fix(kernel-browser-runtime): address UI vat infrastructure issues

- Create logger once at construction time in makeUIVatWorker instead of
  per method call
- Track in-progress launches to prevent concurrent launches with same ID
  from orphaning iframes
- Clean up iframe from DOM when connection establishment fails

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: sirtimid

packages/kernel-browser-runtime/src/ui/UIOrchestrator.ts

@@ -92,6 +92,8 @@ export class UIOrchestrator {
 
   readonly #uiVats: Map<UiVatId, UiVatState> = new Map();
 
+  readonly #launchesInProgress: Set<UiVatId> = new Set();
+
   /**
    * Creates a new UIOrchestrator.
    *
@@ -128,7 +130,7 @@ export class UIOrchestrator {
   async launch(config: UiVatConfig): Promise<MessagePort> {
     const { id, uri, slot, title, visible = true } = config;
 
-    if (this.#uiVats.has(id)) {
+    if (this.#uiVats.has(id) || this.#launchesInProgress.has(id)) {
       throw new Error(`UI vat "${id}" already exists`);
     }
 
@@ -137,13 +139,23 @@ export class UIOrchestrator {
       throw new Error(`Slot "${slot}" not found`);
     }
 
+    this.#launchesInProgress.add(id);
+
     this.#logger.info(`Launching UI vat: ${id} in slot: ${slot}`);
 
     const iframe = this.#createIframe(id, uri, title, visible);
     slotElement.appendChild(iframe);
 
-    // Wait for iframe to load and establish MessageChannel
-    const port = await this.#establishConnection(iframe);
+    let port: MessagePort;
+    try {
+      // Wait for iframe to load and establish MessageChannel
+      port = await this.#establishConnection(iframe);
+    } catch (error) {
+      // Clean up iframe if connection establishment fails
+      iframe.remove();
+      this.#launchesInProgress.delete(id);
+      throw error;
+    }
 
     const state: UiVatState = {
       config,
@@ -153,6 +165,7 @@ export class UIOrchestrator {
       visible,
     };
     this.#uiVats.set(id, state);
+    this.#launchesInProgress.delete(id);
 
     this.#logger.info(`UI vat "${id}" launched successfully in slot: ${slot}`);
     return port;

packages/kernel-browser-runtime/src/ui/makeUIVatWorker.ts

@@ -65,6 +65,8 @@ export const makeUIVatWorker = ({
   visible = true,
   logger,
 }: MakeUIVatWorkerOptions): VatWorker => {
+  const workerLogger = logger ?? new Logger('makeUIVatWorker');
+
   return {
     launch: async (_vatConfig: VatConfig): Promise<[MessagePort, unknown]> => {
       const port = await orchestrator.launch({
@@ -83,12 +85,8 @@ export const makeUIVatWorker = ({
     terminate: async (): Promise<null> => {
       if (orchestrator.has(id)) {
         orchestrator.terminate(id);
-      } else if (logger) {
-        logger.warn(`UI vat "${id}" not found for termination`);
       } else {
-        new Logger('makeUIVatWorker').warn(
-          `UI vat "${id}" not found for termination`,
-        );
+        workerLogger.warn(`UI vat "${id}" not found for termination`);
       }
       return null;
     },