[stipsan]

Description

With beta.reactActivityMode, hiding the Structure tool with a hierarchy open unmounted the whole tree in the background and the reveal rebuilt it. The Studio keeps recently used tools mounted behind <Activity>, which detaches refs while a tool is hidden (callback refs are called with null) and attaches them again on reveal. TreeEditor kept the element its DndProvider needs in state through ref={setContext} and only rendered the tree while that state was set, so the detach dropped the drag-and-drop provider, every row and every document in the "Add more items" list, and the reveal mounted them all again (the same pattern as sanity-io/sanity#15309's useElementState).

The box is always rendered, so the only null React ever passes is that detach; the ref callback now ignores it and the element lives as long as the editor.

What to review

• TreeEditor.tsx: the ref callback on the Box.
• package.json / pnpm-lock.yaml: @testing-library/react and jsdom as catalog: devDependencies for the test (the lockfile change is the two importer entries).

Affects @sanity/hierarchical-document-list.

Testing

• TreeEditor.test.tsx (jsdom, Studio hooks mocked): the box's child, the tree, is the same element while an <Activity> boundary hides the editor and after it shows it again. On main the box is empty while hidden.
• pnpm --filter @sanity/hierarchical-document-list exec vitest run, pnpm build, pnpm lint, pnpm knip, pnpm format are clean.
• Measured in dev/test-studio (Structure → Document list builders → Main table of contents, reactActivityMode on) with a headed Playwright harness that switches to Vision, waits 7s, switches back and records React commits and mounted components until the page is quiet for 30 frames. Before: 8731 components mounted on reveal, starting with DndProvider and 38 DocumentInNodes (3302 in one commit). After: 5005, none of them the tree itself. What remains is not this plugin's: @nosferatu500/react-sortable-tree remounts its rows on every re-render (its mergedProps memo is keyed on props), and the reveal re-renders it three times (the edit state and the preview store reconnecting, the useAllItems refetch), plus the @sanity/ui tooltip contents of the re-resolved document previews. The tool area paints in 1 frame before and after; the background unmount was invisible, only wasteful, and it reset the tree's internal state (open menus, the list's scroll position) on every switch.

Notes for release

Fixes the hierarchy tree being torn down and rebuilt on every switch away from and back to the Structure tool in a Studio with beta.reactActivityMode enabled.

  

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Project	Deployment	Actions	Updated
plugins-studio	Ready	Preview	Oct 27, 2026 12:06pm UTC

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[changeset-bot]

🦋 Changeset detected

Latest commit: baa8bcd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sanity/hierarchical-document-list	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

✅ E2E Tests

🟢 46 passed • view full report • view run

Studio: https://plugins-e2e-test-studio-3ue08fyx9.sanity.dev

Datasets: pr-2181-chromium-40500855181, pr-2181-firefox-40500855181

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	38.77%	7809 / 20138
🔵	Statements	38.72%	8398 / 21686
🔵	Functions	34.51%	2140 / 6201
🔵	Branches	30.84%	4522 / 14662

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
plugins/@sanity/hierarchical-document-list/src/components/TreeEditor.tsx	81.25%	78.94%	57.14%	82.75%	73, 141-193, 200

Generated in workflow #11400 for commit baa8bcd by the Vitest Coverage Report Action

[cursor]

Review: approve

Verified

• TreeEditor.test.tsx passes on this branch. With main's TreeEditor.tsx under the same test it fails with expected null to be <div …> (the box is empty while hidden), so the test fails without the fix.
• The premise holds: the Box is unconditional and nothing else writes context, so the only null the callback ever sees is the detach. The callback returns nothing, so React 19 still calls it with null rather than a cleanup, and the guard is what keeps the element.
• CI green, lockfile diff is the two importer entries, no public API change, changeset is a patch with a consumer-facing summary.

Notes (none blocking)

• The before/after component counts come from a harness that is not in the repo, so I could not reproduce them. The mechanism is pinned by the test, and attributing the remaining remounts to @nosferatu500/react-sortable-tree matches its mergedProps memo being keyed on props.
• fix(core): keep element state while an Activity boundary hides the tool sanity#15309 (useElementState) is still open and @internal, so an inline callback is the right call here; if that lands as public API this becomes a one-line swap.

Verdict

Approve. Small, correct, and the test guards the regression.