From eec1f84b8db9feb50c0e4bdf261088c92342660f Mon Sep 17 00:00:00 2001
From: Josh Stein <josh@threshold.vc>
Date: Wed, 6 May 2026 15:10:13 -0700
Subject: [PATCH] fix(mcp): exit serve process on stdin-close/SIGTERM

MCP stdio server was keeping the bun process alive indefinitely after
the client disconnected. Over days this accumulated 20+ orphaned
gbrain serve processes, all holding the PGLite directory open.
Since PGLite is single-writer, this caused write-lock contention that
made email-sync fail its 15s per-put timeout: 114 puts x 15s = 28.5min
runs with 0 emails written.

Now listens for stdin end/close, transport close, and SIGTERM/SIGINT/
SIGHUP; calls engine.disconnect() and exits cleanly.

Root cause for the no-gbrain-run-in-50h alert.
---
 src/mcp/server.ts | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index e0d4eb794..3724ade7a 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -32,6 +32,26 @@ export async function startMcpServer(engine: BrainEngine) {
 
   const transport = new StdioServerTransport();
   await server.connect(transport);
+
+  // Exit cleanly when MCP client disconnects (stdin EOF) or on signals.
+  // Without this, orphaned serve processes accumulate and contend for the
+  // PGLite write lock, causing ingest jobs (email-sync) to time out.
+  let shuttingDown = false;
+  const shutdown = (reason: string, code = 0) => {
+    if (shuttingDown) return;
+    shuttingDown = true;
+    process.stderr.write(`[gbrain-serve] shutdown: ${reason}\n`);
+    Promise.resolve(engine.disconnect?.())
+      .catch(() => {})
+      .finally(() => process.exit(code));
+  };
+  process.stdin.on('end', () => shutdown('stdin end'));
+  process.stdin.on('close', () => shutdown('stdin close'));
+  // @ts-ignore — SDK exposes onclose on transport
+  transport.onclose = () => shutdown('transport close');
+  process.on('SIGTERM', () => shutdown('SIGTERM'));
+  process.on('SIGINT', () => shutdown('SIGINT'));
+  process.on('SIGHUP', () => shutdown('SIGHUP'));
 }
 
 // Backward compat: used by `gbrain call` command (trusted local path).