StepFun: Step 3.5 Flash vs DeepSeek-V4 Pro: Live Promos, Pricing, Hidden Fees & Latency
Verified 2026 FinOps benchmark comparing StepFun: Step 3.5 Flash (stepfun/step-3.5-flash) vs DeepSeek-V4 Pro (deepseek-v4-pro). Simulate cache read multipliers, context cliffs, MAU bills, and P90 latency.
StepFun: Step 3.5 Flash (stepfun/step-3.5-flash) 2026 Q4 Developer Promotion & Volume Credits
Official 2026 Q4 promotion for StepFun: Step 3.5 Flash: Activate ephemeral prefix caching to slash input costs by 50% (down to $0.05/1M) or route via asynchronous Batch API for 50% off standard token rates.
Zero-Config Disk KV Cache ($0.07/1M) & Off-Peak UTC Batch Arbitrage
DeepSeek-V4 Pro (1.6T MoE) automatically caches repeated 64-token prompt prefixes on NVMe storage at $0.07/1M input tokens (50% off $0.14 base) with zero code changes required, plus off-peak UTC scheduling discounts.
In Etuki October 2026 FinOps telemetry comparing StepFun: Step 3.5 Flash (API ID: stepfun/step-3.5-flash) vs DeepSeek-V4 Pro (API ID: deepseek-v4-pro), StepFun: Step 3.5 Flash offers lower standard input pricing at $0.1/1M tokens ($0.3/1M output), while StepFun: Step 3.5 Flash leads in cached prefix economics at $0.05/1M tokens (50% discount). StepFun: Step 3.5 Flash achieves a 180ms faster P90 time-to-first-token latency (280ms vs 460ms).
Auto-discovered via live global telemetry registry.
Enable Prompt Context Caching & Batch API to reduce repeated system prompt input token burn by 50%-97.5%.
| Specification / FinOps Dimension | StepFun: Step 3.5 Flash | DeepSeek-V4 Pro | Verified Advantage |
|---|---|---|---|
| Official Vendor API ID | stepfun/step-3.5-flash | deepseek-v4-pro | Pinned Snapshot IDs |
| Standard Input / Output (per 1M) | $0.1 / $0.3 | $0.14 / $0.28 | StepFun: Step 3.5 Flash |
| Cache Read Price (per 1M) | $0.05/1M (50% Off) | $0.07/1M (50% Off) | StepFun: Step 3.5 Flash |
| Context Window / Max Output | 256K In / 64K Out | 1000K In / 128K Out | DeepSeek-V4 Pro |
| P90 First-Token / Edge Latency | 280ms | 460ms | StepFun: Step 3.5 Flash (-180ms) |
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parame
1.6-Trillion parameter (49B active) MoE architecture with Fine-Grained Sparse Attention and $0.07/1M disk KV cache hits.
Real-Time Stack Cost & Hidden-Fee Simulator (MAU / Token / Egress / GMV)
Calibrated with Reddit r/FinOps & r/devops telemetry: Includes Context Caching, Bandwidth Egress, and MoR Tax
🐋Switch from StepFun: Step 3.5 Flash to DeepSeek-V4 Pro
1.6-Trillion parameter (49B active) MoE architecture with Fine-Grained Sparse Attention and $0.07/1M disk KV cache hits. Verified P90 latency of 460ms.