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ModelCap

Step 3.5 Flash

All-versions archive #89Arena #145Open weights

StepFun·stepfun/step-3.5-flash

Step 3.5 Flash is a language model published by StepFun. 1 OpenRouter endpoint is published in the latest snapshot. It accepts text input and returns text. The published context limit is 262K tokens. The catalogue declares support for reasoning, tool use.

ModelCap Index · All-versions archive
61.9#89
Measured · 84% support · score interval 61.9–68.5
Market Gravity
36.0
Secondary market signal

Superseded by Step 3.7 Flash. It no longer holds a current-board position; its all-versions archive rank is #89.

Input
$0.10
per 1M tokens
Output
$0.30
per 1M tokens
Context
262K
tokens
Providers
1
endpoint
Gateway spend
—
latest · Vercel share

Providers

Uptime measured over the last 30 minutes
ProviderInputOutputContextQuantUptime
SiliconFlowfp8$0.10$0.30262Kfp8100.0%

Hugging Face Inference Providers

Exact repository identity

Provider economics and telemetry published by the Hugging Face Router. These are operational signals, not benchmark results.

ProviderInputOutputContextTTFTThroughputFeatures
deepinfra
live
$0.10$0.30262K210 ms120.3 tok/stools
featherless-ai
live
——————

Reported evaluation leads (10)

Excluded from score

Structured rows reported in this exact model repository at the pinned revision below. They are useful research leads, but remain quarantined until dataset revision, harness, configuration and identity pass ModelCap’s independent admission review.

Dataset / taskMetricValueRevisionProvenance
cais/hle
hle
—23.1
Unpinned
not published
Reported
Quarantined
harborframework/terminal-bench-2.0
terminalbench_2
—51
Unpinned
not published
Reported
Quarantined
Idavidrein/gpqa
diamond
—83.5
Unpinned
not published
Reported
Quarantined
internlm/WildClawBench
overall
—26.7
Unpinned
not published
Reported
Quarantined
internlm/WildClawBench
avg_time
—430
Unpinned
not published
Reported
Quarantined
internlm/WildClawBench
avg_cost
—6.6
Unpinned
not published
Reported
Quarantined
MathArena/aime_2026
MathArena/aime_2026
—96.67
Unpinned
not published
Reported
Quarantined
MathArena/hmmt_feb_2026
MathArena/hmmt_feb_2026
—86.36
Unpinned
not published
Reported
Quarantined
SWE-bench/SWE-bench_Verified
swe_bench_%_resolved
—74.4
Unpinned
not published
Reported
Quarantined
TIGER-Lab/MMLU-Pro
mmlu_pro
—84.4
Unpinned
not published
Reported
Quarantined

Other versions (1)

ModelCap Index · All-versions archive

Methodology
61.9
Measured · 2 public benchmark observations across 2 boards
All-versions archive
#89
Public rank basis
Measured (measured)
Index support
84.2% · strong
Index interval
61.9–68.5
Rank posterior
Not available
Top 5 / Top 10 probability
Not available / Not available
Posterior as of
Snapshot timestamp unavailable
Identity binding
Exact catalogue product · stepfun/stepfun/step-3.5-flash · aggregates disclosed benchmark configurations · endpoint configuration not claimed · artifact metadata stepfun-ai/Step-3.5-Flash@ab446a3de5e171ea341227e24bb1f090e1b771f7 (not the evaluation revision)
Direct benchmark observations
2
Breadth-adjusted BES point estimate
65.2
Bayesian Evidence Score · measured evidence input only

BES normalizes admitted public benchmark evidence for measured Index rows. Its legacy score and observables prior do not define the public language rank.

Observed capability
65.2
Evidence status
confirmed · 83% mass
General preference
64.5
Coding
68.1
Agents & tools
—
Reasoning
—
Evidence breadth
92%
Evidence coverage
84%
Market and catalogue signals · secondary, never the language Index rank
Usage (OpenRouter popularity)
9.9
Liquidity (providers × uptime)
77.8
Open reach (HF downloads)
57.9
Surface (context / tools / modalities)
75.3
Freshness
48.5
  • · OpenRouter popularity #170
  • · 1 live provider
  • · HF 30d downloads 126978
  • · Catalogue: context 262144, reasoning, tools
  • · First seen 2026-01-29

These adoption and deployment observations remain context only. They do not change this model's ModelCap Index score or rank.

BES evidence selected · measured input only

The bounded 0–100 capability score blends each source’s competitive placement with its published achievement, then combines capability families. Evidence breadth adds a modest uncertainty adjustment; price and popularity are not part of benchmark-led rank.

Deployment readiness

Metadata index
87.5
strong · 98% metadata coverage
Not capability
Artifact reproducibility
100.0
Access & legal clarity
100.0
Deployability
89.0
Evaluation provenance
54.2

Missing: evaluationProvenance.evaluation-dataset-revisions.

A metadata completeness and deployability index—not a safety certification, quality grade, or production-readiness claim.

Market activity

Venue coverage
Market Gravity
36.0
OpenRouter weekly popularity
#170 of 298

Market Gravity uses OpenRouter’s full-catalogue popularity order. Sparse Vercel top-ten observations appear only when published and do not affect the score.

Arena preference

Status
Ranked
Source
Arena
Official rank
#145 of 385
Rating
1394.3
95% confidence interval
1391–1398
Votes
57K
Source snapshot
6 Aug 2026, 13:00 UTC
Category
overall
Identity match confidence
100%

Market Gravity breakdown

Usage55%
9.9

OpenRouter weekly popularity across the full model catalogue.

Liquidity25%
77.8

Independent providers versus the model's open or closed cohort, weighted by uptime.

Open reach15%
57.9

Hugging Face 30-day downloads for open models; neutral for closed models.

Freshness5%
48.5

Time since first public availability, on a six-month half-life.

Specification

Context window
262K tokens
Max output
66K tokens
Inputs
Text
Outputs
Text
Tokenizer
Other
Cached input tokens
Not offered
First seen on OpenRouter
29 Jan 2026

Capabilities

  • Supported: Reasoning
  • Supported: Tool use
  • Not supported: Structured output
  • Not supported: Response format
  • Not supported: Moderated

Weights & access

Open weights. Downloadable weights are published under an OSI or free-culture license in the current repository metadata. This describes weight availability, not whether the full training stack qualifies as Open Source AI.

Access
Open weights
Licence
apache-2.0
Pinned revision
ab446a3de5e1
Parameters
199.4B
Architecture
Step3p5ForCausalLM
Model type
step3p5
Hugging Face downloads (30d)
127K
Downloads (all time)
1.4M
Likes
830
Repository
stepfun-ai/Step-3.5-Flash
Repository updated
17 Mar 2026, 05:54 UTC
Base lineage
stepfun-ai/step-3.5-flash