Simon Willison is a prolific independent software developer, a blogger, and one of the most visible and trusted voices on the impact AI is having on builders. He co-created Django, the web framework that powers Instagram, Pinterest, and tens of thousands of other websites. He coined the term “prompt injection,” popularized the terms “AI slop” and “agentic engineering,” and has built over 100 open source projects, including Datasette, a data analysis tool used by investigative journalists worldwide. What makes Simon unique is that he’s made the leap from traditional software engineering to AI-native development more fully and visibly than almost anyone—and he’s been documenting everything he learns in real time on his blog, SimonWillison.net.

In our in-depth conversation, Simon shares:

1. Why November 2025 was the inflection point when AI coding agents crossed from “mostly works” to “actually works”

2. How Simon writes 95% of his code from his phone now and why he’s mentally exhausted by 11 a.m.

3. Why mid-career engineers (not juniors) are most at risk right now

4. The three agentic engineering patterns Simon uses daily (red/green TDD, templates, hoarding)

5. The next leap: the “dark factory” pattern where nobody writes or reviews code and AI does its own QA

6. Why prompt injection is an unsolved security problem and the “lethal trifecta” that will likely lead to an AI Challenger disaster

7. Why the pelican riding a bicycle became the unofficial benchmark for AI model quality

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Where to find Simon Willison:

• X: https://x.com/simonw

• LinkedIn: https://www.linkedin.com/in/simonwillison

• Website: https://simonwillison.net

• Agentic Engineering Patterns: https://simonwillison.net/guides/agentic-engineering-patterns

Referenced:

• It genuinely feels to me like GPT-5.2 and Opus 4.5 in November represent an inflection point: https://x.com/simonw/status/2007904766756880848

• Claude Code: https://code.claude.com

• Codex: https://chatgpt.com/codex

• Head of Claude Code: What happens after coding is solved | Boris Cherny: https://www.lennysnewsletter.com/p/head-of-claude-code-what-happens

• There’s a new kind of coding I call “vibe coding”: https://x.com/karpathy/status/1886192184808149383

• Firefox: https://www.firefox.com

• Naming expert shares the process behind creating billion-dollar brand names like Azure, Vercel, Windsurf, Sonos, Blackberry, and Impossible Burger | David Placek (Lexicon Branding): https://www.lennysnewsletter.com/p/naming-expert-david-placek

• Windsurf: https://windsurf.com

• Thoughtworks: https://www.thoughtworks.com

• Cloudflare: https://www.cloudflare.com

• Shopify: https://www.shopify.com

• Jensen Huang: Nvidia’s Future, Physical AI, Rise of the Agent, Inference Explosion, AI PR Crisis: https://www.youtube.com/watch?v=gwW8GKwHB3I

• Inside Linear: Building with taste, craft, and focus | Karri Saarinen (co-founder, designer, CEO): https://www.lennysnewsletter.com/p/inside-linear-building-with-taste

• Hacker News: https://news.ycombinator.com

• Dario Amodei on X: https://x.com/DarioAmodei

• Lenny’s post on the job market in tech: https://www.lennysnewsletter.com/p/state-of-the-product-job-market-in-ee9

• Claude app: https://apps.apple.com/us/app/claude-by-anthropic/id6473753684

• Gemini: https://gemini.google.com/app

• Import and export your memory from Claude: https://support.claude.com/en/articles/12123587-import-and-export-your-memory-from-claude

• Wispr Flow: https://wisprflow.ai

• The last six months in LLMs, illustrated by pelicans on bicycles: https://simonwillison.net/2025/Jun/6/six-months-in-llms

• Gemini 3.1 Pro: https://simonwillison.net/2026/Feb/19/gemini-31-pro

• Redis: https://redis.io

• Node.js: https://nodejs.org

• Simon’s tools repository: https://github.com/simonw/tools

• Simon’s research repository: https://github.com/simonw/research

• Tesseract: https://github.com/tesseract-ocr/tesseract

• TDD: https://martinfowler.com/bliki/TestDrivenDevelopment.html

• Red/green TDD: https://simonwillison.net/guides/agentic-engineering-patterns/red-green-tdd

• The lethal trifecta for AI agents: private data, untrusted content, and external communication: https://simonwillison.net/2025/Jun/16/the-lethal-trifecta

• Prompt injection: https://simonwillison.net/series/prompt-injection

• The coming AI security crisis (and what to do about it) | Sander Schulhoff: https://www.lennysnewsletter.com/p/the-coming-ai-security-crisis

• AI prompt engineering in 2025: What works and what doesn’t | Sander Schulhoff (Learn Prompting, HackAPrompt): https://www.lennysnewsletter.com/p/ai-prompt-engineering-in-2025-sander-schulhoff

• The Challenger Disaster: Normalisation of Deviance: https://psychsafety.com/normalisation-of-deviance

• Thanksgiving Day Chart—Behind The Net: https://www.blackswanreport.com/blog/2009/11/thanksgiving-day%C2%A0chart-behind-the-net

• CaMeL offers a promising new direction for mitigating prompt injection attacks: https://simonwillison.net/2025/Apr/11/camel

• OpenClaw: https://openclaw.ai

• Introducing ai.com—Your Private, Personal AI Agent: https://www.youtube.com/watch?v=n7I-D4YXbzg

• Tamagotchi: https://en.wikipedia.org/wiki/Tamagotchi

• NanoClaw: https://nanoclaw.dev

• Spider-Man 2: https://www.imdb.com/title/tt0316654

• Alfred Molina: https://en.wikipedia.org/wiki/Alfred_Molina

• AI for Data Journalism: demonstrating what we can do with this stuff right now: https://simonwillison.net/2024/Apr/17/ai-for-data-journalism

• Kākāpō: https://en.wikipedia.org/wiki/K%C4%81k%C4%81p%C5%8D

• Kākāpō Cam: Rakiura the kākāpō—2026 nest: https://www.youtube.com/live/BfGL7A2YgUY

Production and marketing by https://penname.co/. For inquiries about sponsoring the podcast, email podcast@lennyrachitsky.com.

Lenny may be an investor in the companies discussed.

My biggest takeaways from this conversation:...