diff --git a/lisp/files.el b/lisp/files.el
index 9c105dbe1a5..9f256695011 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -3059,9 +3059,13 @@ auto-mode-alist
      ("\\.dbk\\'" . xml-mode)
      ("\\.dtd\\'" . sgml-mode)
      ("\\.ds\\(ss\\)?l\\'" . dsssl-mode)
-     ("\\.js[mx]?\\'" . javascript-mode)
+     ("\\.js[mx]?\\'" . ,(if (treesit-available-p)
+                             'js-ts-mode
+                           'javascript-mode))
      ;; https://en.wikipedia.org/wiki/.har
-     ("\\.har\\'" . javascript-mode)
+     ("\\.har\\'" . ,(if (treesit-available-p)
+                         'js-ts-mode
+                       'javascript-mode))
      ("\\.json\\'" . js-json-mode)
      ("\\.[ds]?va?h?\\'" . verilog-mode)
      ("\\.by\\'" . bovine-grammar-mode)
diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 3823c553fda..5b89fe917c2 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -35,12 +35,6 @@
 ;; To use these modes by default, assuming you have the respective
 ;; tree-sitter grammars available, do one of the following:
 ;;
-;; - If you have both C and C++ grammars installed, add
-;;
-;;    (require 'c-ts-mode)
-;;
-;;   to your init file.
-;;
 ;; - Add one or mode of the following to your init file:
 ;;
 ;;    (add-to-list 'major-mode-remap-alist '(c-mode . c-ts-mode))
@@ -1539,21 +1533,6 @@ c-or-c++-ts-mode
            'c-ts-mode)))
     (funcall (major-mode-remap mode))))
 
-;; The entries for C++ must come first to prevent *.c files be taken
-;; as C++ on case-insensitive filesystems, since *.C files are C++,
-;; not C.
-(if (treesit-ready-p 'cpp)
-    (add-to-list 'major-mode-remap-defaults
-                 '(c++-mode . c++-ts-mode)))
-
-(when (treesit-ready-p 'c)
-  (add-to-list 'major-mode-remap-defaults '(c++-mode . c++-ts-mode))
-  (add-to-list 'major-mode-remap-defaults '(c-mode . c-ts-mode)))
-
-(when (and (treesit-ready-p 'cpp)
-           (treesit-ready-p 'c))
-  (add-to-list 'major-mode-remap-defaults '(c-or-c++-mode . c-or-c++-ts-mode)))
-
 (when (and c-ts-mode-enable-doxygen (not (treesit-ready-p 'doxygen t)))
   (message "Doxygen syntax highlighting can't be enabled, please install the language grammar."))
 
diff --git a/lisp/progmodes/cc-mode.el b/lisp/progmodes/cc-mode.el
index c5bb075c7f6..867d47ee0a2 100644
--- a/lisp/progmodes/cc-mode.el
+++ b/lisp/progmodes/cc-mode.el
@@ -3377,22 +3377,6 @@ c-submit-bug-report
 	(insert (format "Buffer Style: %s\nc-emacs-features: %s\n"
 			style c-features)))))))
 
-
-;; Make entries in `major-mode-remap-defaults' to ensure that when CC
-;; Mode has been loaded, the symbols `c-mode' etc., will call CC Mode's
-;; modes rather than c-ts-mode etc..
-(when (boundp 'major-mode-remap-defaults)
-  (add-to-list 'major-mode-remap-defaults '(c++-mode . c++-ts-mode))
-  (add-to-list 'major-mode-remap-defaults '(c-mode . c-ts-mode))
-  (add-to-list 'major-mode-remap-defaults '(c-or-c++-mode . c-or-c++-ts-mode))
-  (let (entry)
-    (dolist (mode '(c-mode c++-mode c-or-c++-mode))
-      (if (and (setq entry (assq mode major-mode-remap-defaults))
-	       (null (cdr entry)))
-	  (setq major-mode-remap-defaults
-		(delq entry major-mode-remap-defaults)))
-      (push (cons mode nil) major-mode-remap-defaults))))
-
 
 (cc-provide 'cc-mode)
 
diff --git a/lisp/progmodes/cmake-ts-mode.el b/lisp/progmodes/cmake-ts-mode.el
index 597ef69d9b8..f40147a94b0 100644
--- a/lisp/progmodes/cmake-ts-mode.el
+++ b/lisp/progmodes/cmake-ts-mode.el
@@ -244,7 +244,8 @@ cmake-ts-mode
 
 (derived-mode-add-parents 'cmake-ts-mode '(cmake-mode))
 
