Grok 4.3 vs Step 3.5 Flash
Grok 4.3 leads Step 3.5 Flash on the Artificial Analysis Intelligence Index, 24.9 to 17.0, and Step 3.5 Flash costs 8.3x less per output token ($0.30 vs $2.50 per million). Updated October 21, 2026; 35 benchmarks have a result for both.
Grok 4.3 or Step 3.5 Flash: which to pick
Only Grok 4.3 has a coding score, 37.4 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding.
Pick Step 3.5 Flash for output tokens 8.3x cheaper ($0.30 vs $2.50 per million) and work measured by LMArena Text: coding or LMArena Text: software and IT, where it leads.
- Shared results
- 35
- Grok 4.3 only
- 69
- Step 3.5 Flash only
- 0
- Like-for-like categories
- 7 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
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
Only Grok 4.3 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
Grok 4.3
Grok 4.3 leads, 24.9 against 17.0.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Grok 4.3 has a AA Agentic Index result, 15.5.
Directional only
Reasoning
GPQA Diamond
No call
Only Grok 4.3 has a GPQA Diamond result, 91.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.3 has a MMLU Pro result, 85.8%.
Directional only
Web design
Design Arena: websites
No call
Only Grok 4.3 has a Design Arena: websites result, 1196.
Directional only
Long documents
Listed context window
Grok 4.3
Grok 4.3 takes 1M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 3.5 Flash
Grok 4.3 $0.0025, Step 3.5 Flash $0.0003 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Grok 4.3 has the number, $0.31.
Directional only
At a glance
- Coding index
- Grok 4.3 37.4 from 3 benchmarks, Step 3.5 Flash not benchmarked.
- Widest category
- Intelligence, 7.9 points apart on average over 1 shared benchmark.
- Widest single gap
- IFBench: Grok 4.3 83.3% against Step 3.5 Flash 66.5%, 16.8 points apart on a 0 to 100 scale.
- Output price
- Grok 4.3 $2.50 against Step 3.5 Flash $0.30 per million output tokens, 8.3x apart.
- Context window
- Grok 4.3 takes 1M 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 | Grok 4.3 | Bars | Step 3.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 1 | 2 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 1 | 0 | ||
| Reasoning | 2 | 3 | ||
| Math | 0 | 2 | ||
| Knowledge | 0 | 4 | ||
| General | 11 | 8 | ||
| All shared boards | 16 | 19 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index12
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LMArena WebDev | 1358 | Not measured | Only Grok 4.3 measured |
| AA Coding Index | 42.2 | Not measured | Only Grok 4.3 measured |
| LiveCodeBench (Vals AI) | 84.5% | Not measured | Only Grok 4.3 measured |
| SWE-bench Verified (Vals AI) | 71.4% | Not measured | Only Grok 4.3 measured |
| Vibe Code Bench (Vals AI) | 19.4% | Not measured | Only Grok 4.3 measured |
| Code migration (Vals AI) | 6.8% | Not measured | Only Grok 4.3 measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only Grok 4.3 measured |
| Terminal-Bench 2.1 (Vals AI) | 42.0% | Not measured | Only Grok 4.3 measured |
| SkillsBench (Vals AI) | 40.6% | Not measured | Only Grok 4.3 measured |
| SciCode | 48.3% | Not measured | Only Grok 4.3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | 32.6% | Grok 4.3 |
| WeirdML | 49.9% | Not measured | Only Grok 4.3 measured |
| ALE-Bench | 944.2 | Not measured | Only Grok 4.3 measured |
| LMArena Text: coding | 1415 | 1436 | Step 3.5 Flash |
| LMArena Text: software and IT | 1416 | 1434 | Step 3.5 Flash |
| LMArena WebDev: React | 1353 | Not measured | Only Grok 4.3 measured |
| LMArena WebDev: HTML | 1367 | Not measured | Only Grok 4.3 measured |
| LMArena WebDev: from an image | 1375 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 20 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 24.9 | 17.0 | Grok 4.3 |
| Neither model has a result on the other 1 board here | |||
