fix: reset stopped runs to a pristine terminal

manifest.json

@@ -3,7 +3,7 @@
   "name": "browser.cpp",
   "short_name": "browser.cpp",
   "description": "In-browser C++20 IDE powered by Monaco Editor and WASM Clang",
-  "version": "0.4.8",
+  "version": "0.4.9",
   "minimum_chrome_version": "105",
   "icons": {
     "16": "icons/icon16.png",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "browser.cpp",
-  "version": "0.4.8",
+  "version": "0.4.9",
   "description": "In-browser C++20 IDE with WASM Clang toolchain",
   "private": true,
   "scripts": {

scripts/e2e-terminal-stop.test.mjs

@@ -149,20 +149,55 @@ test('e2e: prompt restoration follows newline-less program output on a new line'
   assert.match(ctx.writes.join(''), /program output\r\n.*browser\.cpp.*:~\$ /);
 });
 
-test('e2e: Ctrl+C while running stops the program once and restores the prompt', async () => {
+test('e2e: Ctrl+C while running resets to one pristine prompt', async () => {
   const ctx = setupTerminalHarness();
 
   assert.equal(await startRun(), true);
   onRunStart({ stdinMode: 'interactive' });
-  __handleTerminalKeyForTesting('', ctrlCEvent());
+  writeStdout('runaway output');
+  const writesBeforeStop = ctx.writes.length;
   __handleTerminalKeyForTesting('', ctrlCEvent());
 
   assert.equal(ctx.runCalls.length, 1);
   assert.deepEqual(ctx.stopCalls, ['stop']);
   assert.deepEqual(ctx.runStateChanges, [true, false]);
   assert.equal(__getTerminalStateForTesting().running, false);
-  assert.ok(ctx.writes.join('').includes('^C'));
-  assert.ok(ctx.writes.join('').includes('Process interrupted.'));
+  const resetWrites = ctx.writes.slice(writesBeforeStop).join('');
+  assert.ok(resetWrites.includes('browser.cpp'));
+  assert.equal(resetWrites.match(/browser\.cpp/g)?.length, 1);
+  assert.ok(!resetWrites.includes('^C'));
+  assert.ok(!resetWrites.includes('Process interrupted.'));
+  assert.equal(ctx.clearCalls.length, 1);
+});
+
+test('e2e: STOP discards stdout queued after a stopped run', async () => {
+  const ctx = setupTerminalHarness();
+
+  showInitialPrompt();
+  assert.equal(await startRun(), true);
+  onRunStart({ stdinMode: 'interactive' });
+  writeStdout('runaway output');
+  assert.equal(stopRun(), true);
+  const writesAfterStop = ctx.writes.length;
+
+  writeStdout('late output');
+
+  assert.equal(ctx.writes.length, writesAfterStop);
+  assert.ok(!ctx.writes.join('').includes('Process interrupted.'));
+});
+
+test('e2e: STOP ignores a late nonzero run result', async () => {
+  const ctx = setupTerminalHarness();
+
+  showInitialPrompt();
+  assert.equal(await startRun(), true);
+  onRunStart({ stdinMode: 'interactive' });
+  assert.equal(stopRun(), true);
+  const writesAfterStop = ctx.writes.length;
+
+  onRunResult({ exitCode: 1 });
+
+  assert.equal(ctx.writes.length, writesAfterStop);
 });
 
 test('e2e: stopRun is idempotent for repeated button presses during one run', async () => {

src/ui/app.js

@@ -139,8 +139,12 @@ window.addEventListener('DOMContentLoaded', async () => {
   if (terminalPanel) resizeObserver.observe(terminalPanel);
   initPanelResizers();
 
-  // 9. Persist session on unload
-  window.addEventListener('beforeunload', () => persistenceGate.persist());
+  // 9. Persist session on unload. Worker teardown is synchronous: browser
+  // unload handlers cannot safely wait for terminal or worker cleanup.
+  window.addEventListener('beforeunload', () => {
+    worker.terminate();
+    persistenceGate.persist();
+  });
 
   editorAPI.focus();
 });

src/ui/terminal.js

@@ -466,17 +466,11 @@ export function onRunStart({ stdinMode = 'none', stdinSessionId = null } = {}) {
  * CPU-bound WASM cannot observe stdin EOF, so the main thread terminates the
  * worker via _onStopRun after terminal state has been reset.
  *
- * @param {{ echoCtrlC?: boolean }} [options]
  * @returns {boolean} true when a running program was stopped
  */
-export function stopRun({ echoCtrlC = false } = {}) {
+export function stopRun() {
   if (!running) return false;
 
-  if (echoCtrlC) {
-    term?.write('^C' + CRLF);
-  } else {
-    term?.write(CRLF);
-  }
   inputBuffer = '';
   _clearSAB();
   setRunPreparationState(false);
@@ -486,7 +480,7 @@ export function stopRun({ echoCtrlC = false } = {}) {
   busy = false;
   runDone?.();
   runDone = null;
-  term?.write(`${C.yellow}Process interrupted.${C.reset}${CRLF}`);
+  clearScreen();
   writePrompt();
   _onStopRun?.();
   return true;
@@ -496,6 +490,7 @@ export function stopRun({ echoCtrlC = false } = {}) {
 
 /** Write stdout text from the running program. */
 export function writeStdout(text) {
+  if (!running) return;
   term?.write(text.replace(/\n/g, CRLF));
 }
 
@@ -531,6 +526,7 @@ export function onCompileResult({ success, diagnostics, outputPath }) {
  * @param {{ exitCode:number }} result
  */
 export function onRunResult({ exitCode }) {
+  if (!running && !preparingRun) return;
   const shouldRestorePrompt = running || preparingRun;
   if (exitCode !== 0) {
     term?.write(`${CRLF}${C.yellow}Process exited with code ${exitCode}.${C.reset}${CRLF}`);
@@ -609,7 +605,7 @@ function handleKey({ key, domEvent }) {
     if (activeStdinMode === 'interactive' || activeStdinMode === 'interactive-message') {
       handleStdinKey(key, domEvent);
     } else if (domEvent.ctrlKey && domEvent.key === 'c') {
-      stopRun({ echoCtrlC: true });
+      stopRun();
     }
     return;
   }
@@ -740,7 +736,7 @@ function handleStdinKey(key, domEvent) {
 
   // Ctrl+C – interrupt the running program
   if (domEvent.ctrlKey && code === 'c') {
-    stopRun({ echoCtrlC: true });
+    stopRun();
     return;
   }