Learnings

2026

1. • useOptimistic: React's official hook for optimistic updates inside an Action. Its setter must be called inside an Action. Calling it outside one produces a warning and shows the optimistic state only briefly.
   • If a project already uses TanStack Query, keep the existing onMutate approach. Reconsider useOptimistic later if the architecture moves toward Server Actions and form Actions.

   react.devuseOptimistic – ReactThe library for web and native user interfaces (opens in a new window)

   Aug 23

2. 

   • When a flex layout contains a long string, overflow-wrap: anywhere avoids having to set min-width: 0 every time, unlike overflow-wrap: break-word.
   • break-word: “Break it if it actually overflows.” The long word still contributes a large intrinsic size, so the text area cannot shrink enough.
   • anywhere: “Break it anywhere if necessary.” The intrinsic-size calculation also accounts for possible breaks.

   tailwindcss.comTailwind CSS v4.1: Text shadows, masks, and tons moreI wasn't sure it would ever happen but we did it — we released a version of Tailwind CSS that includes text shadow utilities. Tailwind CSS v4.1 is here and it's packed with improvements that will help you (or your LLM, you coward) build even better interactive experiences. (opens in a new window)

   Aug 22
3. • On a MacBook, holding Option while dragging a window makes split-screen tiling easy. Dragging a window into a corner also creates a four-way split.

   • AST: Abstract Syntax Tree
     • How was the code written? Syntax-oriented. Used by linters, formatters, and similar tools.
   • HIR: High-level Intermediate Representation
     • What does the code mean at the language level? Removes syntactic sugar and focuses on semantics.
   • MIR: Mid-level Intermediate Representation
     • What control flow does the program have? Execution-oriented.
   • AST, HIR, and MIR are not universal fixed stages shared by every compiler. Their exact boundaries and responsibilities differ between compilers.

   Aug 21
4. • no-extra-boolean-cast
     • Do not use !!, Boolean(), or another unnecessary cast in a context that already evaluates a value as boolean.
     • Disallow unnecessary boolean casts.
   • strict-boolean-expressions
     • Do not depend on implicit truthy/falsy conversion in a boolean context; test explicitly. (e.g. Don't: if (name), Do: if (name !== ""))
     • Forbids usage of non-boolean types in expressions where a boolean is expected. Boolean and never types are always allowed. Additional types considered safe in a boolean context can be configured through options.

   Aug 20
5. • TypeScript does not aim to “Apply a sound or ‘provably correct’ type system.” Instead, its goal is to “strike a balance between correctness and productivity.”

   GitHubTypeScript Design GoalsTypeScript is a superset of JavaScript that compiles to clean JavaScript output. - microsoft/TypeScript (opens in a new window)

   Aug 19
6. • Claude retains sessions for 30 days. You can change the retention period with cleanupPeriodDays.
   • Codex does not have a configured retention period.

   Aug 18
7. • BAML stands for Basically A Made-up Language.
   • In v0 it was a lightweight programming language that gave LLMs a type-safe interface for structured prompting. In v1, its scope expanded and it is introduced as a programming language for agents.

   BoundaryBAMLThe programming language for agents. (opens in a new window)

   BoundaryBAMLThe programming language for agents. (opens in a new window)

   Aug 17