feat: Add support for VertexAI compatible service (#375)

feat: consolidate Vertex AI compatibility with API key support in Gemini

internal/config/config.go

@@ -70,6 +70,10 @@ type Config struct {
 	// GeminiKey defines Gemini API key configurations with optional routing overrides.
 	GeminiKey []GeminiKey `yaml:"gemini-api-key" json:"gemini-api-key"`
 
+	// VertexCompatAPIKey defines Vertex AI-compatible API key configurations for third-party providers.
+	// Used for services that use Vertex AI-style paths but with simple API key authentication.
+	VertexCompatAPIKey []VertexCompatKey `yaml:"vertex-api-key" json:"vertex-api-key"`
+
 	// RequestRetry defines the retry times when the request failed.
 	RequestRetry int `yaml:"request-retry" json:"request-retry"`
 	// MaxRetryInterval defines the maximum wait time in seconds before retrying a cooled-down credential.
@@ -343,6 +347,9 @@ func LoadConfigOptional(configFile string, optional bool) (*Config, error) {
 	// Sanitize Gemini API key configuration and migrate legacy entries.
 	cfg.SanitizeGeminiKeys()
 
+	// Sanitize Vertex-compatible API keys: drop entries without base-url
+	cfg.SanitizeVertexCompatKeys()
+
 	// Sanitize Codex keys: drop entries without base-url
 	cfg.SanitizeCodexKeys()
 
@@ -831,6 +838,7 @@ func shouldSkipEmptyCollectionOnPersist(key string, node *yaml.Node) bool {
 	switch key {
 	case "generative-language-api-key",
 		"gemini-api-key",
+		"vertex-api-key",
 		"claude-api-key",
 		"codex-api-key",
 		"openai-compatibility":

internal/config/vertex_compat.go

@@ -0,0 +1,84 @@
+package config
+
+import "strings"
+
+// VertexCompatKey represents the configuration for Vertex AI-compatible API keys.
+// This supports third-party services that use Vertex AI-style endpoint paths
+// (/publishers/google/models/{model}:streamGenerateContent) but authenticate
+// with simple API keys instead of Google Cloud service account credentials.
+//
+// Example services: zenmux.ai and similar Vertex-compatible providers.
+type VertexCompatKey struct {
+	// APIKey is the authentication key for accessing the Vertex-compatible API.
+	// Maps to the x-goog-api-key header.
+	APIKey string `yaml:"api-key" json:"api-key"`
+
+	// BaseURL is the base URL for the Vertex-compatible API endpoint.
+	// The executor will append "/v1/publishers/google/models/{model}:action" to this.
+	// Example: "https://zenmux.ai/api" becomes "https://zenmux.ai/api/v1/publishers/google/models/..."
+	BaseURL string `yaml:"base-url,omitempty" json:"base-url,omitempty"`
+
+	// ProxyURL optionally overrides the global proxy for this API key.
+	ProxyURL string `yaml:"proxy-url,omitempty" json:"proxy-url,omitempty"`
+
+	// Headers optionally adds extra HTTP headers for requests sent with this key.
+	// Commonly used for cookies, user-agent, and other authentication headers.
+	Headers map[string]string `yaml:"headers,omitempty" json:"headers,omitempty"`
+
+	// Models defines the model configurations including aliases for routing.
+	Models []VertexCompatModel `yaml:"models,omitempty" json:"models,omitempty"`
+}
+
+// VertexCompatModel represents a model configuration for Vertex compatibility,
+// including the actual model name and its alias for API routing.
+type VertexCompatModel struct {
+	// Name is the actual model name used by the external provider.
+	Name string `yaml:"name" json:"name"`
+
+	// Alias is the model name alias that clients will use to reference this model.
+	Alias string `yaml:"alias" json:"alias"`
+}
+
+// SanitizeVertexCompatKeys deduplicates and normalizes Vertex-compatible API key credentials.
+func (cfg *Config) SanitizeVertexCompatKeys() {
+	if cfg == nil {
+		return
+	}
+
+	seen := make(map[string]struct{}, len(cfg.VertexCompatAPIKey))
+	out := cfg.VertexCompatAPIKey[:0]
+	for i := range cfg.VertexCompatAPIKey {
+		entry := cfg.VertexCompatAPIKey[i]
+		entry.APIKey = strings.TrimSpace(entry.APIKey)
+		if entry.APIKey == "" {
+			continue
+		}
+		entry.BaseURL = strings.TrimSpace(entry.BaseURL)
+		if entry.BaseURL == "" {
+			// BaseURL is required for vertex-compat keys
+			continue
+		}
+		entry.ProxyURL = strings.TrimSpace(entry.ProxyURL)
+		entry.Headers = NormalizeHeaders(entry.Headers)
+
+		// Sanitize models: remove entries without valid alias
+		sanitizedModels := make([]VertexCompatModel, 0, len(entry.Models))
+		for _, model := range entry.Models {
+			model.Alias = strings.TrimSpace(model.Alias)
+			model.Name = strings.TrimSpace(model.Name)
+			if model.Alias != "" && model.Name != "" {
+				sanitizedModels = append(sanitizedModels, model)
+			}
+		}
+		entry.Models = sanitizedModels
+
+		// Use API key + base URL as uniqueness key
+		uniqueKey := entry.APIKey + "|" + entry.BaseURL
+		if _, exists := seen[uniqueKey]; exists {
+			continue
+		}
+		seen[uniqueKey] = struct{}{}
+		out = append(out, entry)
+	}
+	cfg.VertexCompatAPIKey = out
+}