From cccc53cade41f6614119ce42b2d32c14cf3f74a5 Mon Sep 17 00:00:00 2001
From: Container <78986709+disonjer@users.noreply.github.com>
Date: Fri, 29 May 2026 10:28:38 +0200
Subject: [PATCH] fix(mcp): redirect console.log/warn to stderr in --mcp stdio
 mode (#2840)

Integrated into release/v3.8.6
---
 bin/omniroute.mjs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/bin/omniroute.mjs b/bin/omniroute.mjs
index e536ac30e0..b03bb3626c 100755
--- a/bin/omniroute.mjs
+++ b/bin/omniroute.mjs
@@ -28,6 +28,16 @@ const __filename = fileURLToPath(import.meta.url);
 const __dirname = dirname(__filename);
 const ROOT = join(__dirname, "..");
 
+// MCP stdio transport uses stdout exclusively for JSON-RPC messages.
+// Redirect console.log/warn to stderr early (before loadEnvFile and DB init)
+// so no startup output corrupts the protocol.
+if (process.argv.includes("--mcp")) {
+  const { Console } = await import("node:console");
+  const stderrConsole = new Console({ stdout: process.stderr, stderr: process.stderr });
+  console.log = stderrConsole.log.bind(stderrConsole);
+  console.warn = stderrConsole.warn.bind(stderrConsole);
+}
+
 function loadEnvFile() {
   const envPaths = [];