https://paulund.co.uk Developer notebook — articles on AI, and software engineering. en Fri, 19 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/stop-blaming-the-model Google just published a 51-page paper on the new SDLC. The single most important idea: your agent is not the model. It is the harness around it. Fri, 19 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/stop-blaming-the-model https://paulund.co.uk/notebook/ai/harness-engineering Cole Medin breaks down what makes a coding agent harness and why it matters more than the model. Here is what I took from his framing and how it maps to... Thu, 18 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/harness-engineering https://paulund.co.uk/notebook/good-code/a-modern-quality-pipeline-and-testing-strategy-for-frontend-projects A practical guide to building a 15-layer frontend quality pipeline, from type safety to observability, and how to adopt it in phases so each layer pays ... Wed, 17 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/good-code/a-modern-quality-pipeline-and-testing-strategy-for-frontend-projects https://paulund.co.uk/notebook/ai/agents-are-cron-jobs-and-markdown-files Ryan Carson runs his startup solo with AI agents. His core thesis is the cleanest articulation yet of what agentic automation actually is: schedulers an... Wed, 17 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/agents-are-cron-jobs-and-markdown-files https://paulund.co.uk/notebook/ai/measure-your-agent-skills-or-delete-them Nick Nisi discovered one of his skills dropped accuracy from 97% to 77%. The lesson: skills actively hurt without measurement. Evaluate or delete. Fri, 12 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/measure-your-agent-skills-or-delete-them https://paulund.co.uk/notebook/career/what-to-do-if-youre-not-detail-oriented Wes Kao four-question self-check for shipping quality work and why you only need to be good enough at details, not in the ninety-fifth percentile for de... Mon, 08 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/career/what-to-do-if-youre-not-detail-oriented https://paulund.co.uk/notebook/career/staying-resilient-in-a-difficult-engineering-job Seven strategies for staying intact when your engineering job drains you, adapted for developers dealing with on-call pressure, toxic environments, and ... Sat, 06 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/career/staying-resilient-in-a-difficult-engineering-job https://paulund.co.uk/notebook/ai/agentic-engineering-patterns Willison agentic engineering guide codifies patterns I use daily in my agent orchestration system. What maps, what does not, and three things I am adopt... Fri, 05 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/agentic-engineering-patterns https://paulund.co.uk/notebook/ai/ai-ate-the-translation-layer Ajey Gore's thesis on AI-native organizations — why the translation layer between business and engineering is collapsing and what the new org chart look... Wed, 03 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/ai-ate-the-translation-layer https://paulund.co.uk/notebook/ai/why-smaller-teams-will-win-with-ai AI narrows the advantage of large teams. Small teams move faster, have fewer handoffs and redesign without process layers. AI amplifies that speed advan... Tue, 02 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/why-smaller-teams-will-win-with-ai https://paulund.co.uk/notebook/ai/ai-code-review-pre-existing-bugs-as-a-side-quest Running multiple AI models in parallel for PR review finds bugs you never knew you had. The catch? It makes you slower, not faster. And that is the point. Mon, 01 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/ai-code-review-pre-existing-bugs-as-a-side-quest https://paulund.co.uk/notebook/ai/software-factory-build-factories-not-features How senior engineers build software factories: agentic pipelines that autonomously plan, build, validate, and ship features, compounding output over time. Mon, 01 Jun 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/software-factory-build-factories-not-features https://paulund.co.uk/notebook/ai/small-npm-packages-are-mostly-dead Why AI-generated code replaces the need for small npm packages, and where the line is between a dependency you still need and one an LLM can write on th... Sat, 30 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/small-npm-packages-are-mostly-dead https://paulund.co.uk/notebook/ai/the-four-levels-of-working-with-ai Matt Maher's four-level framework reveals most developers are stuck at level 2. Here is what level 3 looks like in practice and why it matters to move up. Sat, 30 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/the-four-levels-of-working-with-ai https://paulund.co.uk/notebook/ai/what-happens-to-developers-who-dont-adapt-to-ai Which developer skills depreciate and appreciate in 2026, why half-adopting AI is riskier than refusing it, and advice for engineers who feel left behind. Sat, 30 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/what-happens-to-developers-who-dont-adapt-to-ai https://paulund.co.uk/notebook/ai/software-ecology-and-the-10x-moment A framework for understanding developer ecosystems as socio-technical systems, and what breaks first when AI-driven velocity pushes every node to 10x ca... Fri, 29 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/software-ecology-and-the-10x-moment https://paulund.co.uk/notebook/ai/how-ai-agents-made-me-cli-first How AI agents pulled me into the terminal and changed how I build software, from nested loops and AFK workflows to risk-gated PRs and scheduled orchestr... Wed, 27 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/how-ai-agents-made-me-cli-first