feat: support VertexAI provider (#153)

* support: vertexai

fix

fix

set default for vertexai

added comment

fix

fix

* create schema

* fix README.md

* fix order

* added pupularity

* set tools if tools is exists

restore commentout

* fix comment

* set summarizer model

internal/config/config.go

@@ -235,6 +235,7 @@ func setProviderDefaults() {
 	// 5. OpenRouter
 	// 6. AWS Bedrock
 	// 7. Azure
+	// 8. Google Cloud VertexAI
 
 	// Anthropic configuration
 	if key := viper.GetString("providers.anthropic.apiKey"); strings.TrimSpace(key) != "" {
@@ -299,6 +300,15 @@ func setProviderDefaults() {
 		viper.SetDefault("agents.title.model", models.AzureGPT41Mini)
 		return
 	}
+
+	// Google Cloud VertexAI configuration
+	if hasVertexAICredentials() {
+		viper.SetDefault("agents.coder.model", models.VertexAIGemini25)
+		viper.SetDefault("agents.summarizer.model", models.VertexAIGemini25)
+		viper.SetDefault("agents.task.model", models.VertexAIGemini25Flash)
+		viper.SetDefault("agents.title.model", models.VertexAIGemini25Flash)
+		return
+	}
 }
 
 // hasAWSCredentials checks if AWS credentials are available in the environment.
@@ -327,6 +337,19 @@ func hasAWSCredentials() bool {
 	return false
 }
 
+// hasVertexAICredentials checks if VertexAI credentials are available in the environment.
+func hasVertexAICredentials() bool {
+	// Check for explicit VertexAI parameters
+	if os.Getenv("VERTEXAI_PROJECT") != "" && os.Getenv("VERTEXAI_LOCATION") != "" {
+		return true
+	}
+	// Check for Google Cloud project and location
+	if os.Getenv("GOOGLE_CLOUD_PROJECT") != "" && (os.Getenv("GOOGLE_CLOUD_REGION") != "" || os.Getenv("GOOGLE_CLOUD_LOCATION") != "") {
+		return true
+	}
+	return false
+}
+
 // readConfig handles the result of reading a configuration file.
 func readConfig(err error) error {
 	if err == nil {
@@ -549,6 +572,10 @@ func getProviderAPIKey(provider models.ModelProvider) string {
 		if hasAWSCredentials() {
 			return "aws-credentials-available"
 		}
+	case models.ProviderVertexAI:
+		if hasVertexAICredentials() {
+			return "vertex-ai-credentials-available"
+		}
 	}
 	return ""
 }
@@ -669,6 +696,24 @@ func setDefaultModelForAgent(agent AgentName) bool {
 		return true
 	}
 
+	if hasVertexAICredentials() {
+		var model models.ModelID
+		maxTokens := int64(5000)
+
+		if agent == AgentTitle {
+			model = models.VertexAIGemini25Flash
+			maxTokens = 80
+		} else {
+			model = models.VertexAIGemini25
+		}
+
+		cfg.Agents[agent] = Agent{
+			Model:     model,
+			MaxTokens: maxTokens,
+		}
+		return true
+	}
+
 	return false
 }