GPT-5.3-Codex vs Grok 4.5
GPT-5.3-Codex 
Grok 4.5 Verdict
- Grok 4.5 leads on quality: 63.5 vs 62.5.
- GPT-5.3-Codex is stronger in agents & tools, composite, instruction following, long context.
- Grok 4.5 is stronger in coding, knowledge, multimodal, human preference, reasoning.
- Grok 4.5 is 1.6× cheaper ($3.00 vs $4.81 per 1M blended).
- GPT-5.3-Codex streams 2.3× faster (121 vs 52 tokens per second).
| Metric | GPT-5.3-Codex | Grok 4.5 |
|---|---|---|
| BenchLeader Index | 62.5 | 63.5 |
| Agents & tools score | 62.7 | 58.6 |
| Coding score | 54.8 | 59.8 |
| Composite score | 70.1 | 66.2 |
| Instruction following score | 73.2 | – |
| Knowledge score | 69.3 | 76.2 |
| Long context score | 68.3 | 66.2 |
| Multimodal score | 63.0 | 64.9 |
| Human preference score | – | 67.2 |
| Reasoning score | – | 69.2 |
| Blended price $/M | $4.81 | $3.00 |
| Output speed | 121 tok/s | 52 tok/s |
| Time to first answer | 58.2 s | 13.6 s |
| Context window | 400k | 500k |
| Terminal-Bench | 78.4% | – |
| SimpleBench | – | 70.0% |
| WeirdML | 79.3% | 46.4% |
| APEX-Agents | 31.8% | 34.2% |
| FrontierCode | – | 42.4% |
| Epoch Capabilities Index | 156.6 | 153.9 |
| LMArena Text | – | 1471 |
| LMArena Hard Prompts | – | 1495 |
| LMArena Coding | – | 1523 |
| LMArena WebDev | 1409 | 1556 |
| LMArena Vision | – | 1291 |
| LMArena Agent | – | 3.9 |
| LiveBench | – | 75.8% |
| LiveBench Reasoning | – | 87.2% |
| LiveBench Coding | – | 68.6% |
| LiveBench Agentic Coding | – | 56.5% |
| LiveBench Mathematics | – | 90.8% |
| LiveBench Data Analysis | – | 73.0% |
| LiveBench Language | – | 82.8% |
| AA Intelligence Index | 32.5 | 39.1 |
| IFBench | 75.4% | – |
| AA-LCR | 83.3% | 79.3% |
| MMMU-Pro | 78.5% | 80.4% |
| AA-Omniscience | 10.9 | 25.3 |
| Terminal-Bench Hard | 53.0% | – |
| GPQA Diamond (AA) | 91.5% | 93.1% |
| Humanity's Last Exam (AA) | 42.5% | 42.7% |
| SciCode (AA) | – | 55.0% |
| τ²-Bench Telecom (AA) | 86.0% | – |
| HiL-Bench | 4.3% | – |
| Kagi LLM Benchmark | – | 83.5% |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
GPT-5.3-Codex vs Grok 4.5: questions
- Is GPT-5.3-Codex better than Grok 4.5?
- Grok 4.5 leads on quality: 63.5 vs 62.5. The BenchLeader Index combines every independent quality benchmark; Grok 4.5 is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.3-Codex better than Grok 4.5 for coding?
- Grok 4.5 scores higher in coding (60 vs 55 on the category index, where 50 is average).
- Is GPT-5.3-Codex better than Grok 4.5 for agentic tasks?
- GPT-5.3-Codex scores higher in agentic tasks (63 vs 59 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or Grok 4.5?
- Grok 4.5 is cheaper: $3.00 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or Grok 4.5?
- GPT-5.3-Codex streams faster: 121 against 52 output tokens per second.
- Which has the larger context window?
- Grok 4.5 accepts more context: 500k against 400k tokens.