https://paulund.co.uk/notebook/ai/how-i-build-software-with-agent-loops The AI-assisted development workflow I use every day, from human-in-the-loop planning to AFK implementation, risk-gated PRs, and continuous learning loops. Wed, 27 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/ai/how-i-build-software-with-agent-loops https://paulund.co.uk/releases/paulundgoldcli-v110-caching-layer-keeps-you-under-the-api-free-tier goldcli v1.1.0 adds local caching for gold price API responses, cutting redundant requests and keeping you safely inside the 100-request-per-month free ... Tue, 26 May 2026 00:00:00 GMT https://paulund.co.uk/releases/paulundgoldcli-v110-caching-layer-keeps-you-under-the-api-free-tier https://paulund.co.uk/notebook/react/higher-order-components-and-why-hooks-replaced-them What higher-order components are, how they worked in class-based React, and why hooks are a better solution for the same cross-cutting concern problems. Mon, 25 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/higher-order-components-and-why-hooks-replaced-them https://paulund.co.uk/notebook/react/pure-components-and-why-purity-matters-in-react Learn why React treats your components like pure functions and how keeping renders side-effect free makes your app predictable, testable, and less buggy. Mon, 18 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/pure-components-and-why-purity-matters-in-react https://paulund.co.uk/notebook/react/react-fragments-and-when-you-actually-need-them Why React components must return a single root element, how Fragments solve this without polluting the DOM, and the three different ways to write them. Mon, 11 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/react-fragments-and-when-you-actually-need-them https://paulund.co.uk/notebook/react/refs-and-when-useref-beats-usestate I used to reach for useState for everything. Here is why useRef is often the better tool for values that do not need to trigger a component re-render. Thu, 07 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/refs-and-when-useref-beats-usestate https://paulund.co.uk/notebook/react/default-props-and-optional-props-in-react How to type optional props in TypeScript and set sensible default values without reaching for the deprecated defaultProps API in modern React applications. Fri, 01 May 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/default-props-and-optional-props-in-react https://paulund.co.uk/notebook/react/handling-form-submission-in-react How to handle form submission in React including async submit handlers, loading states, error display, and resetting the form after a successful submiss... Thu, 30 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/handling-form-submission-in-react https://paulund.co.uk/notebook/nextjs/client-side-validation-before-server-actions-in-nextjs Server Actions do not replace client validation. Catch invalid form input early and prevent unhandled errors from becoming five hundred server error res... Wed, 29 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/nextjs/client-side-validation-before-server-actions-in-nextjs https://paulund.co.uk/notebook/typescript/type-safe-adapter-registries-with-as-const-and-satisfies Learn how to replace hard-coded service calls with a type-safe adapter registry using TypeScript's as const, satisfies, and derived union types for safety. Wed, 29 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/typescript/type-safe-adapter-registries-with-as-const-and-satisfies https://paulund.co.uk/notebook/typescript/using-service-interfaces-and-null-objects-for-resilient-typescript-scripts How to combine service interfaces, factory functions, and the Null Object pattern to build TypeScript scripts that run without credentials or third-part... Wed, 29 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/typescript/using-service-interfaces-and-null-objects-for-resilient-typescript-scripts https://paulund.co.uk/notebook/typescript/validating-multi-provider-credentials-with-zod-discriminated-unions How to use Zod's discriminatedUnion to validate per-platform credentials, with a runtime-injected discriminant and TypeScript narrowing at call sites. Mon, 27 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/typescript/validating-multi-provider-credentials-with-zod-discriminated-unions https://paulund.co.uk/releases/paulundai-v310-writing-humanizer-skill Version 3.1.0 adds a dedicated Writing Humanizer skill to the paulundai collection, giving Claude Code a way to strip AI-generated patterns from text. Sat, 25 Apr 2026 00:00:00 GMT https://paulund.co.uk/releases/paulundai-v310-writing-humanizer-skill https://paulund.co.uk/notebook/nextjs/building-a-url-shortener-with-nextjs How to design the data model, slug generator, and IP hashing for a short-link service using Prisma, Web Crypto, and HMAC-SHA256 for anonymised click tra... Wed, 22 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/nextjs/building-a-url-shortener-with-nextjs https://paulund.co.uk/notebook/apis/magic-link-authentication-in-nextjs How to build passwordless sign-in with email magic links using Supabase Auth, a React Email template, and a clean service wrapper around the OTP flow. Wed, 22 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/apis/magic-link-authentication-in-nextjs https://paulund.co.uk/notebook/apis/api-key-management-in-nextjs How to generate, hash, store, and revoke API keys in a Next.js app using SHA-256 hashing, server actions, and cross-project guards for secure access con... Tue, 21 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/apis/api-key-management-in-nextjs