diff --git a/packages/angular/cli/src/command-builder/utilities/json-schema.ts b/packages/angular/cli/src/command-builder/utilities/json-schema.ts
index e9fbd7e0e27a..06728f1ee9ac 100644
--- a/packages/angular/cli/src/command-builder/utilities/json-schema.ts
+++ b/packages/angular/cli/src/command-builder/utilities/json-schema.ts
@@ -257,18 +257,18 @@ function getEnumValues(
  */
 function getDefaultValue(
   current: json.JsonObject,
-  type: string,
+  type: ReadonlyArray<string>,
 ): string | number | boolean | unknown[] | undefined {
   const defaultValue = current.default;
   if (defaultValue === undefined) {
     return undefined;
   }
 
-  if (type === 'array') {
+  if (type.includes('array')) {
     return Array.isArray(defaultValue) && defaultValue.length > 0 ? defaultValue : undefined;
   }
 
-  if (typeof defaultValue === type) {
+  if (type.includes(typeof defaultValue)) {
     return defaultValue as string | number | boolean;
   }
 
@@ -343,7 +343,12 @@ export async function parseJsonSchemaToOptions(
       return;
     }
 
-    const [type] = types;
+    // Allow Yargs to infer the option type for string AND boolean options
+    const type =
+      types.length === 2 && types.includes('string') && types.includes('boolean')
+        ? undefined
+        : types[0];
+
     const $default = current.$default;
     const $defaultIndex =
       isJsonObject($default) && $default['$source'] === 'argv' ? $default['index'] : undefined;
@@ -362,7 +367,7 @@ export async function parseJsonSchemaToOptions(
     const option: Option = {
       name,
       description: String(current.description ?? ''),
-      default: getDefaultValue(current, type),
+      default: getDefaultValue(current, types),
       choices: enumValues?.length ? enumValues : undefined,
       required,
       alias: getAliases(current),
diff --git a/packages/angular/cli/src/command-builder/utilities/json-schema_spec.ts b/packages/angular/cli/src/command-builder/utilities/json-schema_spec.ts
index d311373d69f0..df5c624ef2f0 100644
--- a/packages/angular/cli/src/command-builder/utilities/json-schema_spec.ts
+++ b/packages/angular/cli/src/command-builder/utilities/json-schema_spec.ts
@@ -257,6 +257,29 @@ describe('parseJsonSchemaToOptions', () => {
     });
   });
 
+  it(`should not set 'type' when it is a 'string' and a 'boolean'`, async () => {
+    const registry = new schema.CoreSchemaRegistry();
+    const options = await parseJsonSchemaToOptions(
+      registry,
+      {
+        'type': 'object',
+        'properties': {
+          'runner': {
+            'type': ['string', 'boolean'],
+          },
+        },
+      },
+      false,
+    );
+
+    expect(options).toEqual([
+      jasmine.objectContaining({
+        name: 'runner',
+        type: undefined,
+      }),
+    ]);
+  });
+
   describe('with required positional argument', () => {
     it('marks the required argument as required', async () => {
       const jsonSchema = {
diff --git a/tests/legacy-cli/e2e/tests/vitest/runner-config-option.ts b/tests/legacy-cli/e2e/tests/vitest/runner-config-option.ts
new file mode 100644
index 000000000000..92fe754d9b24
--- /dev/null
+++ b/tests/legacy-cli/e2e/tests/vitest/runner-config-option.ts
@@ -0,0 +1,50 @@
+import { ng } from '../../utils/process';
+import { writeMultipleFiles } from '../../utils/fs';
+import { applyVitestBuilder } from '../../utils/vitest';
+import assert from 'node:assert';
+
+export default async function () {
+  await applyVitestBuilder();
+
+  // Test the boolean `true` usage of `--runner-config`.
+  // It should log that it is searching for a config file.
+  const { stdout: boolTrueStdout } = await ng('test', '--runner-config');
+  assert.match(
+    boolTrueStdout,
+    /Automatically searching/,
+    'Expected an automatic search message for --runner-config',
+  );
+  assert.match(boolTrueStdout, /1 passed/, 'Expected 1 test to pass with --runner-config');
+
+  // Test the string usage of `--runner-config`.
+  // It should log that it is using the specified config file.
+  const customConfigPath = 'vitest.custom.mjs';
+  await writeMultipleFiles({
+    [customConfigPath]: `
+      import { defineConfig } from 'vitest/config';
+      export default defineConfig({
+        test: {
+
+        },
+      });
+    `,
+  });
+
+  const { stdout: stringStdout } = await ng('test', `--runner-config=${customConfigPath}`);
+  assert.match(
+    stringStdout,
+    /vitest\.custom\.mjs/,
+    'Expected a message confirming the use of the custom config file.',
+  );
+  assert.match(stringStdout, /1 passed/, 'Expected all tests to pass with string config.');
+
+  // Test the boolean `false` usage of `--runner-config`.
+  // It should not log any messages about searching for or using a config file.
+  const { stdout: boolFalseStdout } = await ng('test', '--no-runner-config');
+  assert.doesNotMatch(
+    boolFalseStdout,
+    /Automatically searching/,
+    'Should not search for a config with --no-runner-config',
+  );
+  assert.match(boolFalseStdout, /1 passed/, 'Expected 1 test to pass with --no-runner-config');
+}