fix(ui): defer live preview iframe rendering

[jacobsfletch]

When navigating to a document with live preview enabled, the respective site is optimistically loaded regardless of whether the user is actively previewing it.

This creates the following problems:

1. If the user's live preview URL is set up to proxy through an endpoint, e.g. to enter draft mode before rendering the page, this will be triggered preemptively, causing "draft mode" to persist for their remaining session. For example, the user may revisit their site after editing a page without live preview, and unexpectedly see draft content.
2. There are unnecessary performance and network costs of rendering the iframe preemptively. Although the admin panel only dispatches events to visible preview windows, the initial page load consumes resources despite not being visible. For example, the underlying page is still downloaded and rendered (if uncached), its db queries are still hit (if dynamic), etc.

Now, the iframe window is conditionally mounted only when the user toggles into live preview mode. To maintain fast loads thereafter, the iframe doesn't unmount when toggled off. Live preview events themselves are paused, but the window itself remains dormant until reactivated.

In the future we may also want to consider adding callbacks to the live preview toggle event. That way you could reverse what your live preview endpoint has done, e.g. exit draft mode.

Before:

Screen.Recording.2026-03-19.at.11.10.22.AM.mp4

After:

Screen.Recording.2026-03-19.at.11.26.28.AM.mp4

Unrelated:

• Deflakes the toggleLivePreview test helper by making is event-driven, e.g. it intercepts preference requests to ensure they are fulfilled before moving on.

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1213727956884077

[github-actions]

📦 esbuild Bundle Analysis for payload

This analysis was generated by esbuild-bundle-analyzer. 🤖

Meta File	Out File	Size (raw)	Note
packages/next/meta_index.json	esbuild/index.js	984.61 KB	✅ No change
packages/payload/meta_index.json	esbuild/index.js	1.34 MB	✅ No change
packages/payload/meta_shared.json	esbuild/exports/shared.js	190.93 KB	✅ No change
packages/richtext-lexical/meta_client.json	esbuild/exports/client_optimized/index.js	280.56 KB	✅ No change
packages/ui/meta_client.json	esbuild/exports/client_optimized/index.js	1.18 MB	⚠️ +143 B (+0.0%)
packages/ui/meta_shared.json	esbuild/exports/shared_optimized/index.js	16.32 KB	✅ No change

Largest paths

These visualization shows top 20 largest paths in the bundle.

Meta file: packages/next/meta_index.json, Out file: esbuild/index.js

Path	Size
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dist/views/Versions	${{\color{Goldenrod}{ ▏ }}}$ 0.6%, 6.17 KB
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dist/elements/DocumentHeader	${{\color{Goldenrod}{ ▏ }}}$ 0.5%, 4.81 KB
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dist/views/ForgotPassword	${{\color{Goldenrod}{ }}}$ 0.3%, 3.09 KB
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Meta file: packages/payload/meta_index.json, Out file: esbuild/index.js

Path	Size
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dist/queues/operations	${{\color{Goldenrod}{ ▎ }}}$ 1.0%, 12.80 KB
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dist/database/migrations	${{\color{Goldenrod}{ ▏ }}}$ 0.6%, 7.54 KB
dist/collections/endpoints	${{\color{Goldenrod}{ ▏ }}}$ 0.5%, 6.23 KB
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Meta file: packages/payload/meta_shared.json, Out file: esbuild/exports/shared.js

Path	Size
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dist/fields/validations.js	${{\color{Goldenrod}{ █▍ }}}$ 5.6%, 10.54 KB
dist/config/orderable	${{\color{Goldenrod}{ ▍ }}}$ 1.7%, 3.13 KB
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dist/utilities/deepCopyObject.js	${{\color{Goldenrod}{ ▎ }}}$ 1.4%, 2.54 KB
dist/auth/cookies.js	${{\color{Goldenrod}{ ▏ }}}$ 0.8%, 1.55 KB
dist/utilities/flattenTopLevelFields.js	${{\color{Goldenrod}{ ▏ }}}$ 0.8%, 1.42 KB
dist/fields/config	${{\color{Goldenrod}{ ▏ }}}$ 0.7%, 1.28 KB
dist/utilities/getVersionsConfig.js	${{\color{Goldenrod}{ ▏ }}}$ 0.6%, 1.04 KB
dist/utilities/flattenAllFields.js	${{\color{Goldenrod}{ ▏ }}}$ 0.5%, 943 B
dist/folders/utils	${{\color{Goldenrod}{ ▏ }}}$ 0.5%, 916 B
dist/utilities/unflatten.js	${{\color{Goldenrod}{ }}}$ 0.4%, 779 B
dist/utilities/sanitizeUserDataForEmail.js	${{\color{Goldenrod}{ }}}$ 0.4%, 713 B
dist/utilities/getFieldPermissions.js	${{\color{Goldenrod}{ }}}$ 0.3%, 651 B
dist/collections/config	${{\color{Goldenrod}{ }}}$ 0.3%, 570 B
dist/bin/generateImportMap	${{\color{Goldenrod}{ }}}$ 0.3%, 561 B
dist/auth/sessions.js	${{\color{Goldenrod}{ }}}$ 0.3%, 525 B
dist/fields/getFieldPaths.js	${{\color{Goldenrod}{ }}}$ 0.3%, 485 B
dist/errors/APIError.js	${{\color{Goldenrod}{ }}}$ 0.2%, 438 B
dist/utilities/getSafeRedirect.js	${{\color{Goldenrod}{ }}}$ 0.2%, 423 B
(other)	${{\color{Goldenrod}{ █████▏ }}}$ 20.7%, 38.75 KB

