Block Insert (Alt-LeftMouse) does not work properly

_This issue has been moved from [a ticket on Developer Community](https://developercommunity.visualstudio.com/t/Block-Insert-Alt-LeftMouse-does-not-wo/10882328)._

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\[severity:It’s more difficult to complete my work\]
Whenever you try to insert a block before a number of code line, i.e, press Alt and then use the mouse to mark multiple lines and then insert a clipboard value, the first line cursor gets out of syn and subsequent edits replace part of the pasted value. See video.
[BlockInsert2.mp4](https://aka.ms/dc/file?name=B05a4a4d43e4442f5b8ca5f419507715a638790088767460563_BlockInsert2.mp4&tid=05a4a4d43e4442f5b8ca5f419507715a638790088767460563)

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### Original Comments

#### Feedback Bot on 3/31/2025, 04:18 AM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

The payload names no source file, test, or entry point. Start by reproducing the Alt+LeftMouse block-insert sequence from the issue and compare the first-line cursor with later edits; done means pasted block insertion leaves the cursor synchronized and subsequent edits affect the intended text.

Written by the indexing model from the issue text.