diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index bbc3aaf..52bbc62 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -71,8 +71,17 @@ jobs:
             found=$(curl -fsS -H "Authorization: Bearer $GH_TOKEN" -H "Accept: application/vnd.github+json" \
               "https://api.github.com/repos/${{ github.repository }}/actions/artifacts?name=$label&per_page=5" \
               | jq -r '[.artifacts[] | select(.expired|not)] | sort_by(.created_at) | last | select(. != null) | "run \(.workflow_run.id), expires \(.expires_at)"')
+            # The plan the publish job makes, made here before a runner is
+            # asked for: a tree the channel already holds at master's version
+            # (a re-run, or a dispatch naming a package that is fine) needs
+            # no build, and an x86 rebuild would wait minutes for a droplet
+            # to find that out in seconds.
+            plan=""
+            [[ -n "$found" ]] || plan=$(bin/build --dry-run --mirror edge --arch "$arch" --package "$package" 2>&1 | grep -E '^==> Plan complete' || true)
             if [[ -n "$found" ]]; then
               decision="reuse the build artifact ($found)"
+            elif [[ -n "$plan" && -z "$(sed -E 's/.*would build: *//' <<<"$plan" | tr -d '[:space:]')" ]]; then
+              decision="already published at master's version, nothing to build"
             elif [[ $arch == aarch64 ]]; then
               decision="no build artifact: rebuild natively on ubuntu-24.04-arm"
               rebuild+=("$(jq -c '. + {runner: "[\"ubuntu-24.04-arm\"]"}' <<<"$entry")")