MacOS: GHOSTTY_QUICK_TERMINAL not inherited by split panes in Quick Terminal

[52dyd]

What do you want to change?

I want to fix a macOS-specific bug: GHOSTTY_QUICK_TERMINAL=1 is not present in split panes within a Quick Terminal window.

Symptom: Opening a Quick Terminal and running echo $GHOSTTY_QUICK_TERMINAL outputs 1. But after splitting via Cmd+D in that same Quick Terminal, the same command in the new pane outputs nothing. Two community reports confirm this (#11637, #12652). Both reports are on macOS. There are no equivalent complaints on GTK. I verified that GTK behavior is indeed correct — making this a macOS-specific defect.

Root cause: PR #9673 used different mechanisms on the two platforms. On GTK, surface.zig's defaultTermioEnv() dynamically queries window.isQuickTerminal() every time it builds a subprocess environment — so every surface in a Quick Terminal window, including splits, naturally inherits the env var. On macOS, QuickTerminalController.animateIn() writes the env var into the first surface's SurfaceConfiguration.environmentVariables — a one-shot, per-surface setting. When a split is created, ghostty_surface_inherited_config() is called, which does not propagate env_vars. Fundamentally, a per-window property was misplaced at the per-surface level.

Fix: Override newSplit() in QuickTerminalController to inject GHOSTTY_QUICK_TERMINAL=1 into the split surface's configuration before calling super.newSplit(). This matches the GTK semantics exactly: every surface created from a Quick Terminal controller carries the marker. Six lines of code, no public API changes.

Location: macos/Sources/Features/QuickTerminal/QuickTerminalController.swift

override func newSplit(
    at oldView: Ghostty.SurfaceView,
    direction: SplitTree<Ghostty.SurfaceView>.NewDirection,
    baseConfig config: Ghostty.SurfaceConfiguration? = nil
) -> Ghostty.SurfaceView? {
    var config = config ?? Ghostty.SurfaceConfiguration()
    config.environmentVariables["GHOSTTY_QUICK_TERMINAL"] = "1"
    return super.newSplit(at: oldView, direction: direction, baseConfig: config)
}

Why do you want to make this change?

Quick Terminal detection serves real user needs. Users need to know whether their shell is running inside a Quick Terminal, for use cases including:

• Skipping automatic tmux attach (the original motivation, #3985)
• Auto-launching AI CLI tools
• Adjusting prompts or disabling certain plugins
• Setting different shell behaviors (e.g., ignore_eof)

I encountered the split issue in my own usage. After investigation, I found that the original implementation uses asymmetric mechanisms on macOS and GTK — GTK got it right as a per-window property, while macOS placed the same property at the wrong level (per-surface, one-shot configuration).

I manually verified seven scenarios, all passing:

Scenario	Result
Quick Terminal initial surface	✓
Cmd+D split (multiple directions)	✓
Normal windows unaffected	✓
Normal window splits unaffected	✓
Split dragged out of Quick Terminal	✓ (existing behavior preserved)
Split dragged into Quick Terminal	✓ (no change, as expected)
Undo/Redo	✓

The fix is on 52dyd/ghostty:fix/macos-quick-terminal-split-env.

I acknowledge that:

• I have read the Contributing Guide and understand the contribution process.
• I have read and agree to follow the AI Usage Policy.
• I wrote this vouch request myself, in my own voice, without AI generating it.

[52dyd]

This change affects macOS only. It does not affect any other platform. Reasons:

1. The modified file QuickTerminalController.swift lives under macos/ and is compiled exclusively by Xcode for the macOS app target. GTK builds go through src/apprt/gtk/ and never touch Swift code. The same applies to embedded and WASM builds.
2. The modified method is an override in QuickTerminalController, a class that exists only on macOS — it inherits from BaseTerminalController (macOS-exclusive), which depends on NSWindowController (AppKit). GTK and embedded backends have no corresponding concept.
3. The modified logic only changes how config is passed during split creation within the macOS Quick Terminal. It does not modify ghostty_surface_inherited_config() or any cross-platform core code. The Zig core layer is entirely untouched.

[52dyd]

@bo2themax @pluiedev @mitchellh Would appreciate your time reviewing this Vouch Request. You were the reviewers of the original PR #9673 that introduced the GHOSTTY_QUICK_TERMINAL environment variable. At the time, the GTK implementation correctly inherited the variable across all split surfaces, but the macOS implementation did not cover the split path — this gap has since been reported multiple times by the community (#11637 #12652). This fix completes the behavior on macOS. Six lines of code, affects QuickTerminalController only. If the direction and implementation look good, a !vouch would be much appreciated. Thank you.

[bo2themax]

!vouch

LGTM