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macos: disable NSAutoFillHeuristicController on macOS 26

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Fixes #8616

macOS 26 (as of RC1) has some pathological performance bug where the
terminal becomes unusably slow after some period of time. We aren't 100%
sure what triggers the slowdown, but it is app-wide (new tabs or windows
don't resolve it) and Instruments traces point directly to
NSAutoFillHeuristicController. Specifically, to the `debounceTextUpdate`
selector.

This is all not documented as far as I can find and also not open
source, so I have no idea what's going on.

The best I can tell is that the NSAutoFillHeuristicController has
something to do with enabling heuristic-based autofill such as SMS auth
codes in text input fields. I don't know what is causing it to go
haywire.

SMS autofill is not desirable in a terminal app, nor is any of the other
automatic autofill in macOS I know of (contact info, passwords, etc.).
So, we can just disable it.

This default isn't documented but I found it via a strings dump of the
AppKit binary blob and comparing it to the disassembly to see how it is
used. In my limited testing, this seems to work around the problem.
This commit is contained in:
Mitchell Hashimoto
2025-09-14 13:04:55 -07:00
parent ab5cd0b709
commit 431364cf16
1 changed files with 10 additions and 0 deletions
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10
macos/Sources/App/macOS/AppDelegate.swift
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@@ -147,6 +147,16 @@ class AppDelegate: NSObject,
// Disable the automatic full screen menu item because we handle
// it manually.
"NSFullScreenMenuItemEverywhere": false,
// On macOS 26 RC1, the autofill heuristic controller causes unusable levels
// of slowdowns and CPU usage in the terminal window under certain [unknown]
// conditions. We don't know exactly why/how. This disables the full heuristic
// controller.
//
// Practically, this means things like SMS autofill don't work, but that is
// a desirable behavior to NOT have happen for a terminal, so this is a win.
// Manual autofill via the `Edit => AutoFill` menu item still work as expected.
"NSAutoFillHeuristicControllerEnabled": false,
])
}