-(if (treesit-ready-p 'cmake)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist
                  '("\\(?:CMakeLists\\.txt\\|\\.cmake\\)\\'" . cmake-ts-mode)))
 
diff --git a/lisp/progmodes/csharp-mode.el b/lisp/progmodes/csharp-mode.el
index b86555b1d87..dbf169a048c 100644
--- a/lisp/progmodes/csharp-mode.el
+++ b/lisp/progmodes/csharp-mode.el
@@ -1089,9 +1089,11 @@ csharp-ts-mode
                 ("Struct" "\\`struct_declaration\\'" nil nil)
                 ("Method" "\\`method_declaration\\'" nil nil)))
 
-  (treesit-major-mode-setup)
+  (treesit-major-mode-setup))
 
-  (add-to-list 'auto-mode-alist '("\\.cs\\'" . csharp-ts-mode)))
+;;;###autoload
+(if (treesit-available-p)
+    (add-to-list 'auto-mode-alist '("\\.cs\\'" . csharp-ts-mode)))
 
 (derived-mode-add-parents 'csharp-ts-mode '(csharp-mode))
 
diff --git a/lisp/progmodes/dockerfile-ts-mode.el b/lisp/progmodes/dockerfile-ts-mode.el
index 42fa7482a87..2d33c6c2c65 100644
--- a/lisp/progmodes/dockerfile-ts-mode.el
+++ b/lisp/progmodes/dockerfile-ts-mode.el
@@ -167,7 +167,8 @@ dockerfile-ts-mode
 
 (derived-mode-add-parents 'dockerfile-ts-mode '(dockerfile-mode))
 
-(if (treesit-ready-p 'dockerfile)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist
                  ;; NOTE: We can't use `rx' here, as it breaks bootstrap.
                  '("\\(?:Dockerfile\\(?:\\..*\\)?\\|\\.[Dd]ockerfile\\)\\'"
diff --git a/lisp/progmodes/elixir-ts-mode.el b/lisp/progmodes/elixir-ts-mode.el
index cacdb266298..a3b9f7d5611 100644
--- a/lisp/progmodes/elixir-ts-mode.el
+++ b/lisp/progmodes/elixir-ts-mode.el
@@ -755,7 +755,8 @@ elixir-ts-mode
 
 (derived-mode-add-parents 'elixir-ts-mode '(elixir-mode))
 
-(if (treesit-ready-p 'elixir)
+;;;###autoload
+(if (treesit-available-p)
     (progn
       (add-to-list 'auto-mode-alist '("\\.elixir\\'" . elixir-ts-mode))
       (add-to-list 'auto-mode-alist '("\\.ex\\'" . elixir-ts-mode))
diff --git a/lisp/progmodes/go-ts-mode.el b/lisp/progmodes/go-ts-mode.el
index 86e74ad58a8..3e1bc4bea40 100644
--- a/lisp/progmodes/go-ts-mode.el
+++ b/lisp/progmodes/go-ts-mode.el
@@ -305,7 +305,8 @@ go-ts-mode
 
 (derived-mode-add-parents 'go-ts-mode '(go-mode))
 
-(if (treesit-ready-p 'go)
+;;;###autoload
+(if (treesit-available-p)
     ;; FIXME: Should we instead put `go-mode' in `auto-mode-alist'
     ;; and then use `major-mode-remap-defaults' to map it to `go-ts-mode'?
     (add-to-list 'auto-mode-alist '("\\.go\\'" . go-ts-mode)))
@@ -562,7 +563,8 @@ go-mod-ts-mode
 
 (derived-mode-add-parents 'go-mod-ts-mode '(go-mod-mode))
 
-(if (treesit-ready-p 'gomod)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("/go\\.mod\\'" . go-mod-ts-mode)))
 
 (provide 'go-ts-mode)
diff --git a/lisp/progmodes/heex-ts-mode.el b/lisp/progmodes/heex-ts-mode.el
index 84fd513525c..3f26f0a9b14 100644
--- a/lisp/progmodes/heex-ts-mode.el
+++ b/lisp/progmodes/heex-ts-mode.el
@@ -191,7 +191,8 @@ heex-ts-mode
 
 (derived-mode-add-parents 'heex-ts-mode '(heex-mode))
 
