feat: make MCP server registrations persistent across peer disconnects

Persistent MCP servers (opt-in via `persistent: true`) survive host
disconnects — they appear as offline in mcp_list and auto-restore when
the host reconnects. Ephemeral servers (default) still clean up on
disconnect. Offline servers return a clear error on mcp_call with
time-since-disconnect info.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/broker/src/index.ts

@@ -196,6 +196,14 @@ interface McpRegisteredServer {
 /** Keyed by "meshId:serverName" */
 const mcpRegistry = new Map<string, McpRegisteredServer>();
 
+/** Human-readable relative time string from an ISO timestamp. */
+function relativeTimeStr(iso: string): string {
+  const ms = Date.now() - new Date(iso).getTime();
+  if (ms < 60_000) return `${Math.round(ms / 1000)}s ago`;
+  if (ms < 3_600_000) return `${Math.round(ms / 60_000)}m ago`;
+  return `${Math.round(ms / 3_600_000)}h ago`;
+}
+
 /** Pending MCP call forwards: callId → { resolve, timer } */
 const mcpCallResolvers = new Map<string, {
   resolve: (result: { result?: unknown; error?: string }) => void;
@@ -1236,6 +1244,34 @@ function handleConnection(ws: WebSocket): void {
             if (peer.meshId !== joinedConn.meshId) continue;
             sendToPeer(pid, joinMsg);
           }
+          // Restore persistent MCP servers owned by this member
+          for (const [, entry] of mcpRegistry) {
+            if (entry.memberId === joinedConn.memberId && entry.meshId === joinedConn.meshId && !entry.online) {
+              entry.online = true;
+              entry.presenceId = presenceId;
+              entry.offlineSince = undefined;
+              entry.hostedByName = joinedConn.displayName;
+              // Broadcast restoration
+              const restoreMsg: WSPushMessage = {
+                type: "push",
+                subtype: "system",
+                event: "mcp_restored",
+                eventData: { serverName: entry.serverName, hostedBy: joinedConn.displayName },
+                messageId: crypto.randomUUID(),
+                meshId: joinedConn.meshId,
+                senderPubkey: "system",
+                priority: "low",
+                nonce: "",
+                ciphertext: "",
+                createdAt: new Date().toISOString(),
+              };
+              for (const [pid2, peer2] of connections) {
+                if (peer2.meshId !== joinedConn.meshId) continue;
+                sendToPeer(pid2, restoreMsg);
+              }
+              log.info("mcp_restored", { server: entry.serverName, member: joinedConn.displayName });
+            }
+          }
         }
         return;
       }
@@ -2625,7 +2661,7 @@ function handleConnection(ws: WebSocket): void {
             description: mr.description,
             tools: mr.tools,
             hostedByName: conn.displayName,
-            persistent: !!(mr as any).persistent,
+            persistent: !!mr.persistent,
             online: true,
             memberId: conn.memberId,
             registeredAt: new Date().toISOString(),
@@ -2700,6 +2736,8 @@ function handleConnection(ws: WebSocket): void {
             description: string;
             hostedBy: string;
             tools: Array<{ name: string; description: string }>;
+            online: boolean;
+            offlineSince?: string;
           }> = [];
           for (const [, entry] of mcpRegistry) {
             if (entry.meshId !== conn.meshId) continue;
@@ -2708,6 +2746,8 @@ function handleConnection(ws: WebSocket): void {
               description: entry.description,
               hostedBy: entry.hostedByName,
               tools: entry.tools.map((t) => ({ name: t.name, description: t.description })),
+              online: entry.online,
+              ...(entry.offlineSince ? { offlineSince: entry.offlineSince } : {}),
             });
           }
           sendToPeer(presenceId, {
@@ -2733,10 +2773,28 @@ function handleConnection(ws: WebSocket): void {
             });
             break;
           }
+          // Check if server is offline (persistent but host disconnected)
+          if (!server.online) {
+            const ago = server.offlineSince
+              ? ` who disconnected ${relativeTimeStr(server.offlineSince)}`
+              : "";
+            sendToPeer(presenceId, {
+              type: "mcp_call_result",
+              error: `Server '${mc.serverName}' is offline — hosted by ${server.hostedByName}${ago}. It will restore when they reconnect.`,
+              ...(_reqId ? { _reqId } : {}),
+            });
+            break;
+          }
           // Check hosting peer is still connected
           const hostConn = connections.get(server.presenceId);
           if (!hostConn) {
-            mcpRegistry.delete(callKey);
+            if (server.persistent) {
+              server.online = false;
+              server.offlineSince = new Date().toISOString();
+              server.presenceId = "";
+            } else {
+              mcpRegistry.delete(callKey);
+            }
             sendToPeer(presenceId, {
               type: "mcp_call_result",
               error: `MCP server "${mc.serverName}" host disconnected`,

apps/broker/src/types.ts

@@ -737,6 +737,7 @@ export interface WSMcpRegisterMessage {
   serverName: string;
   description: string;
   tools: Array<{ name: string; description: string; inputSchema: Record<string, unknown> }>;
+  persistent?: boolean;
   _reqId?: string;
 }
 
@@ -787,6 +788,8 @@ export interface WSMcpListResultMessage {
     description: string;
     hostedBy: string;
     tools: Array<{ name: string; description: string }>;
+    online: boolean;
+    offlineSince?: string;
   }>;
   _reqId?: string;
 }

apps/cli/src/mcp/server.ts

@@ -1144,27 +1144,32 @@ Your message mode is "${messageMode}".
 
