feat(ai-proxy): add default system prompt and Bash tool for Claude Code mode

- Add default Claude Code system prompt if not present in request
- Add default Bash tool if not present in request
- Only inject defaults when claudeCodeMode is enabled and fields are missing

plugins/wasm-go/extensions/ai-proxy/provider/claude.go

@@ -21,8 +21,11 @@ const (
 	claudeDefaultMaxTokens = 4096
 
 	// Claude Code mode constants
-	claudeCodeUserAgent    = "claude-cli/2.1.2 (external, cli)"
-	claudeCodeBetaFeatures = "oauth-2025-04-20,interleaved-thinking-2025-05-14,claude-code-20250219"
+	claudeCodeUserAgent      = "claude-cli/2.1.2 (external, cli)"
+	claudeCodeBetaFeatures   = "oauth-2025-04-20,interleaved-thinking-2025-05-14,claude-code-20250219"
+	claudeCodeSystemPrompt   = "You are Claude Code, Anthropic's official CLI for Claude."
+	claudeCodeBashToolName   = "Bash"
+	claudeCodeBashToolDesc   = "Run bash commands"
 )
 
 type claudeProviderInitializer struct{}
@@ -440,8 +443,11 @@ func (c *claudeProvider) buildClaudeTextGenRequest(origRequest *chatCompletionRe
 		claudeRequest.MaxTokens = claudeDefaultMaxTokens
 	}
 
+	// Track if system message exists in original request
+	hasSystemMessage := false
 	for _, message := range origRequest.Messages {
 		if message.Role == roleSystem {
+			hasSystemMessage = true
 			// In Claude Code mode, use array format with cache_control
 			if c.config.claudeCodeMode {
 				claudeRequest.System = &claudeSystemPrompt{
@@ -521,6 +527,22 @@ func (c *claudeProvider) buildClaudeTextGenRequest(origRequest *chatCompletionRe
 		claudeRequest.Messages = append(claudeRequest.Messages, claudeMessage)
 	}
 
+	// In Claude Code mode, add default system prompt if not present
+	if c.config.claudeCodeMode && !hasSystemMessage {
+		claudeRequest.System = &claudeSystemPrompt{
+			ArrayValue: []claudeChatMessageContent{
+				{
+					Type: contentTypeText,
+					Text: claudeCodeSystemPrompt,
+					CacheControl: map[string]interface{}{
+						"type": "ephemeral",
+					},
+				},
+			},
+			IsArray: true,
+		}
+	}
+
 	for _, tool := range origRequest.Tools {
 		claudeTool := claudeTool{
 			Name:        tool.Function.Name,
@@ -530,6 +552,32 @@ func (c *claudeProvider) buildClaudeTextGenRequest(origRequest *chatCompletionRe
 		claudeRequest.Tools = append(claudeRequest.Tools, claudeTool)
 	}
 
+	// In Claude Code mode, add Bash tool if not present
+	if c.config.claudeCodeMode {
+		hasBashTool := false
+		for _, tool := range claudeRequest.Tools {
+			if tool.Name == claudeCodeBashToolName {
+				hasBashTool = true
+				break
+			}
+		}
+		if !hasBashTool {
+			claudeRequest.Tools = append(claudeRequest.Tools, claudeTool{
+				Name:        claudeCodeBashToolName,
+				Description: claudeCodeBashToolDesc,
+				InputSchema: map[string]interface{}{
+					"type": "object",
+					"properties": map[string]interface{}{
+						"command": map[string]interface{}{
+							"type": "string",
+						},
+					},
+					"required": []string{"command"},
+				},
+			})
+		}
+	}
+
 	if tc := origRequest.getToolChoiceObject(); tc != nil {
 		claudeRequest.ToolChoice = &claudeToolChoice{
 			Name:                   tc.Function.Name,