diff --git a/src/acp/helpers.py b/src/acp/helpers.py
index 701cda7..8830c43 100644
--- a/src/acp/helpers.py
+++ b/src/acp/helpers.py
@@ -20,6 +20,7 @@
     PlanEntryPriority,
     PlanEntryStatus,
     ResourceContentBlock,
+    SessionInfoUpdate,
     SessionNotification,
     TerminalToolCallContent,
     TextContentBlock,
@@ -45,6 +46,7 @@
     | UserMessageChunk
     | ToolCallStart
     | ToolCallProgress
+    | SessionInfoUpdate
 )
 
 ToolCallContentVariant = ContentToolCallContent | FileEditToolCallContent | TerminalToolCallContent