diff --git a/src/scripts/repl-init.ts b/src/scripts/repl-init.ts
index 4e14a28..268ac75 100644
--- a/src/scripts/repl-init.ts
+++ b/src/scripts/repl-init.ts
@@ -54,7 +54,7 @@ class Footer extends HTMLElement {
 
 export default Footer;
 
-customElements.define('wcc-footer', Footer);
+customElements.define('x-footer', Footer);
 `;
 
 monaco.editor.defineTheme("custom-theme", {
@@ -72,12 +72,38 @@ const commonSettings = {
   theme: "custom-theme",
 };
 
+// https://gist.github.com/RoboPhred/f767bea5cbc972e04155a625dc11da11
+// Important Bit #1: Typescript must see the 'file' it is editing as having a .tsx extension
+const modelUri = monaco.Uri.file("file.tsx");
+
+// Important Bit #2
+// By default, monaco use the "value" property to create its own model without any extensions, so typescript assumes ".ts"
+// We need to create a custom model using the desired file name (uri). See the last arg.
+const codeModel = monaco.editor.createModel(
+  inputContents.trim(),
+  "typescript",
+  modelUri, // Pass the file name to the model here.
+);
+
+// Important Bit #3: Tell typescript to use 'react' for jsx files.
+// TODO: support wc-compiler jsxImportSource
+monaco.typescript.typescriptDefaults.setCompilerOptions({
+  jsx: monaco.typescript.JsxEmit.Preserve,
+});
+
+// TODO: additional diagnostics
+monaco.typescript.typescriptDefaults.setDiagnosticsOptions({
+  noSemanticValidation: false,
+  noSyntaxValidation: false,
+});
+
 document.addEventListener("DOMContentLoaded", () => {
   console.log("Initializing Editor...");
+  const languageSelector = document.getElementById("input-language") as HTMLSelectElement;
 
   const inputEditor = monaco.editor.create(inputContainer, {
     value: inputContents.trim(),
-    language: "javascript",
+    language: "typescript",
     ...commonSettings,
   });
   const outputEditor = monaco.editor.create(outputContainer, {
@@ -86,13 +112,22 @@ document.addEventListener("DOMContentLoaded", () => {
     readOnly: true,
   });
 
+  inputEditor.setModel(codeModel);
+  monaco.editor.setModelLanguage(inputEditor.getModel()!, "typescript");
+
   // listen for changes in the input editor and send the updated code to the worker for compilation
   inputEditor.onDidChangeModelContent(() => {
-    worker.postMessage([inputEditor.getValue()]);
+    worker.postMessage([inputEditor.getValue(), languageSelector.value ?? "javascript"]);
   });
 
   // once the worker sends back the compiled HTML, update the output editor with the result
   worker.onmessage = (result) => {
+    if (result.data.err) {
+      console.error("Error in worker:", result.data.err);
+      outputEditor.setValue(`Error: ${result.data.err.message || result.data.err}`);
+      return;
+    }
+
     outputEditor.setValue(prettify(result.data.output));
   };
 
diff --git a/src/scripts/repl.ts b/src/scripts/repl.ts
index bc61558..d38eddc 100644
--- a/src/scripts/repl.ts
+++ b/src/scripts/repl.ts
@@ -3,9 +3,12 @@ import { renderToString } from "wc-compiler";
 onmessage = async (e) => {
   console.log("Worker: Message received from main script", { e });
   const input = e.data[0];
-  const props = e.data[1] ?? null;
+  const language = e.data[1] ?? "javascript";
+  const props = e.data[2] ?? null;
   const wrappingEntryTag = true;
 
+  console.log({ input, language, props });
+
   let err;
   let output;