Codex

Reference for the theme/settings system. The rules new code must follow live in AGENTS.md; this document explains the machinery behind them. Single CSS source: src/app/globals.css.

raw values            semantic variables          utilities
:root / .dark    →    --primary, --card-ring, …   →   @theme inline → bg-primary, …
[data-*] blocks       (overridden by settings)        components consume ONLY these

Components never see raw colors. Settings never touch components. Everything meets in the middle at the semantic variables, which is why every setting is a few lines of CSS instead of component logic.

State lives in a zustand store (src/lib/stores/settings-store.ts), persisted to localStorage under ytemplate-settings (versioned, with migrate). Two consumers reflect it onto <html>:

These two must stay mirrored. Any new setting applied in the effect but not the script will flash the default on every load; any migration added to the store but not the script will flash the pre-migration value.

SettingsScript is rendered as the first child of <body> inside a hidden <div> whose <script> lives in dangerouslySetInnerHTML — not as a React <script> element. The parser still executes it before anything below it paints, but React never client-creates a script element, so the react-dom dev warning "Encountered a script tag while rendering React component" can't fire when hydration bails and the root client-renders (version skew while editing, Fast Refresh error recovery, a real mismatch anywhere). For the same reason the script also owns the pre-paint light/dark application (theme class + color-scheme, reading next-themes' theme localStorage key), and next-themes' own inline script is rendered inert via scriptProps={{ type: "text/x-preapplied" }} in providers.tsx — keep the script's theme block in sync with the ThemeProvider props there. Runtime theme switching stays with next-themes.

What lands on <html>:

1. src/lib/settings/config.ts — type, options constant, DEFAULT_SETTINGS entry
2. settings-store.ts — setter (+ version bump & migrate only if changing the meaning of an existing persisted value; new keys merge in via defaults)
3. settings-effect.tsx — reflect onto <html>
4. settings-script.tsx — mirror the reflection (and any migration) in the inline script
5. settings-drawer.tsx — UI + add to the isDirty comparison
6. globals.css — the [data-*] block or var the setting drives

[data-preset="…"] blocks swap --primary / --sidebar-primary and the chart ladder. The ladder walks fixed lightness steps at the preset's hue (chart-1 ≈ L 0.797 at half chroma → chart-5 ≈ L 0.407), so multi-series charts stay harmonized across presets.

The custom preset derives the same shape at runtime: src/lib/settings/color.ts converts the picked hex to OKLCH and builds the 9 brand vars. They are precomputed at pick time and persisted verbatim so the FOUC script can replay them without color math. Because they're applied as inline styles (which beat any stylesheet block), SettingsEffect must remove them when a stock preset is re-selected — see CUSTOM_VAR_KEYS.

Every grey-bearing token is parameterized:

--muted-foreground: oklch(0.552 calc(0.016 * var(--neutral-tint)) var(--neutral-hue));

--neutral-hue + --neutral-tint (a chroma multiplier; zinc = 1) are the only things a [data-neutral="…"] block sets, and the whole UI re-temperatures — light and dark, including borders and the contrast tint.

Rule: any new token that encodes a grey must use the parameterized form, or it won't follow the base-color setting.

Light-mode hairlines are translucent neutral grey (≈ #919EAB @ 20%), not a solid step of the palette — they blend over any surface. Contrast mode bumps the alpha, dark mode uses white-alpha.

shadcn has no elevation tokens; this repo defines two semantic pairs, and surfaces fall into exactly two classes:

Both shadow recipes are tinted with the neutral family (--neutral-hue/--neutral-tint), so elevation follows the base color.

Notes:

• Dropdown / Popover / Select / Dialog already ship a clean shadow-2xl + ring-foreground/5 hybrid upstream — left as is.
• Components opt out with shadow-none / ring-0 (e.g. the sidebar promo card); cn()/tailwind-merge resolves the conflict correctly.
• Flat states must be 0 0 #0000, never none: ring-* and shadow-* utilities compose into one box-shadow list, and a none entry invalidates the whole declaration.

The vertical sidebar and the horizontal top bar consume the --sidebar-* token family (bg-sidebar text-sidebar-foreground border-sidebar-border), so the nav-color setting needs no per-layout logic:

• integrate → --sidebar: var(--background) (blends into the page)
• apparent → dark navy panel in light mode; dark mode's lifted card surface already reads as "apparent"

Generic components embedded in a dark nav surface would flash light-grey --accent hovers; the surface carries data-surface="nav" and a scoped rule re-points --accent to the sidebar palette inside it. Portaled content (dropdowns) is outside the scope and keeps popover styling. Reuse this pattern for any future component hosted on a dark surface.

Anything inside the nav should inherit color (currentColor) rather than hardcode text-foreground — that's how the logo and header icons adapt.

• Turbopack stale CSS (Next 16.2.x): globals.css edits are sometimes served stale even across reloads and lint-clean builds. Verify via computed styles / CSSOM, and fix with: stop dev server → rm -rf .next/dev → restart.
• Don't test dark mode by toggling the dark class manually — next-themes fights the mutation; use the Mode control (or localStorage.theme + reload).
• Recharts entry animations freeze at frame 0 in hidden/background tabs (rAF throttling) — blank charts in a preview tab are not a regression.