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DeepSeek V3.1 Terminus vs Step 3.5 Flash

Updated October 21, 2026. 27 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace DeepSeek V3.1 Terminus Replace Step 3.5 Flash
DeepSeek V3.1 TerminusDeepSeek
Coding
No data
Overall
14.8
Output $/M
$1.0142
18
Step 3.5 FlashStepFun
Coding
No data
Overall
17.0
Output $/M
$0.30
9
vs boards won of 27 shared

Decision reading

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

DeepSeek V3.1 Terminus has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Model ADeepSeek V3.1 TerminusDeepSeekNot benchmarkedNo coding benchmarkNo cost per solved taskModel BStep 3.5 FlashStepFunNot benchmarkedNo coding benchmarkNo cost per solved task
Shared results
27
DeepSeek V3.1 Terminus only
17
Step 3.5 Flash only
8
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
DeepSeek V3.1 Terminus not benchmarked, Step 3.5 Flash not benchmarked.
Widest category
Agentic work, 57.3 points apart on average over 1 shared benchmark.
Widest single gap
τ²-Bench Telecom: DeepSeek V3.1 Terminus 37.1% against Step 3.5 Flash 94.4%, 57.3 points apart on a 0 to 100 scale.
Output price
DeepSeek V3.1 Terminus $1.0142 against Step 3.5 Flash $0.30 per million output tokens, 3.4x apart.
Context window
DeepSeek V3.1 Terminus takes 164K 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
CategoryDeepSeek V3.1 TerminusBarsStep 3.5 FlashTies
Coding03
Intelligence01
Agentic work01
Reasoning22
Math01
Knowledge40
General121
All shared boards189
CodingLike-for-likeSix of these boards feed the Vibe Coding Index03
Coding benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
AA Coding Index43.5Not measuredOnly DeepSeek V3.1 Terminus measured
LiveCodeBench (Artificial Analysis run)79.8%Not measuredOnly DeepSeek V3.1 Terminus measured
SciCode38.0%Not measuredOnly DeepSeek V3.1 Terminus measured
Terminal-Bench Hard (Artificial Analysis run)31.8%32.6%Step 3.5 Flash
ALE-Bench745.2Not measuredOnly DeepSeek V3.1 Terminus measured
LMArena Text: coding14251436Step 3.5 Flash
LMArena Text: software and IT14261434Step 3.5 Flash
Neither model has a result on the other 31 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
Intelligence benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
AA Intelligence Index14.817.0Step 3.5 Flash
Neither model has a result on the other 1 board here
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
Agentic work benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
AA Agentic Index6.8Not measuredOnly DeepSeek V3.1 Terminus measured
τ²-Bench Telecom37.1%94.4%Step 3.5 Flash
Neither model has a result on the other 37 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index22
Reasoning benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
GPQA Diamond (Artificial Analysis run)79.2%83.1%Step 3.5 Flash
Humanity's Last Exam (Artificial Analysis run)16.4%24.5%Step 3.5 Flash
LMArena Text: hard prompts14261411DeepSeek V3.1 Terminus
LMArena Text: expertNot measured1421Only Step 3.5 Flash measured
LMArena Text: hard prompts in English14321421DeepSeek V3.1 Terminus
Neither model has a result on the other 16 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index01
Math benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
AA Math Index89.7Not measuredOnly DeepSeek V3.1 Terminus measured
AIME 2025 (Artificial Analysis run)89.7%Not measuredOnly DeepSeek V3.1 Terminus measured
LMArena Text: math14021408Step 3.5 Flash
LMArena Text: mathematical workNot measured1421Only Step 3.5 Flash measured
Neither model has a result on the other 9 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
Knowledge benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
MMLU Pro (Artificial Analysis run)85.1%Not measuredOnly DeepSeek V3.1 Terminus measured
LMArena Text: science14511415DeepSeek V3.1 Terminus
LMArena Text: medicine and healthcare14681408DeepSeek V3.1 Terminus
LMArena Text: legal and government14571408DeepSeek V3.1 Terminus
LMArena Text: business and finance14141394DeepSeek V3.1 Terminus
Neither model has a result on the other 12 boards here
Web designDirectional onlyPublic boards, shown as published, kept out of the index7 boards, none shared
Web design benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
Design Arena: websites1187Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: UI components1182Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: game dev1131Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: data viz1167Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: 3D1141Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: all code categories1175Not measuredOnly DeepSeek V3.1 Terminus measured
Design Arena: SVG1065Not measuredOnly DeepSeek V3.1 Terminus measured
Neither model has a result on the other 2 boards here
GeneralLike-for-likePublic boards, shown as published, kept out of the index121
General benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 3.5 FlashLeader
IFBench57.0%66.5%Step 3.5 Flash
Long context reasoning (AA-LCR)69.3%63.0%DeepSeek V3.1 Terminus
DTBench81.3%Not measuredOnly DeepSeek V3.1 Terminus measured
LMCA28.6%Not measuredOnly DeepSeek V3.1 Terminus measured
LMArena Text14191403DeepSeek V3.1 Terminus
LMArena Text: instruction following14041385DeepSeek V3.1 Terminus
LMArena Text: creative writing14031357DeepSeek V3.1 Terminus
LMArena Text: English14291417DeepSeek V3.1 Terminus
LMArena Text: non-English14081385DeepSeek V3.1 Terminus
LMArena Text: ChineseNot measured1446Only Step 3.5 Flash measured
LMArena Text: GermanNot measured1405Only Step 3.5 Flash measured
LMArena Text: JapaneseNot measured1353Only Step 3.5 Flash measured
LMArena Text: KoreanNot measured1351Only Step 3.5 Flash measured
LMArena Text: FrenchNot measured1421Only Step 3.5 Flash measured
LMArena Text: SpanishNot measured1419Only Step 3.5 Flash measured
LMArena Text: Russian14351385DeepSeek V3.1 Terminus
LMArena Text: Polish14271389DeepSeek V3.1 Terminus
LMArena Text: multi-turn14111404DeepSeek V3.1 Terminus
LMArena Text: longer queries14221402DeepSeek V3.1 Terminus
LMArena Text: writing and language14091372DeepSeek V3.1 Terminus
LMArena Text: entertainment and media13911360DeepSeek V3.1 Terminus
Neither model has a result on the other 25 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for DeepSeek V3.1 Terminus and Step 3.5 Flash
BenchmarkDeepSeek V3.1 TerminusStep 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

