[autocomplete] update default listbox paper elevation

[namansancheti]

• [X ] I have followed (at least) the PR section of the contributing guide.

Fixes #48933

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Bundle size

Bundle	Parsed size	Gzip size
@mui/material	🔺+30B(+0.01%)	🔺+7B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/private-theming	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

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[namansancheti]

The label breaking change needs to be added, but I don't seem to have the permission to add:

namans@Namans-MacBook-Pro material-ui % gh pr edit 49110 --add-label "breaking change"
GraphQL: namansancheti does not have the correct permissions to execute AddLabelsToLabelable (addLabelsToLabelable)

[namansancheti]

Also, per my understanding the major version will get bumped automatically, once the breaking change label is added ?

(Ref: https://mui.com/material-ui/getting-started/versions/#versioning-strategy)

[silviuaavram]

Thanks @namansancheti !

[silviuaavram]

@claude review

[Copilot]

🔵 Needs a closer look

The breaking visual change and unresolved migration-documentation concern warrant human review.

Pull request overview

Updates Autocomplete popup elevation to align with Select/Menu.

Changes:

• Changes the default Paper elevation from 1 to 8.
• Tests default and custom elevation behavior.
• Requires migration documentation for preserving the previous appearance.

File summaries

File	Description
packages/mui-material/src/Autocomplete/Autocomplete.test.js	Tests default and overridden elevations.
packages/mui-material/src/Autocomplete/Autocomplete.js	Sets elevation to 8; migration guidance remains requested.

Review details

Suppressed comments (1)

packages/mui-material/src/Autocomplete/Autocomplete.js:622

• This changes the rendered shadow for every Autocomplete and is explicitly tracked as a breaking change, but the active v9 migration guide has no corresponding entry. Please document the elevation change from 1 to 8 under Autocomplete and show slotProps={{ paper: { elevation: 1 } }} for consumers who need to preserve the previous appearance.

      elevation: 8,

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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[namansancheti]

@silviuaavram
Thanks for reviewing - noticed the comment above by Copilot AI regarding migration guide update and the visual change.

Please let me know, in case any additional changes are required.