Apply trick to insert font-locked strings in a font-locked buffer

kagi.el

@@ -257,6 +257,21 @@ https://help.kagi.com/kagi/api/fastgpt.html for more information."
                                       nil)
     (buffer-string)))
 
+(defun kagi--fontify-using-faces (s)
+  "Set the fontified property in the string S.
+
+This is needed to insert a font-locked string (generated by
+`kagi--apply-markdown-font-lock') in a font-lock enabled buffer."
+  ;; Inspired by this answer at Emacs StackExchange:
+  ;; https://emacs.stackexchange.com/a/5408
+  (let ((pos 0)
+        (next))
+    (while (setq next (next-single-property-change pos 'face s))
+      (put-text-property pos next 'font-lock-face (get-text-property pos 'face s) s)
+      (setq pos next))
+    (add-text-properties 0 (length s) '(fontified t) s)
+    s))
+
 (defun kagi--curl-flags ()
   "Collect flags for a `curl' command to call the Kagi API."
   (let ((token (cond ((functionp kagi-api-token) (funcall kagi-api-token))
@@ -402,7 +417,9 @@ object (created with `make-shell-maker-config')."
    :execute-command
    (lambda (command _history callback error-callback)
      (condition-case err
-         (funcall callback (kagi-fastgpt-prompt command) nil)
+         (funcall callback
+                  (kagi--fontify-using-faces (kagi-fastgpt-prompt command))
+                  nil)
        (json-parse-error (funcall error-callback
                                   (format "Could not parse the server response %s" (cdr err))))
        (error (funcall error-callback (format "An error occurred during the request %s" (cdr err)))))))