Independent reproduction on 7.6.6 stable, with the exact zh-Hans numbers:

• PowerShell 7.6.6 (MSI x64), Windows 10 22H2, UI culture zh-CN
• Interactive ConPTY terminal, $Host.UI.SupportsVirtualTerminal = True
• Update cache contained update1_v7.6.7_2026-10-13 (7.08 days old at startup), so the notification path ran
• zh-Hans StableUpdateNotificationMessage: line 1 = 38 chars, line 3 = 58 chars
• 38 - 58 + 3 = -17 -> PadRight(-17) -> FailFast, matching the reported stack exactly
• The same terminal starts normally with POWERSHELL_UPDATECHECK=Off, confirming the notification is the only trigger

The line-2 expression is positive for zh-Hans, but the other locale reports show it can also go negative, so clamping both expressions in this PR is the right minimal fix. The template-length assumption is the real bug; console width is not involved.

wait4x (@wait4xx) Thanks for the fix! I prepared some additional test coverage for the update notification padding issue in my fork:

https://github.com/boylin0/PowerShell/tree/fix/update-notification-padding

BTW, besides adding the tests, the commit also moves the message formatting in ShowUpdateNotification into an internal FormatUpdateNotification method so it can be unit tested. The formatting logic itself is unchanged.

Feel free to take a look! If you find these tests useful, you can git cherry-pick 29fd033ce. Alternatively, If you'd rather keep this PR minimal, I can open a follow-up PR after this one is merged.

Thanks!

GitHub

GitHub - boylin0/PowerShell at fix/update-notification-padding

PowerShell for every system! Contribute to boylin0/PowerShell development by creating an account on GitHub.

Thanks BOYI (@boylin0)! Since your commit is based directly on the PR head, I fast-forwarded the branch to 29fd033ce and took it verbatim — authorship preserved as-is.

I also double-checked that the test assembly (powershell-tests) already gets internals visibility from Microsoft.PowerShell.ConsoleHost, and verified the neutral-template equal-width assertions against the shipped templates. PR description updated to cover the extraction and the new tests.

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