diff --git a/runner/harness/generic.py b/runner/harness/generic.py
index 60a0057..b714a33 100644
--- a/runner/harness/generic.py
+++ b/runner/harness/generic.py
@@ -163,7 +163,14 @@ def assert_upgraded(domain: str, meta: dict) -> None:
             "PR-head checkout (the code under test was not exercised by the upgrade)"
         )
         # chaos-version is an abbreviated commit (e.g. '8a026066'); head_ref may be full or short.
-        assert head_ref.startswith(chaos) or chaos.startswith(head_ref), (
+        # abra appends a working-tree-state marker (e.g. '+U' = untracked file present) to the
+        # chaos-version when a cc-ci DEPLOY OVERLAY sits in the recipe checkout as an untracked file
+        # (e.g. ghost's compose.ccci-health.yml, provided by install_steps). That marker is NOT part
+        # of the commit identity — strip it before the HC1 commit match. HC1 is preserved: the
+        # underlying COMMIT must still equal head_ref; a stale prev-checkout chaos redeploy would
+        # stamp prev's commit (also '+U' if overlaid) and STILL not match head_ref after stripping.
+        chaos_commit = chaos.split("+", 1)[0]
+        assert head_ref.startswith(chaos_commit) or chaos_commit.startswith(head_ref), (
             f"{domain}: upgrade deployed chaos commit {chaos!r}, not the intended PR-head "
             f"{head_ref[:12]!r} — the re-checkout to the code under test failed, so the upgrade is "
             "not exercising the PR's changes (HC1)"