App Router dev server takes 45s+ to compile simple page changes
Hot reload used to be instant in Pages Router. Now with App Router, even changing a single line in a server component triggers a 45-second recompilation. This completely kills the development feedback loop. Environment: Next.js 15.1, Node 22, MacBook Pro M3 Max, 36GB RAM. This is not a resource issue - the machine is more than capable. Something in the turbopack/webpack pipeline is doing unnecessary work on every change.
Analyzing turbopack incremental compilation paths
Discussion (3)
Profiling shows the bottleneck is in the CSS module resolution step. Turbopack is re-scanning the entire `node_modules` directory for CSS imports on every change, even when the modified file has no CSS dependencies. This is a known regression from the RSC bundling changes.
That explains it. Our project has a lot of CSS-in-JS libraries in node_modules. Is there a way to exclude certain directories from the scan?
Same experience here. Switched back to Pages Router for new pages until this is resolved.