DeepSeek V3.1 Terminus$0.0008Fits 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

DeepSeek V3.1 Terminus$0.018Fits 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

DeepSeek V3.1 Terminus$0.071Exceeds 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 DeepSeek V3.1 Terminus and Step 3.5 Flash
SpecificationDeepSeek V3.1 TerminusStepFun Step 3.5 Flash
MakerDeepSeekStepFun
WeightsOpen weightsOpen weights
ReleasedSeptember 22, 2025January 29, 2026
Context window164K262K
Input $/Mtok$0.3063$0.10
Output $/Mtok$1.0142$0.30
Coding indexNot benchmarkedNot benchmarked
Independent measurements behind it00
Cost per solved taskNot computableNot computable
SourceOpenRouter listingOpenRouter listing

Questions

Is DeepSeek V3.1 Terminus better than Step 3.5 Flash for coding?

Neither model has a coding score yet, so the two cannot be ranked on coding. DeepSeek V3.1 Terminus has the edge where what matters is Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.

Which is cheaper, DeepSeek V3.1 Terminus or Step 3.5 Flash?

DeepSeek V3.1 Terminus costs $0.3063 per million input tokens and $1.0142 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, DeepSeek V3.1 Terminus or Step 3.5 Flash?

Step 3.5 Flash, with 262K tokens against 164K.

How many benchmarks is the DeepSeek V3.1 Terminus vs Step 3.5 Flash comparison based on?

27 benchmarks have a result for both models as of October 21, 2026. DeepSeek V3.1 Terminus'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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