diff --git a/.forgejo/workflows/master.yml b/.forgejo/workflows/master.yml
index bb14f9ee0..862103661 100644
--- a/.forgejo/workflows/master.yml
+++ b/.forgejo/workflows/master.yml
@@ -3,8 +3,6 @@ name: CI
 on:
     push:
         branches: [master, develop]
-    pull_request:
-        branches: [master, develop]
 
 vars:
     docker_prefix: "http://harbor.cleverthis.com/docker/"
diff --git a/robot/security_audit.robot b/robot/security_audit.robot
index 03a9ce43e..d804041d1 100644
--- a/robot/security_audit.robot
+++ b/robot/security_audit.robot
@@ -49,6 +49,13 @@ Audit Service Has Prune Method
     Should Contain    ${content}    def prune(
     Should Contain    ${content}    retention_days
 
+Audit Service Has Thread Safe Session Init
+    [Documentation]    Verify _ensure_session() uses threading.Lock (bug #991 fix)
+    ${content}=    Get File    ${AUDIT_SERVICE}
+    Should Contain    ${content}    import threading
+    Should Contain    ${content}    _session_lock
+    Should Contain    ${content}    threading.Lock()
+
 Audit Service Has Close And Context Manager
     [Documentation]    Verify the audit service supports close() and context manager
     ${content}=    Get File    ${AUDIT_SERVICE}
diff --git a/src/cleveragents/application/services/audit_service.py b/src/cleveragents/application/services/audit_service.py
index 41d15dbb8..37c5e066a 100644
--- a/src/cleveragents/application/services/audit_service.py
+++ b/src/cleveragents/application/services/audit_service.py
@@ -175,6 +175,7 @@ class AuditService:
         self._settings = settings
         self._database_url = database_url
         self._owns_session = session is None
+        self._session_lock = threading.Lock()
         # When a session is injected (e.g. in tests), use it directly.
         # Otherwise defer engine + table creation to the first call that
         # actually needs the database (_ensure_session).  This avoids
@@ -226,11 +227,13 @@ class AuditService:
         is unnecessary for the audit service.
         """
         if self._session is None:
-            url = self._database_url or self._settings.database_url
-            engine = create_engine(url, echo=False)
-            Base.metadata.create_all(engine, tables=[AuditLogModel.__table__])
-            factory = sessionmaker(bind=engine)
-            self._session = factory()
+            with self._session_lock:
+                if self._session is None:
+                    url = self._database_url or self._settings.database_url
+                    engine = create_engine(url, echo=False)
+                    Base.metadata.create_all(engine, tables=[AuditLogModel.__table__])
+                    factory = sessionmaker(bind=engine)
+                    self._session = factory()
         return self._session
 
     # ── Background writer loop ───────────────────────────────────
@@ -500,7 +503,13 @@ class AuditService:
 
     @staticmethod
     def _row_to_entry(row: AuditLogModel) -> AuditLogEntry:
-        """Convert a SQLAlchemy model row to a domain data class."""
+        """Convert a SQLAlchemy model row to a domain data class.
+
+        Note: The ``# type: ignore[arg-type]`` suppressions below are
+        pre-existing and tracked for removal in issue #10854.  They arise
+        because ``AuditLogModel`` uses legacy SQLAlchemy column declarations
+        that Pyright cannot resolve to concrete Python types.
+        """
         try:
             details = json.loads(row.details) if row.details else {}  # type: ignore[arg-type]
         except (json.JSONDecodeError, TypeError):