fix: reconnect MCP bridge on SSE timeout + pre-parse server body (#900, #768)

1. **happyMcpStdioBridge.ts**: Auto-reconnect when HTTP MCP client drops.
   transport.onclose/client.onclose reset the client reference. Failed
   calls close the stale client to free SSE streams/timers and let the
   next invocation create a fresh connection.

2. **startHappyServer.ts**: Pre-parse POST body and pass as `parsedBody`
   to transport.handleRequest(), bypassing @hono/node-server stream
   conversion that causes HTTP 500. Invalid JSON returns proper 400.

Closes #900, closes #768

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

packages/happy-cli/src/claude/utils/startHappyServer.ts

@@ -77,17 +77,34 @@ export async function startHappyServer(client: ApiSessionClient) {
     const server = createServer(async (req, res) => {
         const mcp = createMcpServer(handler);
         try {
+            // Pre-parse body to avoid @hono/node-server stream conversion issues
+            let parsedBody: unknown;
+            if (req.method === 'POST') {
+                const chunks: Buffer[] = [];
+                for await (const chunk of req) {
+                    chunks.push(typeof chunk === 'string' ? Buffer.from(chunk) : chunk);
+                }
+                try {
+                    parsedBody = JSON.parse(Buffer.concat(chunks).toString());
+                } catch {
+                    res.writeHead(400, { 'Content-Type': 'application/json' });
+                    res.end(JSON.stringify({ jsonrpc: '2.0', error: { code: -32700, message: 'Parse error' }, id: null }));
+                    mcp.close();
+                    return;
+                }
+            }
+
             const transport = new StreamableHTTPServerTransport({
                 sessionIdGenerator: undefined
             });
             await mcp.connect(transport);
-            await transport.handleRequest(req, res);
+            await transport.handleRequest(req, res, parsedBody);
             res.on('close', () => {
                 transport.close();
                 mcp.close();
             });
         } catch (error) {
-            logger.debug("Error handling request:", error);
+            logger.debug("[happyMCP] Error handling request:", error);
             if (!res.headersSent) {
                 res.writeHead(500).end();
             }

packages/happy-cli/src/codex/happyMcpStdioBridge.ts

@@ -56,7 +56,18 @@ async function main() {
           { capabilities: {} }
         );
         const transport = new StreamableHTTPClientTransport(new URL(baseUrl));
+        transport.onclose = () => {
+          // Reset client on transport close so next call reconnects
+          if (httpClient === client) {
+            httpClient = null;
+          }
+        };
         await client.connect(transport);
+        client.onclose = () => {
+          if (httpClient === client) {
+            httpClient = null;
+          }
+        };
         httpClient = client;
         return client;
       } finally {
@@ -87,9 +98,12 @@ async function main() {
       try {
         const client = await ensureHttpClient();
         const response = await client.callTool({ name: 'change_title', arguments: args });
-        // Pass-through response from HTTP server
         return response as any;
       } catch (error) {
+        // Clean up stale client so the next invocation reconnects
+        const staleClient = httpClient;
+        httpClient = null;
+        try { await staleClient?.close(); } catch { /* ignore close errors */ }
         return {
           content: [
             { type: 'text', text: `Failed to change chat title: ${error instanceof Error ? error.message : String(error)}` },