diff --git a/build-logic/gradle.properties b/build-logic/gradle.properties
index 7c9329c6a7..fb65f3b3ff 100644
--- a/build-logic/gradle.properties
+++ b/build-logic/gradle.properties
@@ -25,7 +25,9 @@ org.gradle.jvmargs=-Xmx2g -XX:+UseParallelGC -Dfile.encoding=UTF-8
 org.gradle.parallel=true
 org.gradle.caching=true
 org.gradle.configuration-cache=true
-org.gradle.isolated-projects=true
+# Kept in sync with the root gradle.properties -- see its comment for why (wasmJs web target,
+# feat/web-wasmjs-target).
+org.gradle.isolated-projects=false
 org.gradle.configureondemand=false
 
 # Kotlin
diff --git a/gradle.properties b/gradle.properties
index 887bc1f10c..50b0848bd7 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -20,7 +20,14 @@ ksp.project.isolation.enabled=true
 # --- Gradle ---
 org.gradle.caching=true
 org.gradle.configuration-cache=true
-org.gradle.isolated-projects=true
+# Disabled for the wasmJs web target (feat/web-wasmjs-target): registering a second Gradle
+# project's wasmJs() target under Isolated Projects trips a violation inside Kotlin Gradle
+# Plugin's own cross-project IncrementalModuleInfoBuildService -- confirmed via a real build,
+# not fixable per-module, and unrelated to wasmJs's browser()/npm tooling (a separate,
+# also-confirmed IP incompatibility). JetBrains' own docs say JS/Wasm + Isolated Projects isn't
+# supported yet. Re-enable once upstream closes that gap, if reinstating IP's build-speed/IDE-sync
+# benefit outweighs carrying wasmJs as a target by then.
+org.gradle.isolated-projects=false
 org.gradle.jvmargs=-Xmx8g -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:+UseStringDeduplication -XX:ReservedCodeCacheSize=512m -XX:MaxMetaspaceSize=2g -Xss2m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8 -Djava.awt.headless=true -Dapple.awt.UIElement=true
 org.gradle.parallel=true
 # Run the daemon and its workers at low OS priority so full builds don't starve