DeepSeek Just Released V4.1-Flash-1017, Scores 77.0 on DeepSWE, Opens Search API

DeepSeek has just released DeepSeek-V4.1-Flash-1017, a new checkpoint of its V4.1-Flash model. It is live on the DeepSeek website, app and API. DeepSeek claims stronger scores, faster task completion and shorter outputs than the September V4.1-Flash release. The company calls it a Pareto improvement in performance and cost. Alongside it, DeepSeek opened its Search and Fetch APIs to every developer. For agent builders, that means a cheaper coding model plus a first-party web layer behind one API key.

TL;aDR

• Size: 552B backbone parameters plus 196B Engram parameters. It activates 8B parameters per token in prefill and 16B in decode. Context is 1M tokens, with up to 384K output tokens.
• Runs on: DeepSeek API as deepseek-flash. September V4.1-Flash weights (763B parameters, FP8) are MIT-licensed on Hugging Face. Hardware requirements and 1017 weights: Not disclosed.
• Performance: Beats the previous V4.1-Flash on all 11 benchmarks DeepSeek reported, by 2.0 to 11.1 points.
• Best: 77.0 on DeepSWE v1.1, above Claude Opus 5 (74.0) in DeepSeek’s table.
• Worst: 42.6 on HLE without tools, versus 56.3 for Claude Opus 5.

What is DeepSeek-V4.1-Flash-1017?

DeepSeek-V4.1-Flash-1017 is an updated post-training checkpoint of DeepSeek-V4.1-Flash, served through the deepseek-flash model name. The architecture details below come from the V4.1-Flash technical report.

DeepSeek team states that DeepSeek-V4.1-Flash-1017 uses reinforcement learning with self-feedback for end-to-end project work. Its examples run from game creation to 3D modeling. It is tuned for DeepSeek Harness, Tencent CodeBuddy and WorkBuddy. DeepSeek recommends DeepSeek Harness v0.2.1-rc.1 or later.

How does the V4.1-Flash architecture work?

V4.1-Flash is a multimodal Mixture-of-Experts model with 40 Transformer layers. They split into a 20-layer causal encoder and a 20-layer decoder.

• Causal Encoder-Decoder (CED): Decoder global KV is projected from the final encoder hidden states. This nearly halves prefill compute.
• Compressed Sparse Attention 2 (CSA2): Layers run in Full, Reindex or Reuse mode. They share main KV and indexer keys across layers.
• FP4 main KV cache: Global KV drops to 890 bytes per token, about 1/4 of V4-Flash.
• SWA Bounded Replay: Persistent KV cache shrinks to roughly 1/8 of V4-Flash.
• Reasoning effort: A 1 to 100 scalar. The API tiers low, high and max map to 50, 75 and 100.

DeepSeek-V4.1-Flash-1017 benchmarks

All scores below are DeepSeek’s own figures. DeepSeek ran Terminal-Bench 4.0 in Claude Code and DeepSWE in Mini-SWE-V2. ZeroBench-main uses Pass@5.

*Text-only HLE subset.

The 1017 checkpoint leads on DeepSWE, Automation-Bench, Agents’ Last Exam and Apex Bench. Claude Opus 5 still leads on Terminal-Bench 4.0, ProgramBench, NL2Repo and HLE.

How does it compare with open-weight rivals?

What are DeepSeek’s Search and Fetch APIs?

The Search API returns ranked web results for a query. The Fetch API returns a single page as Markdown. DeepSeek says its in-house engine serves hundreds of millions of requests daily.

• Endpoints: POST /v1/tools/search and POST /v1/tools/fetch on api.deepseek.com.
• Search options: 1 to 50 results, optional page content, and operators like site:, lang:, after: and before:.
• Result fields: Each result has a 0 to 3 rerank score and a 0 to 4 authority tier.
• Price: $0.75 per 1,000 successful requests for each endpoint. Empty results and failures are free.
• Rate limit: 5 QPS per account for each API.
• Free window: Server-side calls via DeepSeek Harness, Claude Code or Codex stay free until November 1, 2026.

Deployment and pricing

Call the model with deepseek-flash through OpenAI or Anthropic-format endpoints. Peak pricing is $0.30 per 1M cache-miss input tokens and $1.20 per 1M output tokens. Off-peak rates are half.

Key Takeaways

• 1017 scores 77.0 on DeepSWE v1.1, up from 74.2.
• It leads Automation-Bench (60.5) and Agents’ Last Exam (35.4).
• Claude Opus 5 still wins on HLE and Terminal-Bench 4.0.
• Search and Fetch cost $0.75 per 1,000 calls each.
• Agent harness calls stay free until November 1, 2026.