Fix(Go): prevent global state pollution in local model connection check (#14669)

### What problem does this PR solve?

1. **Fix Global State Pollution in Local Providers (Critical Bug):** -
Resolved a severe concurrency and architecture issue in
`model_service.go`. Previously, `ListSupportedModels` would permanently
overwrite the global provider singleton with a localized URL instance
(`driver.NewInstance`). This caused cross-request contamination in
multi-tenant environments.
- Fixed `CheckProviderConnection` for local models (LM Studio, vLLM,
Ollama). It now properly creates a localized driver copy and injects the
`base_url` before testing the connection, entirely eliminating the
false-positive `missing base URL` error without polluting the global
state.
2. **Implement `VolcEngine` Embeddings:** - Fully implemented the
`Encode` method for the `volcengine` provider, enabling text embedding
capabilities for VolcEngine models.
3. **Enhance Region Validation in `SiliconFlow`:** - Added a strict
empty string check (`*apiConfig.Region != ""`) alongside the existing
`nil` check when parsing regions. This ensures that if an empty string
is passed, the system safely falls back to the `"default"` region,
preventing malformed URL requests and `unsupported protocol scheme`
errors.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)

internal/entity/models/lmstudio.go

@@ -442,27 +442,8 @@ func (l *LmStudioModel) Balance(apiConfig *APIConfig) (map[string]interface{}, e
 	return nil, fmt.Errorf("no such method")
 }
 
-// CheckConnection verifies that the configured LM Studio base URL
-// is reachable and that the API key (if any) is accepted, by issuing
-// a lightweight ListModels call. The empty-URL guard runs first so
-// a user who has not yet set the local access address gets a clear,
-// actionable error instead of a low-level transport message.
+// CheckConnection verifies that the configured LM Studio base URL is reachable
 func (l *LmStudioModel) CheckConnection(apiConfig *APIConfig) error {
-	var region = "default"
-	if apiConfig != nil && apiConfig.Region != nil && *apiConfig.Region != "" {
-		region = *apiConfig.Region
-	}
-
-	baseURL := l.BaseURL[region]
-	if baseURL == "" {
-		baseURL = l.BaseURL["default"]
-	}
-	if baseURL == "" {
-		return fmt.Errorf("missing base URL: please configure the local access address for LM Studio (e.g., http://127.0.0.1:1234/v1)")
-	}
-
-	if _, err := l.ListModels(apiConfig); err != nil {
-		return fmt.Errorf("connection check failed: %w", err)
-	}
-	return nil
+	_, err := l.ListModels(apiConfig)
+	return err
 }

internal/entity/models/ollama.go

@@ -440,27 +440,8 @@ func (o *OllamaModel) Balance(apiConfig *APIConfig) (map[string]interface{}, err
 	return nil, fmt.Errorf("no such method")
 }
 
-// CheckConnection verifies that the configured Ollama base URL is
-// reachable and that the API key (if any) is accepted, by issuing a
-// lightweight ListModels call. The empty-URL guard runs first so a
-// user who has not yet set the local access address gets a clear,
-// actionable error instead of a low-level transport message.
+// CheckConnection verifies that the configured Ollama base URL is reachable
 func (o *OllamaModel) CheckConnection(apiConfig *APIConfig) error {
-	var region = "default"
-	if apiConfig != nil && apiConfig.Region != nil && *apiConfig.Region != "" {
-		region = *apiConfig.Region
-	}
-
-	baseURL := o.BaseURL[region]
-	if baseURL == "" {
-		baseURL = o.BaseURL["default"]
-	}
-	if baseURL == "" {
-		return fmt.Errorf("missing base URL: please configure the local access address for Ollama (e.g., http://127.0.0.1:11434/v1)")
-	}
-
-	if _, err := o.ListModels(apiConfig); err != nil {
-		return fmt.Errorf("connection check failed: %w", err)
-	}
-	return nil
+	_, err := o.ListModels(apiConfig)
+	return err
 }

internal/entity/models/siliconflow.go

@@ -474,7 +474,7 @@ func (s *SiliconflowModel) Encode(modelName *string, texts []string, apiConfig *
 
 func (z *SiliconflowModel) ListModels(apiConfig *APIConfig) ([]string, error) {
 	var region = "default"
-	if apiConfig.Region != nil {
+	if apiConfig.Region != nil && *apiConfig.Region != "" {
 		region = *apiConfig.Region
 	}
 

internal/entity/models/vllm.go

@@ -455,29 +455,10 @@ func (z *VllmModel) Balance(apiConfig *APIConfig) (map[string]interface{}, error
 	return nil, fmt.Errorf("no such method")
 }
 
