diff --git a/.gitmodules b/.gitmodules
index 4fe1718..c5c5f09 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -34,3 +34,9 @@
 [submodule "hlinum-mode"]
 	path = hlinum-mode
 	url = https://github.com/ffailla/hlinum-mode.git
+[submodule "sage-shell-mode"]
+	path = sage-shell-mode
+	url = https://github.com/stakemori/sage-shell-mode.git
+[submodule "emacs-deferred"]
+	path = emacs-deferred
+	url = https://github.com/kiwanami/emacs-deferred.git
diff --git a/emacs-deferred b/emacs-deferred
new file mode 160000
index 0000000..896d4b5
--- /dev/null
+++ b/emacs-deferred
@@ -0,0 +1 @@
+Subproject commit 896d4b53210289afe489e1ee7db4e12cb9248109
diff --git a/init.el b/init.el
index 48e52ab..6403cbd 100644
--- a/init.el
+++ b/init.el
@@ -249,6 +249,9 @@
 (global-set-key (kbd "C-M-o") 'up-list)	  ;; -o stands for /out/
 (global-unset-key (kbd "C-M-u"))
 
+;; experimental: try to force myself to use the buffer commands
+(global-unset-key (kbd "M-["))
+(global-unset-key (kbd "M-]"))
 
 (require 'visible-mark)
 (visible-mark-mode t)
diff --git a/sage-shell-mode b/sage-shell-mode
new file mode 160000
index 0000000..8fc9cd7
--- /dev/null
+++ b/sage-shell-mode
@@ -0,0 +1 @@
+Subproject commit 8fc9cd7d065bbea8ac5caacbcb3ee86b3900697e