fix: improve error handling for AI responding state clearance in chat streaming

surfsense_backend/app/tasks/chat/stream_new_chat.py

@@ -15,6 +15,8 @@ from dataclasses import dataclass
 from typing import Any
 from uuid import UUID
 
+import logging
+
 from langchain_core.messages import HumanMessage
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.future import select
@@ -28,7 +30,7 @@ from app.agents.new_chat.llm_config import (
     load_agent_config,
     load_llm_config_from_yaml,
 )
-from app.db import ChatVisibility, Document, Report, SurfsenseDocsDocument
+from app.db import ChatVisibility, Document, Report, SurfsenseDocsDocument, async_session_maker
 from app.prompts import TITLE_GENERATION_PROMPT_TEMPLATE
 from app.services.chat_session_state_service import (
     clear_ai_responding,
@@ -1276,8 +1278,21 @@ async def stream_new_chat(
         yield streaming_service.format_done()
 
     finally:
-        # Clear AI responding state for live collaboration
-        await clear_ai_responding(session, chat_id)
+        # Clear AI responding state for live collaboration.
+        # The original session may be broken (client disconnect / CancelledError
+        # can corrupt the underlying DB connection), so we try a rollback first
+        # and fall back to a fresh session if the original is unusable.
+        try:
+            await session.rollback()
+            await clear_ai_responding(session, chat_id)
+        except Exception:
+            try:
+                async with async_session_maker() as fresh_session:
+                    await clear_ai_responding(fresh_session, chat_id)
+            except Exception:
+                logging.getLogger(__name__).warning(
+                    "Failed to clear AI responding state for thread %s", chat_id
+                )
 
 
 async def stream_resume_chat(
@@ -1397,4 +1412,14 @@ async def stream_resume_chat(
         yield streaming_service.format_done()
 
     finally:
-        await clear_ai_responding(session, chat_id)
+        try:
+            await session.rollback()
+            await clear_ai_responding(session, chat_id)
+        except Exception:
+            try:
+                async with async_session_maker() as fresh_session:
+                    await clear_ai_responding(fresh_session, chat_id)
+            except Exception:
+                logging.getLogger(__name__).warning(
+                    "Failed to clear AI responding state for thread %s", chat_id
+                )