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o1 vs Step 3.5 Flash

Updated October 21, 2026. 34 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace o1 Replace Step 3.5 Flash
o1OpenAI
Coding
No data
Overall
15.2
Output $/M
$60.00
3
Step 3.5 FlashStepFun
Coding
No data
Overall
17.0
Output $/M
$0.30
31
vs boards won of 34 shared

Decision reading

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

o1 has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Model Ao1OpenAINot benchmarkedNo coding benchmarkNo cost per solved taskModel BStep 3.5 FlashStepFunNot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
34
o1 only
34
Step 3.5 Flash only
1
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
o1 not benchmarked, Step 3.5 Flash not benchmarked.
Widest category
Agentic work, 31.9 points apart on average over 1 shared benchmark.
Widest single gap
τ²-Bench Telecom: o1 62.6% against Step 3.5 Flash 94.4%, 31.9 points apart on a 0 to 100 scale.
Output price
o1 $60.00 against Step 3.5 Flash $0.30 per million output tokens, 200.0x apart.
Context window
o1 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
Categoryo1BarsStep 3.5 FlashTies
Coding03
Intelligence01
Agentic work01
Reasoning05
Math02
Knowledge04
General315
All shared boards331
CodingLike-for-likeSix of these boards feed the Vibe Coding Index03
Coding benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
Aider polyglot61.7%Not measuredOnly o1 measured
AA Coding Index39.7Not measuredOnly o1 measured
LiveCodeBench (Vals AI)50.3%Not measuredOnly o1 measured
LiveCodeBench (Artificial Analysis run)67.9%Not measuredOnly o1 measured
Terminal-Bench Hard (Artificial Analysis run)12.9%32.6%Step 3.5 Flash
WeirdML46.1%Not measuredOnly o1 measured
LMArena Text: coding13671436Step 3.5 Flash
LMArena Text: software and IT13661434Step 3.5 Flash
Neither model has a result on the other 30 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
Intelligence benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
AA Intelligence Index15.217.0Step 3.5 Flash
Epoch Capabilities Index141.7Not measuredOnly o1 measured
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
τ²-Bench Telecom62.6%94.4%Step 3.5 Flash
METR time horizons51.1%Not measuredOnly o1 measured
Neither model has a result on the other 37 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index05
Reasoning benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
GPQA Diamond73.2%Not measuredOnly o1 measured
MMMU Pro (Vals AI)77.4%Not measuredOnly o1 measured
GPQA Diamond (Artificial Analysis run)74.7%83.1%Step 3.5 Flash
Humanity's Last Exam (Artificial Analysis run)7.0%24.5%Step 3.5 Flash
GPQA Diamond (Epoch AI run)76.8%Not measuredOnly o1 measured
ARC-AGI30.7%Not measuredOnly o1 measured
SimpleBench40.1%Not measuredOnly o1 measured
Chess puzzles10.0%Not measuredOnly o1 measured
VPCT37.0%Not measuredOnly o1 measured
LMArena Text: hard prompts13711411Step 3.5 Flash
LMArena Text: expert13611421Step 3.5 Flash
LMArena Text: hard prompts in English13721421Step 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 o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
AIME71.5%Not measuredOnly o1 measured
MATH 500 (Vals AI)90.4%Not measuredOnly o1 measured
MGSM (Vals AI)89.3%Not measuredOnly o1 measured
OTIS Mock AIME73.3%Not measuredOnly o1 measured
FrontierMath, tiers 1 to 314.7%Not measuredOnly o1 measured
MATH level 594.7%Not measuredOnly o1 measured
LMArena Text: math13881408Step 3.5 Flash
LMArena Text: mathematical work13901421Step 3.5 Flash
Neither model has a result on the other 5 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index04
Knowledge benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
MMLU Pro83.5%Not measuredOnly o1 measured
LegalBench (Vals AI)80.4%Not measuredOnly o1 measured
TaxEval (Vals AI)74.3%Not measuredOnly o1 measured
MedQA (Vals AI)96.5%Not measuredOnly o1 measured
MMLU Pro (Artificial Analysis run)84.1%Not measuredOnly o1 measured
SimpleQA Verified41.1%Not measuredOnly o1 measured
GeoBench80.0%Not measuredOnly o1 measured
LMArena Text: science13691415Step 3.5 Flash
LMArena Text: medicine and healthcare13551408Step 3.5 Flash
LMArena Text: legal and government13681408Step 3.5 Flash
LMArena Text: business and finance13281394Step 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 o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
Neither model has a result on 9 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index315
General benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 3.5 FlashLeader
IFBench70.3%66.5%o1
Long context reasoning (AA-LCR)65.0%63.0%o1
DTBench74.7%Not measuredOnly o1 measured
LMCA22.3%Not measuredOnly o1 measured
Fiction.LiveBench83.3%Not measuredOnly o1 measured
Creative writing (Lech Mazur)70.2%Not measuredOnly o1 measured
LMArena Text13661403Step 3.5 Flash
LMArena Text: instruction following13671385Step 3.5 Flash
LMArena Text: creative writing13471357Step 3.5 Flash
LMArena Vision1168Not measuredOnly o1 measured
LMArena Text: English13721417Step 3.5 Flash
LMArena Text: non-English13581385Step 3.5 Flash
LMArena Text: Chinese13941446Step 3.5 Flash
LMArena Text: German13371405Step 3.5 Flash
LMArena Text: Japanese13461353Step 3.5 Flash
LMArena Text: Korean13961351o1
LMArena Text: French13441421Step 3.5 Flash
LMArena Text: Spanish13451419Step 3.5 Flash
LMArena Text: Russian13561385Step 3.5 Flash
LMArena Text: PolishNot measured1389Only Step 3.5 Flash measured
LMArena Text: multi-turn13551404Step 3.5 Flash
LMArena Text: longer queries13781402Step 3.5 Flash
LMArena Text: writing and language13601372Step 3.5 Flash
LMArena Text: entertainment and media13581360Step 3.5 Flash
LMArena Vision: English1162Not measuredOnly o1 measured
LMArena Vision: Chinese1235Not measuredOnly o1 measured
Neither model has a result on the other 20 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for o1 and Step 3.5 Flash
Benchmarko1Step 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

o1$0.045Fits 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

o1$0.930Fits 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

o1$3.60Exceeds 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 o1 and Step 3.5 Flash
SpecificationOpenAI o1StepFun Step 3.5 Flash
MakerOpenAIStepFun
WeightsNo public weights listedOpen weights
ReleasedDecember 17, 2024January 29, 2026
Context window200K262K
Input $/Mtok$15.00$0.10
Output $/Mtok$60.00$0.30
Coding indexNot benchmarkedNot benchmarked
Independent measurements behind it00
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is o1 better than Step 3.5 Flash for coding?

Neither model has a coding score yet, so the two cannot be ranked on coding. o1 has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Which is cheaper, o1 or Step 3.5 Flash?

o1 costs $15.00 per million input tokens and $60.00 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, o1 or Step 3.5 Flash?

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

How many benchmarks is the o1 vs Step 3.5 Flash comparison based on?

34 benchmarks have a result for both models as of October 21, 2026. o1'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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