diff --git a/tests/lib/feature-query.js b/tests/lib/feature-query.js
index 3f49b14..09c6938 100644
--- a/tests/lib/feature-query.js
+++ b/tests/lib/feature-query.js
@@ -1,5 +1,5 @@
 import test from 'ava';
-import { FeatureQuery } from '../../tools/lib/feature-query.js';
+import { FeatureQuery, FeatureQueryModern } from '../../tools/lib/feature-query.js';
 
 test('most stable channel is preferred', (t) => {
   const featureQuery = new FeatureQuery({});
@@ -25,6 +25,28 @@ test('extension features are preferred', (t) => {
   );
 });
 
+test('extension_types "all" is preferred like an explicit list', (t) => {
+  const featureQuery = new FeatureQuery({});
+
+  // Chrome's feature files may give extension_types as the string "all" rather than an array
+  // (see feature_compiler.py's `allow_all`). That still has to count as including "extension".
+  t.deepEqual(
+    featureQuery.mergeComplexFeature([
+      { channel: 'stable', extension_types: ['hosted_app'] },
+      { channel: 'stable', min_manifest_version: 3, extension_types: 'all' }
+    ]),
+    { channel: 'stable', min_manifest_version: 3, extension_types: 'all' }
+  );
+});
+
+test('MV3+ filter keeps extension_types "all"', (t) => {
+  // This is the site that dropped runtime.lastError: extension_types: "all" has to pass the
+  // same as an explicit array containing "extension".
+  const featureQuery = new FeatureQueryModern({});
+
+  t.assert(featureQuery.filter({ channel: 'stable', extension_types: 'all' }));
+});
+
 test('non-location specific features are preferred', (t) => {
   const featureQuery = new FeatureQuery({});
 
diff --git a/tools/lib/feature-query.js b/tools/lib/feature-query.js
index e612112..89d358c 100644
--- a/tools/lib/feature-query.js
+++ b/tools/lib/feature-query.js
@@ -70,7 +70,7 @@ export class FeatureQuery {
     }
 
     // Filter by extension (prefer).
-    const extensionFilter = q.filter(({ extension_types }) => extension_types?.includes('extension'));
+    const extensionFilter = q.filter(({ extension_types }) => extensionTypesInclude(extension_types, 'extension'));
     if (extensionFilter.length === 1) {
       return extensionFilter[0];
     }
@@ -214,6 +214,46 @@ export class FeatureQuery {
 }
 
 
+/**
+ * Checks whether an `extension_types` value includes the given type. Chrome's feature compiler
+ * allows this field to be the literal string "all" instead of a list, meaning every extension
+ * type is allowed, so a plain `includes` call would run as a substring test and misread "all" as
+ * excluding everything.
+ *
+ * @param {chromeTypes.MinArray<chromeTypes.ExtensionType>|chromeTypes.All|undefined} extensionTypes
+ * @param {chromeTypes.ExtensionType} type
+ * @return {boolean}
+ */
+export function extensionTypesInclude(extensionTypes, type) {
+  return extensionTypes === 'all' || (extensionTypes?.includes(type) ?? false);
+}
+
+/**
+ * A FeatureQuery that only allows APIs available in MV3+, used to render the main chrome-types
+ * bundle (everything except the `-a`/`--all` output, which keeps MV2 and Platform Apps too).
+ */
+export class FeatureQueryModern extends FeatureQuery {
+
+  /**
+   * @param {chromeTypes.FeatureSpec} f
+   * @return {boolean}
+   */
+  filter(f) {
+    // Don't show anything that maxes out before MV3.
+    if (f.max_manifest_version && f.max_manifest_version < 3) {
+      return false;
+    }
+
+    // Remove non-extension APIs.
+    if (f.extension_types && !extensionTypesInclude(f.extension_types, 'extension')) {
+      return false;
+    }
+
+    return super.filter(f);
+  }
+
+}
+
 /**
  * @param {chromeTypes.FeatureSpec} f
  * @return {boolean}
@@ -243,10 +283,10 @@ function basicFilter(f) {
   }
 
