How Does Hot Reload Work with a Compiler?

Part of: Questions & Answers · The Story of Morph

Good question — you'd think "compiled" means "restart to see changes." It doesn't.

Dev mode works like this:

1. The app stays running — the window and the layout tree live in a dev runtime binary (morph_devrt)
2. Your component logic lives in a shared library — logic.so — compiled separately from the runtime
3. You save — Morph detects the change, recompiles only the logic into a fresh logic.so
4. The runtime swaps it — dlopen loads the new library and the live-reload machinery swaps the changed nodes in the tree, without restarting the window

So the compiled core (the renderer, the window, the layout engine) never restarts — only your logic module is hot-swapped. It's the same technique dynamic plugin systems use, applied to your own code.

CSS and JSX structure changes re-run the front of the pipeline (parse → IR → node tree) and re-mount the affected part of the tree. Your app state persists across the swap, and the loop is near-instant for small changes.

The Dev Mode page has the full pipeline diagram. And when the compiler moves to Rust (Rust Compiler & Native CLI), this loop gets dramatically faster — compile time is the only slow part of the cycle.