diff --git a/packages/angular_devkit/build_angular/src/builders/karma/index.ts b/packages/angular_devkit/build_angular/src/builders/karma/index.ts
index dd545daf7f22..a4a5d580f43b 100644
--- a/packages/angular_devkit/build_angular/src/builders/karma/index.ts
+++ b/packages/angular_devkit/build_angular/src/builders/karma/index.ts
@@ -146,6 +146,14 @@ export function execute(
         logger: context.logger,
       };
 
+      // Workaround https://github.com/angular/angular-cli/issues/28271, by clearing context by default
+      // for single run executions.
+      if (karmaOptions.client?.clearContext === undefined) {
+        const singleRun = karmaOptions.singleRun ?? false; // Defaults to `false` per Karma docs.
+        karmaOptions.client ??= {};
+        karmaOptions.client.clearContext = singleRun;
+      }
+
       const parsedKarmaConfig = await karma.config.parseConfig(
         options.karmaConfig && path.resolve(context.workspaceRoot, options.karmaConfig),
         transforms.karmaOptions ? transforms.karmaOptions(karmaOptions) : karmaOptions,
@@ -208,9 +216,6 @@ function getBuiltInKarmaConfig(
       'karma-coverage',
       '@angular-devkit/build-angular/plugins/karma',
     ].map((p) => workspaceRootRequire(p)),
-    client: {
-      clearContext: false, // leave Jasmine Spec Runner output visible in browser
-    },
     jasmineHtmlReporter: {
       suppressAll: true, // removes the duplicated traces
     },
diff --git a/packages/schematics/angular/config/files/karma.conf.js.template b/packages/schematics/angular/config/files/karma.conf.js.template
index bac55a495a5b..f8da22b16e55 100644
--- a/packages/schematics/angular/config/files/karma.conf.js.template
+++ b/packages/schematics/angular/config/files/karma.conf.js.template
@@ -19,7 +19,6 @@ module.exports = function (config) {
         // for example, you can disable the random execution with `random: false`
         // or set a specific seed with `seed: 4321`
       },
-      clearContext: false // leave Jasmine Spec Runner output visible in browser
     },
     jasmineHtmlReporter: {
       suppressAll: true // removes the duplicated traces