From 6a9bc911e40aeacf38758b0c2ccb03bc853d89f2 Mon Sep 17 00:00:00 2001
From: 7hokerz <hamahama0925@gmail.com>
Date: Wed, 21 Jan 2026 13:40:41 +0900
Subject: [PATCH 1/2] feat(js/plugin/compat-oai): preserve legacy image URL
 handling when contentType is missing

---
 js/plugins/compat-oai/src/model.ts             | 12 ++++++++++++
 js/plugins/compat-oai/tests/compat_oai_test.ts | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/js/plugins/compat-oai/src/model.ts b/js/plugins/compat-oai/src/model.ts
index d2ce7cce99..e5c6cf74d2 100644
--- a/js/plugins/compat-oai/src/model.ts
+++ b/js/plugins/compat-oai/src/model.ts
@@ -187,6 +187,18 @@ export function toOpenAITextAndMedia(
       };
     }
 
+    // If no contentType is provided, preserve legacy behavior by treating the media
+    // as an image URL (e.g. signed URLs or remote images without metadata)
+    if (!contentType) {
+      return {
+        type: 'image_url',
+        image_url: {
+          url: part.media.url,
+          detail: visualDetailLevel,
+        },
+      };
+    }
+
     // For non-image types (like PDF), use the file type
     // OpenAI expects the full data URL (with data: prefix) in file_data
     if (part.media.url.startsWith('data:')) {
diff --git a/js/plugins/compat-oai/tests/compat_oai_test.ts b/js/plugins/compat-oai/tests/compat_oai_test.ts
index 93844e3fba..295d76a9d1 100644
--- a/js/plugins/compat-oai/tests/compat_oai_test.ts
+++ b/js/plugins/compat-oai/tests/compat_oai_test.ts
@@ -171,6 +171,21 @@ describe('toOpenAiTextAndMedia', () => {
     });
   });
 
+  it('should transform image from signed URLs', () => {
+    const part: Part = {
+      media: {
+        url: 'https://storage.googleapis.com/bucket/image.png?X-Goog-Signature=fake',
+      },
+    };
+    expect(toOpenAITextAndMedia(part, 'low')).toStrictEqual({
+      type: 'image_url',
+      image_url: {
+        url: 'https://storage.googleapis.com/bucket/image.png?X-Goog-Signature=fake',
+        detail: 'low',
+      },
+    });
+  });
+
   it('should throw error for file URLs (non-base64 PDFs)', () => {
     const part: Part = {
       media: {

From cfd5b44d8ce2694917ab005601a7857853c565d5 Mon Sep 17 00:00:00 2001
From: 7hokerz <hamahama0925@gmail.com>
Date: Fri, 23 Jan 2026 02:19:03 +0900
Subject: [PATCH 2/2] refactor: Reduce duplication

---
 js/plugins/compat-oai/src/model.ts | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/js/plugins/compat-oai/src/model.ts b/js/plugins/compat-oai/src/model.ts
index e5c6cf74d2..b3567fb51e 100644
--- a/js/plugins/compat-oai/src/model.ts
+++ b/js/plugins/compat-oai/src/model.ts
@@ -177,19 +177,9 @@ export function toOpenAITextAndMedia(
     }
 
     // Check if this is an image type
-    if (isImageContentType(contentType)) {
-      return {
-        type: 'image_url',
-        image_url: {
-          url: part.media.url,
-          detail: visualDetailLevel,
-        },
-      };
-    }
-
     // If no contentType is provided, preserve legacy behavior by treating the media
     // as an image URL (e.g. signed URLs or remote images without metadata)
-    if (!contentType) {
+    if (!contentType || isImageContentType(contentType)) {
       return {
         type: 'image_url',
         image_url: {