fix: /api/diagnostics 500 « dictionary changed size during iteration » — snapshot des dicts avant itération BUG-079

backend/main.py

@@ -4231,7 +4231,9 @@ async def api_diagnostics(current_user=Depends(require_admin)):
     vault_stats = {}
     total_files = 0
     total_tags = 0
-    for vname, vdata in index.items():
+    # Snapshot both dicts first: the indexer mutates them from background
+    # threads, and iterating a live dict raises "dictionary changed size".
+    for vname, vdata in list(index.items()):
         file_count = len(vdata.get("files", []))
         tag_count = len(vdata.get("tags", {}))
         vault_stats[vname] = {"file_count": file_count, "tag_count": tag_count}
@@ -4239,7 +4241,8 @@ async def api_diagnostics(current_user=Depends(require_admin)):
         total_tags += tag_count
 
     # Memory estimate for inverted index
-    word_index_entries = sum(len(docs) for docs in inv.word_index.values())
+    word_index = inv.word_index.copy()
+    word_index_entries = sum(len(docs) for docs in word_index.values())
     mem_estimate_mb = round(
         (sys.getsizeof(inv.word_index) + word_index_entries * 80
          + len(inv.doc_info) * 200
@@ -4253,7 +4256,7 @@ async def api_diagnostics(current_user=Depends(require_admin)):
             "vaults": vault_stats,
         },
         "inverted_index": {
-            "unique_tokens": len(inv.word_index),
+            "unique_tokens": len(word_index),
             "total_postings": word_index_entries,
             "documents": inv.doc_count,
             "sorted_tokens": len(inv._sorted_tokens),