Gemini 3.8 Flash vs GPT-5.3-Codex
Gemini 3.8 Flash 
GPT-5.3-Codex Verdict
- Gemini 3.8 Flash (medium) leads on quality: 63.6 vs 62.5.
- Gemini 3.8 Flash (medium) is stronger in coding, composite, knowledge, long context, multimodal.
- GPT-5.3-Codex is stronger in agents & tools, instruction following.
- Gemini 3.8 Flash (medium) is 3.2× cheaper ($1.50 vs $4.81 per 1M blended).
- GPT-5.3-Codex streams 1.4× faster (121 vs 90 tokens per second).
| Metric | Gemini 3.8 Flash (medium) | GPT-5.3-Codex |
|---|---|---|
| BenchLeader Index | 63.6 | 62.5 |
| Coding score | 63.8 | 54.8 |
| Composite score | 79.6 | 70.1 |
| Knowledge score | 77.7 | 69.3 |
| Long context score | 68.6 | 68.3 |
| Multimodal score | 68.8 | 63.0 |
| Agents & tools score | – | 62.7 |
| Instruction following score | – | 73.2 |
| Blended price $/M | $1.50 | $4.81 |
| Output speed | 90 tok/s | 121 tok/s |
| Time to first answer | 11.7 s | 58.2 s |
| Context window | 1M | 400k |
| Terminal-Bench | – | 78.4% |
| SciCode | 54.4% | – |
| WeirdML | – | 79.3% |
| APEX-Agents | – | 31.8% |
| Epoch Capabilities Index | – | 156.6 |
| LMArena WebDev | – | 1409 |
| AA Intelligence Index | 40 | 32.5 |
| IFBench | – | 75.4% |
| AA-LCR | 84.0% | 83.3% |
| MMMU-Pro | 84.2% | 78.5% |
| AA-Omniscience | 28.6 | 10.9 |
| Terminal-Bench Hard | – | 53.0% |
| GPQA Diamond (AA) | 93.5% | 91.5% |
| Humanity's Last Exam (AA) | 42.1% | 42.5% |
| SciCode (AA) | 55.1% | – |
| 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.
Gemini 3.8 Flash vs GPT-5.3-Codex: questions
- Is Gemini 3.8 Flash better than GPT-5.3-Codex?
- Gemini 3.8 Flash (medium) leads on quality: 63.6 vs 62.5. The BenchLeader Index combines every independent quality benchmark; Gemini 3.8 Flash (medium) is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is Gemini 3.8 Flash better than GPT-5.3-Codex for coding?
- Gemini 3.8 Flash scores higher in coding (64 vs 55 on the category index, where 50 is average).
- Which is cheaper, Gemini 3.8 Flash or GPT-5.3-Codex?
- Gemini 3.8 Flash is cheaper: $1.50 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, Gemini 3.8 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?
- Gemini 3.8 Flash accepts more context: 1M against 400k tokens.