That’s expected behavior with Brave PWAs on i3 — the “title bar” you’re seeing is not a GTK header, it’s i3’s window title decoration.

To remove it completely, you must tell i3 (not Brave) to disable borders after the window is fully created.

Because this is a Flatpak PWA, timing matters.

✅ The fix that actually works (Flatpak-safe)

Use border none applied after the window appears

In your ~/.config/i3/config:

# Brave PWA – remove title bar completely
assign [instance="crx_abcdef123456"] workspace 4

for_window [instance="crx_abcdef123456"] move to workspace 4
for_window [instance="crx_abcdef123456"] exec --no-startup-id i3-msg border none

Reload i3:

Mod+Shift+r

Then launch the PWA again.

👉 This removes:

• Title bar
• Window frame
• All decorations

❌ Why border pixel 0 often DOES NOT work

On Flatpak Brave PWAs:

• border pixel 0 is applied too early
• Brave re-parents the window