       // --- MCP Proxy ---
       case "mesh_mcp_register": {
-        const { server_name, description, tools: regTools } = (args ?? {}) as {
+        const { server_name, description, tools: regTools, persistent: regPersistent } = (args ?? {}) as {
           server_name?: string;
           description?: string;
           tools?: Array<{ name: string; description: string; inputSchema: Record<string, unknown> }>;
+          persistent?: boolean;
         };
         if (!server_name || !description || !regTools?.length)
           return text("mesh_mcp_register: `server_name`, `description`, and `tools` required", true);
         const client = allClients()[0];
         if (!client) return text("mesh_mcp_register: not connected", true);
-        const result = await client.mcpRegister(server_name, description, regTools);
+        const result = await client.mcpRegister(server_name, description, regTools, regPersistent);
         if (!result) return text("mesh_mcp_register: broker did not acknowledge", true);
-        return text(`Registered MCP server "${result.serverName}" with ${result.toolCount} tool(s). Other peers can now call its tools via mesh_tool_call.`);
+        const persistLabel = regPersistent ? " (persistent — survives disconnect)" : "";
+        return text(`Registered MCP server "${result.serverName}" with ${result.toolCount} tool(s)${persistLabel}. Other peers can now call its tools via mesh_tool_call.`);
       }
       case "mesh_mcp_list": {
         const client = allClients()[0];
         if (!client) return text("mesh_mcp_list: not connected", true);
         const servers = await client.mcpList();
         if (servers.length === 0) return text("No MCP servers registered in the mesh.");
-        const lines = servers.map((s) => {
-          const toolList = s.tools.map((t) => `    - **${t.name}**: ${t.description}`).join("\n");
-          return `- **${s.name}** (hosted by ${s.hostedBy}): ${s.description}\n${toolList}`;
+        const lines = servers.map((s: any) => {
+          const toolList = s.tools.map((t: any) => `    - **${t.name}**: ${t.description}`).join("\n");
+          const status = s.online === false
+            ? ` [OFFLINE${s.offlineSince ? ` since ${s.offlineSince}` : ""}]`
+            : "";
+          return `- **${s.name}** (hosted by ${s.hostedBy})${status}: ${s.description}\n${toolList}`;
         });
         return text(`${servers.length} MCP server(s) in mesh:\n${lines.join("\n")}`);
       }
@@ -1383,6 +1388,8 @@ Your message mode is "${messageMode}".
           content = `[system] New MCP server available: "${data.serverName}" (hosted by ${data.hostedBy}). Tools: ${tools}. Use mesh_tool_call to invoke.`;
         } else if (eventName === "mcp_unregistered") {
           content = `[system] MCP server "${data.serverName}" removed (was hosted by ${data.hostedBy})`;
+        } else if (eventName === "mcp_restored") {
+          content = `[system] MCP server "${data.serverName}" is back online (hosted by ${data.hostedBy})`;
         } else {
           content = `[system] ${eventName}: ${JSON.stringify(data)}`;
         }

apps/cli/src/mcp/tools.ts

@@ -682,6 +682,10 @@ export const TOOLS: Tool[] = [
           },
           description: "Tool definitions to expose",
         },
+        persistent: {
+          type: "boolean",
+          description: "If true, registration survives peer disconnect. Other peers see it as 'offline' until you reconnect. Default: false",
+        },
       },
       required: ["server_name", "description", "tools"],
     },

apps/cli/src/ws/client.ts

@@ -931,6 +931,7 @@ export class BrokerClient {
     serverName: string,
     description: string,
     tools: Array<{ name: string; description: string; inputSchema: Record<string, unknown> }>,
+    persistent?: boolean,
   ): Promise<{ serverName: string; toolCount: number } | null> {
     if (!this.ws || this.ws.readyState !== this.ws.OPEN) return null;
     return new Promise((resolve) => {
@@ -938,7 +939,7 @@ export class BrokerClient {
       this.mcpRegisterResolvers.set(reqId, { resolve, timer: setTimeout(() => {
         if (this.mcpRegisterResolvers.delete(reqId)) resolve(null);
       }, 5_000) });
-      this.ws!.send(JSON.stringify({ type: "mcp_register", serverName, description, tools, _reqId: reqId }));
+      this.ws!.send(JSON.stringify({ type: "mcp_register", serverName, description, tools, ...(persistent ? { persistent: true } : {}), _reqId: reqId }));
     });
   }