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Agentic Index | 15.5 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building web apps | 1126 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building full-stack apps | 1006 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building mobile apps | 1059 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building Android apps | 961 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building Godot games | 914 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building games | 1007 | Not measured | Only Grok 4.3 measured |
| Design Arena: HTML slides | 1008 | Not measured | Only Grok 4.3 measured |
| Design Arena: PowerPoint slides | 1013 | Not measured | Only Grok 4.3 measured |
| Finance Agent (Vals AI) | 37.7% | Not measured | Only Grok 4.3 measured |
| Tax Agent Bench (Vals AI) | 6.2% | Not measured | Only Grok 4.3 measured |
| Legal Research Bench (Vals AI) | 15.4% | Not measured | Only Grok 4.3 measured |
| Excel Modeling Benchmark (Vals AI) | 18.4% | Not measured | Only Grok 4.3 measured |
| τ²-Bench Telecom | 97.7% | 94.4% | Grok 4.3 |
| Vending-Bench 2 | $35 | Not measured | Only Grok 4.3 measured |
| LMArena Search | 1166 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 23 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index23
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| GPQA Diamond | 91.4% | Not measured | Only Grok 4.3 measured |
| MMMU Pro (Vals AI) | 83.1% | Not measured | Only Grok 4.3 measured |
| GPQA Diamond (Artificial Analysis run) | 90.1% | 83.1% | Grok 4.3 |
| Humanity's Last Exam (Artificial Analysis run) | 37.2% | 24.5% | Grok 4.3 |
| GPQA Diamond (Epoch AI run) | 88.8% | Not measured | Only Grok 4.3 measured |
| Chess puzzles | 18.0% | Not measured | Only Grok 4.3 measured |
| LMArena Text: hard prompts | 1396 | 1411 | Step 3.5 Flash |
| LMArena Text: expert | 1384 | 1421 | Step 3.5 Flash |
| LMArena Text: hard prompts in English | 1402 | 1421 | Step 3.5 Flash |
| LMArena Vision: diagrams | 1241 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: homework | 1241 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 10 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| OTIS Mock AIME | 93.3% | Not measured | Only Grok 4.3 measured |
| FrontierMath, tiers 1 to 3 | 42.8% | Not measured | Only Grok 4.3 measured |
| FrontierMath, tier 4 | 14.6% | Not measured | Only Grok 4.3 measured |
| ProofBench | 11.0% | Not measured | Only Grok 4.3 measured |
| LMArena Text: math | 1387 | 1408 | Step 3.5 Flash |
| LMArena Text: mathematical work | 1396 | 1421 | Step 3.5 Flash |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| MMLU Pro | 85.8% | Not measured | Only Grok 4.3 measured |
| LegalBench (Vals AI) | 84.5% | Not measured | Only Grok 4.3 measured |
| CaseLaw (Vals AI) | 79.3% | Not measured | Only Grok 4.3 measured |
| CorpFin (Vals AI) | 68.5% | Not measured | Only Grok 4.3 measured |
| TaxEval (Vals AI) | 70.8% | Not measured | Only Grok 4.3 measured |
| MortgageTax (Vals AI) | 48.3% | Not measured | Only Grok 4.3 measured |
| MedCode (Vals AI) | 38.1% | Not measured | Only Grok 4.3 measured |
| SimpleQA Verified | 33.2% | Not measured | Only Grok 4.3 measured |
| LMArena Text: science | 1399 | 1415 | Step 3.5 Flash |
| LMArena Text: medicine and healthcare | 1384 | 1408 | Step 3.5 Flash |
| LMArena Text: legal and government | 1386 | 1408 | Step 3.5 Flash |
| LMArena Text: business and finance | 1381 | 1394 | Step 3.5 Flash |
| Neither model has a result on the other 5 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1196 | Not measured | Only Grok 4.3 measured |
| Design Arena: UI components | 1192 | Not measured | Only Grok 4.3 measured |
| Design Arena: game dev | 1174 | Not measured | Only Grok 4.3 measured |
| Design Arena: data viz | 1179 | Not measured | Only Grok 4.3 measured |
