diff --git a/Dockerfile b/Dockerfile
index 223746eac98..a2b0ae08ee0 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -167,7 +167,7 @@ RUN mkdir -p \
     && touch superset/static/version_info.json
 
 # Install Playwright and optionally setup headless browsers
-ARG INCLUDE_CHROMIUM="true"
+ARG INCLUDE_CHROMIUM="false"
 ARG INCLUDE_FIREFOX="false"
 RUN --mount=type=cache,target=${SUPERSET_HOME}/.cache/uv \
     if [ "$INCLUDE_CHROMIUM" = "true" ] || [ "$INCLUDE_FIREFOX" = "true" ]; then \
diff --git a/UPDATING.md b/UPDATING.md
index ab2d788fd66..793f0781362 100644
--- a/UPDATING.md
+++ b/UPDATING.md
@@ -23,6 +23,7 @@ This file documents any backwards-incompatible changes in Superset and
 assists people when migrating to a new version.
 
 ## Next
+- [34258](https://github.com/apache/superset/pull/34258) changing the default in Dockerfile to INCLUDE_CHROMIUM="false" (from "true") in the past. This ensures the `lean` layer is lean by default, and people can opt-in to the `chromium` layer by setting the build arg `INCLUDE_CHROMIUM=true`. This is a breaking change for anyone using the `lean` layer, as it will no longer include Chromium by default.
 - [34204](https://github.com/apache/superset/pull/33603) OpenStreetView has been promoted as the new default for Deck.gl visualization since it can be enabled by default without requiring an API key. If you have Mapbox set up and want to disable OpenStreeView in your environment, please follow the steps documented here [https://superset.apache.org/docs/configuration/map-tiles].
 - [33116](https://github.com/apache/superset/pull/33116) In Echarts Series charts (e.g. Line, Area, Bar, etc.) charts, the `x_axis_sort_series` and `x_axis_sort_series_ascending` form data items have been renamed with `x_axis_sort` and `x_axis_sort_asc`.
   There's a migration added that can potentially affect a significant number of existing charts.