Add /mcp update command to reload MCP servers without restart

- MCP Client: add Reconnect() method that closes old connections,
  rebuilds servers from new config, re-initializes, and re-embeds tools
- Agent: add ReloadMCP() to expose reconnect to the handler layer
- Telegram: add /mcp command with "update"/"reload" subcommands
  that re-reads config/mcp.json and reconnects all MCP servers

https://claude.ai/code/session_01VtMjyBkcnrX8AZDuPj67XT

Author: claude

internal/agent/agent.go

@@ -9,6 +9,7 @@ import (
 	"time"
 	"unicode/utf8"
 
+	"telegram-agent/internal/config"
 	"telegram-agent/internal/llm"
 	"telegram-agent/internal/mcp"
 	"telegram-agent/internal/store"
@@ -231,6 +232,15 @@ func (a *Agent) EmbedText(ctx context.Context, text string) ([]float32, error) {
 	return a.mcp.EmbedText(ctx, text)
 }
 
+// ReloadMCP re-reads the MCP config file, reconnects all servers, and re-discovers tools.
+// Returns the number of tools available after reload.
+func (a *Agent) ReloadMCP(ctx context.Context, configs map[string]config.MCPServerConfig) (int, error) {
+	if a.mcp == nil {
+		return 0, fmt.Errorf("MCP client not initialized")
+	}
+	return a.mcp.Reconnect(ctx, configs)
+}
+
 func (a *Agent) ListTools() []ToolInfo {
 	var result []ToolInfo
 	if a.mcp != nil {

internal/mcp/client.go

@@ -228,6 +228,57 @@ func (c *Client) Close() {
 	}
 }
 
+// Reconnect closes existing connections, replaces the server list with new configs,
+// re-initializes all servers, and re-embeds tools if embeddings were enabled.
+// Returns the number of tools discovered after reconnect.
+func (c *Client) Reconnect(ctx context.Context, configs map[string]config.MCPServerConfig) (int, error) {
+	// Close old connections.
+	c.Close()
+
+	// Reset state.
+	c.servers = make(map[string]*server)
+	c.tools = nil
+	c.toolServers = make(map[string]string)
+	c.embeddingsReady = false
+
+	// Build new servers (same logic as NewClient).
+	for name, cfg := range configs {
+		if err := validateServerURL(cfg.URL); err != nil {
+			c.logger.Warn("mcp server URL rejected", "server", name, "url", cfg.URL, "err", err)
+			continue
+		}
+		srv := &server{
+			name:    name,
+			url:     cfg.URL,
+			headers: cfg.Headers,
+			http:    &http.Client{Timeout: 30 * time.Second},
+		}
+		if len(cfg.AllowTools) > 0 {
+			srv.allowTools = make(map[string]bool, len(cfg.AllowTools))
+			for _, t := range cfg.AllowTools {
+				srv.allowTools[t] = true
+			}
+		}
+		if len(cfg.DenyTools) > 0 {
+			srv.denyTools = make(map[string]bool, len(cfg.DenyTools))
+			for _, t := range cfg.DenyTools {
+				srv.denyTools[t] = true
+			}
+		}
+		c.servers[name] = srv
+	}
+
+	// Initialize and discover tools.
+	c.Initialize(ctx)
+
+	// Re-embed tools if embeddings were configured.
+	if c.embeddingCfg.APIKey != "" || c.embeddingCfg.BaseURL != "" {
+		c.EmbedTools(ctx)
+	}
+
+	return len(c.tools), nil
+}
+
 // CallTool executes a tool on the appropriate MCP server.
 // On network failure it attempts one reconnect before giving up.
 func (c *Client) CallTool(ctx context.Context, name string, argsJSON string) (string, error) {

internal/telegram/handler.go

@@ -633,6 +633,7 @@ func (h *Handler) handleCommand(msg *tgbotapi.Message) {
 				"/model <name> — switch model\n"+
 				"/model reset — back to auto\\-routing\n"+
 				"/tools — list MCP tools\n"+
+				"/mcp update — reload MCP servers\n"+
 				"/help — this help\n\n"+
 				"*Model:* `%s`\n"+
 				"Responses longer than 4096 chars are sent as a `.md` file\\.",
@@ -690,6 +691,8 @@ func (h *Handler) handleCommand(msg *tgbotapi.Message) {
 		h.bot.Send(msg) //nolint:errcheck
 	case "tools":
 		h.handleToolsCommand(chatID)
+	case "mcp":
+		h.handleMCPCommand(chatID, msg.CommandArguments())
 	case "stats":
 		h.handleStatsCommand(chatID)
 	default:
@@ -991,13 +994,42 @@ func registerCommands(bot *tgbotapi.BotAPI) error {
 		{Command: "model", Description: "Show / switch model"},
 		{Command: "routing", Description: "Configure routing (inline UI)"},
 		{Command: "tools", Description: "List connected MCP tools"},
+		{Command: "mcp", Description: "MCP management (update/reload)"},
 		{Command: "stats", Description: "Show history size, model, last compact"},
 		{Command: "help", Description: "Help"},
 	}
 	_, err := bot.Request(tgbotapi.NewSetMyCommands(commands...))
 	return err
 }
 
+func (h *Handler) handleMCPCommand(chatID int64, args string) {
+	switch strings.TrimSpace(args) {
+	case "update", "reload":
+		h.sendPlain(chatID, "Reloading MCP servers...")
+		configs, err := config.LoadMCPServers("config/mcp.json")
+		if err != nil {
+			h.sendPlain(chatID, "Error loading mcp.json: "+err.Error())
+			return
+		}
+		if len(configs) == 0 {
+			h.sendPlain(chatID, "No MCP servers configured in mcp.json.")
+			return
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+		defer cancel()
+		toolCount, err := h.agent.ReloadMCP(ctx, configs)
+		if err != nil {
+			h.sendPlain(chatID, "Error: "+err.Error())
+			return
+		}
+		h.sendPlain(chatID, fmt.Sprintf("MCP reloaded: %d servers, %d tools.", len(configs), toolCount))
+	default:
+		h.send(chatID,
+			"*MCP commands:*\n\n"+
+				"/mcp update — reload mcp\\.json and reconnect all servers")
+	}
+}
+
 func (h *Handler) handleToolsCommand(chatID int64) {
 	tools := h.agent.ListTools()
 	if len(tools) == 0 {