Unable to force:source:push ExperienceBundle from API version 50.0 with API version 51.0

Yesterday I was trying to deploy some source including an Experience Cloud Site (using ExperienceBundle) created with API version 50.0 to a scratch org but it failed when I updated the API version to 51.0 in sfdx-project.json . Deploying with API version 50.0 worked just fine. The deploy (w/ API version 51.0) failed with the following message:

Error  force-app/main/default/experiences/Digital_Capability_Assessment_Aura1.site-meta.xml  You seem to be missing the property configurationTags in Digital_Capability_Assessment_Aura1/routes/register.json with component ID: f7c5ea49-0bde-4848-a72f-82ace4ea6760

And the error message was right – that key is not in the file but that’s was also true for some of the other Experience Cloud files. Deploying with API version 50.0 and trying to pull with API version 51.0 didn’t change any source. Clever people told me that this was expected as nothing changed in the org (regardless of a publish or similar).

Solution was to deploy with force:source:push with API version 50.0 and then do a force:source:retrieve specifying API version 51.0 on the command line. Then afterwards toggle the API version in sfdx-project.json.

sfdx force:source:retrieve -u dca_scratch_comm -a 51.0 -m ExperienceBundle