Claude Opus 4.1 vs Step 3.5 Flash
Updated October 21, 2026. 29 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Neither model has a coding score yet, so the two cannot be ranked on coding.
Claude Opus 4.1 has the edge where the benchmark that matters is LMArena Text: Chinese, where it leads.
- Shared results
- 29
- Claude Opus 4.1 only
- 42
- Step 3.5 Flash only
- 6
- Like-for-like categories
- 6 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Neither has a coding score yet.
One side not measured
Intelligence
AA Intelligence Index
Claude Opus 4.1
Claude Opus 4.1 leads, 22.8 against 17.0.
Same board, both measured
Reasoning
GPQA Diamond
No call
Only Claude Opus 4.1 has a GPQA Diamond result, 76.3%.
Directional only
Math
AIME
No call
Only Claude Opus 4.1 has a AIME result, 78.2%.
Directional only
Knowledge
MMLU Pro
No call
Only Claude Opus 4.1 has a MMLU Pro result, 87.9%.
Directional only
Web design
Design Arena: websites
No call
Only Claude Opus 4.1 has a Design Arena: websites result, 1177.
Directional only
Long documents
Listed context window
Step 3.5 Flash
Step 3.5 Flash takes 262K tokens against 200K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 3.5 Flash
Claude Opus 4.1 $0.052, Step 3.5 Flash $0.0003 per turn.
List prices
At a glance
- Coding index
- Claude Opus 4.1 not benchmarked, Step 3.5 Flash not benchmarked.
- Widest category
- Intelligence, 5.8 points apart on average over 1 shared benchmark.
- Widest single gap
- LMArena Text: creative writing: Claude Opus 4.1 1412 against Step 3.5 Flash 1357, 9.1 points apart on a 0 to 100 scale.
- Output price
- Claude Opus 4.1 $75.00 against Step 3.5 Flash $0.30 per million output tokens, 250.0x apart.
- Context window
- Claude Opus 4.1 takes 200K tokens, Step 3.5 Flash 262K.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Claude Opus 4.1 | Bars | Step 3.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 2 | 0 | ||
| Intelligence | 1 | 0 | ||
| Reasoning | 3 | 0 | ||
| Math | 2 | 0 | ||
| Knowledge | 4 | 0 | ||
| General | 16 | 1 | ||
| All shared boards | 28 | 1 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index20
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LMArena WebDev | 1390 | Not measured | Only Claude Opus 4.1 measured |
| LiveCodeBench (Vals AI) | 66.5% | Not measured | Only Claude Opus 4.1 measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 32.6% | Only Step 3.5 Flash measured |
| Terminal-Bench | 38.0% | Not measured | Only Claude Opus 4.1 measured |
| WeirdML | 45.9% | Not measured | Only Claude Opus 4.1 measured |
| Cybench | 42.0% | Not measured | Only Claude Opus 4.1 measured |
| LMArena Text: coding | 1479 | 1436 | Claude Opus 4.1 |
| LMArena Text: software and IT | 1456 | 1434 | Claude Opus 4.1 |
| LMArena WebDev: HTML | 1399 | Not measured | Only Claude Opus 4.1 measured |
| Neither model has a result on the other 29 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 22.8 | 17.0 | Claude Opus 4.1 |
| Epoch Capabilities Index | 144.1 | Not measured | Only Claude Opus 4.1 measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index4 boards, none shared
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| τ²-Bench Telecom | Not measured | 94.4% | Only Step 3.5 Flash measured |
| METR time horizons | 66.8% | Not measured | Only Claude Opus 4.1 measured |
| GDPval | 43.6% | Not measured | Only Claude Opus 4.1 measured |
| DeepResearch Bench | 48.3% | Not measured | Only Claude Opus 4.1 measured |
| Neither model has a result on the other 35 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| GPQA Diamond | 76.3% | Not measured | Only Claude Opus 4.1 measured |
| MMMU Pro (Vals AI) | 77.5% | Not measured | Only Claude Opus 4.1 measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 83.1% | Only Step 3.5 Flash measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 24.5% | Only Step 3.5 Flash measured |
| GPQA Diamond (Epoch AI run) | 77.3% | Not measured | Only Claude Opus 4.1 measured |
| SimpleBench | 60.0% | Not measured | Only Claude Opus 4.1 measured |
| Mystery game puzzles | 21.0% | Not measured | Only Claude Opus 4.1 measured |
| EBR-bench | 7.9% | Not measured | Only Claude Opus 4.1 measured |
| VPCT | 35.0% | Not measured | Only Claude Opus 4.1 measured |
| LMArena Text: hard prompts | 1442 | 1411 | Claude Opus 4.1 |
| LMArena Text: expert | 1438 | 1421 | Claude Opus 4.1 |
| LMArena Text: hard prompts in English | 1451 | 1421 | Claude Opus 4.1 |
| Neither model has a result on the other 9 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AIME | 78.2% | Not measured | Only Claude Opus 4.1 measured |
| MATH 500 (Vals AI) | 95.4% | Not measured | Only Claude Opus 4.1 measured |
| MGSM (Vals AI) | 94.4% | Not measured | Only Claude Opus 4.1 measured |
| OTIS Mock AIME | 68.9% | Not measured | Only Claude Opus 4.1 measured |
| FrontierMath, tiers 1 to 3 | 12.6% | Not measured | Only Claude Opus 4.1 measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only Claude Opus 4.1 measured |
