diff --git a/package.json b/package.json
index 2624d98..f95f83a 100644
--- a/package.json
+++ b/package.json
@@ -14,6 +14,7 @@
   },
   "dependencies": {
     "@automerge/automerge": "^2.2.8",
+    "@encryptid/sdk": "file:../encryptid-sdk",
     "@lit/reactive-element": "^2.0.4",
     "hono": "^4.11.7",
     "postgres": "^3.4.5",
diff --git a/server/community-store.ts b/server/community-store.ts
index 5c2c867..3a82263 100644
--- a/server/community-store.ts
+++ b/server/community-store.ts
@@ -3,10 +3,14 @@ import * as Automerge from "@automerge/automerge";
 
 const STORAGE_DIR = process.env.STORAGE_DIR || "./data/communities";
 
+export type SpaceVisibility = 'public' | 'public_read' | 'authenticated' | 'members_only';
+
 export interface CommunityMeta {
 	name: string;
 	slug: string;
 	createdAt: string;
+	visibility: SpaceVisibility;
+	ownerDID: string | null;
 }
 
 export interface ShapeData {
@@ -138,13 +142,20 @@ export async function saveCommunity(slug: string): Promise<void> {
 /**
  * Create a new community
  */
-export async function createCommunity(name: string, slug: string): Promise<Automerge.Doc<CommunityDoc>> {
+export async function createCommunity(
+	name: string,
+	slug: string,
+	ownerDID: string | null = null,
+	visibility: SpaceVisibility = 'public_read',
+): Promise<Automerge.Doc<CommunityDoc>> {
 	let doc = Automerge.init<CommunityDoc>();
 	doc = Automerge.change(doc, "Create community", (d) => {
 		d.meta = {
 			name,
 			slug,
 			createdAt: new Date().toISOString(),
+			visibility,
+			ownerDID,
 		};
 		d.shapes = {};
 	});
diff --git a/server/index.ts b/server/index.ts
index 153079a..4896f22 100644
--- a/server/index.ts
+++ b/server/index.ts
@@ -11,6 +11,30 @@ import {
 	removePeerSyncState,
 	updateShape,
 } from "./community-store";
+import type { SpaceVisibility } from "./community-store";
+import {
+	verifyEncryptIDToken,
+	evaluateSpaceAccess,
+	extractToken,
+	authenticateWSUpgrade,
+} from "@encryptid/sdk/server";
+import type { EncryptIDClaims, SpaceAuthConfig } from "@encryptid/sdk/server";
+
+/** Resolve a community slug to its SpaceAuthConfig for the SDK guard */
+async function getSpaceConfig(slug: string): Promise<SpaceAuthConfig | null> {
+	let doc = getDocumentData(slug);
+	if (!doc) {
+		await loadCommunity(slug);
+		doc = getDocumentData(slug);
+	}
+	if (!doc) return null;
+	return {
+		spaceSlug: slug,
+		visibility: (doc.meta.visibility || "public_read") as SpaceVisibility,
+		ownerDID: doc.meta.ownerDID || undefined,
+		app: "rspace",
+	};
+}
 
 const PORT = Number(process.env.PORT) || 3000;
 const DIST_DIR = resolve(import.meta.dir, "../dist");
@@ -19,6 +43,8 @@ const DIST_DIR = resolve(import.meta.dir, "../dist");
 interface WSData {
 	communitySlug: string;
 	peerId: string;
+	claims: EncryptIDClaims | null;
+	readOnly: boolean;
 }
 
 // Track connected clients per community (for broadcasting)
@@ -97,13 +123,29 @@ const server = Bun.serve<WSData>({
 		const host = req.headers.get("host");
 		const subdomain = getSubdomain(host);
 
-		// Handle WebSocket upgrade
+		// Handle WebSocket upgrade (with auth for non-public communities)
 		if (url.pathname.startsWith("/ws/")) {
 			const communitySlug = url.pathname.split("/")[2];
 			if (communitySlug) {
+				// Check space visibility — authenticate if needed
+				const spaceConfig = await getSpaceConfig(communitySlug);
+				const claims = await authenticateWSUpgrade(req);
+				let readOnly = false;
+
+				if (spaceConfig) {
+					const vis = spaceConfig.visibility;
+					if (vis === "authenticated" || vis === "members_only") {
+						if (!claims) {
+							return new Response("Authentication required to join this space", { status: 401 });
+						}
+					} else if (vis === "public_read") {
+						readOnly = !claims;
+					}
+				}
+
 				const peerId = generatePeerId();
 				const upgraded = server.upgrade(req, {
-					data: { communitySlug, peerId },
+					data: { communitySlug, peerId, claims, readOnly },
 				});
 				if (upgraded) return undefined;
 			}
@@ -189,6 +231,14 @@ const server = Bun.serve<WSData>({
 				const msg = JSON.parse(message.toString());
 