   // Only allow a limited set of extension types.
-  if (Array.isArray(f.extension_types)) {
+  if (f.extension_types !== undefined) {
     /** @type {chromeTypes.ExtensionType[]} */
     const allowedTypes = ['extension', 'platform_app'];
-    const ok = allowedTypes.some((check) => f.extension_types?.includes(check));
+    const ok = allowedTypes.some((check) => extensionTypesInclude(f.extension_types, check));
     if (!ok) {
       return false;
     }
diff --git a/tools/override.js b/tools/override.js
index 99a6964..a587bf4 100644
--- a/tools/override.js
+++ b/tools/override.js
@@ -24,7 +24,7 @@ import * as chromeTypes from '../types/chrome.js';
 import * as overrideTypes from '../types/override.js';
 import { leastReleasedChannel, mostReleasedChannel } from './lib/channel.js';
 import { buildNamespaceAwareMarkdownRewrite } from './lib/comment.js';
-import { FeatureQuery } from './lib/feature-query.js';
+import { FeatureQuery, extensionTypesInclude } from './lib/feature-query.js';
 import { namespaceNameFromId, parentId } from './lib/traverse.js';
 import { isDeepEqual } from './lib/equal.js';
 
@@ -182,7 +182,7 @@ export class RenderOverride extends EmptyRenderOverride {
    * @param {string} id
    */
   isPlatformAppsOnly(id) {
-    return !this.#fq.checkFeature(id, (f) => !f.extension_types || [...f.extension_types].some((t) => t !== "platform_app"));
+    return !this.#fq.checkFeature(id, (f) => !f.extension_types || f.extension_types === 'all' || f.extension_types.some((t) => t !== "platform_app"));
   }
 
   /**
@@ -546,7 +546,7 @@ export class RenderOverride extends EmptyRenderOverride {
 
       (f.platforms ?? []).forEach((platform) => platforms.add(platform));
 
-      if (f.extension_types && !f.extension_types.includes('extension') && f.extension_types.includes('platform_app')) {
+      if (f.extension_types && !extensionTypesInclude(f.extension_types, 'extension') && extensionTypesInclude(f.extension_types, 'platform_app')) {
         isOnlyPlatformApps = true;
       }
 
diff --git a/tools/render-tsd.js b/tools/render-tsd.js
index fc00089..d9b8327 100755
--- a/tools/render-tsd.js
+++ b/tools/render-tsd.js
@@ -26,7 +26,7 @@ import * as chromeTypes from '../types/chrome.js';
 import * as fs from 'fs';
 import mri from 'mri';
 import { RenderContext } from './lib/render-context.js';
-import { FeatureQuery } from './lib/feature-query.js';
+import { FeatureQuery, FeatureQueryModern } from './lib/feature-query.js';
 import log from 'fancy-log';
 import { RenderOverride } from './override.js';
 
@@ -148,27 +148,4 @@ function loadHistory(path) {
 }
 
 
-class FeatureQueryModern extends FeatureQuery {
-
-  /**
-   * @param {chromeTypes.FeatureSpec} f
-   * @return {boolean}
-   */
-  filter(f) {
-    // Don't show anything that maxes out before MV3.
-    if (f.max_manifest_version && f.max_manifest_version < 3) {
-      return false;
-    }
-
-    // Remove non-extension APIs.
-    if (f.extension_types && !f.extension_types.includes('extension')) {
-      return false;
-    }
-
-    return super.filter(f);
-  }
-
-}
-
-
 await run();
diff --git a/types/chrome.d.ts b/types/chrome.d.ts
index 6d1c3ba..59616cb 100644
--- a/types/chrome.d.ts
+++ b/types/chrome.d.ts
@@ -40,7 +40,7 @@ export type MinArray<T> = T[];
 export type Channel = 'stable' | 'beta' | 'dev' | 'canary' | 'trunk';
 export type Platform = 'chromeos' | 'lacros' | 'linux' | 'mac' | 'win' | 'desktop_android';
 export type Context = 'blessed_extension' | 'blessed_web_page' | 'content_script' | 'lock_screen_extension' | 'web_page' | 'webui' | 'webui_untrusted' | 'unblessed_extension';
-export type ExtensionType = 'extension' | 'hosted_app' | 'legacy_packaged_app' | 'platform_app' | 'shared_module' | 'theme' | 'login_screen_extension';
+export type ExtensionType = 'extension' | 'hosted_app' | 'legacy_packaged_app' | 'platform_app' | 'shared_module' | 'theme' | 'login_screen_extension' | 'chromeos_system_extension';
 export type All = 'all';
 export type SessionType = 'regular' | 'kiosk' | 'kiosk.autolaunched';
 export type Location = 'component' | 'external_component' | 'policy' | 'unpacked';