Real-time collaboration: Persist CRDT documents on autosave #75105
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chriszarate
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[Type] Bug
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Size Change: +23 B (0%) Total Size: 3 MB
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Flaky tests detected in c63d85e. 🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/21531356336
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alecgeatches
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Jan 30, 2026
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alecgeatches
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Tested according to your instructions and was able to reproduce on trunk but not in this branch. 👍
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What?
Persist CRDT documents on autosaves (in addition to manual saves).
Why?
We persist CRDT documents in order to solve the "initialization" problem and avoid duplicate updates. When saving a post, we also save a persisted CRDT document alongside it (in post meta) that represents its current state. This document is used as a "shared starting point" for all users in the session.
If the post is updated "out-of-band" (e.g., by a WP-CLI command), then we can compare the post against the persisted CRDT document, compute the necessary updates, and apply them to the CRDT document.
We recently discovered that autosaves are sometimes applied to the post itself instead of a revision:
https://github.com/WordPress/wordpress-develop/blob/dc62ecbc345ca1b8d1801eca794d71755b7568f1/src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php#L235-L244
In those situations, the post data becomes out of sync with the persisted CRDT document. If a editor in a collaboration session refreshes the browser, or a new editor joins, they will perceive the autosave as an "out-of-band" update, compute the necessary updates, and apply them to the CRDT document—which will then be synced to peers.
Therefore, whatever updates were captured by the autosave will effectively be duplicated on every page load, for the lifetime of that collaboration session.
To avoid this, we need to persist CRDT documents with autosaves as well. This does result in nominally increased bandwidth and storage, but should not be significant.
How?
Unfortunately, simply adding the persisted CRDT document to the payload of the autosave is not sufficient. In the problematic code path, the backend calls
wp_update_post(withoutmeta_input) and does not call the special post meta handling increate_post_autosave.To navigate this, we filter
rest_prepare_autosaveand update the post meta manually.Testing Instructions
Screenshots or screencast
Before
before.mov
After
after.mov