diff --git a/docs/environment-variables.md b/docs/environment-variables.md
index e63a14a00..55b530b27 100644
--- a/docs/environment-variables.md
+++ b/docs/environment-variables.md
@@ -372,7 +372,7 @@ These are read as runtime signals; they are usually set by the terminal/OS rathe
 | `COLORFGBG`                                                                                                        | Terminal background light/dark auto-detection             |
 | `TERM_PROGRAM`, `TERM_PROGRAM_VERSION`, `TERMINAL_EMULATOR`                                                        | Terminal identity in system prompt/context                |
 | `KDE_FULL_SESSION`, `XDG_CURRENT_DESKTOP`, `DESKTOP_SESSION`, `XDG_SESSION_DESKTOP`, `GDMSESSION`, `WINDOWMANAGER` | Desktop/window-manager detection in system prompt/context |
-| `KITTY_WINDOW_ID`, `TMUX_PANE`, `TERM_SESSION_ID`, `WT_SESSION`                                                    | Stable per-terminal session breadcrumb IDs                |
+| `KITTY_WINDOW_ID`, `TMUX_PANE`, `TERM_SESSION_ID`, `WT_SESSION`, `CMUX_SURFACE_ID`                                    | Stable per-terminal session breadcrumb IDs                |
 | `SHELL`, `ComSpec`, `TERM_PROGRAM`, `TERM`                                                                         | System info diagnostics                                   |
 | `APPDATA`, `XDG_CONFIG_HOME`                                                                                       | lspmux config path resolution                             |
 | `HOME`                                                                                                             | Path shortening in MCP command UI                         |
diff --git a/docs/session-switching-and-recent-listing.md b/docs/session-switching-and-recent-listing.md
index faa2f2eac..1e8d0371f 100644
--- a/docs/session-switching-and-recent-listing.md
+++ b/docs/session-switching-and-recent-listing.md
@@ -67,7 +67,7 @@ For `SessionInfo` list entries:
 3. If breadcrumb is invalid/missing, fall back to newest file by mtime in the session dir (`findMostRecentSession`)
 4. If none found, create a new session
 
-Terminal ID derivation prefers TTY path and falls back to env-based identifiers (`KITTY_WINDOW_ID`, `TMUX_PANE`, `TERM_SESSION_ID`, `WT_SESSION`).
+Terminal ID derivation prefers TTY path and falls back to env-based identifiers (`KITTY_WINDOW_ID`, `TMUX_PANE`, `TERM_SESSION_ID`, `WT_SESSION`, `CMUX_SURFACE_ID`).
 
 Breadcrumb writes are best-effort and non-fatal.