Noometry

Model comparison

Claude Opus 5.5 vs Step 3.5 Flash

Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 41.7 on the Noometry Index. Step 3.5 Flash costs 53× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Last verified . 12 shared benchmarks.

Claude Opus 5.5 Anthropic

68.5

Rank #3 Confirmed

Step 3.5 Flash StepFun

41.7

Rank #116 Confirmed

Summary

  • They share 12 benchmarks with published results for both. Claude Opus 5.5 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 5.5 leads 79.5 to 21.2.
  • The biggest single-benchmark swing is NYT Connections (extended): 88.5% for Claude Opus 5.5 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 $4 / $20 for Claude Opus 5.5.
  • Claude Opus 5.5 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 5.5Step 3.5 Flash
ProviderAnthropicStepFun
Noometry Index68.541.7
Released2026-09-222026-01-29
WeightsProprietaryOpen
Context window1M256K
Max output128K256K
Input $ / M tokens$4$0.10
Output $ / M tokens$20$0.30
Results tracked3519

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Category by category

Coding Claude Opus 5.5 leads

Claude Opus 5.5: 71.4 (#1), Step 3.5 Flash: 41.7 (#106)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Coding15451436
FrontierCode54.4%—
CursorBench57.8%—
LMArena WebDev1820—
FrontierSWE62.3%—
SciCode66.9%—
MirrorCode77.4%—

Agentic & Tool Use Not comparable

Claude Opus 5.5: 45.3 (#13), Step 3.5 Flash: —

BenchmarkClaude Opus 5.5Step 3.5 Flash
APEX-Agents73.5%—
GDP.pdf30.6%—

Reasoning Claude Opus 5.5 leads

Claude Opus 5.5: 79.5 (#2), Step 3.5 Flash: 21.2 (#202)

BenchmarkClaude Opus 5.5Step 3.5 Flash
NYT Connections (extended)88.5%28.4%
LMArena Hard Prompts15451411
ARC-AGI-292.5%—
ARC-AGI-197.5%—
CritPt31.7%—
EBR-Bench71.4%—
Mystery Game Puzzles71%—
DTBench98.9%—
LMCA68.2%—

Math Claude Opus 5.5 leads

Claude Opus 5.5: 92.4 (#2), Step 3.5 Flash: 40.6 (#77)

BenchmarkClaude Opus 5.5Step 3.5 Flash
FrontierMath (Tiers 1-3)91.2%—
FrontierMath Tier 495%—
MathArena Final-Answer Competitions—66.8%
OTIS Mock AIME 2024-2025100%—
ProofBench100%—
LMArena Math—1408

Knowledge Claude Opus 5.5 leads

Claude Opus 5.5: 66.6 (#9), Step 3.5 Flash: 39.0 (#127)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Expert15641422
GPQA Diamond90.6%—
SimpleQA Verified72.2%—

Multimodal Not comparable

Claude Opus 5.5: 56.5 (#2), Step 3.5 Flash: —

BenchmarkClaude Opus 5.5Step 3.5 Flash
Furniture Assembly83.3%—

Multilingual Claude Opus 5.5 leads

Claude Opus 5.5: 59.8 (#1), Step 3.5 Flash: 50.7 (#115)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Non-English15131386
LMArena Chinese15721448
LMArena Russian15321385
LMArena French—1421
LMArena German—1404
LMArena Japanese—1353
LMArena Korean—1350
LMArena Spanish—1419

Instruction Following Claude Opus 5.5 leads

Claude Opus 5.5: 80.1 (#2), Step 3.5 Flash: 73.3 (#119)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Instruction Following15351385

Long Context Claude Opus 5.5 leads

Claude Opus 5.5: 47.3 (#18), Step 3.5 Flash: 42.8 (#112)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Longer Query15401402

Writing & Preference Claude Opus 5.5 leads

Claude Opus 5.5: 78.7 (#3), Step 3.5 Flash: 59.0 (#108)

BenchmarkClaude Opus 5.5Step 3.5 Flash
LMArena Text15181403
LMArena Creative Writing15381357
LMArena Multi-Turn15201405
EQ-Bench Creative Writing2050—

Frequently asked questions

Is Claude Opus 5.5 better than Step 3.5 Flash?

Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 41.7 on the Noometry Index. Step 3.5 Flash costs 53× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

Which is cheaper, Claude Opus 5.5 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 5.5 lists at $4 and $20.

Is Claude Opus 5.5 or Step 3.5 Flash better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.4 versus 41.7 in the Noometry coding category.

Which has the bigger context window?

Claude Opus 5.5 does, with 1M tokens against 256K.

How many benchmarks do Claude Opus 5.5 and Step 3.5 Flash share?

12 benchmarks have published results for both models. Claude Opus 5.5 has 35 scored results on Noometry and Step 3.5 Flash has 19.

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