Kibana (8.16.0) does not consistently render Vega grammar with colours

[Vince-dS]

Kibana version: 8.16.0

Elasticsearch version: 8.16.0

Server OS version: on Elastic Cloud

Browser version: Chrome Version 131.0.6778.205 (Official Build) (arm64)

Browser OS version: Mac OS 15.2

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug: copy/paste Vega-lite grammar does not render the code in colours as it use to.

Steps to reproduce:

1. Dashboard > Add Custom Viz > already the default Vega code is in black not with colours.
2. copy/paste sample code (i.e. the snippet from https://vega.github.io/vega-lite/docs/calculate.html )
3. add the line on the top (after opening { for instance ):

"$schema": "https://vega.github.io/schema/vega-lite/v5.json",

4. vega-lite code stays in black. Sometimes, after few edits, colours are showing up.

Expected behavior:

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[markov00]

I can't reproduce that in main so probably got fixed in the mean time. I'm going to look how that was fixed and try to see if we can backport it to a patch release.
Saw that 8.17 has the same issue

[eokoneyo]

Took a look at this, it's interesting it seems this issue only happens on cloud as I attempted reproducing it the same version in stateful Kibana and I wasn't able to. Adding sharedUX tag so this can be triaged.

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)