diff --git a/backend/Dockerfile b/backend/Dockerfile
index 3afd554..13d4fa6 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -30,9 +30,14 @@ RUN --mount=type=cache,target=/root/go/pkg/mod \
       -o /out/healthcheck ./cmd/healthcheck
 
 # ── backend service ──────────────────────────────────────────────────────────
-FROM gcr.io/distroless/static:nonroot AS backend
+# Uses Alpine (not distroless) so ffmpeg is available for on-demand voice
+# sample generation via pocket-tts (WAV→MP3 transcoding).
+FROM alpine:3.21 AS backend
+RUN apk add --no-cache ffmpeg ca-certificates && \
+    addgroup -S appgroup && adduser -S appuser -G appgroup
 COPY --from=builder /out/healthcheck /healthcheck
 COPY --from=builder /out/backend /backend
+USER appuser
 ENTRYPOINT ["/backend"]
 
 # ── runner service ───────────────────────────────────────────────────────────