diff --git a/cmd/brief/enrich.go b/cmd/brief/enrich.go
index cdb13c2..0d6c000 100644
--- a/cmd/brief/enrich.go
+++ b/cmd/brief/enrich.go
@@ -30,7 +30,7 @@ func cmdEnrich(args []string) {
 	keep := fs.Bool("keep", false, "Keep downloaded remote source")
 	depth := fs.Int("depth", -1, "Git clone depth (0 = full clone, default shallow)")
 	dir := fs.String("dir", "", "Directory to clone remote source into")
-	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (default 4)")
+	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (0 = unlimited)")
 	skip := fs.String("skip", "", "Additional directories to skip, comma-separated")
 	_ = fs.Parse(args)
 
diff --git a/cmd/brief/main.go b/cmd/brief/main.go
index d564168..7efe2c4 100644
--- a/cmd/brief/main.go
+++ b/cmd/brief/main.go
@@ -70,7 +70,7 @@ func cmdScan(args []string) {
 	keep := fs.Bool("keep", false, "Keep downloaded remote source")
 	depth := fs.Int("depth", -1, "Git clone depth (0 = full clone, default shallow)")
 	dir := fs.String("dir", "", "Directory to clone remote source into")
-	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (default 4)")
+	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (0 = unlimited)")
 	skip := fs.String("skip", "", "Additional directories to skip, comma-separated")
 	tracked := fs.Bool("tracked", false, "Only consider files tracked by git")
 	version := fs.Bool("version", false, "Print version and exit")
diff --git a/cmd/brief/threat.go b/cmd/brief/threat.go
index f2189ca..1dbe839 100644
--- a/cmd/brief/threat.go
+++ b/cmd/brief/threat.go
@@ -30,7 +30,7 @@ func runDetection(name string, args []string) (*detect.Engine, *brief.Report, ou
 	jsonFlag := fs.Bool("json", false, "Force JSON output")
 	humanFlag := fs.Bool("human", false, "Force human-readable output")
 	markdownFlag := fs.Bool("markdown", false, "Force markdown output")
-	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (default 4)")
+	scanDepth := fs.Int("scan-depth", 0, "Max directory depth for language detection (0 = unlimited)")
 	skip := fs.String("skip", "", "Additional directories to skip, comma-separated")
 	_ = fs.Parse(args)
 
diff --git a/detect/detect.go b/detect/detect.go
index c781499..f3a3d4c 100644
--- a/detect/detect.go
+++ b/detect/detect.go
@@ -28,7 +28,7 @@ import (
 )
 
 const (
-	defaultScanDepth = 4      // max directory depth for language detection
+	extScanFileLimit = 10000  // max files to visit when collecting extensions
 	microsPerMS      = 1000.0 // microseconds per millisecond
 	globSplitParts   = 2      // expected parts when splitting "**/" patterns
 
@@ -41,7 +41,7 @@ const (
 type Engine struct {
 	KB           *kb.KnowledgeBase
 	Root         string
-	ScanDepth    int      // max directory depth for recursive detection (0 = default 4)
+	ScanDepth    int      // optional max directory depth for recursive detection (0 = unlimited)
 	SkipDirs     []string // additional directories to skip during walks
 	TrackedOnly  bool     // only consider files tracked by git
 	filesChecked int
@@ -109,6 +109,7 @@ var skipDirs = map[string]bool{
 	"third_party":  true,
 	"thirdparty":   true,
 	"external":     true,
+	"testdata":     true,
 	"tmp":          true,
 	"temp":         true,
 	"cache":        true,
@@ -564,35 +565,34 @@ func (e *Engine) recursiveGlob(pattern string) bool {
 	return found
 }
 
