Model comparison
Claude Opus 4.8 vs Step 3.5 Flash
Claude Opus 4.8 is the stronger model overall, scoring 60.7 to 42.3 on the Noometry Index. Step 3.5 Flash costs 67× less per token, which makes it the better buy when Claude Opus 4.8's lead doesn't matter for your workload.
Last verified . 19 shared benchmarks.
StepFunSummary
- They share 19 benchmarks with published results for both. Claude Opus 4.8 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 Claude Opus 4.8 leads 64.7 to 22.2.
- The biggest single-benchmark swing is NYT Connections (extended): 91.1% for Claude Opus 4.8 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 $5 / $25 for Claude Opus 4.8.
- Claude Opus 4.8 accepts more context: 1M tokens versus 256K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| Claude Opus 4.8 | Step 3.5 Flash | |
|---|---|---|
| Provider | Anthropic | StepFun |
| Noometry Index | 60.7 | 42.3 |
| Released | 2026-05-28 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 1M | 256K |
| Max output | 128K | 256K |
| Input $ / M tokens | $5 | $0.10 |
| Output $ / M tokens | $25 | $0.30 |
| Results tracked | 65 | 19 |
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Category by category
Coding Claude Opus 4.8 leads
Claude Opus 4.8: 59.9 (#12), Step 3.5 Flash: 42.4 (#105)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1490 | 1436 |
| DeepSWE | 59% | — |
| FrontierCode | 46.5% | — |
| LMArena WebDev | 1556 | — |
| SciCode | 53.5% | — |
| GSO | 47.1% | — |
| WeirdML | 82.9% | — |
| ALE-Bench | 1,564 | — |
Agentic & Tool Use Not comparable
Claude Opus 4.8: 47.6 (#11), Step 3.5 Flash: —
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| APEX-Agents | 48.9% | — |
| OSWorld 2.0 | 20.6% | — |
| Remote Labor Index | 8.3% | — |
| τ²-bench Banking | 39.7% | — |
| DeepResearch Bench | 50.2% | — |
| PostTrainBench | 33.8% | — |
| GBAEval | 70.9% | — |
| GDP.pdf | 24% | — |
| LMArena Search | 1204 | — |
| Vending-Bench 2 | 5,787 | — |
Reasoning Claude Opus 4.8 leads
Claude Opus 4.8: 64.7 (#16), Step 3.5 Flash: 22.2 (#202)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| NYT Connections (extended) | 91.1% | 28.4% |
| LMArena Hard Prompts | 1482 | 1411 |
| ARC-AGI-2 | 72.1% | — |
| SimpleBench | 64.8% | — |
| Kagi LLM Benchmark | 88.8% | — |
| ARC-AGI-1 | 92.5% | — |
| CritPt | 20.9% | — |
| Chess Puzzles | 34% | — |
| EnigmaEval | 23.5% | — |
| EBR-Bench | 28.6% | — |
| Mystery Game Puzzles | 36% | — |
| DTBench | 94.9% | — |
| LMCA | 57.5% | — |
| Surface Evolver Bench | 87.5% | — |
| Bench to the Future 3 | 0.14 | — |
| Epoch Capabilities Index | 158.21 | — |
| ForecastBench | 59.9 | — |
Math Claude Opus 4.8 leads
Claude Opus 4.8: 78.4 (#13), Step 3.5 Flash: 42.6 (#84)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| MathArena Final-Answer Competitions | 91.8% | 66.8% |
| LMArena Math | 1487 | 1408 |
| FrontierMath (Tiers 1-3) | 80% | — |
| FrontierMath Tier 4 | 56.1% | — |
| OTIS Mock AIME 2024-2025 | 98.3% | — |
| ProofBench | 69% | — |
| FrontierMath (Feb 2025 set) | 47.2% | — |
| FrontierMath Tier 4 (v1) | 31.3% | — |
Knowledge Claude Opus 4.8 leads
Claude Opus 4.8: 61.3 (#29), Step 3.5 Flash: 39.6 (#132)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1502 | 1421 |
| GPQA Diamond | 91% | — |
| SimpleQA Verified | 53% | — |
Multimodal Not comparable
Claude Opus 4.8: 42.9 (#26), Step 3.5 Flash: —
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Vision | 1294 | — |
| Blueprint-Bench 2 | 14.5% | — |
| Furniture Assembly | 42.5% | — |
| LMArena Document | 1475 | — |
Multilingual Claude Opus 4.8 leads
Claude Opus 4.8: 55.2 (#33), Step 3.5 Flash: 50.5 (#119)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1450 | 1385 |
| LMArena Chinese | 1507 | 1447 |
| LMArena French | 1481 | 1421 |
| LMArena German | 1472 | 1405 |
| LMArena Japanese | 1440 | 1354 |
| LMArena Korean | 1432 | 1352 |
| LMArena Russian | 1474 | 1385 |
| LMArena Spanish | 1466 | 1419 |
Instruction Following Claude Opus 4.8 leads
Claude Opus 4.8: 77.4 (#24), Step 3.5 Flash: 73.1 (#124)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1476 | 1385 |
Long Context Claude Opus 4.8 leads
Claude Opus 4.8: 45.4 (#35), Step 3.5 Flash: 42.8 (#117)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1483 | 1402 |
Writing & Preference Claude Opus 4.8 leads
Claude Opus 4.8: 72.0 (#16), Step 3.5 Flash: 58.8 (#113)
| Benchmark | Claude Opus 4.8 | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1461 | 1403 |
| LMArena Creative Writing | 1454 | 1357 |
| LMArena Multi-Turn | 1476 | 1405 |
| EQ-Bench Creative Writing | 1840 | — |
| EQ-Bench 4 | 1281 | — |
Frequently asked questions
Is Claude Opus 4.8 better than Step 3.5 Flash?
Claude Opus 4.8 is the stronger model overall, scoring 60.7 to 42.3 on the Noometry Index. Step 3.5 Flash costs 67× less per token, which makes it the better buy when Claude Opus 4.8's lead doesn't matter for your workload.
Which is cheaper, Claude Opus 4.8 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; Claude Opus 4.8 lists at $5 and $25.
Is Claude Opus 4.8 or Step 3.5 Flash better for coding?
Claude Opus 4.8 scores higher on coding benchmarks: 59.9 versus 42.4 in the Noometry coding category.
Which has the bigger context window?
Claude Opus 4.8 does, with 1M tokens against 256K.
How many benchmarks do Claude Opus 4.8 and Step 3.5 Flash share?
19 benchmarks have published results for both models. Claude Opus 4.8 has 65 scored results on Noometry and Step 3.5 Flash has 19.