diff --git a/scip-gradle-plugin/src/main/java/org/scip_code/scip_java/gradle/ScipGradlePlugin.java b/scip-gradle-plugin/src/main/java/org/scip_code/scip_java/gradle/ScipGradlePlugin.java
index e4c9845b9..76f0e1674 100644
--- a/scip-gradle-plugin/src/main/java/org/scip_code/scip_java/gradle/ScipGradlePlugin.java
+++ b/scip-gradle-plugin/src/main/java/org/scip_code/scip_java/gradle/ScipGradlePlugin.java
@@ -1,11 +1,14 @@
 package org.scip_code.scip_java.gradle;
 
 import java.io.File;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.HexFormat;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -271,7 +274,8 @@ private static Set<String> addJavacPlugin(Project project, Object javacPluginDep
   }
 
   /**
-   * Dumps the sources and classpath of a Kotlin compile task to {@code kotlin-configs/<task>.txt}.
+   * Dumps the sources and classpath of a Kotlin compile task to {@code
+   * kotlin-configs/<task>-<hash>.txt}.
    */
   private static void writeKotlinConfig(Task task, String sourceRoot, String targetRoot) {
     try {
@@ -317,7 +321,14 @@ private static void writeKotlinConfig(Task task, String sourceRoot, String targe
 
       Path configDir = Paths.get(targetRoot, "kotlin-configs");
       Files.createDirectories(configDir);
-      String fileName = task.getPath().replaceAll("[^A-Za-z0-9]", "-") + ".txt";
+      // Task paths are only unique within one build, and every build of a
+      // composite (included builds, buildSrc) writes here, so the build's
+      // root directory is part of the identity. Hashing, unlike sanitizing,
+      // keeps ":a-b:x" and ":a:b:x" apart; NUL cannot occur in a path.
+      String identity = task.getProject().getRootDir().getAbsolutePath() + "\0" + task.getPath();
+      byte[] hash =
+          MessageDigest.getInstance("SHA-256").digest(identity.getBytes(StandardCharsets.UTF_8));
+      String fileName = task.getName() + "-" + HexFormat.of().formatHex(hash, 0, 8) + ".txt";
       Files.write(configDir.resolve(fileName), lines);
     } catch (Exception exc) {
       throw new RuntimeException(
diff --git a/scip-java/src/test/kotlin/tests/GradleBuildToolTest.kt b/scip-java/src/test/kotlin/tests/GradleBuildToolTest.kt
index cdf0f6bbf..43473973c 100644
--- a/scip-java/src/test/kotlin/tests/GradleBuildToolTest.kt
+++ b/scip-java/src/test/kotlin/tests/GradleBuildToolTest.kt
@@ -204,6 +204,11 @@ class GradleBuildToolTest : BuildToolHarness() {
                 runs = 2,
             )
         )
+        // Regression test: Kotlin compile tasks whose paths are equal in different
+        // builds of a composite (`:compileKotlin` in the root and included build),
+        // or equal after sanitizing (`:a-b` and `:a:b`), overwrote each other's
+        // configs, so only one of their sources was indexed.
+        add(checkGradleBuild("kotlin-composite", "gradle/kotlin-composite", expectedScipFiles = 4))
         add(
             checkGradleBuild(
                 "implementation-deps",
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/build.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/build.gradle
new file mode 100644
index 000000000..4f01298ec
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/build.gradle
@@ -0,0 +1,3 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm'
+}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/src/main/kotlin/ab/Dashed.kt b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/src/main/kotlin/ab/Dashed.kt
new file mode 100644
index 000000000..6813cdb68
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a-b/src/main/kotlin/ab/Dashed.kt
@@ -0,0 +1,2 @@
+package ab
+object Dashed {}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/build.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/build.gradle
new file mode 100644
index 000000000..4f01298ec
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/build.gradle
@@ -0,0 +1,3 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm'
+}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/src/main/kotlin/ab/Nested.kt b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/src/main/kotlin/ab/Nested.kt
new file mode 100644
index 000000000..b733bdce6
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/a/b/src/main/kotlin/ab/Nested.kt
@@ -0,0 +1,2 @@
+package ab
+object Nested {}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/build.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/build.gradle
new file mode 100644
index 000000000..d5d67742f
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/build.gradle
@@ -0,0 +1,12 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm' version '2.4.0'
+}
+allprojects {
+    repositories {
+        mavenCentral()
+    }
+}
+// `scipCompileAll` only runs tasks of the root build.
+tasks.named('compileKotlin') {
+    dependsOn gradle.includedBuild('included').task(':compileKotlin')
+}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/build.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/build.gradle
new file mode 100644
index 000000000..c1066d9c5
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/build.gradle
@@ -0,0 +1,6 @@
+plugins {
+    id 'org.jetbrains.kotlin.jvm' version '2.4.0'
+}
+repositories {
+    mavenCentral()
+}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/settings.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/settings.gradle
new file mode 100644
index 000000000..6bb0b29ca
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/settings.gradle
@@ -0,0 +1 @@
+rootProject.name = 'included'
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/src/main/kotlin/included/Included.kt b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/src/main/kotlin/included/Included.kt
new file mode 100644
index 000000000..2a8247a72
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/included/src/main/kotlin/included/Included.kt
@@ -0,0 +1,2 @@
+package included
+object Included {}
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/settings.gradle b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/settings.gradle
new file mode 100644
index 000000000..179d8caf4
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/settings.gradle
@@ -0,0 +1,5 @@
+rootProject.name = 'kotlin-composite'
+// `:a-b` and `:a:b` both sanitize to `-a-b-compileKotlin`.
+include 'a-b', 'a:b'
+// Also has a `:compileKotlin` task.
+includeBuild 'included'
diff --git a/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/src/main/kotlin/root/Root.kt b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/src/main/kotlin/root/Root.kt
new file mode 100644
index 000000000..c3da0fd1f
--- /dev/null
+++ b/scip-java/src/test/resources/fixtures/gradle/kotlin-composite/src/main/kotlin/root/Root.kt
@@ -0,0 +1,2 @@
+package root
+object Root {}