-(if (treesit-ready-p 'heex)
+;;;###autoload
+(if (treesit-available-p)
     ;; Both .heex and the deprecated .leex files should work
     ;; with the tree-sitter-heex grammar.
     (add-to-list 'auto-mode-alist '("\\.[hl]?eex\\'" . heex-ts-mode)))
diff --git a/lisp/progmodes/java-ts-mode.el b/lisp/progmodes/java-ts-mode.el
index 177f914160c..860cb433f71 100644
--- a/lisp/progmodes/java-ts-mode.el
+++ b/lisp/progmodes/java-ts-mode.el
@@ -436,7 +436,8 @@ java-ts-mode
 
 (derived-mode-add-parents 'java-ts-mode '(java-mode))
 
-(if (treesit-ready-p 'java)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.java\\'" . java-ts-mode)))
 
 (when (and java-ts-mode-enable-doxygen (not (treesit-ready-p 'doxygen t)))
diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el
index f74b8ab1c46..a4d4399012c 100644
--- a/lisp/progmodes/js.el
+++ b/lisp/progmodes/js.el
@@ -3961,10 +3961,7 @@ js-ts-mode
                                         "method_definition")
                                 eos)
                    nil nil)))
-    (treesit-major-mode-setup)
-
-    (add-to-list 'auto-mode-alist
-                 '("\\(\\.js[mx]\\|\\.har\\)\\'" . js-ts-mode))))
+    (treesit-major-mode-setup)))
 
 (derived-mode-add-parents 'js-ts-mode '(js-mode))
 
diff --git a/lisp/progmodes/json-ts-mode.el b/lisp/progmodes/json-ts-mode.el
index 7409c6be833..e0d8cf72841 100644
--- a/lisp/progmodes/json-ts-mode.el
+++ b/lisp/progmodes/json-ts-mode.el
@@ -166,7 +166,8 @@ json-ts-mode
 
 (derived-mode-add-parents 'json-ts-mode '(json-mode))
 
-(if (treesit-ready-p 'json)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist
                  '("\\.json\\'" . json-ts-mode)))
 
diff --git a/lisp/progmodes/lua-ts-mode.el b/lisp/progmodes/lua-ts-mode.el
index 20bc1f3e158..58328332e68 100644
--- a/lisp/progmodes/lua-ts-mode.el
+++ b/lisp/progmodes/lua-ts-mode.el
@@ -837,7 +837,8 @@ lua-ts-mode
 
 (derived-mode-add-parents 'lua-ts-mode '(lua-mode))
 
-(when (treesit-ready-p 'lua)
+;;;###autoload
+(if (treesit-available-p)
   (add-to-list 'auto-mode-alist '("\\.lua\\'" . lua-ts-mode)))
 
 (provide 'lua-ts-mode)
diff --git a/lisp/progmodes/php-ts-mode.el b/lisp/progmodes/php-ts-mode.el
index 07a0c266d78..b090da01ce8 100644
--- a/lisp/progmodes/php-ts-mode.el
+++ b/lisp/progmodes/php-ts-mode.el
@@ -1824,7 +1824,8 @@ php-ts-mode-kill-process
   (with-current-buffer php-ts-mode-inferior-php-buffer
     (kill-buffer-and-window)))
 
-(when (treesit-ready-p 'php)
+;;;###autoload
+(when (treesit-available-p)
   (add-to-list
    'auto-mode-alist '("\\.\\(?:php[s345]?\\|phtml\\)\\'" . php-ts-mode))
   (add-to-list
diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 283a545bfb4..f8903771aa2 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -287,9 +287,13 @@ python--auto-mode-alist-regexp
       eos))
 
 ;;;###autoload
-(add-to-list 'auto-mode-alist (cons python--auto-mode-alist-regexp 'python-mode))
+(add-to-list 'auto-mode-alist
+             (cons python--auto-mode-alist-regexp
+                   (if (treesit-available-p) 'python-ts-mode 'python-mode)))
 ;;;###autoload
-(add-to-list 'interpreter-mode-alist (cons (purecopy "python[0-9.]*") 'python-mode))
+(add-to-list 'interpreter-mode-alist
+             (cons (purecopy "python[0-9.]*")
+                   (if (treesit-available-p) 'python-ts-mode 'python-mode)))
 
 (defgroup python nil
   "Python Language's flying circus support for Emacs."
diff --git a/lisp/progmodes/ruby-ts-mode.el b/lisp/progmodes/ruby-ts-mode.el
index aff0b8911b9..646de8a4ec3 100644
--- a/lisp/progmodes/ruby-ts-mode.el
+++ b/lisp/progmodes/ruby-ts-mode.el
@@ -1237,7 +1237,8 @@ ruby-ts-mode
 
