diff --git a/README.md b/README.md
index bcecdf6..2072a9e 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,7 @@ For persistent environment variables, add them to `container-home/.bashrc` (or `
 
 - `XDG_DATA_HOME`: Override default data directory (default: `~/.local/share`)
 - `AGENT_CONTAINER_RUNTIME`: Container runtime to use (default: `podman`, set to `docker` for the old behaviour)
+- `AGENT_CONTAINER=1`: Set inside every container, so tools and skills running there can tell they are not on the host. The environment is fixed at container creation time, so containers that predate the marker are recreated on the next run.
 
 ## Usage
 
@@ -171,6 +172,8 @@ agent-container update
 
 This rebuilds the image with a freshly pulled base but keeps all existing containers and everything installed in them. The persistent home directory is not affected.
 
+Release notes for each tagged version, including what to do when upgrading, are in [CHANGELOG.md](CHANGELOG.md).
+
 ### Purge
 
 To remove all containers, the image, and the persistent home directory: