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#4896 : Fix deadlock in MCPTool.message_handler when server sends tool/prompt… #4898

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manjunathshiva wants to merge 2 commits into from
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#4896 : Fix deadlock in MCPTool.message_handler when server sends tool/prompt… #4898

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6f1195e
Fix deadlock in MCPTool.message_handler when server sends tool/prompt…
Mar 25, 2026
6125b5c
Merge branch 'main' into fix/mcp-message-handler-deadlock
manjunathshiva Mar 25, 2026
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9 changes: 7 additions & 2 deletions python/packages/core/agent_framework/_mcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -804,9 +804,14 @@ async def message_handler(
if isinstance(message, types.ServerNotification):
match message.root.method:
case "notifications/tools/list_changed":
await self.load_tools()
# Only log here. Calling load_tools() — even as a background task —
# causes a deadlock: load_tools() → _ensure_connected() → send_ping(),
# but the session cannot process the ping while an in-flight call_tool
# request is waiting for its response. Tools will be up-to-date on the
# next explicit load_tools() or connect(reset=True) call.
logger.debug("Tools list changed notification received; reload on next connect.")
case "notifications/prompts/list_changed":
await self.load_prompts()
logger.debug("Prompts list changed notification received; reload on next connect.")
case _:
logger.debug("Unhandled notification: %s", message.root.method)

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