diff --git a/desloppify/languages/kotlin/__init__.py b/desloppify/languages/kotlin/__init__.py
index cd9e40cd5..3c850a18a 100644
--- a/desloppify/languages/kotlin/__init__.py
+++ b/desloppify/languages/kotlin/__init__.py
@@ -2,6 +2,7 @@
 
 from desloppify.languages._framework.generic_support.core import generic_lang
 from desloppify.languages._framework.treesitter import KOTLIN_SPEC
+from desloppify.languages.kotlin._zones import KOTLIN_ZONE_RULES
 
 generic_lang(
     name="kotlin",
@@ -20,9 +21,11 @@
     depth="shallow",
     detect_markers=["build.gradle.kts", "build.gradle"],
     treesitter_spec=KOTLIN_SPEC,
+    zone_rules=KOTLIN_ZONE_RULES,
 )
 
 __all__ = [
     "generic_lang",
     "KOTLIN_SPEC",
+    "KOTLIN_ZONE_RULES",
 ]
diff --git a/desloppify/languages/kotlin/_zones.py b/desloppify/languages/kotlin/_zones.py
new file mode 100644
index 000000000..ca5559cb3
--- /dev/null
+++ b/desloppify/languages/kotlin/_zones.py
@@ -0,0 +1,44 @@
+"""Zone/path classification rules for Kotlin.
+
+Kotlin projects are laid out by Gradle source sets, not by a top-level ``test/``
+directory. Kotlin Multiplatform in particular names every test source set
+``<target>Test`` — ``src/commonTest/kotlin``, ``src/jvmTest/kotlin``,
+``src/iosTest/kotlin``, ``src/androidUnitTest/kotlin`` — none of which contain the
+``/test/`` path segment the common rules look for. Without these rules every test
+file is scored as production code.
+"""
+
+from __future__ import annotations
+
+from desloppify.engine.policy.zones import COMMON_ZONE_RULES, Zone, ZoneRule
+
+KOTLIN_ZONE_RULES = [
+    # Gradle/KMP test source sets: src/test/, src/androidTest/, src/commonTest/,
+    # src/jvmTest/, src/iosTest/, src/androidUnitTest/, src/nativeTest/, ...
+    # The pattern has no leading "." / trailing "_" so it matches as a path substring.
+    ZoneRule(
+        Zone.TEST,
+        [
+            "/src/test/",
+            "/src/androidTest/",
+            "/src/testFixtures/",
+            "Test/kotlin/",
+            "Test/java/",
+            "Test/resources/",
+        ],
+    ),
+    ZoneRule(Zone.GENERATED, ["/generated/", "/build/generated/"]),
+    ZoneRule(
+        Zone.CONFIG,
+        [
+            "build.gradle.kts",
+            "settings.gradle.kts",
+            "build.gradle",
+            "settings.gradle",
+            "gradle.properties",
+            "gradle/libs.versions.toml",
+        ],
+    ),
+] + COMMON_ZONE_RULES
+
+__all__ = ["KOTLIN_ZONE_RULES"]
diff --git a/desloppify/tests/lang/common/test_kotlin_zones.py b/desloppify/tests/lang/common/test_kotlin_zones.py
new file mode 100644
index 000000000..d0be7d747
--- /dev/null
+++ b/desloppify/tests/lang/common/test_kotlin_zones.py
@@ -0,0 +1,67 @@
+"""Regression tests for Kotlin/Gradle zone classification.
+
+Kotlin projects are organised by Gradle source sets rather than a top-level
+``test/`` directory, so the common rules classify every test file as production.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from desloppify.engine.policy.zones import Zone, classify_file
+from desloppify.languages.kotlin._zones import KOTLIN_ZONE_RULES
+
+
+def _zone(rel_path: str) -> Zone:
+    return classify_file(rel_path, KOTLIN_ZONE_RULES)
+
+
+@pytest.mark.parametrize(
+    "rel_path",
+    [
+        # Kotlin Multiplatform source sets
+        "shared/src/commonTest/kotlin/com/example/FormEngineTest.kt",
+        "sync/src/jvmTest/kotlin/com/example/SubmissionStoreTest.kt",
+        "sync/src/iosTest/kotlin/com/example/DeviceCryptoTest.kt",
+        "composeApp/src/androidUnitTest/kotlin/com/example/RendererTest.kt",
+        "shared/src/nativeTest/kotlin/com/example/ParserTest.kt",
+        # Plain Gradle JVM / Android layouts
+        "app/src/test/java/com/example/HelperTest.kt",
+        "app/src/androidTest/java/com/example/LoginFlowTest.kt",
+        "lib/src/testFixtures/kotlin/com/example/Fixtures.kt",
+    ],
+)
+def test_gradle_test_source_sets_are_test_zone(rel_path):
+    assert _zone(rel_path) == Zone.TEST
+
+
+@pytest.mark.parametrize(
+    "rel_path",
+    [
+        "shared/src/commonMain/kotlin/com/example/FormEngine.kt",
+        "sync/src/jvmMain/kotlin/com/example/SubmissionStore.kt",
+        "composeApp/src/androidMain/kotlin/com/example/Renderer.kt",
+        "composeApp/src/iosMain/kotlin/com/example/MapSeam.ios.kt",
+    ],
+)
+def test_main_source_sets_stay_production(rel_path):
+    assert _zone(rel_path) == Zone.PRODUCTION
+
+
+@pytest.mark.parametrize(
+    "rel_path",
+    [
+        "build.gradle.kts",
+        "settings.gradle.kts",
+        "androidApp/build.gradle.kts",
+        "gradle.properties",
+        "gradle/libs.versions.toml",
+    ],
+)
+def test_gradle_build_files_are_config_zone(rel_path):
+    assert _zone(rel_path) == Zone.CONFIG
+
+
+def test_latest_is_not_mistaken_for_a_test_source_set():
+    """A directory merely ending in 'Test' must still need the source-set suffix."""
+    assert _zone("shared/src/commonMain/kotlin/com/example/LatestKotlinThing.kt") == Zone.PRODUCTION