fix(environments): revoke library blob urls only after their replacement lands

CHANGELOG.md

@@ -23,6 +23,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 - Capture the Three.js group once in `VrmAvatar` so effect cleanup detaches from the same container the model was attached to (avoids orphan scenes on avatar swap). (#34)
 - Drop unused `audioFile` prop from `VoicePanel` (file input is uncontrolled). (#34)
 - `npm run dev:desktop` now passes `concurrently -k` so closing the Electron window (or killing Vite) tears down both processes and frees port 5173. (#37, #38)
+- Custom environment library blob URLs are revoked only after the replacement list is in state, so the stage/picker never briefly reference dead `blob:` URLs while a Directories folder switch loads. (#39, #40)
 
 ## [0.5.0] — 2026-08-06
 

avatar/src/components/AvatarStage.jsx

@@ -362,27 +362,37 @@ export function AvatarStage() {
     let cancelled = false;
 
     async function refreshEnvLibrary() {
-      revokeEnvironmentBlobUrls(libraryEnvironmentsRef.current);
+      // Revoking before the await left the stage and the picker pointing at
+      // urls that no longer resolve for as long as the replacement took to
+      // load. Already-decoded images survive revocation, so nothing changed on
+      // screen — but a remount in that window loaded nothing. Hold the old list
+      // and drop it only once its replacement is in state (#39).
+      const previous = libraryEnvironmentsRef.current;
       const useLibrary =
         desktopMode &&
         directories.environments.mode === 'custom' &&
         Boolean(directories.environments.path);
 
       if (!useLibrary) {
         setLibraryCustomEnvironments([]);
-        if (!cancelled) setLibraryEnvironments([]);
+        if (!cancelled) {
+          setLibraryEnvironments([]);
+          revokeEnvironmentBlobUrls(previous);
+        }
         return;
       }
 
       const { environments: next, error } = await loadLibraryEnvironments(
         directories.environments.path,
       );
       if (cancelled) {
+        // A newer run captured the same `previous` and owns retiring it.
         revokeEnvironmentBlobUrls(next);
         return;
       }
       setLibraryEnvironments(next);
       setLibraryCustomEnvironments(next);
+      revokeEnvironmentBlobUrls(previous);
       if (error) {
         setDirectoriesNotice(error);
         setDirectories((prev) => ({
@@ -391,6 +401,7 @@ export function AvatarStage() {
         }));
         setLibraryEnvironments([]);
         setLibraryCustomEnvironments([]);
+        revokeEnvironmentBlobUrls(next);
         setSelectedBg((prev) =>
           prev.type === 'env' && String(prev.id).startsWith('lib-env-')
             ? { type: 'color', value: defaultColor }
@@ -408,6 +419,7 @@ export function AvatarStage() {
         }));
         setLibraryEnvironments([]);
         setLibraryCustomEnvironments([]);
+        revokeEnvironmentBlobUrls(next);
         setSelectedBg((prev) =>
           prev.type === 'env' && String(prev.id).startsWith('lib-env-')
             ? { type: 'color', value: defaultColor }