elkay: lesson.py 506-521

phase/Student_view/lesson.py

@@ -504,17 +504,13 @@ def _render_lesson():
             st.button(label, key=f"jump_{i}", on_click=lambda j=i: st.session_state.update({"topic_idx": j}) or st.rerun())
 
 def _get_topics(level: str, module_id: int) -> List[Tuple[str, str]]:
-    """
-    Build the six-topic plan from metadata titles, try backend for each,
-    and if content is missing, provide a short fallback paragraph.
-    """
     cache_key = (level, module_id)
-    if cache_key in st.session_state.topics_cache:
-        return st.session_state.topics_cache[cache_key]
+    cached = st.session_state.topics_cache.get(cache_key)
+    if isinstance(cached, list) and len(cached) > 0:   # only trust non-empty cache
+        return cached
 
-    plan = _topic_plan(level, module_id)   # six titles max
+    plan = _topic_plan(level, module_id)
     out: List[Tuple[str, str]] = []
-
     for idx in range(len(plan)):
         title, content = _fetch_topic_from_backend(level, module_id, idx)
         if not content: