Why does Argo Image Updater ignore my filter-tag regex for SNAPSHOT images?

Below is one likely explanation and workaround for your issue.

When using Argo Image Updater, by default it tries to compare image tags as semantic versions. Even though you set a regular‑expression filter (or even try using allow‑tags), if your tags (here “SNAPSHOT” tags) don’t conform to semver the updater may still pick “latest” based on lexicographic or “latest release” sorting.

A common solution is to explicitly tell Argo Image Updater that your image tags should be treated using a regex–based (i.e. non‑semver) selection strategy. In our experience this is done by adding an annotation that sets the tag comparison strategy to regex. For example, try adding an annotation like:

HCLCopied
"argocd-image-updater.argoproj.io/rtm.tag-strategy" = "regex"

Your complete annotation block would then look like:

HCLCopied
"argocd-image-updater.argoproj.io/git-branch"         = "main"
"argocd-image-updater.argoproj.io/image-list"           = "rtm=<redacted>.azurecr.io/rtm"
"argocd-image-updater.argoproj.io/rtm.filter-tag"       = "^.*SNAPSHOT.*$"
"argocd-image-updater.argoproj.io/rtm.tag-strategy"     = "regex"
"argocd-image-updater.argoproj.io/rtm.pull-secret"      = "pullsecret:argo/acr-credentials"
"argocd-image-updater.argoproj.io/write-back-method"    = "git"

This extra annotation directs the updater not to expect semver formatted tags, but instead to work solely with your regex filter. Be sure that the key prefix (here “rtm”) exactly matches the identifier you used in the image list.

Other points to double‑check:

• Ensure your image list entry exactly matches the naming in the filter annotations.
• Confirm that the Argo Image Updater version you’re using supports the non‑semver strategy in this way (if not, consider upgrading).
• Review the log output again after applying the change to verify that the filtering logic picks up only the tags containing “SNAPSHOT.”

This approach has resolved similar issues in our experience, where changes in tag–selection behavior needed an explicit tag strategy annotation.

If problems persist after the change, consider checking the GitHub issues and documentation for your specific version of Argo Image Updater for any known bugs or changes regarding tag filtering.