Gemini 3 Flash vs GPT-5.2-Codex
Gemini 3 Flash 
GPT-5.2-Codex Verdict
- Gemini 3 Flash (thinking) and GPT-5.2-Codex are level on quality (61.6 vs 60.8).
- Gemini 3 Flash (thinking) is stronger in agents & tools, composite, instruction following, knowledge, multimodal.
- GPT-5.2-Codex is stronger in long context, coding.
- Gemini 3 Flash (thinking) is 4.3× cheaper ($1.13 vs $4.81 per 1M blended).
- Gemini 3 Flash (thinking) streams 7.2× faster (180 vs 25 tokens per second).
| Metric | Gemini 3 Flash (thinking) | GPT-5.2-Codex |
|---|---|---|
| BenchLeader Index | 61.6 | 60.8 |
| Agents & tools score | 67.4 | 63.5 |
| Composite score | 62.3 | 56.8 |
| Instruction following score | 75.4 | 75.1 |
| Knowledge score | 69.0 | 63.1 |
| Long context score | 65.5 | 67.8 |
| Multimodal score | 64.4 | 60.7 |
| Coding score | – | 55.7 |
| Blended price $/M | $1.13 | $4.81 |
| Output speed | 180 tok/s | 25 tok/s |
| Time to first answer | 6.1 s | 6.7 s |
| Context window | 1M | 400k |
| Terminal-Bench | – | 66.5% |
| APEX-Agents | – | 27.6% |
| LMArena WebDev | – | 1339 |
| LiveBench | – | 74.0% |
| LiveBench Reasoning | – | 77.7% |
| LiveBench Coding | – | 83.6% |
| LiveBench Agentic Coding | – | 49.4% |
| LiveBench Mathematics | – | 88.8% |
| LiveBench Data Analysis | – | 78.2% |
| LiveBench Language | – | 73.7% |
| AA Intelligence Index | 26.3 | 28.5 |
| IFBench | 78.0% | 77.6% |
| AA-LCR | 78.0% | 82.3% |
| MMMU-Pro | 79.9% | 76.3% |
| AA-Omniscience | 10.1 | -2.2 |
| Terminal-Bench Hard | 38.6% | 37.1% |
| GPQA Diamond (AA) | 89.8% | 89.9% |
| Humanity's Last Exam (AA) | 36.6% | 35.7% |
| τ²-Bench Telecom (AA) | 80.4% | 92.1% |
| LiveCodeBench | – | 88.0% |
| SWE-Bench Pro | – | 41.0% |
| SWE-bench Verified (bash only) | – | 72.8% |
| SWE-bench Verified (any scaffold) | – | 72.8% |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
Gemini 3 Flash vs GPT-5.2-Codex: questions
- Is Gemini 3 Flash better than GPT-5.2-Codex?
- Gemini 3 Flash (thinking) and GPT-5.2-Codex are level on quality (61.6 vs 60.8). The BenchLeader Index combines every independent quality benchmark; Gemini 3 Flash (thinking) is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is Gemini 3 Flash better than GPT-5.2-Codex for agentic tasks?
- Gemini 3 Flash scores higher in agentic tasks (67 vs 64 on the category index, where 50 is average).
- Which is cheaper, Gemini 3 Flash or GPT-5.2-Codex?
- Gemini 3 Flash is cheaper: $1.13 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, Gemini 3 Flash or GPT-5.2-Codex?
- Gemini 3 Flash streams faster: 180 against 25 output tokens per second.
- Which has the larger context window?
- Gemini 3 Flash accepts more context: 1M against 400k tokens.