-// loadFileExts walks the project to a bounded depth to collect file extensions.
-// Cached for the lifetime of the engine. Default depth of 4 covers most layouts
-// (src/main/java/*.java, lib/something/*.rb).
+// loadFileExts walks the project to collect file extension counts. Cached for
+// the lifetime of the engine. The walk is bounded by extScanFileLimit rather
+// than directory depth so that deep source layouts such as
+// app/src/main/java/<package>/ are reached; skipDirs already prunes the
+// expensive vendor/build directories.
 // Uses WalkDir instead of Walk to avoid following symlinks into directories.
 func (e *Engine) loadFileExts() {
 	if e.fileExts != nil {
 		return
 	}
 	e.fileExts = make(map[string]int)
-	maxDepth := e.ScanDepth
-	if maxDepth == 0 {
-		maxDepth = defaultScanDepth
-	}
 	rootLen := len(e.Root)
+	seen := 0
+	errDone := errors.New("done")
 	_ = filepath.WalkDir(e.Root, func(path string, d os.DirEntry, err error) error {
 		if err != nil {
 			return nil
 		}
+		rel := strings.TrimPrefix(path[rootLen:], string(filepath.Separator))
 		if d.IsDir() {
 			name := d.Name()
 			if name != "." && e.shouldSkipDir(name) {
 				return filepath.SkipDir
 			}
-			rel := path[rootLen:]
-			depth := strings.Count(rel, string(filepath.Separator))
-			if depth > maxDepth {
+			if e.ScanDepth > 0 && strings.Count(rel, string(filepath.Separator))+1 > e.ScanDepth {
 				return filepath.SkipDir
 			}
-			if !e.isTracked(strings.TrimPrefix(rel, string(filepath.Separator))) {
+			if !e.isTracked(rel) {
 				return filepath.SkipDir
 			}
 			return nil
@@ -600,13 +600,17 @@ func (e *Engine) loadFileExts() {
 		if d.Type()&os.ModeSymlink != 0 {
 			return nil
 		}
-		if !e.isTracked(strings.TrimPrefix(path[rootLen:], string(filepath.Separator))) {
+		if !e.isTracked(rel) {
 			return nil
 		}
 		ext := filepath.Ext(d.Name())
 		if ext != "" {
 			e.fileExts[ext]++
 		}
+		seen++
+		if seen >= extScanFileLimit {
+			return errDone
+		}
 		return nil
 	})
 }
diff --git a/detect/detect_test.go b/detect/detect_test.go
index caf5a18..76546eb 100644
--- a/detect/detect_test.go
+++ b/detect/detect_test.go
@@ -609,6 +609,59 @@ func TestPythonProject(t *testing.T) {
 	}
 }
 
+func TestGradleJavaKotlinDSL(t *testing.T) {
+	// Regression for #84: a Java project that uses the Kotlin DSL for its
+	// Gradle build scripts must be reported as Java, not Kotlin.
+	r := runOn(t, "../testdata/gradle-java-kotlin-dsl")
+
+	if len(r.Languages) != 1 || r.Languages[0].Name != "Java" {
+		t.Fatalf("expected only Java language, got %v", languageNames(r))
+	}
+	if !slices.Contains(packageManagerNames(r), "Gradle") {
+		t.Errorf("expected Gradle package manager, got %v", packageManagerNames(r))
+	}
+}
+
+func TestGradleJavaGroovyDSL(t *testing.T) {
+	// Regression for #84: with build.gradle in app/ and source under
+	// app/src/main/java/<pkg>/, both Java and Gradle must be detected.
+	r := runOn(t, "../testdata/gradle-java-groovy-dsl")
+
+	if len(r.Languages) == 0 || r.Languages[0].Name != "Java" {
+		t.Fatalf("expected Java language, got %v", languageNames(r))
+	}
+	for _, l := range r.Languages {
+		if l.Name == "Groovy" {
+			t.Errorf("did not expect Groovy language for build script only, got %v", languageNames(r))
+		}
+	}
+	if !slices.Contains(packageManagerNames(r), "Gradle") {
+		t.Errorf("expected Gradle package manager, got %v", packageManagerNames(r))
+	}
+}
+
+func TestScanDepthOverride(t *testing.T) {
+	engine := New(loadKB(t), "../testdata/gradle-java-groovy-dsl")
+	engine.ScanDepth = 2
+	r, err := engine.Run()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	for _, l := range r.Languages {
+		if l.Name == "Java" {
+			t.Errorf("expected ScanDepth=2 to miss app/src/main/java/..., got %v", languageNames(r))
+		}
+	}
+}
+
+func languageNames(r *brief.Report) []string {
+	names := make([]string, 0, len(r.Languages))
+	for _, l := range r.Languages {
+		names = append(names, l.Name)
+	}
+	return names
+}
+
 func writeProjectFile(t *testing.T, dir, path, content string) {
 	t.Helper()
 	full := filepath.Join(dir, path)
diff --git a/knowledge/java/language.toml b/knowledge/java/language.toml
index 7db4644..396f9eb 100644
--- a/knowledge/java/language.toml
+++ b/knowledge/java/language.toml
@@ -6,7 +6,7 @@ docs = "https://docs.oracle.com/en/java/"
 description = "General-purpose, class-based, object-oriented programming language"
 