| Design Arena: 3D | 1125 | Not measured | Only Grok 4.3 measured |
| Design Arena: all code categories | 1187 | Not measured | Only Grok 4.3 measured |
| Design Arena: SVG | 1081 | Not measured | Only Grok 4.3 measured |
| Design Arena: ASCII art | 1125 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index118
| Benchmark | Grok 4.3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Public Benefits Bench (Vals AI) | 51.7% | Not measured | Only Grok 4.3 measured |
| SAGE (Vals AI) | 19.7% | Not measured | Only Grok 4.3 measured |
| MedScribe (Vals AI) | 74.4% | Not measured | Only Grok 4.3 measured |
| Vals Multimodal Index | 43.3% | Not measured | Only Grok 4.3 measured |
| IFBench | 83.3% | 66.5% | Grok 4.3 |
| Long context reasoning (AA-LCR) | 75.0% | 63.0% | Grok 4.3 |
| DTBench | 90.7% | Not measured | Only Grok 4.3 measured |
| LMCA | 38.3% | Not measured | Only Grok 4.3 measured |
| LMArena Text | 1397 | 1403 | Step 3.5 Flash |
| LMArena Text: instruction following | 1366 | 1385 | Step 3.5 Flash |
| LMArena Text: creative writing | 1380 | 1357 | Grok 4.3 |
| LMArena Vision | 1229 | Not measured | Only Grok 4.3 measured |
| LMArena Text: English | 1404 | 1417 | Step 3.5 Flash |
| LMArena Text: non-English | 1385 | 1385 | Grok 4.3 |
| LMArena Text: Chinese | 1422 | 1446 | Step 3.5 Flash |
| LMArena Text: German | 1395 | 1405 | Step 3.5 Flash |
| LMArena Text: Japanese | 1379 | 1353 | Grok 4.3 |
| LMArena Text: Korean | 1354 | 1351 | Grok 4.3 |
| LMArena Text: French | 1411 | 1421 | Step 3.5 Flash |
| LMArena Text: Spanish | 1399 | 1419 | Step 3.5 Flash |
| LMArena Text: Russian | 1399 | 1385 | Grok 4.3 |
| LMArena Text: Polish | 1398 | 1389 | Grok 4.3 |
| LMArena Text: multi-turn | 1406 | 1404 | Grok 4.3 |
| LMArena Text: longer queries | 1393 | 1402 | Step 3.5 Flash |
| LMArena Text: writing and language | 1385 | 1372 | Grok 4.3 |
| LMArena Text: entertainment and media | 1370 | 1360 | Grok 4.3 |
| LMArena Vision: English | 1235 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: Chinese | 1257 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: reading text | 1235 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: humor | 1222 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: recognizing things | 1217 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: creative writing | 1237 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.3 | 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 | SpaceXAI Grok 4.3 | StepFun Step 3.5 Flash |
|---|---|---|
| Maker | xAI | StepFun |
| Weights | No public weights listed | Open weights |
| Released | April 30, 2026 | January 29, 2026 |
| Context window | 1M | 262K |
| Input $/Mtok | $1.25 | $0.10 |
| Output $/Mtok | $2.50 | $0.30 |
| Coding index | 37.4 | Not benchmarked |
| Independent measurements behind it | 3 | 0 |
| Cost per solved task | $0.31 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.3 better than Step 3.5 Flash for coding?
Only Grok 4.3 has a coding score, 37.4 on the Vibe Coding Index; Step 3.5 Flash has none, so the two cannot be ranked on coding. Pick Step 3.5 Flash for output tokens 8.3x cheaper ($0.30 vs $2.50 per million) and work measured by LMArena Text: coding or LMArena Text: software and IT, where it leads.
Which is cheaper, Grok 4.3 or Step 3.5 Flash?
Grok 4.3 costs $1.25 per million input tokens and $2.50 per million output tokens; Step 3.5 Flash costs $0.10 and $0.30. Cost per solved task is known for Grok 4.3 only.
Which has the bigger context window, Grok 4.3 or Step 3.5 Flash?
Grok 4.3, with 1M tokens against 262K.
How many benchmarks is the Grok 4.3 vs Step 3.5 Flash comparison based on?
35 benchmarks have a result for both models as of October 21, 2026. Grok 4.3's coding index rests on 3 independent benchmarks and Step 3.5 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.