fix: preserve image_url parts in OpenAI converter on message retrieval (#357)

The OpenAI converter silently dropped image parts when retrieving
multimodal messages. URL-based images (stored in Part.Meta["url"])
were lost because the converter only checked GetAssetURL() which
returns empty for non-uploaded assets. Added Meta URL fallback
matching the Anthropic and Gemini converters.

Also fixed GetAssetURL key mismatch: lookup used asset.S3Key but
the publicURLs map is keyed by asset.SHA256.

Made-with: Cursor

Author: GenerQAQ

src/server/api/go/internal/pkg/converter/converter_test.go

@@ -585,6 +585,41 @@ func TestGetConvertedMessagesOutput_MixedMetas(t *testing.T) {
 	assert.Equal(t, map[string]interface{}{}, result.Metas[2])
 }
 
+func TestGetAssetURL_LookupBySHA256(t *testing.T) {
+	t.Run("resolves by SHA256 key", func(t *testing.T) {
+		asset := &model.Asset{
+			S3Key:  "parts/project-id/abc.json",
+			SHA256: "deadbeef1234",
+		}
+		publicURLs := map[string]service.PublicURL{
+			"deadbeef1234": {URL: "https://cdn.example.com/signed-url"},
+		}
+
+		result := GetAssetURL(asset, publicURLs)
+		assert.Equal(t, "https://cdn.example.com/signed-url", result)
+	})
+
+	t.Run("nil asset returns empty", func(t *testing.T) {
+		result := GetAssetURL(nil, map[string]service.PublicURL{
+			"key": {URL: "https://example.com"},
+		})
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("missing SHA256 in map returns empty", func(t *testing.T) {
+		asset := &model.Asset{
+			S3Key:  "parts/project-id/abc.json",
+			SHA256: "not-in-map",
+		}
+		publicURLs := map[string]service.PublicURL{
+			"deadbeef1234": {URL: "https://cdn.example.com/signed-url"},
+		}
+
+		result := GetAssetURL(asset, publicURLs)
+		assert.Equal(t, "", result)
+	})
+}
+
 func TestGetConvertedMessagesOutput_EmptyMessages_HasEmptyMetas(t *testing.T) {
 	messages := []model.Message{}
 

src/server/api/go/internal/pkg/converter/openai.go

@@ -66,6 +66,11 @@ func (c *OpenAIConverter) convertToUserMessage(msg model.Message, publicURLs map
 			contentParts = append(contentParts, openai.TextContentPart(part.Text))
 		case model.PartTypeImage:
 			imageURL := GetAssetURL(part.Asset, publicURLs)
+			if imageURL == "" && part.Meta != nil {
+				if url := part.GetMetaString(model.MetaKeyURL); url != "" {
+					imageURL = url
+				}
+			}
 			if imageURL != "" {
 				detail := part.GetMetaString(model.MetaKeyDetail)
 				imgParam := openai.ChatCompletionContentPartImageImageURLParam{

src/server/api/go/internal/pkg/converter/openai_test.go

@@ -111,6 +111,98 @@ func TestOpenAIConverter_Convert_ThinkingDowngradedToText(t *testing.T) {
 	})
 }
 
+func TestOpenAIConverter_Convert_ImagePartFromMetaURL(t *testing.T) {
+	converter := &OpenAIConverter{}
+
+	t.Run("image with external URL in meta", func(t *testing.T) {
+		messages := []model.Message{
+			createTestMessage(model.RoleUser, []model.Part{
+				{Type: model.PartTypeText, Text: "What is in this image?"},
+				{
+					Type: model.PartTypeImage,
+					Meta: map[string]any{
+						model.MetaKeyURL:    "https://example.com/cat.png",
+						model.MetaKeyDetail: "high",
+					},
+				},
+			}, nil),
+		}
+
+		result, err := converter.Convert(messages, nil)
+		require.NoError(t, err)
+
+		msgs := result.([]openai.ChatCompletionMessageParamUnion)
+		require.Len(t, msgs, 1)
+
+		user := msgs[0].OfUser
+		require.NotNil(t, user)
+
+		parts := user.Content.OfArrayOfContentParts
+		require.Len(t, parts, 2, "should have text + image parts")
+
+		assert.NotNil(t, parts[0].OfText)
+		assert.Equal(t, "What is in this image?", parts[0].OfText.Text)
+
+		assert.NotNil(t, parts[1].OfImageURL)
+		assert.Equal(t, "https://example.com/cat.png", parts[1].OfImageURL.ImageURL.URL)
+		assert.Equal(t, "high", parts[1].OfImageURL.ImageURL.Detail)
+	})
+
+	t.Run("image with data URL in meta", func(t *testing.T) {
+		dataURL := "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
+		messages := []model.Message{
+			createTestMessage(model.RoleUser, []model.Part{
+				{
+					Type: model.PartTypeImage,
+					Meta: map[string]any{
+						model.MetaKeyURL:    dataURL,
+						model.MetaKeyDetail: "low",
+					},
+				},
+			}, nil),
+		}
+
+		result, err := converter.Convert(messages, nil)
+		require.NoError(t, err)
+
+		msgs := result.([]openai.ChatCompletionMessageParamUnion)
+		require.Len(t, msgs, 1)
+
+		user := msgs[0].OfUser
+		require.NotNil(t, user)
+
+		parts := user.Content.OfArrayOfContentParts
+		require.Len(t, parts, 1, "should have image part")
+
+		assert.NotNil(t, parts[0].OfImageURL)
+		assert.Equal(t, dataURL, parts[0].OfImageURL.ImageURL.URL)
+		assert.Equal(t, "low", parts[0].OfImageURL.ImageURL.Detail)
+	})
+
+	t.Run("image with nil asset and no meta URL is skipped", func(t *testing.T) {
+		messages := []model.Message{
+			createTestMessage(model.RoleUser, []model.Part{
+				{Type: model.PartTypeText, Text: "Hello"},
+				{Type: model.PartTypeImage, Meta: map[string]any{}},
+			}, nil),
+		}
+
+		result, err := converter.Convert(messages, nil)
+		require.NoError(t, err)
+
+		msgs := result.([]openai.ChatCompletionMessageParamUnion)
+		require.Len(t, msgs, 1)
+
+		user := msgs[0].OfUser
+		require.NotNil(t, user)
+
+		parts := user.Content.OfArrayOfContentParts
+		require.Len(t, parts, 1, "empty image should be skipped, leaving only text")
+		assert.NotNil(t, parts[0].OfText)
+		assert.Equal(t, "Hello", parts[0].OfText.Text)
+	})
+}
+
 func TestOpenAIConverter_Convert_ToolResult(t *testing.T) {
 	converter := &OpenAIConverter{}
 

src/server/api/go/internal/pkg/converter/utils.go

@@ -23,7 +23,7 @@ func GetAssetURL(asset *model.Asset, publicURLs map[string]service.PublicURL) st
 	if asset == nil {
 		return ""
 	}
-	if publicURL, ok := publicURLs[asset.S3Key]; ok {
+	if publicURL, ok := publicURLs[asset.SHA256]; ok {
 		return publicURL.URL
 	}
 	return ""