 [detect]
-files = ["pom.xml", "build.gradle", "build.gradle.kts", "*.java", "**/*.java"]
+files = ["pom.xml", "*.java", "**/*.java"]
 ecosystems = ["java"]
 
 [taxonomy]
diff --git a/knowledge/kotlin/language.toml b/knowledge/kotlin/language.toml
index 49823bb..636f798 100644
--- a/knowledge/kotlin/language.toml
+++ b/knowledge/kotlin/language.toml
@@ -7,7 +7,7 @@ repo = "https://github.com/JetBrains/kotlin"
 description = "Modern, concise programming language for the JVM"
 
 [detect]
-files = ["*.kt", "**/*.kt", "*.kts", "build.gradle.kts"]
+files = ["*.kt", "**/*.kt"]
 ecosystems = ["kotlin"]
 
 [taxonomy]
diff --git a/testdata/gradle-java-groovy-dsl/app/build.gradle b/testdata/gradle-java-groovy-dsl/app/build.gradle
new file mode 100644
index 0000000..e611be9
--- /dev/null
+++ b/testdata/gradle-java-groovy-dsl/app/build.gradle
@@ -0,0 +1,7 @@
+plugins {
+    id 'application'
+}
+
+application {
+    mainClass = 'org.example.App'
+}
diff --git a/testdata/gradle-java-groovy-dsl/app/src/main/java/org/example/App.java b/testdata/gradle-java-groovy-dsl/app/src/main/java/org/example/App.java
new file mode 100644
index 0000000..1232146
--- /dev/null
+++ b/testdata/gradle-java-groovy-dsl/app/src/main/java/org/example/App.java
@@ -0,0 +1,7 @@
+package org.example;
+
+public class App {
+    public static void main(String[] args) {
+        System.out.println("hello");
+    }
+}
diff --git a/testdata/gradle-java-groovy-dsl/settings.gradle b/testdata/gradle-java-groovy-dsl/settings.gradle
new file mode 100644
index 0000000..8cb2fb9
--- /dev/null
+++ b/testdata/gradle-java-groovy-dsl/settings.gradle
@@ -0,0 +1,2 @@
+rootProject.name = 'test-gradle'
+include('app')
diff --git a/testdata/gradle-java-kotlin-dsl/app/build.gradle.kts b/testdata/gradle-java-kotlin-dsl/app/build.gradle.kts
new file mode 100644
index 0000000..c52ccb3
--- /dev/null
+++ b/testdata/gradle-java-kotlin-dsl/app/build.gradle.kts
@@ -0,0 +1,7 @@
+plugins {
+    application
+}
+
+application {
+    mainClass = "org.example.App"
+}
diff --git a/testdata/gradle-java-kotlin-dsl/app/src/main/java/org/example/App.java b/testdata/gradle-java-kotlin-dsl/app/src/main/java/org/example/App.java
new file mode 100644
index 0000000..1232146
--- /dev/null
+++ b/testdata/gradle-java-kotlin-dsl/app/src/main/java/org/example/App.java
@@ -0,0 +1,7 @@
+package org.example;
+
+public class App {
+    public static void main(String[] args) {
+        System.out.println("hello");
+    }
+}
diff --git a/testdata/gradle-java-kotlin-dsl/settings.gradle.kts b/testdata/gradle-java-kotlin-dsl/settings.gradle.kts
new file mode 100644
index 0000000..27ee486
--- /dev/null
+++ b/testdata/gradle-java-kotlin-dsl/settings.gradle.kts
@@ -0,0 +1,2 @@
+rootProject.name = "test-gradle"
+include("app")