debug: add ctx-diag logging to trace session hydration and message assembly

core/session_manager.py

@@ -383,6 +383,10 @@ class SessionManager:
             cached = self.sessions[session_id]
             # Lazy hydrate: metadata-only entries get their messages on first read.
             if not cached.history:
+                logger.info(
+                    "[ctx-diag] lazy hydrating session=%s (history empty, msg_count=%d)",
+                    session_id, getattr(cached, "message_count", 0),
+                )
                 self._load_session_from_db(session_id)
 
         # Keep model/endpoint metadata fresh. Endpoint deletion can clear the

routes/chat_helpers.py

@@ -751,7 +751,13 @@ async def build_chat_context(
         sess.model = norm
 
     # Build messages
-    messages = preface + sess.get_context_messages()
+    _ctx_msgs = sess.get_context_messages()
+    logger.info(
+        "[ctx-diag] session=%s history_len=%d ctx_messages=%d preface=%d roles=%s",
+        session_id, len(sess.history), len(_ctx_msgs), len(preface),
+        [m.get("role") for m in _ctx_msgs[-5:]] if _ctx_msgs else [],
+    )
+    messages = preface + _ctx_msgs
 
     # Current date/time — injected as a standalone *user*-role context message
     # placed immediately before the latest user turn, NOT folded into the