-// CheckConnection verifies that the configured vLLM base URL is
-// reachable and that the API key (if any) is accepted, by issuing a
-// lightweight ListModels call. The empty-URL guard runs first so a
-// user who has not yet set the local access address gets a clear,
-// actionable error instead of a low-level transport message.
+// CheckConnection verifies that the configured vLLM base URL is reachable
 func (z *VllmModel) CheckConnection(apiConfig *APIConfig) error {
-	var region = "default"
-	if apiConfig != nil && apiConfig.Region != nil && *apiConfig.Region != "" {
-		region = *apiConfig.Region
-	}
-
-	baseURL := z.BaseURL[region]
-	if baseURL == "" {
-		baseURL = z.BaseURL["default"]
-	}
-	if baseURL == "" {
-		return fmt.Errorf("missing base URL: please configure the local access address for vLLM (e.g., http://127.0.0.1:8000/v1)")
-	}
-
-	if _, err := z.ListModels(apiConfig); err != nil {
-		return fmt.Errorf("connection check failed: %w", err)
-	}
-	return nil
+	_, err := z.ListModels(apiConfig)
+	return err
 }
 
 // Rerank calculates similarity scores between query and texts

internal/entity/models/volcengine.go

@@ -408,7 +408,86 @@ func (z *VolcEngine) ChatStreamlyWithSender(modelName string, messages []Message
 
 // Encode encodes a list of texts into embeddings
 func (z *VolcEngine) Encode(modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig) ([][]float64, error) {
-	return nil, fmt.Errorf("not implemented")
+	if len(texts) == 0 {
+		return [][]float64{}, nil
+	}
+
+	var region = "default"
+	if apiConfig != nil && apiConfig.Region != nil && *apiConfig.Region != "" {
+		region = *apiConfig.Region
+	}
+
+	url := fmt.Sprintf("%s/%s", z.BaseURL[region], z.URLSuffix.Embedding)
+
+	embeddings := make([][]float64, len(texts))
+
+	for i, text := range texts {
+
+		reqBody := map[string]interface{}{
+			"model":           *modelName,
+			"encoding_format": "float",
+			"input": []map[string]interface{}{
+				{
+					"type": "text",
+					"text": text,
+				},
+			},
+		}
+
+		jsonData, err := json.Marshal(reqBody)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"failed to marshal request: %w",
+				err,
+			)
+		}
+
+		req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonData))
+		if err != nil {
+			return nil, fmt.Errorf("failed to create request: %w", err)
+		}
+
+		req.Header.Set("Content-Type", "application/json")
+		req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))
+
+		resp, err := z.httpClient.Do(req)
+		if err != nil {
+			return nil, fmt.Errorf("failed to send request: %w", err)
+		}
+
+		body, err := io.ReadAll(resp.Body)
+		resp.Body.Close()
+
+		if err != nil {
+			return nil, fmt.Errorf("failed to read response: %w", err)
+		}
+
+		if resp.StatusCode != http.StatusOK {
+			return nil, fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
+		}
+
+		// Volcengine multimodal embedding response
+		type VolcengineEmbeddingResponse struct {
+			Data struct {
+				Embedding []float64 `json:"embedding"`
+				Object    string    `json:"object"`
+			} `json:"data"`
+		}
+
+		var result VolcengineEmbeddingResponse
+
+		if err = json.Unmarshal(body, &result); err != nil {
+			return nil, fmt.Errorf("failed to parse response: %w", err)
+		}
+
+		if len(result.Data.Embedding) == 0 {
+			return nil, fmt.Errorf("empty embedding in response")
+		}
+
+		embeddings[i] = result.Data.Embedding
+	}
+
+	return embeddings, nil
 }
 
 // Rerank calculates similarity scores between query and texts