Model comparison
Kimi K3 vs Step 3.5 Flash
Kimi K3 is the stronger model overall, scoring 59.5 to 42.3 on the Noometry Index. Step 3.5 Flash costs 40× less per token, which makes it the better buy when Kimi K3's lead doesn't matter for your workload.
Last verified . 19 shared benchmarks.
StepFunSummary
- They share 19 benchmarks with published results for both. Kimi K3 scores higher in 8 categories and Step 3.5 Flash in 0 categories; 8 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Kimi K3 leads 63.0 to 22.2.
- The biggest single-benchmark swing is NYT Connections (extended): 93.6% for Kimi K3 and 28.4% for Step 3.5 Flash.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $3 / $15 for Kimi K3.
- Kimi K3 accepts more context: 1.05M tokens versus 256K.
Side by side
| Kimi K3 | Step 3.5 Flash | |
|---|---|---|
| Provider | Moonshot AI | StepFun |
| Noometry Index | 59.5 | 42.3 |
| Released | 2026-07-16 | 2026-01-29 |
| Weights | Open | Open |
| Context window | 1.05M | 256K |
| Max output | 1.05M | 256K |
| Input $ / M tokens | $3 | $0.10 |
| Output $ / M tokens | $15 | $0.30 |
| Results tracked | 53 | 19 |
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Category by category
Coding Kimi K3 leads
Kimi K3: 61.0 (#10), Step 3.5 Flash: 42.4 (#105)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1508 | 1436 |
| DeepSWE | 68.5% | — |
| FrontierCode | 44.2% | — |
| LMArena WebDev | 1654 | — |
| FrontierSWE | 25.9% | — |
| SciCode | 59.5% | — |
| WeirdML | 82.6% | — |
| ALE-Bench | 1,524 | — |
Agentic & Tool Use Not comparable
Kimi K3: 41.8 (#20), Step 3.5 Flash: —
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| APEX-Agents | 50.6% | — |
| τ²-bench Banking | 37.1% | — |
| PostTrainBench | 32% | — |
| GBAEval | 48.3% | — |
| GDP.pdf | 19% | — |
| Vending-Bench 2 | 5,165 | — |
Reasoning Kimi K3 leads
Kimi K3: 63.0 (#17), Step 3.5 Flash: 22.2 (#202)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| NYT Connections (extended) | 93.6% | 28.4% |
| LMArena Hard Prompts | 1496 | 1411 |
| ARC-AGI-2 | 60.4% | — |
| SimpleBench | 60.7% | — |
| ARC-AGI-1 | 94.5% | — |
| CritPt | 23.4% | — |
| Chess Puzzles | 39% | — |
| Mystery Game Puzzles | 26% | — |
| DTBench | 91.2% | — |
| LMCA | 52.7% | — |
| Surface Evolver Bench | 95% | — |
| Epoch Capabilities Index | 157.45 | — |
| ForecastBench | 61.1 | — |
Math Kimi K3 leads
Kimi K3: 74.2 (#16), Step 3.5 Flash: 42.6 (#84)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | 87.8% | 66.8% |
| LMArena Math | 1491 | 1408 |
| FrontierMath (Tiers 1-3) | 72.2% | — |
| FrontierMath Tier 4 | 39% | — |
| OTIS Mock AIME 2024-2025 | 97.2% | — |
| ProofBench | 87% | — |
Knowledge Kimi K3 leads
Kimi K3: 63.2 (#21), Step 3.5 Flash: 39.6 (#132)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1521 | 1421 |
| GPQA Diamond | 93.1% | — |
| SimpleQA Verified | 50.6% | — |
Multimodal Not comparable
Kimi K3: 37.8 (#70), Step 3.5 Flash: —
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| Blueprint-Bench 2 | 29.5% | — |
| Furniture Assembly | 34.2% | — |
Multilingual Kimi K3 leads
Kimi K3: 56.3 (#21), Step 3.5 Flash: 50.5 (#119)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1466 | 1385 |
| LMArena Chinese | 1529 | 1447 |
| LMArena French | 1491 | 1421 |
| LMArena German | 1488 | 1405 |
| LMArena Japanese | 1487 | 1354 |
| LMArena Korean | 1458 | 1352 |
| LMArena Russian | 1482 | 1385 |
| LMArena Spanish | 1472 | 1419 |
Instruction Following Kimi K3 leads
Kimi K3: 77.7 (#14), Step 3.5 Flash: 73.1 (#124)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1483 | 1385 |
Long Context Kimi K3 leads
Kimi K3: 45.8 (#29), Step 3.5 Flash: 42.8 (#117)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1494 | 1402 |
Writing & Preference Kimi K3 leads
Kimi K3: 76.6 (#4), Step 3.5 Flash: 58.8 (#113)
| Benchmark | Kimi K3 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1476 | 1403 |
| LMArena Creative Writing | 1454 | 1357 |
| LMArena Multi-Turn | 1488 | 1405 |
| EQ-Bench Creative Writing | 2082 | — |
| EQ-Bench 4 | 1339 | — |
Frequently asked questions
Is Kimi K3 better than Step 3.5 Flash?
Kimi K3 is the stronger model overall, scoring 59.5 to 42.3 on the Noometry Index. Step 3.5 Flash costs 40× less per token, which makes it the better buy when Kimi K3's lead doesn't matter for your workload.
Which is cheaper, Kimi K3 or Step 3.5 Flash?
Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; Kimi K3 lists at $3 and $15.
Is Kimi K3 or Step 3.5 Flash better for coding?
Kimi K3 scores higher on coding benchmarks: 61.0 versus 42.4 in the Noometry coding category.
Which has the bigger context window?
Kimi K3 does, with 1.05M tokens against 256K.
How many benchmarks do Kimi K3 and Step 3.5 Flash share?
19 benchmarks have published results for both models. Kimi K3 has 53 scored results on Noometry and Step 3.5 Flash has 19.