fix: don't overwrite the parent session when creating a child Client

crates/matrix-sdk/src/authentication.rs

@@ -80,6 +80,15 @@ impl AuthSession {
         }
     }
 
+    /// Take the matrix user information of this session.
+    pub fn into_meta(self) -> SessionMeta {
+        match self {
+            AuthSession::Matrix(session) => session.meta,
+            #[cfg(feature = "experimental-oidc")]
+            AuthSession::Oidc(session) => session.user.meta,
+        }
+    }
+
     /// Get the access token of this session.
     pub fn access_token(&self) -> &str {
         match self {

crates/matrix-sdk/src/client/mod.rs

@@ -1905,9 +1905,15 @@ impl Client {
             )),
         };
 
-        // Copy the parent's session into the child.
+        // Copy the parent's session meta into the child. This initializes the in-memory
+        // state store of the child client with `SessionMeta`, and regenerates
+        // the `OlmMachine` if needs be.
+        //
+        // Note: we don't need to do a full `restore_session`, because this would
+        // overwrite the session information shared with the parent too, and it
+        // must be initialized at most once.
         if let Some(session) = self.session() {
-            client.restore_session(session).await?;
+            client.base_client().set_session_meta(session.into_meta()).await?;
         }
 
         Ok(client)