diff --git a/runner/run_recipe_ci.py b/runner/run_recipe_ci.py
index 19d8167..e2dbc40 100644
--- a/runner/run_recipe_ci.py
+++ b/runner/run_recipe_ci.py
@@ -175,6 +175,36 @@ def resolve_upgrade_base(
             flush=True,
         )
         rec = None
+    # STALE-CANONICAL GUARD (phase relbase): the canonical is only "last-green", NOT "current". Its
+    # promotion can fail for reasons unrelated to any PR (the WC5 promote deploys a warm-<recipe> app
+    # and health-checks it), and a failed promote leaves the canonical pinned at an OLD release
+    # indefinitely — gitea sat at 3.5.3+1.24.2 from 2026-06-17 to 2026-08-10 because warm-gitea
+    # crash-looped on a read-only app.ini. Basing the upgrade tier on that stale release tests a
+    # transition no deployment performs, and can silently MISS breaks in the transition users do
+    # perform: gitea 3.5.3→head crosses an APP_INI_VERSION change (v21→v22) so Swarm creates a fresh
+    # config, while the real 3.6.1→3.6.2 upgrade keeps v22 and aborts on Swarm's immutable-config
+    # rule. Prefer the newest published release older than head whenever it is newer than the
+    # canonical: that is what real installs upgrade from.
+    if rec and rec.get("version") and not skip_canonicals and head_version:
+        _rel_tags = warm_reconcile.recipe_tags(recipe)
+        if floor:
+            _rel_tags = [t for t in _rel_tags if not _below_floor(t)]
+        newest_rel = warm_reconcile.newest_older_version(_rel_tags, head_version)
+        if newest_rel and warm_reconcile.version_key(newest_rel) > warm_reconcile.version_key(
+            rec["version"]
+        ):
+            print(
+                f"== upgrade base: newest published release {newest_rel} is NEWER than the "
+                f"last-green canonical {rec['version']} — using the release (what deployments "
+                f"actually upgrade from); canonical is stale, check its WC5 promote",
+                flush=True,
+            )
+            return BasePlan(
+                "version",
+                newest_rel,
+                None,
+                f"newest published release older than head (canonical {rec['version']} is stale)",
+            )
     if rec and rec.get("version") and not skip_canonicals:
         canon = rec["version"]
         same = head_version is not None and warm_reconcile.version_key(