https://paulund.co.uk/releases/pauundai-v300-skills-only-layout-and-new-planning-skills Version 3.0.0 removes the Claude plugin system for a flat skills directory and adds plan, ship, and several developer workflow skills to the collection. Tue, 21 Apr 2026 00:00:00 GMT https://paulund.co.uk/releases/pauundai-v300-skills-only-layout-and-new-planning-skills https://paulund.co.uk/notebook/nextjs/transactional-email-with-resend-and-react-email How to build a mailer module that renders React Email templates and sends through Resend, with test-time capture so you never send real emails from CI. Tue, 21 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/nextjs/transactional-email-with-resend-and-react-email https://paulund.co.uk/notebook/typescript/type-annotations-vs-type-inference TypeScript can infer most types on its own, but knowing when to add an explicit annotation anyway is what separates readable code from a sea of colons. Tue, 21 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/typescript/type-annotations-vs-type-inference https://paulund.co.uk/notebook/react/the-compound-component-pattern-in-react Learn how the compound component pattern lets you build flexible and composable React UI components that share state without prop drilling or complex APIs. Mon, 20 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/the-compound-component-pattern-in-react https://paulund.co.uk/notebook/react/the-render-prop-pattern-in-react How the render prop pattern lets you share behaviour between components, why hooks mostly replaced it, and the cases where render props still earn their... Mon, 20 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/the-render-prop-pattern-in-react https://paulund.co.uk/notebook/react/usereducer-for-complex-state Learn when and how to use useReducer in React to manage complex component state that has multiple related values or state transitions depending on each ... Sun, 19 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/usereducer-for-complex-state https://paulund.co.uk/newsletter/2026-w16 This week's links cover dynamic OG images, dyslexia and engineering, git commands for reading new codebases, and a new Claude Design tool from Anthropic. Sun, 19 Apr 2026 00:00:00 GMT https://paulund.co.uk/newsletter/2026-w16 https://paulund.co.uk/notebook/react/the-react-context-api-shared-state-without-a-library Learn how to use React's built-in Context API to share state across components without prop drilling or reaching for a third-party state management libr... Sat, 18 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/the-react-context-api-shared-state-without-a-library https://paulund.co.uk/notebook/nextjs/dynamic-og-images-in-nextjs-with-opengraph-imagetsx How to generate a unique Open Graph image per page at build time using Next.js App Router's opengraph-image.tsx convention, with static export support. Fri, 17 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/nextjs/dynamic-og-images-in-nextjs-with-opengraph-imagetsx https://paulund.co.uk/notebook/react/lifting-state-up-in-react When two components need to share state, you move it to their closest common ancestor. Here is what that looks like in practice and why the pattern works. Fri, 17 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/lifting-state-up-in-react https://paulund.co.uk/notebook/react/conditional-rendering-patterns-in-react A practical look at the different ways to conditionally render content in React, covering when to use each pattern and which approaches you should avoid. Thu, 16 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/conditional-rendering-patterns-in-react https://paulund.co.uk/notebook/react/lists-and-keys-in-react-why-they-actually-matter React keys do more than silence console warnings. Understanding how React uses keys during reconciliation reveals why the wrong key introduces subtle bugs. Wed, 15 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/lists-and-keys-in-react-why-they-actually-matter https://paulund.co.uk/notebook/career/why-dyslexia-made-me-a-better-software-engineer A personal essay on how dyslexia shaped debugging instincts, pattern recognition, and systems thinking across a software engineering career of over a de... Wed, 15 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/career/why-dyslexia-made-me-a-better-software-engineer https://paulund.co.uk/notebook/react/event-handling-in-react How React's event system works, why it differs from vanilla JS, and how to handle clicks, form inputs, and keyboard events correctly with TypeScript types. Tue, 14 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/event-handling-in-react https://paulund.co.uk/notebook/git/git-commands-for-reading-new-codebases Five git commands to run before opening a single file in a new project, revealing churn hotspots, bus factor, bug clusters, and commit velocity at a gla... Tue, 14 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/git/git-commands-for-reading-new-codebases https://paulund.co.uk/notebook/react/props-children-and-component-composition-in-react Learn how props and the children prop work in React components, and how to use component composition to build flexible user interfaces without tight cou... Mon, 13 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/react/props-children-and-component-composition-in-react https://paulund.co.uk/notebook/nextjs/extracting-a-queries-layer-from-nextjs-server-components How to introduce a typed queries layer in a Next.js and Prisma app, moving read functions out of page components to improve discoverability and reuse. Sun, 12 Apr 2026 00:00:00 GMT https://paulund.co.uk/notebook/nextjs/extracting-a-queries-layer-from-nextjs-server-components