---
id: "2026-10-17-deepseek-v4-1-flash-1017"
url: "https://postcutoff.com/e/2026-10-17-deepseek-v4-1-flash-1017/"
as_of: "2026-10-17T13:26:00+02:00"
date: "2026-10-17"
date_precision: day
category: model-release
importance: 3
confidence: high
status: [Confirmed]
sources: 8
editor: human editor
human_review: null
version: null
---

As of: 2026-10-17 13:26 CEST.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-10-17-deepseek-v4-1-flash-1017/

# DeepSeek-V4.1-Flash-1017 update: big agentic-coding gains, same price

Full title: DeepSeek-V4.1-Flash-1017: MIT-licensed update lifts Terminal-Bench 4.0 from 31.2 to 42.3 and HLE to 42.6 at unchanged API prices

On Oct 17, 2026 DeepSeek replaced V4.1-Flash on its web app, mobile app and API (still called `deepseek-flash`, prices unchanged) with DeepSeek-V4.1-Flash-1017, a "minor update" with open MIT-licensed weights on Hugging Face. Official scores rose sharply on agentic benchmarks (Terminal-Bench 4.0 31.2 → 42.3, ProgramBench 20.3 → 29.1, HLE without tools 36.8 → 42.6), and DeepSeek says the model also finishes tasks faster with shorter outputs. Its own table puts it ahead of GPT-5.6 Sol on most listed agent benchmarks, behind Claude Opus 5.

## Key facts
- Announced Oct 17, 2026 on DeepSeek's API news page ('DeepSeek-V4.1-Flash-1017: Wish-Driven Programming Made Real') and on X (@deepseek_ai, ~872k views and ~12.9k likes by 13:00 CEST)
- Availability: web, app and API; 'The API calling method and pricing remain unchanged — simply use deepseek-flash' (API changelog). OpenRouter lists deepseek/deepseek-v4.1-flash-1017 at $0.15 / $0.60 per 1M input/output tokens with a 1,048,576-token context
- Open weights: huggingface.co/deepseek-ai/DeepSeek-V4.1-Flash-1017, MIT license, created Oct 17 02:40 UTC; Hugging Face's safetensors metadata counts about 763B stored parameters (mostly FP8/INT8 tensors); recommended temperature 1.0, top_p 1.0, max_tokens ≥ 256K
- Official scores, 1017 vs the Sept 10 V4.1-Flash: HLE w/o tools 42.6 (text subset 44.0) vs 36.8 (39.1); Terminal-Bench 4.0 42.3 vs 31.2 (Claude Code harness); DeepSWE v1.1 77.0 vs 74.2 (mini-SWE-v2 harness); ProgramBench 29.1 vs 20.3; NL2Repo-Bench 68.2 vs 65.4; Automation-Bench 60.5 vs 54.8; Agents' Last Exam 35.4 vs 31.8; Apex Bench v1.1 72.1 vs 64.6; Chartography 83.0, BabyVision 92.5, ZeroBench-main 51.0 (pass@5)
- Same table's comparison columns (DeepSeek's numbers): GPT-5.6 Sol HLE 44.5, Terminal-Bench 4.0 39.9, DeepSWE 73.0; Claude Opus 5 HLE 56.3, Terminal-Bench 4.0 51.8, ProgramBench 37.0; Kimi K3 and GLM-5.3 trail on most rows
- Training note (news page): 'uses reinforcement learning with self-feedback to improve end-to-end project development', with demos of a 3D Forbidden City model, a web racing game, a Portal 2 recreation in Godot and a 3D 'Valley of Ages' scene
- Tuned for DeepSeek Harness (v0.2.1-rc.1 or later), Tencent CodeBuddy and WorkBuddy; no Jinja chat template, instead an encoding reference implementation and the Rust 'deepseek-recipe' library that converts Messages, Chat Completions and Responses API requests into DeepSeek prompts
- Pandaily (Oct 17) reported that the '1017' snapshot surfaced briefly, unannounced, alongside the DeepSeek Harness v0.2.1-rc1 release before the launch post
- Hacker News: two front-page threads on Oct 17 (Hugging Face page 180 points; OpenRouter page 168 points)

## What happened

Five weeks after V4.1-Flash (Sept 10), DeepSeek shipped a dated snapshot, **DeepSeek-V4.1-Flash-1017**, on Saturday Oct 17, 2026. It
became the default model on DeepSeek's website, app and API under the same `deepseek-flash` name and price. The weights are on Hugging
Face under the MIT license. DeepSeek calls it a "minor update", but the gains on its agentic benchmarks are large: Terminal-Bench 4.0 rose
by 11 points, ProgramBench by 9 and Humanity's Last Exam (no tools) by about 6. DeepSeek also says the model finishes tasks faster and with
shorter outputs, which it calls a Pareto improvement in performance and cost. The same post opened the Search and Fetch APIs to everyone
(covered in [2026-10-16-deepseek-search-fetch-api](https://postcutoff.com/e/2026-10-16-deepseek-search-fetch-api/index.md)).

