diff --git a/docs/config.html b/docs/config.html
index da45276..6311f7f 100644
--- a/docs/config.html
+++ b/docs/config.html
@@ -415,7 +415,7 @@
                       <td><code>PI_WEB_DATA_DIR</code></td>
                       <td>Process/env</td>
                       <td>Not supported locally</td>
-                      <td>Restart services before changing; moves managed state location</td>
+                      <td>Restart services before changing; selects a new state location without moving existing state</td>
                     </tr>
                     <tr>
                       <td>Session daemon socket</td>
diff --git a/docs/config.md b/docs/config.md
index f28cf05..0934a6f 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -141,6 +141,8 @@ Rows with JSON key `—` are runtime-only environment variables, not config-file
 
 `PI_WEB_DATA_DIR` sets the root for PI WEB-managed runtime state and defaults to `~/.pi-web`. Unless a more specific path override is configured, PI WEB stores its project and machine registries, locally discovered plugins, default session-daemon socket, and session archives beneath this root.
 
+Changing `PI_WEB_DATA_DIR` only selects where state lives; it never moves or copies existing state. Each data directory is independent, so after pointing PI WEB at a new root it starts there with empty registries and no session archives. To carry session archives over, stop PI WEB, then copy `archived-sessions.json` and the `archived-sessions/` directory from the old data directory into the new one before starting it again.
+
 This setting does not change the PI WEB config file selected by `PI_WEB_CONFIG` or Pi-owned state such as the active session files selected by `PI_CODING_AGENT_SESSION_DIR`.
 
 ### External path access