diff --git a/src/langbot/pkg/provider/tools/loaders/mcp_stdio.py b/src/langbot/pkg/provider/tools/loaders/mcp_stdio.py
index fe7ccd11a..57b5e60c5 100644
--- a/src/langbot/pkg/provider/tools/loaders/mcp_stdio.py
+++ b/src/langbot/pkg/provider/tools/loaders/mcp_stdio.py
@@ -142,7 +142,15 @@ class BoxStdioSessionRuntime:
             read_only_rootfs=self.config.read_only_rootfs if self.config.read_only_rootfs is not None else False,
             image=self.config.image,
             cpus=self.config.cpus,
-            memory_mb=self.config.memory_mb,
+            # Node.js runtimes (npx/bunx) reserve large virtual address space and
+            # load WebAssembly modules (llhttp) on startup; the default 512 MB
+            # cgroup_mem_max is too small and causes OOM kills (return_code=137).
+            # Auto-bump to 1024 MB when the runner is npx/bunx/pnpm dlx.
+            memory_mb=(
+                (self.config.memory_mb or 1024)
+                if self.server_config.get('command', '') in ('npx', 'bunx', 'pnpm')
+                else self.config.memory_mb
+            ),
             pids_limit=self.config.pids_limit,
             persistent=True,
         )