Meta file: packages/richtext-lexical/meta_client.json, Out file: esbuild/exports/client_optimized/index.js

Path	Size
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dist/lexical/plugins	${{\color{Goldenrod}{ ██▉ }}}$ 11.5%, 32.00 KB
dist/lexical/ui	${{\color{Goldenrod}{ ██▏ }}}$ 8.8%, 24.36 KB
dist/features/experimental_table	${{\color{Goldenrod}{ ██▏ }}}$ 8.5%, 23.70 KB
dist/packages/@lexical	${{\color{Goldenrod}{ █▋ }}}$ 6.8%, 18.99 KB
dist/features/link	${{\color{Goldenrod}{ █▋ }}}$ 6.6%, 18.24 KB
dist/features/toolbars	${{\color{Goldenrod}{ █▍ }}}$ 5.8%, 16.08 KB
dist/features/upload	${{\color{Goldenrod}{ █▎ }}}$ 5.0%, 13.77 KB
dist/features/textState	${{\color{Goldenrod}{ █ }}}$ 4.0%, 11.08 KB
dist/features/relationship	${{\color{Goldenrod}{ ▊ }}}$ 3.3%, 9.03 KB
dist/lexical/utils	${{\color{Goldenrod}{ ▊ }}}$ 3.1%, 8.49 KB
dist/features/debug	${{\color{Goldenrod}{ ▋ }}}$ 2.7%, 7.39 KB
dist/utilities/fieldsDrawer	${{\color{Goldenrod}{ ▋ }}}$ 2.6%, 7.15 KB
dist/features/converters	${{\color{Goldenrod}{ ▋ }}}$ 2.5%, 7.05 KB
dist/lexical/config	${{\color{Goldenrod}{ ▍ }}}$ 1.8%, 5.08 KB
dist/features/lists	${{\color{Goldenrod}{ ▍ }}}$ 1.8%, 5.00 KB
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dist/lexical/LexicalEditor.js	${{\color{Goldenrod}{ ▎ }}}$ 1.2%, 3.22 KB
dist/lexical/theme	${{\color{Goldenrod}{ ▏ }}}$ 0.9%, 2.62 KB
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Meta file: packages/ui/meta_client.json, Out file: esbuild/exports/client_optimized/index.js

Path	Size
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dist/elements/FolderView	${{\color{Goldenrod}{ ▋ }}}$ 2.5%, 29.37 KB
dist/elements/BulkUpload	${{\color{Goldenrod}{ ▌ }}}$ 2.4%, 27.80 KB
dist/views/Edit	${{\color{Goldenrod}{ ▍ }}}$ 1.5%, 17.30 KB
dist/elements/WhereBuilder	${{\color{Goldenrod}{ ▍ }}}$ 1.5%, 17.29 KB
dist/forms/Form	${{\color{Goldenrod}{ ▎ }}}$ 1.4%, 15.85 KB
dist/fields/Relationship	${{\color{Goldenrod}{ ▎ }}}$ 1.3%, 15.78 KB
dist/elements/Table	${{\color{Goldenrod}{ ▎ }}}$ 1.3%, 15.77 KB
dist/fields/Upload	${{\color{Goldenrod}{ ▎ }}}$ 1.2%, 14.24 KB
dist/fields/Blocks	${{\color{Goldenrod}{ ▎ }}}$ 1.2%, 13.89 KB
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dist/elements/PublishButton	${{\color{Goldenrod}{ ▏ }}}$ 0.8%, 9.09 KB
dist/providers/Folders	${{\color{Goldenrod}{ ▏ }}}$ 0.7%, 8.47 KB
dist/elements/LivePreview	${{\color{Goldenrod}{ ▏ }}}$ 0.7%, 8.43 KB
dist/elements/HTMLDiff	${{\color{Goldenrod}{ ▏ }}}$ 0.7%, 8.38 KB
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Meta file: packages/ui/meta_shared.json, Out file: esbuild/exports/shared_optimized/index.js

Path	Size
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dist/utilities/handleTakeOver.js	${{\color{Goldenrod}{ ▋ }}}$ 2.8%, 440 B
dist/utilities/traverseForLocalizedFields.js	${{\color{Goldenrod}{ ▋ }}}$ 2.6%, 399 B
dist/elements/withMergedProps	${{\color{Goldenrod}{ ▌ }}}$ 2.2%, 339 B
dist/utilities/getVisibleEntities.js	${{\color{Goldenrod}{ ▌ }}}$ 2.1%, 329 B
dist/utilities/getNavGroups.js	${{\color{Goldenrod}{ ▍ }}}$ 1.9%, 301 B
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(other)	${{\color{Goldenrod}{ ████████████████████ }}}$ 80.0%, 12.51 KB

Details

Next to the size is how much the size has increased or decreased compared with the base branch of this PR.

• ‼️: Size increased by 20% or more. Special attention should be given to this.
• ⚠️: Size increased in acceptable range (lower than 20%).
• ✅: No change or even downsized.
• 🗑️: The out file is deleted: not found in base branch.
• 🆕: The out file is newly found: will be added to base branch.

[jacobsfletch]

Here we're intercepting the setter to perform a side-effect, which in this case, switches the one-way setShouldRenderIframe property on.

This is a good example of event-driven > effect-driven state.

[jacobsfletch]

Another good example of event-driven patterns, this time to deflake the test helper by intercepting the route itself.

[github-actions]

🚀 This is included in version v3.80.0