From 478b4c3dfd434859074d9945bbf2b43f218371de Mon Sep 17 00:00:00 2001
From: Erik Eldridge <erikeldridge@google.com>
Date: Wed, 14 May 2025 17:29:36 -0700
Subject: [PATCH 1/3] Guard against undefined mode, ie the non-hybrid common
 case

---
 packages/ai/src/methods/chrome-adapter.test.ts | 18 ++++++++++++++++--
 packages/ai/src/methods/chrome-adapter.ts      | 17 +++++++++++------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/packages/ai/src/methods/chrome-adapter.test.ts b/packages/ai/src/methods/chrome-adapter.test.ts
index fbe7ec1a5c5..adb9ae47d87 100644
--- a/packages/ai/src/methods/chrome-adapter.test.ts
+++ b/packages/ai/src/methods/chrome-adapter.test.ts
@@ -109,6 +109,14 @@ describe('ChromeAdapter', () => {
     });
   });
   describe('isAvailable', () => {
+    it('returns false if mode is undefined', async () => {
+      const adapter = new ChromeAdapter();
+      expect(
+        await adapter.isAvailable({
+          contents: []
+        })
+      ).to.be.false;
+    });
     it('returns false if mode is only cloud', async () => {
       const adapter = new ChromeAdapter(undefined, 'only_in_cloud');
       expect(
@@ -239,7 +247,10 @@ describe('ChromeAdapter', () => {
       const createStub = stub(languageModelProvider, 'create').returns(
         downloadPromise
       );
-      const adapter = new ChromeAdapter(languageModelProvider);
+      const adapter = new ChromeAdapter(
+        languageModelProvider,
+        'prefer_on_device'
+      );
       await adapter.isAvailable({
         contents: [{ role: 'user', parts: [{ text: 'hi' }] }]
       });
@@ -260,7 +271,10 @@ describe('ChromeAdapter', () => {
       const createStub = stub(languageModelProvider, 'create').returns(
         downloadPromise
       );
-      const adapter = new ChromeAdapter(languageModelProvider);
+      const adapter = new ChromeAdapter(
+        languageModelProvider,
+        'prefer_on_device'
+      );
       await adapter.isAvailable({
         contents: [{ role: 'user', parts: [{ text: 'hi' }] }]
       });
diff --git a/packages/ai/src/methods/chrome-adapter.ts b/packages/ai/src/methods/chrome-adapter.ts
index d6de108668d..40fa4883a4f 100644
--- a/packages/ai/src/methods/chrome-adapter.ts
+++ b/packages/ai/src/methods/chrome-adapter.ts
@@ -68,7 +68,7 @@ export class ChromeAdapter {
    * separation of concerns.</p>
    */
   async isAvailable(request: GenerateContentRequest): Promise<boolean> {
-    if (this.mode === 'only_in_cloud') {
+    if (!this.mode || this.mode === 'only_in_cloud') {
       logger.debug(
         `On-device inference unavailable because mode is "only_in_cloud".`
       );
@@ -83,20 +83,25 @@ export class ChromeAdapter {
     }
 
     // Applies prefer_on_device logic.
-    if (availability !== Availability.available) {
+    const isAvailable = availability === Availability.available;
+    const isOnDeviceRequest = ChromeAdapter.isOnDeviceRequest(request);
+    if (isAvailable && isOnDeviceRequest) {
+      return true;
+    }
+
+    if (!isAvailable) {
       logger.debug(
         `On-device inference unavailable because availability is "${availability}".`
       );
-      return false;
     }
-    if (!ChromeAdapter.isOnDeviceRequest(request)) {
+
+    if (!isOnDeviceRequest) {
       logger.debug(
         `On-device inference unavailable because request is incompatible.`
       );
-      return false;
     }
 
-    return true;
+    return false;
   }
 
   /**

From 65de23cd563b3dfde1156f17d81e94a79f45cce9 Mon Sep 17 00:00:00 2001
From: Erik Eldridge <erikeldridge@google.com>
Date: Wed, 14 May 2025 17:42:13 -0700
Subject: [PATCH 2/3] Revert default value changes

---
 packages/ai/src/methods/chrome-adapter.ts | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/packages/ai/src/methods/chrome-adapter.ts b/packages/ai/src/methods/chrome-adapter.ts
index 40fa4883a4f..16e0319b5fb 100644
--- a/packages/ai/src/methods/chrome-adapter.ts
+++ b/packages/ai/src/methods/chrome-adapter.ts
@@ -83,25 +83,20 @@ export class ChromeAdapter {
     }
 
     // Applies prefer_on_device logic.
-    const isAvailable = availability === Availability.available;
-    const isOnDeviceRequest = ChromeAdapter.isOnDeviceRequest(request);
-    if (isAvailable && isOnDeviceRequest) {
-      return true;
-    }
-
-    if (!isAvailable) {
+    if (availability !== Availability.available) {
       logger.debug(
         `On-device inference unavailable because availability is "${availability}".`
       );
+      return false;
     }
-
-    if (!isOnDeviceRequest) {
+    if (!ChromeAdapter.isOnDeviceRequest(request)) {
       logger.debug(
         `On-device inference unavailable because request is incompatible.`
       );
+      return false;
     }
 
-    return false;
+    return true;
   }
 
   /**

From 205a25b5629ae44593900f00617ff870aec5ad5e Mon Sep 17 00:00:00 2001
From: Erik Eldridge <erikeldridge@google.com>
Date: Thu, 15 May 2025 08:34:00 -0700
Subject: [PATCH 3/3] Use standalone guard for undefined mode for consistency

---
 packages/ai/src/methods/chrome-adapter.ts | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/packages/ai/src/methods/chrome-adapter.ts b/packages/ai/src/methods/chrome-adapter.ts
index 16e0319b5fb..b61ad9b5f09 100644
--- a/packages/ai/src/methods/chrome-adapter.ts
+++ b/packages/ai/src/methods/chrome-adapter.ts
@@ -68,7 +68,13 @@ export class ChromeAdapter {
    * separation of concerns.</p>
    */
   async isAvailable(request: GenerateContentRequest): Promise<boolean> {
-    if (!this.mode || this.mode === 'only_in_cloud') {
+    if (!this.mode) {
+      logger.debug(
+        `On-device inference unavailable because mode is undefined.`
+      );
+      return false;
+    }
+    if (this.mode === 'only_in_cloud') {
       logger.debug(
         `On-device inference unavailable because mode is "only_in_cloud".`
       );