feat(mcp): add SSE transport support and related configuration options

internal/mcpserver/server.go

@@ -46,7 +46,28 @@ type ToolSet struct {
 	Describe      *tools.DescribeTool
 }
 
+// Handlers groups the HTTP handlers produced for an MCP server instance.
+type Handlers struct {
+	// StreamableHTTP is the primary MCP handler (always non-nil).
+	StreamableHTTP http.Handler
+	// SSE is the SSE transport handler; nil when SSEPath is empty.
+	// SSE is the de facto transport for MCP over the internet and is required by most hosted MCP clients.
+	SSE http.Handler
+}
+
+// New builds the StreamableHTTP MCP handler. It is a convenience wrapper
+// around NewHandlers for callers that only need the primary transport.
 func New(cfg config.MCPConfig, logger *slog.Logger, toolSet ToolSet, onSessionClosed func(string)) (http.Handler, error) {
+	h, err := NewHandlers(cfg, logger, toolSet, onSessionClosed)
+	if err != nil {
+		return nil, err
+	}
+	return h.StreamableHTTP, nil
+}
+
+// NewHandlers builds MCP HTTP handlers for both transports.
+// SSE is nil when cfg.SSEPath is empty.
+func NewHandlers(cfg config.MCPConfig, logger *slog.Logger, toolSet ToolSet, onSessionClosed func(string)) (Handlers, error) {
 	instructions := cfg.Instructions
 	if instructions == "" {
 		instructions = string(amcsllm.MemoryInstructions)
@@ -77,7 +98,7 @@ func New(cfg config.MCPConfig, logger *slog.Logger, toolSet ToolSet, onSessionCl
 		registerDescribeTools,
 	} {
 		if err := register(server, logger, toolSet); err != nil {
-			return nil, err
+			return Handlers{}, err
 		}
 	}
 
@@ -89,9 +110,19 @@ func New(cfg config.MCPConfig, logger *slog.Logger, toolSet ToolSet, onSessionCl
 		opts.EventStore = newCleanupEventStore(mcp.NewMemoryEventStore(nil), onSessionClosed)
 	}
 
-	return mcp.NewStreamableHTTPHandler(func(*http.Request) *mcp.Server {
-		return server
-	}, opts), nil
+	h := Handlers{
+		StreamableHTTP: mcp.NewStreamableHTTPHandler(func(*http.Request) *mcp.Server {
+			return server
+		}, opts),
+	}
+
+	if strings.TrimSpace(cfg.SSEPath) != "" {
+		h.SSE = mcp.NewSSEHandler(func(*http.Request) *mcp.Server {
+			return server
+		}, nil)
+	}
+
+	return h, nil
 }
 
 // buildServerIcons returns icon definitions referencing the server's own /images/icon.png endpoint.