DeepSeek V4.1 Flash + DeepSeek Harness = Full SaaS In 18 Mins (Cost: $0.12)
DeepSeek just released V4.1 Flash. On paper it beats Claude Opus 5 on Terminal-Bench 2.1 (90.6 vs 89.1), scores 3471 on Codeforces, runs at 270 tokens per second, has a 1M token context window, and a 552B backbone. So I ran it through my standard test: the exact same SaaS prompt I give every model, inside the open-source DeepSeek Harness, with Convex, Clerk, Stripe and Vercel. 18 minutes. $0.12. And an honest verdict you won't see in the benchmark charts. In this video: • How to set up the DeepSeek Harness in one command (and have Claude Code do it for you) • My standard SaaS benchmark prompt and env-variable setup • DeepSeek V4.1 Flash vs V4 Flash vs V4 Pro vs GPT-6 vs Fable 5.1 on the same build • Why "test-and-build" systems are the thing that makes any model reliable • The real cost, speed and quality result, with receipts Work with us (websites, SaaS, CRMs, SEO): https://incomestreamsurfer.com DeepSeek Harness on GitHub: search "DeepSeek Harness" #DeepSeek #DeepSeekV41Flash #AICoding #ClaudeCode #OpenSource ## Chapters 0:00 A new DeepSeek model (and why I'm not using GPT-6) 0:31 Launching the DeepSeek Harness with one command 0:52 Setting it up: let Claude Code install it for you 1:28 My standard SaaS benchmark prompt (Convex, Clerk, Stripe) 2:38 First impressions: this is fast 2:45 What GPT-6 inside Claude Code built with the same prompt 3:24 How Fable 5.1 compared 4:06 V4.1 Flash asks qualifying questions 4:58 Want a site like this? Work with us 6:41 Why my system tests everything before it ships 8:03 The business-in-a-box we resell (Ballinderry Park CRM) 9:04 I still use Claude Code for everything 9:36 Who the DeepSeek Harness is actually for 11:04 The result: 18 minutes, $0.12 11:41 It's multimodal: 552B, 1M context 12:07 Testing the build: dashboard, login, uploads 12:35 Honest verdict: worse than V4 Flash 13:26 V4 Pro vs V4.1 Flash, and what I'd use instead 14:02 Outro deepseek v4.1 flash, deepseek 4.1 flash, deepseek v4.1, deepseek harness, deepseek harness setup, deepseek flash review, deepseek vs claude opus 5, deepseek vs gpt 6, deepseek coding, deepseek coding agent, open source coding agent, cheap ai coding, ai coding tools, claude code, claude code alternative, deepseek v4 flash, deepseek v4 pro, build saas with ai, ai saas builder, convex clerk stripe, terminal bench, deepseek benchmarks, income stream surfers
