diff --git a/gradle.properties b/gradle.properties
index 0f7b4eb87a..887bc1f10c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -26,4 +26,10 @@ org.gradle.parallel=true
 # Run the daemon and its workers at low OS priority so full builds don't starve
 # the foreground UI on developer laptops. Negligible on dedicated CI runners.
 org.gradle.priority=low
+# Studio passes -Dorg.gradle.tooling.parallel.ignore-legacy-default=true on every sync,
+# which strips org.gradle.parallel's implication for Tooling API model building — so IDE
+# sync needs this explicit opt-in. Inert while org.gradle.isolated-projects=true (that
+# path parallelises model building on its own) and never read by a CI build; kept so sync
+# stays parallel if Isolated Projects is ever off.
+org.gradle.tooling.parallel=true
 org.gradle.welcome=never