diff --git a/graphify/extract.py b/graphify/extract.py
index a4ac6cbbd..01b69fc5c 100644
--- a/graphify/extract.py
+++ b/graphify/extract.py
@@ -1051,9 +1051,10 @@ def extract_python(path: Path) -> dict:
 
 def extract_js(path: Path) -> dict:
     """Extract classes, functions, arrow functions, and imports from a .js/.ts/.tsx/.mts/.cts file."""
-    if path.suffix == ".tsx":
+    suffix = path.suffix.lower()
+    if suffix == ".tsx":
         config = _TSX_CONFIG
-    elif path.suffix in (".ts", ".mts", ".cts"):
+    elif suffix in (".ts", ".mts", ".cts"):
         config = _TS_CONFIG
     else:
         config = _JS_CONFIG
diff --git a/tests/test_typescript_module_extensions.py b/tests/test_typescript_module_extensions.py
index 41091a552..33c8493d2 100644
--- a/tests/test_typescript_module_extensions.py
+++ b/tests/test_typescript_module_extensions.py
@@ -78,6 +78,13 @@ def test_cts_uses_the_typescript_grammar(tmp_path):
     }
 
 
+def test_uppercase_typescript_extensions_use_typescript_grammar(tmp_path):
+    for ext in (".TS", ".TSX", ".MTS", ".CTS"):
+        labels = _labels(_extract(tmp_path, ext))
+        assert any("Mode" in label for label in labels), f"TS `type` alias missing for {ext}"
+        assert any("Options" in label for label in labels), f"TS `interface` missing for {ext}"
+
+
 def test_mts_cts_route_to_extract_js():
     from graphify.extract import _DISPATCH, extract_js
     assert _DISPATCH.get(".mts") is extract_js