Validation of deprecated io.buildpacks.stack.id is too aggressive

[kevin-wimmer]

Starting with Ubuntu Resolute, Paketo no longer provides "tiny" builder images. The recommendation from the Paketo team is to use one of the standard builders with a "tiny" run image. However, validation performed by org.springframework.boot.buildpack.platform.build.Builder (see "assertStackIdsMatch" method) prevents use of the "tiny" run image with any Paketo builder (because no builder matches stack id "io.buildpacks.stacks.resolute.tiny").

Expected Behavior

Spring Boot builds docker images via the Gradle bootBuildImage task using the "paketobuildpacks/ubuntu-resolute-builder" and "paketobuildpacks/ubuntu-resolute-run-tiny" images.

Current Behavior

The build fails with the following error:
Run image stack 'io.buildpacks.stacks.resolute.tiny' does not match builder stack 'io.buildpacks.stacks.resolute'

Possible Solution (Short Term)

Relax validation to allow images where the stack id of the run image starts with the stack id of the builder.

Possible Solution (Long Term)

Avoid the use of stack ids altogether--stack ids have been deprecated as of Platform API 0.12 and Buildpack API 0.10. Either remove validation entirely or change validation to match container metadata like "io.buildpacks.base.distro.name" and/or "io.buildpacks.base.distro.version."

[adityaanikam]

Verified against current main — Builder.assertStackIdsMatch() does exactly what you described:

Assert.state(runImageStackId.equals(builderImageStackId), () -> "Run image stack '" + runImageStackId
        + "' does not match builder stack '" + builderImageStackId + "'");

A plain .equals() check, so io.buildpacks.stacks.resolute.tiny (Paketo's new tiny run image) can never match io.buildpacks.stacks.resolute (the builder), even though the tiny image is explicitly meant to pair with that builder now that Paketo dropped separate tiny builders.

I'd like to work on this. Your short-term fix (prefix match instead of equality) looks like the right minimal change, but given stack IDs are already deprecated as of Platform API 0.12 / Buildpack API 0.10 per your long-term note, I'll check whether there's an existing distro-metadata-based check elsewhere in this class we should be reusing instead of adding another stack-id special case. Will propose whichever is less likely to need a second patch when stack IDs are eventually removed.

[scottfrederick]

stack ids have been deprecated as of Platform API 0.12

For the sake of completeness, that deprecation was done in Buildpacks RFC 0096, which was closed in Feb 2025.

In response to this, the pack CLI changed their validation from an error to a warning. Since Spring Boot's CNB integration generally tries to maintain parity with pack, Spring Boot should make a similar change.

This deprecation was finalized quite a while ago, so I think this could qualify as a bug in Spring Boot. If the team agrees after triaging the issue, I have a commit on a 4.0.x branch that I can submit as a PR.

[wilkinsona]

Yes please, @scottfrederick. Thank you.

[wilkinsona]

Closing in favor of #51390.