diff --git a/skills/fix-plan/scripts/plane_sync.py b/skills/fix-plan/scripts/plane_sync.py
index 95012dc8..3d52a437 100644
--- a/skills/fix-plan/scripts/plane_sync.py
+++ b/skills/fix-plan/scripts/plane_sync.py
@@ -35,8 +35,11 @@
 # plane_create_comment.py, the in-repo precedent that already clears the WAF.
 UA = "Mozilla/5.0 (plane-backlog)"
 
+# The identifier prefix is a Plane project identifier, which may contain digits
+# (e.g. ES6KR-117). A letters-only prefix class silently matched nothing for such
+# workspaces, so every sync reported "0 index lines" instead of failing loudly.
 INDEX_LINE_RE = re.compile(
-    r'^(?P<indent>\s*)-\s+\[(?P<marker>[^\]]*)\]\s+\[(?P<ident>[A-Z]+-\d+)\]\s+(?P<title>.+?)\s+'
+    r'^(?P<indent>\s*)-\s+\[(?P<marker>[^\]]*)\]\s+\[(?P<ident>[A-Z][A-Z0-9]*-\d+)\]\s+(?P<title>.+?)\s+'
     r'(?:→|->)\s+Plane\s+\((?P<url>https://[^\s)]+)\)(?P<rest>.*)$'
 )
 
diff --git a/tests/test_plane_profile.py b/tests/test_plane_profile.py
index 14bbeca4..86c857e5 100644
--- a/tests/test_plane_profile.py
+++ b/tests/test_plane_profile.py
@@ -202,6 +202,12 @@ def test_k3s_fallback_script_survives_quote_in_workspace_slug(monkeypatch):
     plane_create_issue = importlib.util.module_from_spec(spec)
     spec.loader.exec_module(plane_create_issue)
 
+    # create_via_k3s_fallback() returns before subprocess.run() when kubectl is
+    # absent from PATH. Without this stub the test asserts on ambient tooling
+    # rather than on the escaping behaviour it is about, and fails on any host
+    # (or git hook with a trimmed PATH) that has no kubectl installed.
+    monkeypatch.setattr(plane_create_issue.shutil, "which", lambda _cmd: "/usr/bin/kubectl")
+
     captured_cmd = {}
 
     class _FakeCompletedProcess:
diff --git a/tests/test_plane_script_defects.py b/tests/test_plane_script_defects.py
index 7607ae2b..31934ae5 100644
--- a/tests/test_plane_script_defects.py
+++ b/tests/test_plane_script_defects.py
@@ -194,3 +194,29 @@ def test_k3s_fallback_skips_gracefully_without_kubectl(script_path, monkeypatch)
     assert res["success"] is False
     assert "kubectl" in res["reason"]
     assert not ran, "fallback must not shell out when kubectl is absent"
+
+
+def test_index_line_re_matches_identifier_prefix_containing_digits():
+    """A Plane project identifier may contain digits (e.g. ES6KR-117).
+
+    INDEX_LINE_RE previously matched the prefix with `[A-Z]+`, so no index line
+    from such a workspace ever matched. plane_sync then reported "0 index lines"
+    and every marker stayed unsynced — a silent no-op rather than a loud error.
+    """
+    mod = load_module(FIX_PLAN_SCRIPTS / "plane_sync.py", "plane_sync_ident")
+    url = (
+        "https://plane.example.invalid/acme/projects/"
+        "4b4d8bfc-5e5d-495b-bd4c-301fe89e5bb0/issues/"
+        "016a702b-11aa-424d-834c-53a818e9de0c"
+    )
+
+    for ident in ("ES6KR-117", "INFRA-12", "A1-3"):
+        line = f"- [ ] [{ident}] some tracked item → Plane ({url})"
+        match = mod.INDEX_LINE_RE.match(line)
+        assert match, f"index line with identifier {ident} must match"
+        assert match.group("ident") == ident
+
+    # The prefix must still start with a letter — a purely numeric prefix is not
+    # a Plane identifier and must not be absorbed.
+    numeric = f"- [ ] [123-4] not an identifier → Plane ({url})"
+    assert mod.INDEX_LINE_RE.match(numeric) is None