| LMArena Text: math | 1431 | 1408 | Claude Opus 4.1 |
| LMArena Text: mathematical work | 1434 | 1421 | Claude Opus 4.1 |
| Neither model has a result on the other 5 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| MMLU Pro | 87.9% | Not measured | Only Claude Opus 4.1 measured |
| LegalBench (Vals AI) | 83.5% | Not measured | Only Claude Opus 4.1 measured |
| TaxEval (Vals AI) | 73.7% | Not measured | Only Claude Opus 4.1 measured |
| MortgageTax (Vals AI) | 61.1% | Not measured | Only Claude Opus 4.1 measured |
| MedQA (Vals AI) | 93.6% | Not measured | Only Claude Opus 4.1 measured |
| MedCode (Vals AI) | 47.2% | Not measured | Only Claude Opus 4.1 measured |
| LMArena Text: science | 1422 | 1415 | Claude Opus 4.1 |
| LMArena Text: medicine and healthcare | 1416 | 1408 | Claude Opus 4.1 |
| LMArena Text: legal and government | 1421 | 1408 | Claude Opus 4.1 |
| LMArena Text: business and finance | 1406 | 1394 | Claude Opus 4.1 |
| Neither model has a result on the other 7 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1177 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: UI components | 1164 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: game dev | 1171 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: data viz | 1166 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: 3D | 1153 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: all code categories | 1171 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: SVG | 1152 | Not measured | Only Claude Opus 4.1 measured |
| Design Arena: ASCII art | 1167 | Not measured | Only Claude Opus 4.1 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index161
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 31.4% | Not measured | Only Claude Opus 4.1 measured |
| MedScribe (Vals AI) | 73.9% | Not measured | Only Claude Opus 4.1 measured |
| IFBench | Not measured | 66.5% | Only Step 3.5 Flash measured |
| Long context reasoning (AA-LCR) | Not measured | 63.0% | Only Step 3.5 Flash measured |
| DTBench | 80.0% | Not measured | Only Claude Opus 4.1 measured |
| LMCA | 37.1% | Not measured | Only Claude Opus 4.1 measured |
| Creative writing (Lech Mazur) | 84.7% | Not measured | Only Claude Opus 4.1 measured |
| LMArena Text | 1419 | 1403 | Claude Opus 4.1 |
| LMArena Text: instruction following | 1435 | 1385 | Claude Opus 4.1 |
| LMArena Text: creative writing | 1412 | 1357 | Claude Opus 4.1 |
| LMArena Text: English | 1433 | 1417 | Claude Opus 4.1 |
| LMArena Text: non-English | 1405 | 1385 | Claude Opus 4.1 |
| LMArena Text: Chinese | 1427 | 1446 | Step 3.5 Flash |
| LMArena Text: German | 1413 | 1405 | Claude Opus 4.1 |
| LMArena Text: Japanese | 1377 | 1353 | Claude Opus 4.1 |
| LMArena Text: Korean | 1381 | 1351 | Claude Opus 4.1 |
| LMArena Text: French | 1433 | 1421 | Claude Opus 4.1 |
| LMArena Text: Spanish | 1448 | 1419 | Claude Opus 4.1 |
| LMArena Text: Russian | 1422 | 1385 | Claude Opus 4.1 |
| LMArena Text: Polish | 1413 | 1389 | Claude Opus 4.1 |
| LMArena Text: multi-turn | 1444 | 1404 | Claude Opus 4.1 |
| LMArena Text: longer queries | 1455 | 1402 | Claude Opus 4.1 |
| LMArena Text: writing and language | 1418 | 1372 | Claude Opus 4.1 |
| LMArena Text: entertainment and media | 1398 | 1360 | Claude Opus 4.1 |
| Neither model has a result on the other 22 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Claude Opus 4.1 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Step 3.5 Flash costs less
Repository review
50K input + 3K output tokens
Step 3.5 Flash costs less
Agent loop
200K input + 10K output tokens
Step 3.5 Flash costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Anthropic Claude Opus 4.1 | StepFun Step 3.5 Flash |
|---|---|---|
| Maker | Anthropic | StepFun |
| Weights | No public weights listed | Open weights |
| Released | August 5, 2025 | January 29, 2026 |
| Context window | 200K | 262K |
| Input $/Mtok | $15.00 | $0.10 |
| Output $/Mtok | $75.00 | $0.30 |
| Coding index | Not benchmarked | Not benchmarked |
| Independent measurements behind it | 1 | 0 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Claude Opus 4.1 better than Step 3.5 Flash for coding?
Neither model has a coding score yet, so the two cannot be ranked on coding. Claude Opus 4.1 has the edge where the benchmark that matters is LMArena Text: Chinese, where it leads.
Which is cheaper, Claude Opus 4.1 or Step 3.5 Flash?
Claude Opus 4.1 costs $15.00 per million input tokens and $75.00 per million output tokens; Step 3.5 Flash costs $0.10 and $0.30. Cost per solved task is known for neither of them.
Which has the bigger context window, Claude Opus 4.1 or Step 3.5 Flash?
Step 3.5 Flash, with 262K tokens against 200K.
How many benchmarks is the Claude Opus 4.1 vs Step 3.5 Flash comparison based on?
29 benchmarks have a result for both models as of October 21, 2026. Claude Opus 4.1's coding index rests on 1 independent benchmark and Step 3.5 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.