diff --git a/understand-anything-plugin/packages/core/src/__tests__/language-registry.test.ts b/understand-anything-plugin/packages/core/src/__tests__/language-registry.test.ts
index 7a3c77495..577dedacf 100644
--- a/understand-anything-plugin/packages/core/src/__tests__/language-registry.test.ts
+++ b/understand-anything-plugin/packages/core/src/__tests__/language-registry.test.ts
@@ -2,6 +2,7 @@ import { describe, it, expect } from "vitest";
 import { LanguageRegistry } from "../languages/language-registry.js";
 import { StrictLanguageConfigSchema } from "../languages/types.js";
 import { typescriptConfig } from "../languages/configs/typescript.js";
+import { javascriptConfig } from "../languages/configs/javascript.js";
 import { pythonConfig } from "../languages/configs/python.js";
 
 describe("LanguageRegistry", () => {
@@ -72,6 +73,9 @@ describe("LanguageRegistry", () => {
       expect(registry.getByExtension(".h")?.id).toBe("c");
       expect(registry.getByExtension(".lua")?.id).toBe("lua");
       expect(registry.getByExtension(".js")?.id).toBe("javascript");
+      expect(registry.getByExtension(".mts")?.id).toBe("typescript");
+      expect(registry.getByExtension(".cts")?.id).toBe("typescript");
+      expect(registry.getForFile("src/server.mts")?.id).toBe("typescript");
     });
 
     it("has no duplicate extension mappings across configs", () => {
@@ -93,6 +97,20 @@ describe("LanguageRegistry", () => {
     });
   });
 
+  describe("typescript config test patterns", () => {
+    it("recognizes both .test.tsx and .spec.tsx test files", () => {
+      expect(typescriptConfig.filePatterns.tests).toContain("*.test.tsx");
+      expect(typescriptConfig.filePatterns.tests).toContain("*.spec.tsx");
+    });
+  });
+
+  describe("javascript config test patterns", () => {
+    it("recognizes .jsx test files for parity with the .tsx patterns", () => {
+      expect(javascriptConfig.filePatterns.tests).toContain("*.test.jsx");
+      expect(javascriptConfig.filePatterns.tests).toContain("*.spec.jsx");
+    });
+  });
+
   describe("Non-code language configs", () => {
     it("detects all non-code file types via extension", () => {
       const registry = LanguageRegistry.createDefault();
diff --git a/understand-anything-plugin/packages/core/src/languages/configs/javascript.ts b/understand-anything-plugin/packages/core/src/languages/configs/javascript.ts
index d89cf4997..851253df8 100644
--- a/understand-anything-plugin/packages/core/src/languages/configs/javascript.ts
+++ b/understand-anything-plugin/packages/core/src/languages/configs/javascript.ts
@@ -23,7 +23,7 @@ export const javascriptConfig = {
   filePatterns: {
     entryPoints: ["index.js", "src/index.js", "main.js"],
     barrels: ["index.js"],
-    tests: ["*.test.js", "*.spec.js"],
+    tests: ["*.test.js", "*.spec.js", "*.test.jsx", "*.spec.jsx"],
     config: ["package.json", "jsconfig.json"],
   },
 } satisfies LanguageConfig;
diff --git a/understand-anything-plugin/packages/core/src/languages/configs/typescript.ts b/understand-anything-plugin/packages/core/src/languages/configs/typescript.ts
index 04a884d74..f94246079 100644
--- a/understand-anything-plugin/packages/core/src/languages/configs/typescript.ts
+++ b/understand-anything-plugin/packages/core/src/languages/configs/typescript.ts
@@ -3,7 +3,12 @@ import type { LanguageConfig } from "../types.js";
 export const typescriptConfig = {
   id: "typescript",
   displayName: "TypeScript",
-  extensions: [".ts", ".tsx"],
+  // Declaration files (.d.ts / .d.mts / .d.cts) are intentionally NOT listed
+  // separately: getForFile() resolves by the final extension, so they fall
+  // through to .ts / .mts / .cts and are parsed as ordinary (types-only)
+  // TypeScript. They carry no runtime exports or call edges, so the extractor
+  // simply yields an empty call graph for them — no special gating is applied.
+  extensions: [".ts", ".tsx", ".mts", ".cts"],
   treeSitter: {
     wasmPackage: "tree-sitter-typescript",
     wasmFile: "tree-sitter-typescript.wasm",
@@ -24,7 +29,7 @@ export const typescriptConfig = {
   filePatterns: {
     entryPoints: ["src/index.ts", "src/main.ts", "src/App.tsx", "index.ts"],
     barrels: ["index.ts"],
-    tests: ["*.test.ts", "*.spec.ts", "*.test.tsx"],
+    tests: ["*.test.ts", "*.spec.ts", "*.test.tsx", "*.spec.tsx"],
     config: ["tsconfig.json"],
   },
 } satisfies LanguageConfig;
diff --git a/understand-anything-plugin/packages/core/src/plugins/tree-sitter-plugin.ts b/understand-anything-plugin/packages/core/src/plugins/tree-sitter-plugin.ts
index 65203d255..9c0bc1010 100644
--- a/understand-anything-plugin/packages/core/src/plugins/tree-sitter-plugin.ts
+++ b/understand-anything-plugin/packages/core/src/plugins/tree-sitter-plugin.ts
@@ -111,7 +111,10 @@ export class TreeSitterPlugin implements AnalyzerPlugin {
   private languageKeyFromPath(filePath: string): string | null {
     const ext = extname(filePath).toLowerCase();
 
-    // Special case: .tsx needs its own grammar
+    // Special case: only .tsx needs the dedicated TSX grammar (it carries JSX).
+    // .mts / .cts deliberately fall through to the plain TypeScript grammar via
+    // _extensionToLang — they cannot contain JSX, so do NOT add them to this
+    // branch by analogy with the .mjs-treated-as-JS pattern.
     if (ext === ".tsx") return "tsx";
 
     return this._extensionToLang.get(ext) ?? null;