diff --git a/Dockerfile.sidecars b/Dockerfile.sidecars
index 93ec77f..8d2e3a0 100644
--- a/Dockerfile.sidecars
+++ b/Dockerfile.sidecars
@@ -95,6 +95,10 @@ RUN mkdir -p \
       /run/supervise/queue \
       /home/mitmproxy/.mitmproxy
 
+# Documentation only — the compose renderer publishes whichever
+# subset the bottle uses.
+EXPOSE 8888 9099 9418 9100
+
 # WORKDIR matches Dockerfile.supervise's prior layout so the
 # in-app same-dir import in supervise_server.py stays deterministic.
 WORKDIR /app