diff --git a/buildSrc/src/main/kotlin/dagger/gradle/build/KotlinJvmConventionPlugin.kt b/buildSrc/src/main/kotlin/dagger/gradle/build/KotlinJvmConventionPlugin.kt
index e5dd52df9df..cf5ee41651f 100644
--- a/buildSrc/src/main/kotlin/dagger/gradle/build/KotlinJvmConventionPlugin.kt
+++ b/buildSrc/src/main/kotlin/dagger/gradle/build/KotlinJvmConventionPlugin.kt
@@ -16,8 +16,10 @@
 
 package dagger.gradle.build
 
+import org.gradle.api.JavaVersion
 import org.gradle.api.Plugin
 import org.gradle.api.Project
+import org.gradle.api.plugins.JavaPluginExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinJvmProjectExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
@@ -30,7 +32,6 @@ class KotlinJvmConventionPlugin : Plugin<Project> {
 
         project.plugins.withId(project.getPluginIdByName("kotlinJvm")) {
             val kotlinProject = project.extensions.getByName("kotlin") as KotlinJvmProjectExtension
-            kotlinProject.explicitApi()
             kotlinProject.jvmToolchain {
                 languageVersion.set(JavaLanguageVersion.of(project.getVersionByName("jdk")))
             }
@@ -39,6 +40,10 @@ class KotlinJvmConventionPlugin : Plugin<Project> {
                 apiVersion.set(KotlinVersion.fromVersion(project.getVersionByName("kotlinTarget")))
                 jvmTarget.set(JvmTarget.fromTarget(project.getVersionByName("jvmTarget")))
             }
+
+            val javaProject = project.extensions.getByName("java") as JavaPluginExtension
+            javaProject.sourceCompatibility = JavaVersion.toVersion(project.getVersionByName("jvmTarget"))
+            javaProject.targetCompatibility = JavaVersion.toVersion(project.getVersionByName("jvmTarget"))
         }
     }
 }
\ No newline at end of file
diff --git a/gradle-projects/dagger-runtime/build.gradle.kts b/gradle-projects/dagger-runtime/build.gradle.kts
index fa1bf61c929..9a479901d67 100644
--- a/gradle-projects/dagger-runtime/build.gradle.kts
+++ b/gradle-projects/dagger-runtime/build.gradle.kts
@@ -37,4 +37,8 @@ dependencies {
     testImplementation(libs.junit)
     testImplementation(libs.truth)
     testImplementation(libs.guava.jre)
+}
+
+kotlin {
+    explicitApi()
 }
\ No newline at end of file
diff --git a/gradle-projects/dagger-spi/build.gradle.kts b/gradle-projects/dagger-spi/build.gradle.kts
new file mode 100644
index 00000000000..38fde9b5429
--- /dev/null
+++ b/gradle-projects/dagger-spi/build.gradle.kts
@@ -0,0 +1,32 @@
+import dagger.gradle.build.daggerSources
+
+plugins {
+    alias(libs.plugins.dagger.kotlinJvm)
+    alias(libs.plugins.dagger.publish)
+}
+
+daggerSources {
+    main.setPackages(
+        listOf(
+            "dagger/internal/codegen/extension",
+            "dagger/model",
+            "dagger/spi",
+            "dagger/spi/model",
+        )
+    )
+}
+
+// TODO(danysantiago): Shadow / jarjar: 1. xprocessing, 2. auto-common and 3. kotlin-metadata-jvm
+dependencies {
+    implementation(project(":dagger"))
+
+    implementation(libs.auto.common)
+    implementation(libs.auto.value.annotations)
+    annotationProcessor(libs.auto.value.compiler)
+    implementation(libs.findBugs)
+    implementation(libs.javaPoet)
+    implementation(libs.javax.inject)
+    implementation(libs.guava.failureAccess)
+    implementation(libs.guava.jre)
+    implementation(libs.ksp.api)
+}
\ No newline at end of file
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 57cd6a02e6f..1ba180db4e8 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -1,21 +1,30 @@
 [versions]
+autoValue = "1.9"
 guava = "33.0.0-jre"
 jdk = "18"
 junit = "4.13"
 jvmTarget = "1.8"
 kotlin = "2.0.21"
 kotlinTarget = "1.9"
+ksp = "2.0.21-1.0.28"
 publish = "0.30.0"
 truth = "1.4.0"
 
 [libraries]
+auto-common = { module = "com.google.auto:auto-common", version = "1.2.1" }
+auto-value-annotations = { module = "com.google.auto.value:auto-value-annotations", version.ref = "autoValue" }
+auto-value-compiler = { module = "com.google.auto.value:auto-value", version.ref = "autoValue" }
+findBugs = { module = "com.google.code.findbugs:jsr305", version = "3.0.1" }
 guava-jre = { module = "com.google.guava:guava", version.ref = "guava" }
+guava-failureAccess = { module = "com.google.guava:failureaccess", version = "1.0.1" }
 jakarta-inject = { module = "jakarta.inject:jakarta.inject-api", version = "2.0.1" }
+javaPoet = { module = "com.squareup:javapoet", version = "1.13.0" }
 javax-inject = { module = "javax.inject:javax.inject", version = "1" }
 jspecify = { module = "org.jspecify:jspecify", version = "1.0.0" }
 junit = { module = "junit:junit", version.ref = "junit" }
 kotlin-gradlePlugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 kotlin-stdlib = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }
+ksp-api = { module = "com.google.devtools.ksp:symbol-processing-api", version.ref = "ksp" }
 publishPlugin = { module = "com.vanniktech:gradle-maven-publish-plugin", version.ref = "publish" }
 truth = { module = "com.google.truth:truth", version.ref = "truth" }
 
@@ -24,4 +33,4 @@ binaryCompatibilityValidator = { id = "org.jetbrains.kotlinx.binary-compatibilit
 dagger-kotlinJvm = { id = "dagger.gradle.build.jvm" }
 dagger-publish = { id = "dagger.gradle.build.publish" }
 kotlinJvm = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
-publish = { id = "com.vanniktech.maven.publish", version.ref = "publish" }
\ No newline at end of file
+publish = { id = "com.vanniktech.maven.publish", version.ref = "publish" }
diff --git a/settings.gradle.kts b/settings.gradle.kts
index c9bbf356bbc..d185ed1843d 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -21,3 +21,4 @@ fun includeProject(name: String, path: String) {
 }
 
 includeProject(":dagger", "gradle-projects/dagger-runtime")
+includeProject(":dagger-spi", "gradle-projects/dagger-spi")