[pedrobonamin]

Summary

Every visible mux.video input rendered a full <MuxPlayer> as soon as the field mounted. While the player's media-chrome controls upgrade, they force several full-document layouts, and the issue reports this freezes Safari for seconds on forms with multiple video fields.

With this change, the form input shows the poster as a play button. <MuxPlayer> mounts (with autoPlay) only after a click.

• VideoPlayer gets an opt-in deferPlayer prop. Only the input's Player sets it. The asset browser (VideoInBrowser, which already defers with its own play button) and the video details dialog behave as before.
• These stay available before the player mounts: the actions menu overlay (upload, browse, thumbnail, captions…), the static-rendition notice, and the thumbnail/captions/mezzanine dialogs. The thumbnail dialog starts at time 0 when no player is mounted, which is the dialog's existing default.
• PlayButton moves out of VideoInBrowser into its own module so both places share it. In the input, the play icon is always visible.

Investigation

• Mechanism (confirmed in the installed media-chrome 4.19.2): media-chrome-button's attributeChangedCallback calls MediaTooltip.updateXOffset on every observed attribute change. That function runs checkVisibility(), getComputedStyle().getPropertyValue() and getBoundingClientRect() on both the tooltip and its container, which matches the reporter's Safari sample. The root cause is in media-chrome; this PR only stops the plugin from triggering it for videos the editor never plays.
• Not reproduced: the Safari freeze itself. No Safari/WebKit is available in this Linux environment, so the timing could not be measured.

Testing

• New src/components/VideoPlayer.test.tsx (jsdom, with @mux/mux-player-react/lazy mocked):
  • By default, the player mounts eagerly and has no play button.
  • With deferPlayer, no player is in the DOM, the poster <img> uses the Mux thumbnail URL, and overlay children render once. After a click, the player mounts with autoPlay.
  • When the deferral is temporarily forced off, the test fails as expected.
• pnpm lint and the sanity-plugin-mux-input build and tests pass. pnpm knip fails only on the root lefthook devDependency, which also fails on a clean tree and is unrelated to this change.
• Manual test in the test studio (Chrome), on a muxTrailer document:
  • Before clicking: the poster and play icon show, and document.querySelectorAll('mux-player').length is 0.
  • Opening the actions menu does not mount the player.
  • Clicking the poster mounts the player (count 1), which autoplays.

Poster before click
Player after click
mux-deferred-player.mp4

Lockfile

The test adds @testing-library/react, @types/react-dom and jsdom as dev dependencies, on the same catalog versions other plugins already lock. Only the three importer entries were added to pnpm-lock.yaml, and pnpm install --frozen-lockfile passes. A plain pnpm install would also re-resolve the next-tagged Studio overrides (sanity 6.17.0-next.112 → 6.18.0-next.21), so that bump is deliberately not included.

Fixes #2068

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9289eb6

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

This PR includes changesets to release 1 package

Name	Type
sanity-plugin-mux-input	Patch

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Project	Deployment	Actions	Updated
plugins-studio	Ready	Preview	Oct 26, 2026 6:47am UTC

1 Skipped Deployment

Project	Deployment	Actions	Updated
plugins-e2e-test-studio	Ignored		Oct 26, 2026 6:47am UTC

[github-actions]

✅ E2E Tests

🟢 46 passed • view full report • view run

Studio: https://plugins-e2e-test-studio-ae7qwgn0i.sanity.dev

Datasets: pr-2074-chromium-40281790840, pr-2074-firefox-40281790840

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	38.44%	7742 / 20137
🔵	Statements	38.41%	8329 / 21684
🔵	Functions	34.11%	2115 / 6200
🔵	Branches	30.62%	4489 / 14660

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
plugins/sanity-plugin-mux-input/src/components/PlayButton.tsx	100%	100%	100%	100%
plugins/sanity-plugin-mux-input/src/components/Player.tsx	2.38%	0%	0%	2.43%	19-127
plugins/sanity-plugin-mux-input/src/components/VideoInBrowser.tsx	0%	0%	0%	0%	31-128
plugins/sanity-plugin-mux-input/src/components/VideoPlayer.tsx	68.96%	58.82%	71.42%	72.22%	68, 72-73, 79, 83-84, 94, 98, 101-105, 131-133, 137, 142, 151-154

Generated in workflow #11356 for commit 9289eb6 by the Vitest Coverage Report Action

[Copilot]

Copilot review overview

🟡 Changes recommended

Deferred state persists across asset replacement, causing replacement videos to mount and autoplay without a new click.

Review effort: Balanced
Findings: 1

Open (1)

• Reset player requested state when replacing an asset · New

What changed in this PR

Defers Mux player mounting in video inputs until the poster is activated, reducing Safari layout stalls while preserving eager playback elsewhere.

Changes:

• Adds opt-in deferred player rendering with an accessible poster button.
• Shares the existing play-button component across views.
• Adds Vitest coverage and required test dependencies.

File	Description
.changeset/​mux-input-defer-player.md	Records the Safari performance fix.
pnpm-lock.yaml	Locks new test dependencies.
plugins/​sanity-plugin-mux-input/​package.json	Adds testing dependencies.
src/​components/​Player.tsx	Enables deferred playback in inputs.
src/​components/​PlayButton.tsx	Extracts the shared play button.
src/​components/​VideoInBrowser.tsx	Uses the shared play button.
src/​components/​VideoPlayer.tsx	Implements poster-first deferred mounting.
src/​components/​VideoPlayer.test.tsx	Tests eager and deferred behavior.

Files not reviewed (1)

• pnpm-lock.yaml: Generated file

---

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[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation addresses the reported performance issue while preserving existing behavior in other player contexts and adding focused regression coverage.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Reset player requested state when replacing an asset

Files not reviewed (1)

• pnpm-lock.yaml: Generated file

[spuppo-mux]

Changes look great; will test it out! Haven't set up my workspace since the repo migration so it may take me a minute. Just in case, did you test this with audio only assets and/or signed assets?

[pedrobonamin]

Changes look great; will test it out! Haven't set up my workspace since the repo migration so it may take me a minute. Just in case, did you test this with audio only assets and/or signed assets?

Thank you @spuppo-mux let us know if you have any difficulties setting up the new workspace, in my experience it should be much simpler now.

No, haven't tested with audio only assets or signed assets, good catch, will test it next week.

[spuppo-mux]

Hi, btw I could test this with no issues. Audio-only, signed and drm cases seemed to work well to me!

[pedrobonamin]

Thank you @spuppo-mux had to rebase due to some conflicts, would you mind approving again?