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o3 Mini vs Step 3.5 Flash

Updated October 21, 2026. 35 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace o3 Mini Replace Step 3.5 Flash
o3 MiniOpenAI
Coding
No data
Overall
12.5
Output $/M
$4.40
1
Step 3.5 FlashStepFun
Coding
No data
Overall
17.0
Output $/M
$0.30
34
vs boards won of 35 shared

Decision reading

Neither model has a coding score yet, so the two cannot be ranked on coding.

o3 Mini has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Model Ao3 MiniOpenAINot benchmarkedNo coding benchmarkNo cost per solved taskModel BStep 3.5 FlashStepFunNot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
35
o3 Mini only
35
Step 3.5 Flash only
0
Like-for-like categories
7 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.

At a glance

Coding index
o3 Mini not benchmarked, Step 3.5 Flash not benchmarked.
Widest category
Agentic work, 63.2 points apart on average over 1 shared benchmark.
Widest single gap
τ²-Bench Telecom: o3 Mini 31.3% against Step 3.5 Flash 94.4%, 63.2 points apart on a 0 to 100 scale.
Output price
o3 Mini $4.40 against Step 3.5 Flash $0.30 per million output tokens, 14.7x apart.
Context window
o3 Mini 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.

Boards won, where both have a result
Categoryo3 MiniBarsStep 3.5 FlashTies
Coding03
Intelligence01
Agentic work01
Reasoning05
Math02
Knowledge04
General118
All shared boards134
CodingLike-for-likeSix of these boards feed the Vibe Coding Index03
Coding benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
Aider polyglot60.4%Not measuredOnly o3 Mini measured
SWE-bench Verified42.4%Not measuredOnly o3 Mini measured
SWE-bench Lite32.3%Not measuredOnly o3 Mini measured
LiveCodeBench (Vals AI)71.5%Not measuredOnly o3 Mini measured
LiveCodeBench (Artificial Analysis run)73.4%Not measuredOnly o3 Mini measured
SciCode42.8%Not measuredOnly o3 Mini measured
Terminal-Bench Hard (Artificial Analysis run)6.8%32.6%Step 3.5 Flash
GSO-Bench1.3%Not measuredOnly o3 Mini measured
WeirdML43.7%Not measuredOnly o3 Mini measured
Cybench22.5%Not measuredOnly o3 Mini measured
LMArena Text: coding13781436Step 3.5 Flash
LMArena Text: software and IT13641434Step 3.5 Flash
Neither model has a result on the other 26 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
Intelligence benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
AA Intelligence Index12.517.0Step 3.5 Flash
Epoch Capabilities Index140.2Not measuredOnly o3 Mini measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
τ²-Bench Telecom31.3%94.4%Step 3.5 Flash
Neither model has a result on the other 38 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index05
Reasoning benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
GPQA Diamond75.5%Not measuredOnly o3 Mini measured
GPQA Diamond (Artificial Analysis run)77.3%83.1%Step 3.5 Flash
Humanity's Last Exam (Artificial Analysis run)12.0%24.5%Step 3.5 Flash
GPQA Diamond (Epoch AI run)77.0%Not measuredOnly o3 Mini measured
ARC-AGI34.5%Not measuredOnly o3 Mini measured
ARC-AGI-23.0%Not measuredOnly o3 Mini measured
SimpleBench22.8%Not measuredOnly o3 Mini measured
Chess puzzles15.0%Not measuredOnly o3 Mini measured
Mystery game puzzles7.0%Not measuredOnly o3 Mini measured
LMArena Text: hard prompts13651411Step 3.5 Flash
LMArena Text: expert13641421Step 3.5 Flash
LMArena Text: hard prompts in English13751421Step 3.5 Flash
Neither model has a result on the other 9 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index02
Math benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
AIME86.5%Not measuredOnly o3 Mini measured
MATH 500 (Vals AI)91.8%Not measuredOnly o3 Mini measured
MGSM (Vals AI)91.3%Not measuredOnly o3 Mini measured
OTIS Mock AIME76.9%Not measuredOnly o3 Mini measured
FrontierMath, tiers 1 to 318.6%Not measuredOnly o3 Mini measured
FrontierMath, tier 40.0%Not measuredOnly o3 Mini measured
MATH level 596.5%Not measuredOnly o3 Mini measured
LMArena Text: math13961408Step 3.5 Flash
LMArena Text: mathematical work13991421Step 3.5 Flash
Neither model has a result on the other 4 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index04
Knowledge benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
MMLU Pro78.7%Not measuredOnly o3 Mini measured
LegalBench (Vals AI)71.5%Not measuredOnly o3 Mini measured
CorpFin (Vals AI)45.3%Not measuredOnly o3 Mini measured
TaxEval (Vals AI)69.4%Not measuredOnly o3 Mini measured
MedQA (Vals AI)94.8%Not measuredOnly o3 Mini measured
MMLU Pro (Artificial Analysis run)80.2%Not measuredOnly o3 Mini measured
SimpleQA Verified15.3%Not measuredOnly o3 Mini measured
LMArena Text: science13391415Step 3.5 Flash
LMArena Text: medicine and healthcare13301408Step 3.5 Flash
LMArena Text: legal and government13281408Step 3.5 Flash
LMArena Text: business and finance13131394Step 3.5 Flash
Neither model has a result on the other 6 boards here
Web designNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Web design benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
Neither model has a result on 9 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index118
General benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
IFBench67.1%66.5%o3 Mini
Long context reasoning (AA-LCR)43.0%63.0%Step 3.5 Flash
DTBench68.8%Not measuredOnly o3 Mini measured
LMCA19.0%Not measuredOnly o3 Mini measured
Fiction.LiveBench50.0%Not measuredOnly o3 Mini measured
Creative writing (Lech Mazur)61.7%Not measuredOnly o3 Mini measured
LMArena Text13371403Step 3.5 Flash
LMArena Text: instruction following13371385Step 3.5 Flash
LMArena Text: creative writing12861357Step 3.5 Flash
LMArena Text: English13511417Step 3.5 Flash
LMArena Text: non-English13191385Step 3.5 Flash
LMArena Text: Chinese13791446Step 3.5 Flash
LMArena Text: German13031405Step 3.5 Flash
LMArena Text: Japanese12861353Step 3.5 Flash
LMArena Text: Korean13131351Step 3.5 Flash
LMArena Text: French13341421Step 3.5 Flash
LMArena Text: Spanish13211419Step 3.5 Flash
LMArena Text: Russian13041385Step 3.5 Flash
LMArena Text: Polish12941389Step 3.5 Flash
LMArena Text: multi-turn13201404Step 3.5 Flash
LMArena Text: longer queries13431402Step 3.5 Flash
LMArena Text: writing and language13131372Step 3.5 Flash
LMArena Text: entertainment and media12831360Step 3.5 Flash
Neither model has a result on the other 23 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for o3 Mini and Step 3.5 Flash
Benchmarko3 MiniStep 3.5 FlashLeader
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

