diff --git a/build-logic/build.gradle.kts b/build-logic/build.gradle.kts
index c390a1741..10a3b61bb 100644
--- a/build-logic/build.gradle.kts
+++ b/build-logic/build.gradle.kts
@@ -5,4 +5,10 @@ plugins {
 
 repositories { gradlePluginPortal() }
 
+// Pin the precompiled-script-plugin compilation to Java 17 so the generated plugin classes load on
+// the daemon regardless of which JDK it runs on. Without this, kotlin-dsl targets whatever JDK the
+// daemon happens to use (e.g. 21/25), emitting newer bytecode that a Java 17 daemon cannot load
+// (UnsupportedClassVersionError).
+kotlin { jvmToolchain(17) }
+
 spotless { kotlinGradle { ktfmt().googleStyle() } }
diff --git a/build-logic/gradle.properties b/build-logic/gradle.properties
new file mode 100644
index 000000000..5a91892ce
--- /dev/null
+++ b/build-logic/gradle.properties
@@ -0,0 +1,5 @@
+# build-logic is an included build, so it does NOT inherit the root gradle.properties; its Kotlin
+# compile daemon (which builds the precompiled script plugins) must be sized here. Without this the
+# cold compile fails with an OOM / "internal compiler error" and falls back to a slow no-daemon
+# compile. Raise -Xmx further if you still see those failures on a cold build.
+kotlin.daemon.jvmargs=-Xmx2g
diff --git a/build.gradle.kts b/build.gradle.kts
index 09c233805..26b9fa396 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -62,9 +62,13 @@ allprojects {
       kotlinGradle { ktfmt("0.61").googleStyle() }
       java {
         target("src/*/java/**/*.java")
-        // since kfmt also brings in google-java-format we need to sync versions
-        // https://github.com/facebook/ktfmt/blob/v0.61/gradle/libs.versions.toml#L7
-        googleJavaFormat("1.23.0")
+        // google-java-format 1.28.0: earlier versions (e.g. 1.23.0, which ktfmt 0.61 bundles) call
+        // com.sun.tools.javac internals that changed in recent JDKs, so Spotless throws
+        // NoSuchMethodError/NoClassDefFoundError when the daemon runs on a newer JDK (e.g. 25).
+        // 1.28.0 is the newest release that still runs on JDK 17 (1.29.0+ requires JDK 21+),
+        // matching the daemon/CI toolchain. This Java step has its own formatter classpath,
+        // independent of ktfmt's bundled copy (used only for Kotlin), so they need not match.
+        googleJavaFormat("1.28.0")
         removeUnusedImports()
         trimTrailingWhitespace()
         forbidWildcardImports()