diff --git a/my-labai.el b/my-labai.el
index b81ab85..31e9ba3 100644
--- a/my-labai.el
+++ b/my-labai.el
@@ -9,35 +9,64 @@
 ;; configuration
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-(defvar lab-ai-url
-  "https://amorphous.tf.chiba-u.jp/lab-ai/chat")
+(defgroup lab-ai nil
+  "Lab-AI client."
+  :group 'applications)
 
-(defvar lab-ai-image-url
-  "https://amorphous.tf.chiba-u.jp/lab-ai/image")
+(defconst lab-ai-url
+  "https://amorphous.tf.chiba-u.jp/lab-ai/chat"
+  "Lab-AI chat endpoint.")
 
-(defvar lab-ai-image-edit-url
-  "https://amorphous.tf.chiba-u.jp/lab-ai/image-edit")
+(defconst lab-ai-image-url
+  "https://amorphous.tf.chiba-u.jp/lab-ai/image"
+  "Lab-AI image generation endpoint.")
 
-(defvar lab-ai-image-size
-  "1024x1024")
+(defconst lab-ai-image-edit-url
+  "https://amorphous.tf.chiba-u.jp/lab-ai/image-edit"
+  "Lab-AI image editing endpoint.")
 
+(defconst lab-ai-supported-models
+  '("gpt-5.6-luna"
+    "gpt-5.6-terra"
+    "gpt-5.6-sol")
+  "Models supported by the Lab-AI gateway.")
 
-(defvar lab-ai-models
-  '("gpt-5-mini"
-    "gpt-5"
-    "gpt-5.5"))
+(defcustom lab-ai-model
+  "gpt-5.6-terra"
+  "Default model used by Lab-AI."
+  :type '(choice
+          (const :tag "GPT-5.6 Luna" "gpt-5.6-luna")
+          (const :tag "GPT-5.6 Terra" "gpt-5.6-terra")
+          (const :tag "GPT-5.6 Sol" "gpt-5.6-sol"))
+  :group 'lab-ai)
 
-(defvar lab-ai-model
-  "gpt-5.5")
+(defcustom lab-ai-image-size
+  "1024x1024"
+  "Default image size used by Lab-AI."
+  :type '(choice
+          (const "1024x1024")
+          (const "1024x1536")
+          (const "1536x1024"))
+  :group 'lab-ai)
 
-(defvar lab-ai-timeout
-  "600")
+(defcustom lab-ai-timeout
+  "600"
+  "Timeout in seconds passed to curl."
+  :type 'string
+  :group 'lab-ai)
 
-(defvar lab-ai-max-attachment-size
-  (* 50 1024 1024))
+(defcustom lab-ai-max-attachment-size
+  (* 5 1024 1024)
+  "Maximum attachment size in bytes."
+  :type 'integer
+  :group 'lab-ai)
+
+(defcustom lab-ai-chat-history-max-messages
+  200
+  "Maximum number of chat history messages."
+  :type 'integer
+  :group 'lab-ai)
 
-(defvar lab-ai-chat-history-max-messages
-  200)
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; API
@@ -510,6 +539,8 @@ Run again to clear previews."
                 #'lab-ai-chat-clear-attachments)
     (define-key map (kbd "C-c C-h")
                 #'lab-ai-chat-clear-history)
+    (define-key map (kbd "C-c C-m")
+                #'lab-ai-switch-model)
     map))
 
 
@@ -885,13 +916,16 @@ Run again to clear previews."
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; misc
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(defun lab-ai-show-model ()
+  (interactive)
+  (message "Lab-AI model: %s" lab-ai-model))
 
 (defun lab-ai-switch-model ()
   (interactive)
   (setq lab-ai-model
         (completing-read
          "Model: "
-         lab-ai-models
+         lab-ai-supported-models
          nil t
          lab-ai-model))
   (when (get-buffer lab-ai-chat-buffer)
@@ -899,9 +933,6 @@ Run again to clear previews."
       (lab-ai-chat-update-mode-line)))
   (message "lab-ai model => %s" lab-ai-model))
 
-(defun lab-ai-show-model ()
-  (interactive)
-  (message "Lab-AI model: %s" lab-ai-model))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Keys