All benchmark numbers come from DeepSeek. Several of them (Terminal-Bench 4.0, ProgramBench, Agents' Last Exam) are newer benchmarks with
few independent results yet. The comparison columns use GPT-5.6 Sol and Claude Opus 5, not OpenAI's and Anthropic's current flagships
(GPT-6 Astra, Claude Opus 5.5).

## Why it matters

V4.1-Flash was already the open-weight model many developers used as a cheap coding agent. This update keeps the price at $0.15/$0.60
per million tokens and, by DeepSeek's numbers, beats GPT-5.6 Sol on most agent benchmarks it lists. That widens the price gap between
open Chinese models and the US frontier for agentic coding.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): 170 days after its cutoff
- Claude Opus 5.5 (training cutoff June 2026): 109 days after its cutoff
- Gemini 4 Argon (training cutoff March 2026): 200 days after its cutoff
- Grok 4.7 (training cutoff May 2026): 139 days after its cutoff

## Sources

1. [DeepSeek API news: DeepSeek-V4.1-Flash-1017: Wish-Driven Programming Made Real (2026-10-17)](https://api-docs.deepseek.com/news/news261017) (api-docs.deepseek.com, official)
2. [DeepSeek API change log (V4.1-Flash-1017 update, pricing unchanged)](https://api-docs.deepseek.com/updates/) (api-docs.deepseek.com, official)
3. [DeepSeek on X: DeepSeek-V4.1-Flash-1017 is here!](https://x.com/deepseek_ai/status/2111375640717033777) (x.com, official)
4. [Hugging Face: deepseek-ai/DeepSeek-V4.1-Flash-1017 (MIT)](https://huggingface.co/deepseek-ai/DeepSeek-V4.1-Flash-1017) (huggingface.co, code)
5. [OpenRouter: deepseek/deepseek-v4.1-flash-1017](https://openrouter.ai/deepseek/deepseek-v4.1-flash-1017) (openrouter.ai, docs)
6. [Pandaily: DeepSeek Harness v0.2.1-rc1 arrives as an unannounced V4.1 Flash snapshot briefly surfaces](https://pandaily.com/deepseek-harness-v0-2-1-rc1-plugin-index-working-directory-v4-1-flash-1017-snapshot) (pandaily.com, press)
7. [Hacker News: DeepSeek-v4.1-Flash-1017 (180 points)](https://news.ycombinator.com/item?id=50129045) (news.ycombinator.com, discussion)
8. [Hacker News: DeepSeek v4.1 Flash 1017 on OpenRouter (168 points)](https://news.ycombinator.com/item?id=50129121) (news.ycombinator.com, discussion)

## Changes

- 2026-10-17 (filed): Created (read DeepSeek's news page, change log and Hugging Face card, OpenRouter model list and the X post via fxtwitter)

## Related

- 2026-10-16: [DeepSeek Search and Fetch APIs for agents](https://postcutoff.com/e/2026-10-16-deepseek-search-fetch-api/index.md)
- 2026-10-11: [Two coding-agent tests report that DeepSeek V4.1 Flash used an API key left in its sandbox to call other models (unconfirmed)](https://postcutoff.com/e/2026-10-11-deepseek-v4-1-flash-exposed-api-keys-reports/index.md)
- 2026-09-30: [DeepSeek releases Harness v0.2 preview with desktop apps for macOS and Windows](https://postcutoff.com/e/2026-09-30-deepseek-harness-desktop-v0-2/index.md)
- 2026-09-10: [DeepSeek V4.1-Flash brings a new architecture family, native vision and a cheaper API](https://postcutoff.com/e/2026-09-10-deepseek-v4-1-flash/index.md)
- Archived: 1 post, listed in https://postcutoff.com/e/2026-10-17-deepseek-v4-1-flash-1017/index.json