In Meteor 3.4.1 dev mode, the meteor build-tool process leaks the rspack-generated server bundle and its source-map SourceNode graph on every incremental rebuild (“ => Server modified – restarting… ”). Nothing from the previous compilation is released, so the tool process grows ~linearly with the number of rebuilds and eventually dies with: FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory This is the meteor-tool process (the one launched at ~/.meteor/meteor with –max-old-space-size=4096 ), not the application server — confirmed by the