 				if (msg.type === "sync" && Array.isArray(msg.data)) {
+					// Block sync writes from read-only connections
+					if (ws.data.readOnly) {
+						ws.send(JSON.stringify({
+							type: "error",
+							message: "Authentication required to edit this space",
+						}));
+						return;
+					}
 					// Handle Automerge sync message
 					const syncMessage = new Uint8Array(msg.data);
 					const result = receiveSyncMessage(communitySlug, peerId, syncMessage);
@@ -236,6 +286,10 @@ const server = Bun.serve<WSData>({
 				}
 				// Legacy message handling for backward compatibility
 				else if (msg.type === "update" && msg.id && msg.data) {
+					if (ws.data.readOnly) {
+						ws.send(JSON.stringify({ type: "error", message: "Authentication required to edit" }));
+						return;
+					}
 					updateShape(communitySlug, msg.id, msg.data);
 					// Broadcast to other clients
 					const clients = communityClients.get(communitySlug);
@@ -248,6 +302,10 @@ const server = Bun.serve<WSData>({
 						}
 					}
 				} else if (msg.type === "delete" && msg.id) {
+					if (ws.data.readOnly) {
+						ws.send(JSON.stringify({ type: "error", message: "Authentication required to delete" }));
+						return;
+					}
 					deleteShape(communitySlug, msg.id);
 					// Broadcast to other clients
 					const clients = communityClients.get(communitySlug);
@@ -289,19 +347,42 @@ const server = Bun.serve<WSData>({
 async function handleAPI(req: Request, url: URL): Promise<Response> {
 	const corsHeaders = {
 		"Access-Control-Allow-Origin": "*",
-		"Access-Control-Allow-Methods": "GET, POST, OPTIONS",
-		"Access-Control-Allow-Headers": "Content-Type",
+		"Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
+		"Access-Control-Allow-Headers": "Content-Type, Authorization",
 	};
 
 	if (req.method === "OPTIONS") {
 		return new Response(null, { headers: corsHeaders });
 	}
 
-	// POST /api/communities - Create new community
+	// POST /api/communities - Create new community (requires auth)
 	if (url.pathname === "/api/communities" && req.method === "POST") {
 		try {
-			const body = (await req.json()) as { name?: string; slug?: string };
-			const { name, slug } = body;
+			// Require EncryptID authentication to create a community
+			const token = extractToken(req.headers);
+			if (!token) {
+				return Response.json(
+					{ error: "Authentication required to create a community" },
+					{ status: 401, headers: corsHeaders }
+				);
+			}
+
+			let claims: EncryptIDClaims;
+			try {
+				claims = await verifyEncryptIDToken(token);
+			} catch {
+				return Response.json(
+					{ error: "Invalid or expired authentication token" },
+					{ status: 401, headers: corsHeaders }
+				);
+			}
+
+			const body = (await req.json()) as {
+				name?: string;
+				slug?: string;
+				visibility?: SpaceVisibility;
+			};
+			const { name, slug, visibility = "public_read" } = body;
 
 			if (!name || !slug) {
 				return Response.json(
@@ -318,6 +399,15 @@ async function handleAPI(req: Request, url: URL): Promise<Response> {
 				);
 			}
 
+			// Validate visibility
+			const validVisibilities = ["public", "public_read", "authenticated", "members_only"];
+			if (!validVisibilities.includes(visibility)) {
+				return Response.json(
+					{ error: `Invalid visibility. Must be one of: ${validVisibilities.join(", ")}` },
+					{ status: 400, headers: corsHeaders }
+				);
+			}
+
 			// Check if exists
 			if (await communityExists(slug)) {
 				return Response.json(
@@ -326,12 +416,18 @@ async function handleAPI(req: Request, url: URL): Promise<Response> {
 				);
 			}
 
-			// Create community
-			await createCommunity(name, slug);
+			// Create community with owner and visibility
+			await createCommunity(name, slug, claims.sub, visibility);
 
 			// Return URL to new community
 			return Response.json(
-				{ url: `https://${slug}.rspace.online`, slug, name },
+				{
+					url: `https://${slug}.rspace.online`,
+					slug,
+					name,
+					visibility,
+					ownerDID: claims.sub,
+				},
 				{ headers: corsHeaders }
 			);
 		} catch (e) {
@@ -343,13 +439,25 @@ async function handleAPI(req: Request, url: URL): Promise<Response> {
 		}
 	}
 
-	// GET /api/communities/:slug - Get community info
+	// GET /api/communities/:slug - Get community info (respects visibility)
 	if (url.pathname.startsWith("/api/communities/") && req.method === "GET") {
 		const slug = url.pathname.split("/")[3];
-		const data = getDocumentData(slug);
 
+		// Check space access using SDK guard
+		const token = extractToken(req.headers);
+		const access = await evaluateSpaceAccess(slug, token, req.method, {
+			getSpaceConfig,
+		});
+
+		if (!access.allowed) {
+			return Response.json(
+				{ error: access.reason },
+				{ status: access.claims ? 403 : 401, headers: corsHeaders }
+			);
+		}
+
+		const data = getDocumentData(slug);
 		if (!data) {
-			// Try loading from disk
 			await loadCommunity(slug);
 			const loadedData = getDocumentData(slug);
 			if (!loadedData) {
@@ -358,10 +466,16 @@ async function handleAPI(req: Request, url: URL): Promise<Response> {
 					{ status: 404, headers: corsHeaders }
 				);
 			}
-			return Response.json({ meta: loadedData.meta }, { headers: corsHeaders });
+			return Response.json(
+				{ meta: loadedData.meta, readOnly: access.readOnly },
+				{ headers: corsHeaders }
+			);
 		}
 
-		return Response.json({ meta: data.meta }, { headers: corsHeaders });
+		return Response.json(
+			{ meta: data.meta, readOnly: access.readOnly },
+			{ headers: corsHeaders }
+		);
 	}
 
 	return Response.json({ error: "Not found" }, { status: 404, headers: corsHeaders });