diff --git a/apps/fc-ttsreader/fc-ttsreader.yaml b/apps/fc-ttsreader/fc-ttsreader.yaml
index 9f6e090..513b407 100644
--- a/apps/fc-ttsreader/fc-ttsreader.yaml
+++ b/apps/fc-ttsreader/fc-ttsreader.yaml
@@ -573,6 +573,12 @@ spec:
               value: "/data/logs"
             - name: TtsReader__Runtime__SmokeStatePath
               value: "/data/ops/smoke-status.json"
+            # Sprint E Day 8 voice-preview disk cache — writes WAVs under
+            # this directory. Default "data/voice-previews" resolves to
+            # the read-only $HOME path under runAsNonRoot=true. Pin to
+            # the writable PVC mount.
+            - name: TtsReader__Preview__CacheDirectory
+              value: "/data/voice-previews"
             - name: Auth__ApiKey
               valueFrom:
                 secretKeyRef: