Prepare PL 3.9 Release

[felixarntz]

This issue is to track preparation of the upcoming 3.9.0 release up until publishing, which is due February 13, 2025.

• Create release/3.9.0 branch closer to the release date
• Finalize scope and punt unfinished pull requests to following release (Monday, February 10, 2025)
• Bump versions in milestones according to the scope (Monday, February 10, 2025)
• Smoke test (Tuesday, February 11, 2025)
• Prepare the release (Thursday, February 13, 2025)

Note: The release would normally happen on Monday February 17, but due to a US holiday and following WordCamp Asia the release is moved a few days ahead.

[felixarntz]

Note: This releases marks an important milestone, with both Image Prioritizer and Embed Optimizer graduating to non-experimental status, with their versions being bumped to 1.0.0-beta, similar to Optimization Detective last month.

For Embed Optimizer, this means we will still do a release even though it technically contains no changes.

Other than the plugins from the Optimization Detective family, only Performance Lab will need to be released in a new version, due to the change of the other plugins' experimental status.

[westonruter]

Release branch created: https://github.com/WordPress/performance/tree/release/3.9.0

Scope set to these 4 plugins, with Embed Optimizer just being a version bump:

[westonruter]

PR with version bumps: #1862

[westonruter]

Testing the builds at https://complicated-lyrebird-c797ca.instawp.xyz/

✅ In the new version of Performance Lab, I see Embed Optimizer and Image Prioritizer are no longer shown as experimental:

✅ For Embed Optimizer, I see that a Tweet embed is getting the new CSS range syntax for setting the min-height for a tweet: https://complicated-lyrebird-c797ca.instawp.xyz/tweet/

<style>
@media (width <= 480px) { #embed-optimizer-4b1647ded78fdafc89edd99a29b10f78 { min-height: 693px; } }
@media (480px < width <= 600px) { #embed-optimizer-4b1647ded78fdafc89edd99a29b10f78 { min-height: 696px; } }
@media (600px < width <= 782px) { #embed-optimizer-4b1647ded78fdafc89edd99a29b10f78 { min-height: 333px; } }
@media (782px < width) { #embed-optimizer-4b1647ded78fdafc89edd99a29b10f78 { min-height: 337px; } }
</style>

✅ For Image Prioritizer, I see that it is populating the sizes as expected: https://complicated-lyrebird-c797ca.instawp.xyz/images-in-columns/

<img
  data-od-removed-fetchpriority="high"
  data-od-replaced-sizes="(max-width: 1024px) 100vw, 1024px"
  data-od-xpath="/HTML/BODY/DIV[@class=&#039;wp-site-blocks&#039;]/*[2][self::MAIN]/*[1][self::DIV]/*[3][self::DIV]/*[1][self::DIV]/*[1][self::DIV]/*[1][self::FIGURE]/*[1][self::IMG]"
  decoding="async"
  width="1024"
  height="673"
  src="https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-1024x673.jpg"
  alt=""
  class="wp-image-13"
  srcset="
    https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-1024x673.jpg  1024w,
    https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-300x197.jpg    300w,
    https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-768x505.jpg    768w,
    https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-1536x1010.jpg 1536w,
    https://complicated-lyrebird-c797ca.instawp.xyz/wp-content/uploads/2025/02/bison2-2048x1347.jpg 2048w
  "
  sizes="(width &lt;= 480px) 374px, (480px &lt; width &lt;= 600px) 524px, (600px &lt; width &lt;= 782px) 644px, (782px &lt; width) 136px"
/>

[westonruter]

❌ For Optimization Detective, I discovered a bug where we missed URL-encoding the URLs in the imagesrcset of a Link response header. I've opened #1866 to fix the issue.

[westonruter]

Account for 64 KiB limit for sending beacon data. (1851)

✅ With Optimization Detective, I've confirmed that when the URL Metric size exceeds 64 KiB that it is not attempted to be submitted: https://complicated-lyrebird-c797ca.instawp.xyz/200-images/

Change minimum viewport width to be exclusive whereas the maximum width remains inclusive. (1839)

✅ Verified by looking at output of media queries above.

• Disable URL Metric storage locking by default for administrators. (1835)

✅ Confirmed that when logged-in as an administrator that I am able to submit URL Metrics for each URL. However, when I am logged-out the storage lock is preventing me from submitting URL Metrics as expected:

And if I try to force it by clearing the client-side lock, I get the expected 403 Forbidden:

[westonruter]

• Include active plugins in ETag data and increase default freshness TTL from 1 day to 1 week. (1854)

✅ When I go to a post preview URL https://complicated-lyrebird-c797ca.instawp.xyz/?p=30&preview=true I can confirm that URL Metrics are not being collected: