Noometry

Model comparison

Claude Opus 4.5 vs Step 3.5 Flash

Claude Opus 4.5 is the stronger model overall, scoring 50.5 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 4.5's lead doesn't matter for your workload.

Last verified . 18 shared benchmarks.

Claude Opus 4.5 Anthropic

50.5

Rank #47 Confirmed

Step 3.5 Flash StepFun

42.3

Rank #116 Confirmed

Summary

  • They share 18 benchmarks with published results for both. Claude Opus 4.5 scores higher in 7 categories and Step 3.5 Flash in 1 category; 8 gaps are clear of the uncertainty.
  • The widest gap is in reasoning, where Claude Opus 4.5 leads 42.6 to 22.2.
  • The biggest single-benchmark swing is NYT Connections (extended): 52.5% for Claude Opus 4.5 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 4.5.
  • Step 3.5 Flash accepts more context: 256K tokens versus 200K.
  • Step 3.5 Flash has downloadable open weights; the other is API-only.

Side by side

Claude Opus 4.5Step 3.5 Flash
ProviderAnthropicStepFun
Noometry Index50.542.3
Released2025-11-012026-01-29
WeightsProprietaryOpen
Context window200K256K
Max output64K256K
Input $ / M tokens$5$0.10
Output $ / M tokens$25$0.30
Results tracked6919

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Category by category

Coding Claude Opus 4.5 leads

Claude Opus 4.5: 54.8 (#27), Step 3.5 Flash: 42.4 (#105)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Coding15041436
SWE-bench Verified76.7%—
SWE-bench Verified (bash only)76.8%—
LMArena WebDev1494—
SWE-bench Multilingual70.7%—
GSO26.5%—
WeirdML63.7%—
ALE-Bench1,025—
AlgoTune1.77—

Agentic & Tool Use Not comparable

Claude Opus 4.5: 47.3 (#12), Step 3.5 Flash: —

BenchmarkClaude Opus 4.5Step 3.5 Flash
Terminal-Bench63.1%—
Berkeley Function Calling Leaderboard77.5%—
GDPval45.5%—
Remote Labor Index3.8%—
τ²-bench Airline84%—
τ²-bench Banking24.7%—
τ²-bench Retail79.6%—
τ²-bench Telecom92.3%—
Cybench82%—
DeepResearch Bench54.8%—
OSWorld66.3%—
BALROG43.5%—
LMArena Search1180—
METR Time Horizons75%—
Vending-Bench 24,967—

Reasoning Claude Opus 4.5 leads

Claude Opus 4.5: 42.6 (#51), Step 3.5 Flash: 22.2 (#202)

BenchmarkClaude Opus 4.5Step 3.5 Flash
NYT Connections (extended)52.5%28.4%
LMArena Hard Prompts14761411
ARC-AGI-237.6%—
SimpleBench62%—
Kagi LLM Benchmark80.2%—
ARC-AGI-180%—
Chess Puzzles12%—
EnigmaEval11.9%—
EBR-Bench14.3%—
Mystery Game Puzzles22%—
DTBench89.9%—
LMCA44.5%—
Epoch Capabilities Index150.09—
ForecastBench60.7—

Math Step 3.5 Flash leads

Claude Opus 4.5: 38.6 (#132), Step 3.5 Flash: 42.6 (#84)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Math14631408
FrontierMath (Tiers 1-3)34.4%—
FrontierMath Tier 44.9%—
MathArena Final-Answer Competitions—66.8%
OTIS Mock AIME 2024-202586.1%—
ProofBench36%—
FrontierMath (Feb 2025 set)20.7%—
FrontierMath Tier 4 (v1)4.2%—

Knowledge Claude Opus 4.5 leads

Claude Opus 4.5: 56.5 (#44), Step 3.5 Flash: 39.6 (#132)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Expert14871421
GPQA Diamond86%—
Humanity's Last Exam25.2%—
SimpleQA Verified45.7%—
Vectara Hallucination Rate10.9%—

Multimodal Not comparable

Claude Opus 4.5: 31.4 (#107), Step 3.5 Flash: —

BenchmarkClaude Opus 4.5Step 3.5 Flash
GeoBench75%—
VPCT40%—
Furniture Assembly28.3%—
LMArena Document1462—

Multilingual Claude Opus 4.5 leads

Claude Opus 4.5: 54.3 (#47), Step 3.5 Flash: 50.5 (#119)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Non-English14381385
LMArena Chinese14701447
LMArena French14711421
LMArena German14491405
LMArena Japanese14161354
LMArena Korean14241352
LMArena Russian14471385
LMArena Spanish14581419

Instruction Following Claude Opus 4.5 leads

Claude Opus 4.5: 77.5 (#19), Step 3.5 Flash: 73.1 (#124)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Instruction Following14781385

Long Context Claude Opus 4.5 leads

Claude Opus 4.5: 46.5 (#22), Step 3.5 Flash: 42.8 (#117)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Longer Query14801402
CL-bench21.1%—

Writing & Preference Claude Opus 4.5 leads

Claude Opus 4.5: 68.1 (#28), Step 3.5 Flash: 58.8 (#113)

BenchmarkClaude Opus 4.5Step 3.5 Flash
LMArena Text14511403
LMArena Creative Writing14451357
LMArena Multi-Turn14661405
EQ-Bench Creative Writing1687—

Frequently asked questions

Is Claude Opus 4.5 better than Step 3.5 Flash?

Claude Opus 4.5 is the stronger model overall, scoring 50.5 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 4.5's lead doesn't matter for your workload.

Which is cheaper, Claude Opus 4.5 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 4.5 lists at $5 and $25.

Is Claude Opus 4.5 or Step 3.5 Flash better for coding?

Claude Opus 4.5 scores higher on coding benchmarks: 54.8 versus 42.4 in the Noometry coding category.

Which has the bigger context window?

Step 3.5 Flash does, with 256K tokens against 200K.

How many benchmarks do Claude Opus 4.5 and Step 3.5 Flash share?

18 benchmarks have published results for both models. Claude Opus 4.5 has 69 scored results on Noometry and Step 3.5 Flash has 19.

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