## System details

RTX 5090, Omarchy 4.0.0-1 (also verified against current `quattro` branch source)

## What's wrong?

Stock Omarchy applies no theming at all to GTK4/libadwaita applications. Nautilus, Geary, GNOME Calendar and friends render in default Adwaita colors regardless of the active Omarchy theme.

Steps: `omarchy theme set <any-theme>`, then open Nautilus or Geary — colors never change.

Root cause: libadwaita ignores the `gtk-theme` setting by design. The only user-level lever it honors is `@define-color` overrides in `~/.config/gtk-4.0/gtk.css`, and Omarchy never writes that file. I checked the `quattro` source: the only themed GTK CSS shipped anywhere is for the Hyprland share-picker.

(For the record: #2356, #2789 and #1425 asked for this and were all closed as "COMPLETED" within the same 25-minute window on 2026-02-01 — that looks like a bulk tracker cleanup; nothing was actually implemented.)

## How we solved it locally (offer to contribute)

I've been running a `theme-set` hook since 2026-08-17 that fixes this for GTK4, ~60 lines of bash + sed, no new dependencies:

1. Reads the active theme's `colors.toml` and generates `~/.config/gtk-4.0/gtk.css` with the full set of libadwaita `@define-color` variables (window/view/headerbar/sidebar/card/popover backgrounds and foregrounds, accent, destructive/success/warning/error, selection).
2. Picks the text color drawn *on* the accent with a luma-distance test (whichever of background/foreground is further from the accent in perceived brightness). Verified against all 22 stock themes: worst-case separation is 86/255 (miasma), everything else ≥ 100. A naive "is the accent dark" test fails on the five light themes.
3. Restarts `--gapplication-service` daemons (nautilus, geary, gnome-calendar) after writing the CSS, because libadwaita reads the user stylesheet only at process startup — closing the window is not enough, the daemon survives and keeps painting a days-old theme. SIGTERM is safe: all of them are D-Bus activatable and respawn on demand.

Measured caveats worth knowing before implementing:

- **GTK3 cannot be recolored this way.** `@define-color` in the user stylesheet is provider-scoped and does not reach the theme's rules — Adwaita rendered identically with and without overrides (verified with an offscreen render, not by eye). GTK3 apps still need an approximate binary theme via `gtk-theme`.
- Importing a large third-party CSS first and overriding on top renders identically to pure overrides, so pure overrides are preferable (avoids parsing ~238 KB per app launch).

## Question

Would a PR adding GTK4 palette generation to the theme-set pipeline be desirable? If yes, where should it live — a default hook in `config/omarchy/hooks/theme-set.d/`, or wired into `omarchy-theme-set` directly? Happy to prepare it with before/after captures across several stock themes.