macOS 26 liquid glass (background-blur = macos-glass-regular) is not applied on a new window / at startup, only after reload_config

[dpnolte]

Issue Description

Hi,

First of all thank you for this awesome terminal.

I ran into an issue on MacOS 26 when applying the liquid glass background effect. It didn't apply at startup or when opening new windows. That is, it didn't render with the opaque background with the liquid glass effect but it rendered with (probably) the default background color. Triggering reload config makes the glass effect appear correctly. It seems to be happening with a combination of config settings.

What I tried (window styles):

• window-decoration = false —> ❌ no (opaque until reload)
• macos-titlebar-style = hidden —> ❌ no (opaque until reload)
• macos-titlebar-style = transparent —> ✅ yes
• macos-titlebar-style = tabs —> ✅ yes

I let the AI agent look for a workaround. This is what the AI agent found as root cause:

The glass NSGlassEffectView itself appears to attach fine at creation. The reported cause is that the window is never made non-opaque at creation:

• TerminalWindow.syncAppearance(_:) (which sets isOpaque = false so the glass shows through) begins with guard isVisible else { return } (macos/Sources/Features/Terminal/Window Styles/TerminalWindow.swift, ~L467–472).
• At creation, syncAppearance is called from TerminalController.windowDidLoad (TerminalController.swift ~L1128), but the window is presented one runloop tick later via scheduleInitialPresentation (TerminalController.swift ~L153–167). So isVisible == false at that call and the guard returns early — the window stays opaque and the (attached) glass is hidden behind it.
• Nothing re-runs syncAppearance once the window actually becomes visible for the base window class. reload_config heals it only incidentally: the config change re-publishes the focused surface's @published properties, and the subscription focusedSurface.$backgroundColor.dropFirst().sink { … syncAppearance } (TerminalController.swift ~L1416–1418) then runs syncAppearance while the window is visible.
• The reason transparent / tabs don't show the bug: TransparentTitlebarTerminalWindow (and its Tahoe subclass) override becomeMain() to re-call syncAppearance(...) (TransparentTitlebarTerminalWindow.swift ~L30–34), which fires after the window is visible. The base TerminalWindow and HiddenTitlebarTerminalWindow have no such resync-on-visible hook.

The AI agent suggested a workaround to change background to trigger the syncAppearance (however it is with a flicker since the default background will be rendered first):

Workaround (config + shell)

Because the $backgroundColor subscription above has no removeDuplicates, re-setting the background color at runtime — after the window is visible — forces syncAppearance to run. Emitting an OSC 11 set-background from the outer shell (before any tmux attach) does this with no visible color change:

# in the outer shell rc, guarded to Ghostty and outside tmux
if [[ $TERM_PROGRAM == ghostty && -z $TMUX ]]; then
  bg=$(ghostty +show-config 2>/dev/null | awk -F' = ' '/^background /{print $2; exit}')
  [[ -n $bg ]] && printf '\033]11;%s\a' "$bg"
fi

Expected Behavior

The liquid-glass background should be applied when the window is first shown (i.e., on a new window and after an app restart without needing a reload_config). Or is there some technical constraint that makes that not possible?

Actual Behavior

The window is created with an opaque background; the glass / blur is not visible. It
only appears after a subsequent appearance re-sync — e.g. running reload_config, or a
system light/dark switch.

(With the OSC 11 shell workaround described above, the glass does apply, but the window
is still created opaque, so there is a brief one-frame flash of the default background
before the workaround takes effect.)

Reproduction Steps

Note: the first window opened during a cold app launch often renders correctly, probably because it wins some kind of startup race. The issue is reliably reproducible for every window opened afterwards, as well as for windows restored after restarting Ghostty.

1. Start Ghostty and make sure at least one window is already open and showing the glass effect correctly.
2. Open another window using Cmd+N, New Window, or the new_window action.
3. The new window will have an opaque background: no glass effect and no blur of the content behind it. The original window still renders correctly.
4. Run reload_config, or toggle the macOS light/dark appearance. The glass effect then appears correctly on the affected window.

Ghostty Logs

No response

Ghostty Version

Ghostty 1.3.2-main-+55a3e33ab

Version
  - version: 1.3.2-main-+55a3e33ab
  - channel: tip
Build Config
  - Zig version   : 0.15.2
  - build mode    : .ReleaseFast
  - app runtime   : .none
  - font engine   : .coretext
  - renderer      : renderer.generic.Renderer(renderer.Metal)
  - libxev        : kqueue

OS Version Information

macOS 26.5.2 (build 25F84)

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

background-opacity = 0.25
background-blur = macos-glass-regular
macos-titlebar-style = hidden
# also reproduces with `window-decoration = false` instead of the line above

Additional Relevant Configuration

No response

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[bo2themax]

Thanks #13324