diff --git a/packages/core/src/webviews/main.ts b/packages/core/src/webviews/main.ts
index 2b78eb42df..3c649b5be7 100644
--- a/packages/core/src/webviews/main.ts
+++ b/packages/core/src/webviews/main.ts
@@ -397,8 +397,26 @@ export abstract class VueWebview {
     protected setDidLoad(module: string) {
         this.loadMetadata?.loadTimeout?.dispose()
 
+        /**
+         * The metadata may already be gone by the time the frontend reports success: the 10s
+         * loadTimeout clears it (assuming the load failed), and a second page within the same
+         * webview reporting readiness arrives after the first consumed it. Both are late but
+         * successful loads. Emitting without a duration is fine; throwing is not -- this runs
+         * inside the webview's setUiReady command, so a throw here surfaces to the user as
+         * "Error: Webview error" on the login view (a customer-reported failure in 2.5.0).
+         */
+        if (this.loadMetadata === undefined) {
+            telemetry.toolkit_didLoadModule.emit({
+                passive: true,
+                module,
+                result: 'Succeeded',
+                reason: 'LoadReportedAfterMetadataCleared',
+            })
+            return
+        }
+
         // Represents time from intent to open, to confirmation of a successful load
-        const duration = globals.clock.Date.now() - this.loadMetadata!.start
+        const duration = globals.clock.Date.now() - this.loadMetadata.start
 
         telemetry.toolkit_didLoadModule.emit({
             passive: true,
diff --git a/packages/webpack.vue.config.js b/packages/webpack.vue.config.js
index 1ca91ceed4..f34ffab9ae 100644
--- a/packages/webpack.vue.config.js
+++ b/packages/webpack.vue.config.js
@@ -10,6 +10,7 @@
 const path = require('path')
 const glob = require('glob')
 const { VueLoaderPlugin } = require('vue-loader')
+const { EsbuildPlugin } = require('esbuild-loader')
 const baseConfigFactory = require('./webpack.base.config')
 const { merge } = require('webpack-merge')
 const currentDir = process.cwd()
@@ -71,6 +72,36 @@ module.exports = (env, argv) => {
         plugins: [new VueLoaderPlugin()],
     })
 
+    // Keep esbuild as a pure minifier for these bundles, rather than letting it also choose an output
+    // format.
+    //
+    // esbuild-loader v4 infers `format: 'iife'` whenever the compiler target is 'web' (which this
+    // config sets) and the minifier target is anything other than 'esnext'. The base config's
+    // minifier targets es2021, so that inference fires here. The resulting IIFE wrapper rewrites
+    // top-level `this` into an internal exports object, which silently breaks
+    // `output.libraryTarget: 'this'` above: the bundle's exports are copied onto a dead local object
+    // instead of onto `window`, so nothing is exposed to the classic <script> that loads it.
+    //
+    // The concrete symptom was the Amazon Q chat webview failing with
+    // "Uncaught ReferenceError: HybridChatAdapter is not defined" and rendering blank, because the
+    // inline bootstrap script in the chat webview HTML resolves that class off the global scope.
+    //
+    // Targeting 'esnext' here suppresses the format inference (esbuild then knows it needs no helper
+    // wrapping) without changing what the code is compiled down to -- the loader has already
+    // transpiled to es2021, and these bundles only ever run in the IDE's Chromium webview.
+    //
+    // Note this exact upgrade was reverted once before for the same class of breakage; see
+    // 91a54b0c1 "Revert deps(build): update esbuild-loader to 4.3.0" ("broke loading mynah-ui").
+    config.optimization = {
+        ...config.optimization,
+        minimizer: [
+            new EsbuildPlugin({
+                target: 'esnext',
+                legalComments: 'eof',
+            }),
+        ],
+    }
+
     if (isDevelopment) {
         // add development specific vue config settings
         config = {