Model comparison
GPT-5.3 Codex vs Step 3
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 40.5 on the Noometry Index.
Last verified . 0 shared benchmarks.
StepFunSummary
- The widest gap is in coding, where GPT-5.3 Codex leads 48.6 to 40.1.
- Step 3 has downloadable open weights; the other is API-only.
Side by side
| GPT-5.3 Codex | Step 3 | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 45.8 | 40.5 |
| Released | 2026-02-05 | — |
| Weights | Proprietary | Open |
| Context window | 400K | — |
| Max output | 128K | — |
| Input $ / M tokens | $1.75 | — |
| Output $ / M tokens | $14 | — |
| Results tracked | 8 | 17 |
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Category by category
Coding GPT-5.3 Codex leads
GPT-5.3 Codex: 48.6 (#56), Step 3: 40.1 (#147)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| SWE-bench Verified | 74.8% | — |
| LMArena WebDev | 1409 | — |
| WeirdML | 79.3% | — |
| LMArena Coding | — | 1367 |
| ALE-Bench | 1,655 | — |
Agentic & Tool Use Not comparable
GPT-5.3 Codex: 48.0 (#9), Step 3: —
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| Terminal-Bench | 78.4% | — |
| METR Time Horizons | 74.5% | — |
| Vending-Bench 2 | 5,940 | — |
Reasoning Not comparable
GPT-5.3 Codex: —, Step 3: 28.4 (#105)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| Kagi LLM Benchmark | — | 62.3% |
| LMArena Hard Prompts | — | 1355 |
| Epoch Capabilities Index | 156.77 | — |
Math Not comparable
GPT-5.3 Codex: —, Step 3: 37.6 (#148)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Math | — | 1366 |
Knowledge Not comparable
GPT-5.3 Codex: —, Step 3: 36.8 (#164)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Expert | — | 1333 |
Multimodal Not comparable
GPT-5.3 Codex: —, Step 3: 35.5 (#86)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Vision | — | 1177 |
Multilingual Not comparable
GPT-5.3 Codex: —, Step 3: 46.3 (#159)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Non-English | — | 1327 |
| LMArena Chinese | — | 1397 |
| LMArena German | — | 1371 |
| LMArena Korean | — | 1269 |
| LMArena Russian | — | 1331 |
| LMArena Spanish | — | 1371 |
Instruction Following Not comparable
GPT-5.3 Codex: —, Step 3: 70.4 (#164)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Instruction Following | — | 1332 |
Long Context Not comparable
GPT-5.3 Codex: —, Step 3: 40.3 (#157)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Longer Query | — | 1326 |
Writing & Preference Not comparable
GPT-5.3 Codex: —, Step 3: 54.3 (#151)
| Benchmark | GPT-5.3 Codex | Step 3 |
|---|---|---|
| LMArena Text | — | 1350 |
| LMArena Creative Writing | — | 1321 |
| LMArena Multi-Turn | — | 1341 |
Frequently asked questions
Is GPT-5.3 Codex better than Step 3?
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 40.5 on the Noometry Index.
Is GPT-5.3 Codex or Step 3 better for coding?
GPT-5.3 Codex scores higher on coding benchmarks: 48.6 versus 40.1 in the Noometry coding category.
How many benchmarks do GPT-5.3 Codex and Step 3 share?
0 benchmarks have published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and Step 3 has 17.