Aggregate proposed run changes into a single GitHub PR comment

Workaround

When a PR triggers multiple proposed runs (across different stacks), Spacelift creates separate GitHub PR comments per run or requires a custom aggregator. This creates noise and confusion for PR authors and reviewers who can't see all resource changes in one place. The VCS integration's "Aggregate VCS checks" only groups checks, not the actual resource change comments.

Problem

When a PR triggers multiple proposed runs (across different stacks), Spacelift creates separate GitHub PR comments per run or requires a custom aggregator. This creates noise and confusion for PR authors and reviewers who can't see all resource changes in one place. The VCS integration's "Aggregate VCS checks" only groups checks, not the actual resource change comments.