fix: cap zellij session name length to avoid socket path overflow crash

docs/CHANGELOG.md

@@ -1,5 +1,18 @@
 # Changelog
 
+## 2026-08-03
+
+- Fixed the `zellij-session` fish function in `presets/programs/zellij.nix`
+  truncating the session name (derived from the target directory basename)
+  to 20 characters. Zellij names each session's Unix-domain IPC socket
+  `$TMPDIR/zellij-<uid>/<version>/<name>`, and on macOS the socket path is
+  capped at 103 bytes. The `/var/folders/...` `$TMPDIR` prefix consumes ~79
+  of those, leaving only ~24 chars for the name, so switching into directories
+  with long basenames overflowed the socket path. Because `switch-session`
+  had already detached from the current session by the time the new one failed
+  to bind, the failure took down the entire terminal instead of erroring
+  gracefully.
+
 ## 2026-07-25
 
 - Added jjui config generation to `jujutsu.nix` in Home Manager to include custom GitHub ruleset bypass commands (`ctrl+b` and `ctrl+shift+b`).

platforms/home-manager/modules/nmasur/presets/programs/zellij.nix

@@ -58,8 +58,15 @@ in
               if test "$TARGET_DIR" = $(pwd)
                 return 1
               end
+              # Zellij names each session's IPC socket $TMPDIR/zellij-<uid>/<ver>/<name>.
+              # On macOS the socket path is capped at 103 bytes; the $TMPDIR prefix under
+              # /var/folders/... eats ~79 of those, leaving only ~24 chars for the name.
+              # A longer basename overflows the socket path, and because switch-session has
+              # already detached from the current session by the time the new one fails to
+              # bind, it takes the whole terminal down. Truncate to stay well under the limit.
+              set SESSION_NAME (basename $TARGET_DIR | string sub --length 20)
               echo "$ZELLIJ_SESSION_NAME" > ~/.local/state/zellij-last-session
-              ${lib.getExe pkgs.zellij} action switch-session $(basename $TARGET_DIR) --cwd $TARGET_DIR --layout default
+              ${lib.getExe pkgs.zellij} action switch-session $SESSION_NAME --cwd $TARGET_DIR --layout default
             '';
         };
         gh-run = {