Problem

In src/containers/Edit.tsx, the onEditorChange callback mutates the file object directly:

const onEditorChange = useCallback(
  (newValue: string | undefined) => {
    if (!newValue) return;
    const file = simulation?.files.find(
      (file) => file.fileName === selectedFile?.fileName,
    );
    if (file) {
      file.content = newValue; // ← direct mutation
    }
  },
  [selectedFile?.fileName, simulation?.files],
);

This bypasses easy-peasy's immutability contract. While it may appear to work (because objects are references), it:

• Does not trigger React re-renders for components observing simulation.files
• Breaks time-travel debugging / state snapshots
• Is inconsistent with the rest of the codebase which uses proper actions

Solution

Add an updateFileContent action to the simulation store and dispatch it from onEditorChange instead of mutating the file object directly.