diff --git a/custom-skills/60-gtm-audit/code/docs/common_issues.md b/custom-skills/60-gtm-audit/code/docs/common_issues.md
index 90e3e9c..c1e00f9 100644
--- a/custom-skills/60-gtm-audit/code/docs/common_issues.md
+++ b/custom-skills/60-gtm-audit/code/docs/common_issues.md
@@ -284,6 +284,22 @@ The JHR container has two content group variables for menu categories:
 
 **Gotcha — adding new subdomains**: When a new hotel brand subdomain launches (e.g., `les.josunhotel.com`), the subdomain alternation group `(www|app|...|les|\.)` in ALL main-domain rules must be updated. This affects 14+ rules in the URL-based variable.
 
+### Gotcha — Subdomain Regex Dot Separator
+
+**Bug**: `(www|app|jpg|les|\.)?josunhotel\.com` does NOT match `www.josunhotel.com`.
+
+The `\.` inside the alternation group matches a literal dot OR `www` matches `www`, but neither consumes the `.` between the subdomain and `josunhotel`. The regex engine sees `www` then expects `josunhotel` but finds `.josunhotel`.
+
+**Fix**: Move the dot outside the group as an optional separator:
+```
+BROKEN: (www|app|jpg|gjb|gjj|grp|les|\.)?josunhotel\.com
+FIXED:  (www|app|jpg|gjb|gjj|grp|les)?\.?josunhotel\.com
+```
+
+This correctly matches: `www.josunhotel.com`, `les.josunhotel.com`, `josunhotel.com` (bare), `app.josunhotel.com`.
+
+**Note**: GTM's "Full Matches Only = OFF" means `re.search` (partial match) is used, which may accidentally match the broken pattern on some URLs. But strict `re.match` or JavaScript `pattern.test()` will fail. Always test with the full URL in JavaScript console.
+
 ### Audit Checklist for Content Grouping
 
 - [ ] Run `dtm var info <var_id>` to dump the full regex table
diff --git a/custom-skills/61-gtm-manager/code/docs/common_issues.md b/custom-skills/61-gtm-manager/code/docs/common_issues.md
index 90e3e9c..c1e00f9 100644
--- a/custom-skills/61-gtm-manager/code/docs/common_issues.md
+++ b/custom-skills/61-gtm-manager/code/docs/common_issues.md
@@ -284,6 +284,22 @@ The JHR container has two content group variables for menu categories:
 
 **Gotcha — adding new subdomains**: When a new hotel brand subdomain launches (e.g., `les.josunhotel.com`), the subdomain alternation group `(www|app|...|les|\.)` in ALL main-domain rules must be updated. This affects 14+ rules in the URL-based variable.
 
+### Gotcha — Subdomain Regex Dot Separator
+
+**Bug**: `(www|app|jpg|les|\.)?josunhotel\.com` does NOT match `www.josunhotel.com`.
+
+The `\.` inside the alternation group matches a literal dot OR `www` matches `www`, but neither consumes the `.` between the subdomain and `josunhotel`. The regex engine sees `www` then expects `josunhotel` but finds `.josunhotel`.
+
+**Fix**: Move the dot outside the group as an optional separator:
+```
+BROKEN: (www|app|jpg|gjb|gjj|grp|les|\.)?josunhotel\.com
+FIXED:  (www|app|jpg|gjb|gjj|grp|les)?\.?josunhotel\.com
+```
+
+This correctly matches: `www.josunhotel.com`, `les.josunhotel.com`, `josunhotel.com` (bare), `app.josunhotel.com`.
+
+**Note**: GTM's "Full Matches Only = OFF" means `re.search` (partial match) is used, which may accidentally match the broken pattern on some URLs. But strict `re.match` or JavaScript `pattern.test()` will fail. Always test with the full URL in JavaScript console.
+
 ### Audit Checklist for Content Grouping
 
 - [ ] Run `dtm var info <var_id>` to dump the full regex table