diff --git a/docs/project-summary.md b/docs/project-summary.md
index 9ec9bd7..23e7a75 100644
--- a/docs/project-summary.md
+++ b/docs/project-summary.md
@@ -890,8 +890,14 @@ ships a binary missing whatever landed on main meanwhile, and `rpm -U --force`
 overwrites the good one with it. That happened on 2026-08-10: a build from a
 stale checkout replaced `/usr/bin/mcpctl` with one that had no `statusline`
 command, months after the status line landed. `scripts/check-main-sync.sh`
-(sourced by `build-rpm.sh` and `build-deb.sh`) fetches `main`, compares, and
-fails before any work happens, listing the commits you are missing.
+fetches `main`, compares, and fails before any work happens, listing the commits
+you are missing. It gates every path that produces something others consume:
+`build-rpm.sh`, `build-deb.sh`, `build-mcpd.sh` (each is also run standalone, so
+none can rely on another having checked) and `deploy-k8s.sh` — where a stale
+branch would pin its sha in Pulumi and make it the cluster's source of truth.
+`deploy-k8s.sh --dry-run` skips the check: it builds and cuts over nothing, and
+blocking a read-only inspection only teaches people to export the escape hatch
+permanently, disabling the gate for real deploys too.
 
 ```bash
 git merge main                                   # the fix
diff --git a/scripts/build-mcpd.sh b/scripts/build-mcpd.sh
index 08a7f3a..99ece3a 100755
--- a/scripts/build-mcpd.sh
+++ b/scripts/build-mcpd.sh
@@ -16,6 +16,11 @@ if [ -f .env ]; then
   set -a; source .env; set +a
 fi
 
+# This pushes an image to the registry, so the same staleness gate as the package
+# builds applies. Run standalone as well as from deploy-k8s.sh, hence its own copy.
+source "$SCRIPT_DIR/check-main-sync.sh"
+check_main_sync
+
 # Push directly to internal address (external proxy has body size limit)
 REGISTRY="10.0.0.194:3012"
 IMAGE="mcpd"
diff --git a/scripts/check-main-sync.sh b/scripts/check-main-sync.sh
index 246ada2..05c0e3f 100755
--- a/scripts/check-main-sync.sh
+++ b/scripts/check-main-sync.sh
@@ -84,8 +84,10 @@ check_main_sync() {
   echo "" >&2
   echo "ERROR: '$branch' is $behind commit(s) behind $base — refusing to build." >&2
   echo "" >&2
-  echo "  Building now would package a binary without these, and installing it" >&2
-  echo "  would overwrite a good one with a version missing them:" >&2
+  # Deliberately artifact-agnostic: the same helper gates RPM/DEB packages, the
+  # mcpd image, and the k8s deploy.
+  echo "  Building now would produce an artifact without these, and shipping it" >&2
+  echo "  would replace a good one with a version missing them:" >&2
   echo "" >&2
   git log --oneline --no-decorate "HEAD..$ref" | head -15 | sed 's/^/    /' >&2
   if [ "$behind" -gt 15 ]; then
diff --git a/scripts/deploy-k8s.sh b/scripts/deploy-k8s.sh
index e41efad..eff872a 100755
--- a/scripts/deploy-k8s.sh
+++ b/scripts/deploy-k8s.sh
@@ -80,6 +80,20 @@ cat <<EOF
 EOF
 [ -f "$PULUMI_YAML" ] || die "Pulumi config not found: $PULUMI_YAML"
 
+# ── 0. Staleness gate ──
+# Same hazard as the RPM build, with the cluster on the receiving end: a branch
+# behind main deploys images missing whatever landed there, and the sha pinned in
+# Pulumi makes that the new source of truth. Skipped for --dry-run, which builds
+# and cuts over nothing — blocking a read-only inspection only teaches people to
+# export MCPCTL_ALLOW_BEHIND_MAIN=1 permanently, which would disable the gate for
+# the real deploys too.
+if [ "$DRY_RUN" = true ]; then
+  warn "dry-run: skip the main-sync check"
+else
+  source "$SCRIPT_DIR/check-main-sync.sh"
+  check_main_sync || die "branch is behind main — merge it before deploying"
+fi
+
 # ── 1. Test gate ──
 if [ "$SKIP_TESTS" = true ]; then warn "skipping unit tests (--skip-tests)"; else
   say "1/7  Unit tests (pnpm test:run)"