diff --git a/src/index.tsx b/src/index.tsx
index 166f7f4..0af1d28 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -61,7 +61,7 @@ window.addEventListener('load', async () => {
   
   registerCustomAppHeightCSSProperty();
 
-  const fs = await createEditorFS({prefix: '/', allowPersistence: isInStandaloneMode});
+  const fs = await createEditorFS({prefix: '/libraries/', allowPersistence: isInStandaloneMode});
 
   await registerOpenSCADLanguage(fs, '/', zipArchives);
 
diff --git a/src/runner/openscad-worker.ts b/src/runner/openscad-worker.ts
index cdaae72..aba0d6d 100644
--- a/src/runner/openscad-worker.ts
+++ b/src/runner/openscad-worker.ts
@@ -93,6 +93,11 @@ addEventListener('message', async (e) => {
     if (inputs) {
       for (const source of inputs) {
         try {
+          if (source.path.startsWith('/libraries/')) {  
+            console.log(`Skipping ${source.path}`);
+            continue;
+          }
+          console.log(`Writing ${source.path}`);
           instance.FS.writeFile(source.path, await fetchSource(source));
         } catch (e) {
           console.trace(e);
diff --git a/src/state/model.ts b/src/state/model.ts
index 7ea8ce5..85dbaeb 100644
--- a/src/state/model.ts
+++ b/src/state/model.ts
@@ -118,17 +118,24 @@ export class Model {
   }
 
   openFile(path: string) {
-    // alert(`TODO: open ${path}`);
+    // console.log(`openFile: ${path}`);
     if (this.mutate(s => {
       if (s.params.activePath != path) {
-        s.params.activePath = path;
-        if (!s.params.sources.find(src => src.path === path)) {
-          let content = '';
+        const readSource = (path: string) => {
           try {
-            content = new TextDecoder("utf-8").decode(this.fs.readFileSync(path));
+            return new TextDecoder("utf-8").decode(this.fs.readFileSync(path));
           } catch (e) {
             console.error('Error while reading file:', e);
+            return '';
           }
+        };
+        // Remove source of previous active path if it's unmodified
+        const activePathContent = readSource(s.params.activePath);
+        s.params.sources = s.params.sources.filter(src => src.path !== s.params.activePath || src.content != activePathContent);
+
+        s.params.activePath = path;
+        if (!s.params.sources.find(src => src.path === path)) {
+          const content = readSource(path);
           s.params.sources = [...s.params.sources, {path, content}];
         }
         s.lastCheckerRun = undefined;
@@ -307,6 +314,7 @@ export class Model {
   }
 
   async render({isPreview, mountArchives, now, retryInOtherDim}: {isPreview: boolean, mountArchives?: boolean, now: boolean, retryInOtherDim?: boolean}) {
+    // console.log(JSON.stringify(this.state, null, 2));
     mountArchives ??= true;
     retryInOtherDim ??= true;
     const setRendering = (s: State, value: boolean) => {