https://b128s.dev Writing on AI engineering, startup execution, and the mental models behind building products. en-us https://b128s.dev/blog/Context-Windows-Are-RAM-Not-Memory https://b128s.dev/blog/Context-Windows-Are-RAM-Not-Memory Long-running agents will not become reliable by fitting more tokens into one prompt. They need durable state, selective retrieval, provenance, and a way to recover from bad memory. Sun, 13 Sep 2026 00:00:00 GMT https://b128s.dev/blog/VC-Is-Quietly-Drawing-The-Post-Agent-Stack https://b128s.dev/blog/VC-Is-Quietly-Drawing-The-Post-Agent-Stack Four AI rounds look unrelated until you put them on one diagram. Then they reveal where investors think value will accumulate after the coding agent. Sat, 12 Sep 2026 00:00:00 GMT https://b128s.dev/blog/Autonomous-Agents-Need-Constitutions-Not-Bigger-Contexts https://b128s.dev/blog/Autonomous-Agents-Need-Constitutions-Not-Bigger-Contexts Longer-running agents do not become reliable through more context or more retries. They need evidence, protected rules, durable memory, and clear limits on their authority. Tue, 08 Sep 2026 00:00:00 GMT https://b128s.dev/blog/Vibe-Coding-Made-Computer-Science-More-Important https://b128s.dev/blog/Vibe-Coding-Made-Computer-Science-More-Important AI removed the syntax tax from software development. It did not remove the need to understand state, logic, failure, and verification — it made that knowledge the difference between a demo and a product. Sun, 06 Sep 2026 00:00:00 GMT https://b128s.dev/blog/Instinct-Can-Build-AIs-Next-Great-Moat https://b128s.dev/blog/Instinct-Can-Build-AIs-Next-Great-Moat The first wave of AI applications found its moat in distribution. Instinct may enter the market with one already built: the complexity of making a personal agent actually work. Sat, 05 Sep 2026 00:00:00 GMT https://b128s.dev/blog/The-Wrapper-Era-Ended-On-A-Contract-Clause https://b128s.dev/blog/The-Wrapper-Era-Ended-On-A-Contract-Clause OpenAI cutting Cursor after SpaceX's $60 billion takeover, and Anthropic lining up a trillion-dollar IPO, are not two headlines. They are the same move from different floors — and the application layer is no longer allowed to stay neutral. Sat, 29 Aug 2026 00:00:00 GMT https://b128s.dev/blog/The-Mental-Models-That-Poison-Founders https://b128s.dev/blog/The-Mental-Models-That-Poison-Founders An introduction to the series on founder mental models Wed, 03 Dec 2025 00:00:00 GMT https://b128s.dev/blog/KISS-or-Die https://b128s.dev/blog/KISS-or-Die Senior engineers kill startups by doing exactly what made them senior. $100K in free cloud credits, enterprise experience, "proper" architecture — we had it all. We still failed. Not because we built it wrong. We built it well. That was the problem. Here are the mental models that could have saved us. Sun, 30 Nov 2025 00:00:00 GMT