o3 Mini$0.0033Fits in one request
Step 3.5 Flash$0.0003Fits in one request

Step 3.5 Flash costs less

Repository review

50K input + 3K output tokens

o3 Mini$0.068Fits in one request
Step 3.5 Flash$0.0059Fits in one request

Step 3.5 Flash costs less

Agent loop

200K input + 10K output tokens

o3 Mini$0.264Exceeds the context window
Step 3.5 Flash$0.023Fits in one request

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.

Specifications of o3 Mini and Step 3.5 Flash
SpecificationOpenAI o3 MiniStepFun Step 3.5 Flash
MakerOpenAIStepFun
WeightsNo public weights listedOpen weights
ReleasedJanuary 31, 2025January 29, 2026
Context window200K262K
Input $/Mtok$1.10$0.10
Output $/Mtok$4.40$0.30
Coding indexNot benchmarkedNot benchmarked
Independent measurements behind it00
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is o3 Mini better than Step 3.5 Flash for coding?

Neither model has a coding score yet, so the two cannot be ranked on coding. o3 Mini has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Which is cheaper, o3 Mini or Step 3.5 Flash?

o3 Mini costs $1.10 per million input tokens and $4.40 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, o3 Mini or Step 3.5 Flash?

Step 3.5 Flash, with 262K tokens against 200K.

How many benchmarks is the o3 Mini vs Step 3.5 Flash comparison based on?

35 benchmarks have a result for both models as of October 21, 2026. o3 Mini's coding index rests on 0 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.

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