🗂️ refactor: Read the Search, File and Message Editor Siblings Through the Parts Host

[berry-13]

Summary

Four Messages/Content siblings still read the app directly: SearchContent (the user markdown preference from Recoil, and the message context it re-provides to error parts), Files and FilePreviewDialog (the file map context, and the user atom), and EditMessage (chat direction from Recoil, the messages view providers).

This routes them through the parts host members the two earlier links added or already had: useUserTextPreferences, useFileMap, useUser, useChatDirection and useMessagesEditing. For SearchContent, the package gains MessagePartIndex, which provides the surrounding message to one part at its position, so the sibling no longer reads and respreads MessageContext itself.

This link is kept separate because each file overlaps an open contributor PR: SearchContent with #16496 and #16518, Files with #17017, FilePreviewDialog with #16282, and EditMessage with #16204 and #17017. Every change here is a few lines at the top of the component, so those branches rebase trivially; it can merge now or wait for them. Stacked on #17172.

Type of change

• Refactor

Testing

Tested environments/configuration:

Local jest and typecheck; no runtime configuration matters for this change.

Automated tests:

• cd client && npx jest src/components/Chat/Messages src/components/Share src/components/Files src/Providers src/components/Chat/Subagents: 136 suites, 2,513 tests pass, including the existing SearchContent, EditMessage, Files and file preview specs.
• cd packages/chat && npx jest: 37 suites, 390 tests pass; new react/__tests__/message.spec.tsx covers MessagePartIndex inside and outside a message.
• npx tsc --noEmit for client and packages/chat, and the package build, are clean. ESLint, Prettier and import sorting are clean on every changed file.
• The audit's parts-context.sh over Messages/Content reports 1 of 115 files (5 on ✏️ refactor: Read the Inline Editors' Messages View Through the Parts Host #17172); the remaining one is ActivityPhaseGroup, which waits for ⚛️ refactor: Move Run Display, Live Attachment and PTC Trace Atoms to Jotai #17138.

Screenshots / recordings

No user-facing change.

Risk / compatibility

Low. Each read returns what the component read before through the app's host, and MessagePartIndex provides the same value the inline spread did.

Checklist

• I reviewed my own changes
• Relevant tests have been added or updated
• Existing relevant tests pass
• The change does not introduce new warnings or errors

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T20:50:15.094600Z	e665669	New commits
🔒 Security Review	✅ Completed 2026-10-15T18:04:52.866510Z	bcc0f8d	Draft marked ready

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