diff --git a/partner_communication/__manifest__.py b/partner_communication/__manifest__.py
index b0d020061..44b156191 100644
--- a/partner_communication/__manifest__.py
+++ b/partner_communication/__manifest__.py
@@ -30,7 +30,7 @@
 # pylint: disable=C8101
 {
     "name": "Partner Communication",
-    "version": "18.0.1.0.1",
+    "version": "18.0.1.0.2",
     "category": "Other",
     "author": "Compassion Switzerland",
     "license": "AGPL-3",
diff --git a/partner_communication/migrations/18.0.1.0.2/post-migration.py b/partner_communication/migrations/18.0.1.0.2/post-migration.py
new file mode 100644
index 000000000..5d113a955
--- /dev/null
+++ b/partner_communication/migrations/18.0.1.0.2/post-migration.py
@@ -0,0 +1,59 @@
+import json
+import logging
+
+from openupgradelib import openupgrade
+
+_logger = logging.getLogger(__name__)
+
+# T3274: found while investigating why sponsorship onboarding communications
+# crashed - the "Donation - Thank You Letter" template had its ">"/"<"/'"'/"'"
+# QWeb comparison/string-literal operators double-escaped
+# (e.g. "&amp;gt;" instead of "&gt;"), so Odoo 18's stricter QWeb compiler
+# tried to evaluate the still-escaped "&amp;gt;" text as a Python operator
+# and crashed. This is a purely mechanical unescape, safe to apply to any
+# mail_template regardless of which module (if any) owns it - many of the
+# affected templates were created directly via the UI and have no owning
+# module at all, so a per-module migration could never reach them.
+ENTITY_FIXES = (
+    ("&amp;gt;", "&gt;"),
+    ("&amp;lt;", "&lt;"),
+    ("&amp;quot;", "&quot;"),
+    ("&amp;apos;", "&apos;"),
+)
+
+
+def _fix_body(body):
+    if not body:
+        return body
+    for broken, fixed in ENTITY_FIXES:
+        body = body.replace(broken, fixed)
+    return body
+
+
+@openupgrade.migrate()
+def migrate(env, version):
+    env.cr.execute(
+        """
+        SELECT id, body_html FROM mail_template
+        WHERE body_html::text LIKE '%&amp;gt;%'
+           OR body_html::text LIKE '%&amp;lt;%'
+           OR body_html::text LIKE '%&amp;quot;%'
+           OR body_html::text LIKE '%&amp;apos;%'
+        """
+    )
+    rows = env.cr.fetchall()
+    fixed_count = 0
+    for template_id, body_html in rows:
+        fixed = {lang: _fix_body(body) for lang, body in body_html.items()}
+        if fixed != body_html:
+            env.cr.execute(
+                "UPDATE mail_template SET body_html = %s WHERE id = %s",
+                (json.dumps(fixed), template_id),
+            )
+            fixed_count += 1
+    _logger.info(
+        "T3274: unescaped double-escaped &gt;/&lt;/&quot;/&apos; entities "
+        "in %s/%s mail_template rows",
+        fixed_count,
+        len(rows),
+    )