Default stack choices

Settled preferences — applied without asking, departed from only with a stated reason.

These are settled. Apply them without asking; depart only with a stated reason.

Frontend

Situation	Choice
Styling, always	Tailwind + shadcn/ui. shadcn is copied source we own and edit, not a component library dependency. No CSS-in-JS, no CSS Modules, no SCSS.
Website — content-led: marketing, docs, editorial, brochure, blog	Astro. Ship HTML; hydrate an island only where a component genuinely needs state.
Application, no SSR	Vite + TanStack Router
Application, SSR	TanStack Start
Never	Next.js — with one exception

The one place Next.js is allowed

A documentation site built on a generator that happens to run on Next.js — Fumadocs is the one in use. The exception is narrow and it is about who owns the framework choice: you are adopting a docs generator, not choosing an application framework, and the generator's own runtime is not yours to pick.

Two conditions, both required:

The framework is an implementation detail of a tool you did not write. Choosing Next.js and then building on it is the thing the rule forbids.
Nothing product-shaped lives there. A docs site renders content. The moment auth, forms or long-lived client state appear, it is an application and the standing rule applies again.

Inheriting a Next.js codebase is not this exception either — that is a migration question, answered by reversal cost like any other.

Say the exception out loud when you use it. A rule with an unwritten exception teaches the next reader that the rules are negotiable, which costs more than the rule was worth.

The line between website and application

If the product is pages — content is the point, most of it static — it is a website → Astro. If it is sessions — auth, dashboards, forms, long-lived client state — it is an application → Vite or Start.

A website that grows a real app section keeps Astro and mounts the app, rather than converting the site.

Backend

Situation	Choice
JVM service	Java + Spring Boot with Modulith
Go service	Go + the service shape

Both sit inside the standing architecture default: hexagonal, feature-first, dependency rule enforced by a test.

Platforms

Platform	Page
Railway	Railway

Reading a stack page

Every page opens with a Verified line naming the date and the versions it was checked against. That line, and the rules for what to do when a page and the code disagree, are on how to read this.