 80.0% | 83.3% |
| MMMU-Pro | – | 78.5% |
| AA-Omniscience | 7.5 | 10.9 |
| Terminal-Bench Hard | – | 53.0% |
| GPQA Diamond (AA) | 91.2% | 91.5% |
| Humanity's Last Exam (AA) | 39.9% | 42.5% |
| SciCode (AA) | 51.6% | – |
| τ²-Bench Telecom (AA) | – | 86.0% |
| HiL-Bench | – | 4.3% |
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-5.3-Codex: questions
- Is GLM 5.3 Flash better than GPT-5.3-Codex?
- GPT-5.3-Codex leads on quality: 62.5 vs 61.1. The BenchLeader Index combines every independent quality benchmark; GPT-5.3-Codex is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GLM 5.3 Flash better than GPT-5.3-Codex for coding?
- GLM 5.3 Flash scores higher in coding (64 vs 55 on the category index, where 50 is average).
- Is GLM 5.3 Flash better than GPT-5.3-Codex for agentic tasks?
- GPT-5.3-Codex scores higher in agentic tasks (63 vs 52 on the category index, where 50 is average).
- Which is cheaper, GLM 5.3 Flash or GPT-5.3-Codex?
- GLM 5.3 Flash is cheaper: $0.119 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, GLM 5.3 Flash or GPT-5.3-Codex?
- GPT-5.3-Codex streams faster: 121 against 90 output tokens per second.
- Which has the larger context window?
- GLM 5.3 Flash accepts more context: 1M against 400k tokens.