 (derived-mode-add-parents 'ruby-ts-mode '(ruby-mode))
 
-(if (treesit-ready-p 'ruby)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'major-mode-remap-defaults
                  '(ruby-mode . ruby-ts-mode)))
 
diff --git a/lisp/progmodes/rust-ts-mode.el b/lisp/progmodes/rust-ts-mode.el
index e52ea3b125a..4ee671e16e4 100644
--- a/lisp/progmodes/rust-ts-mode.el
+++ b/lisp/progmodes/rust-ts-mode.el
@@ -566,7 +566,8 @@ rust-ts-mode
 
 (derived-mode-add-parents 'rust-ts-mode '(rust-mode))
 
-(if (treesit-ready-p 'rust)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.rs\\'" . rust-ts-mode)))
 
 (provide 'rust-ts-mode)
diff --git a/lisp/progmodes/typescript-ts-mode.el b/lisp/progmodes/typescript-ts-mode.el
index ef5dbe51ada..bfb7f1afc84 100644
--- a/lisp/progmodes/typescript-ts-mode.el
+++ b/lisp/progmodes/typescript-ts-mode.el
@@ -535,7 +535,8 @@ typescript-ts-mode
 
 (derived-mode-add-parents 'typescript-ts-mode '(typescript-mode))
 
-(if (treesit-ready-p 'typescript)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.ts\\'" . typescript-ts-mode)))
 
 ;;;###autoload
@@ -631,7 +632,8 @@ tsx-ts--syntax-propertize-captures
       (put-text-property ns (1+ ns) 'syntax-table syntax)
       (put-text-property (1- ne) ne 'syntax-table syntax))))
 
-(if (treesit-ready-p 'tsx)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.tsx\\'" . tsx-ts-mode)))
 
 (provide 'typescript-ts-mode)
diff --git a/lisp/textmodes/css-mode.el b/lisp/textmodes/css-mode.el
index c8da28187ee..04e1cce807e 100644
--- a/lisp/textmodes/css-mode.el
+++ b/lisp/textmodes/css-mode.el
@@ -1826,12 +1826,14 @@ css-ts-mode
     (setq-local treesit-simple-imenu-settings
                 `(( nil ,(rx bos (or "rule_set" "media_statement") eos)
                     nil nil)))
-    (treesit-major-mode-setup)
-
-    (add-to-list 'auto-mode-alist '("\\.css\\'" . css-ts-mode))))
+    (treesit-major-mode-setup)))
 
 (derived-mode-add-parents 'css-ts-mode '(css-mode))
 
+;;;###autoload
+(if (treesit-available-p)
+    (add-to-list 'auto-mode-alist '("\\.css\\'" . css-ts-mode)))
+
 ;;;###autoload
 (define-derived-mode css-mode css-base-mode "CSS"
   "Major mode to edit Cascading Style Sheets (CSS).
diff --git a/lisp/textmodes/html-ts-mode.el b/lisp/textmodes/html-ts-mode.el
index f78fbdde1da..c21d187be28 100644
--- a/lisp/textmodes/html-ts-mode.el
+++ b/lisp/textmodes/html-ts-mode.el
@@ -136,7 +136,8 @@ html-ts-mode
 
 (derived-mode-add-parents 'html-ts-mode '(html-mode))
 
-(if (treesit-ready-p 'html)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.html\\'" . html-ts-mode)))
 
 (provide 'html-ts-mode)
diff --git a/lisp/textmodes/toml-ts-mode.el b/lisp/textmodes/toml-ts-mode.el
index 806f045c23b..fcb9a056353 100644
--- a/lisp/textmodes/toml-ts-mode.el
+++ b/lisp/textmodes/toml-ts-mode.el
@@ -155,7 +155,8 @@ toml-ts-mode
 
 (derived-mode-add-parents 'toml-ts-mode '(toml-mode))
 
-(if (treesit-ready-p 'toml)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.toml\\'" . toml-ts-mode)))
 
 (provide 'toml-ts-mode)
diff --git a/lisp/textmodes/yaml-ts-mode.el b/lisp/textmodes/yaml-ts-mode.el
index 42d7c2e1798..b39d32148c0 100644
--- a/lisp/textmodes/yaml-ts-mode.el
+++ b/lisp/textmodes/yaml-ts-mode.el
@@ -171,7 +171,8 @@ yaml-ts-mode
 
 (derived-mode-add-parents 'yaml-ts-mode '(yaml-mode))
 
-(if (treesit-ready-p 'yaml)
+;;;###autoload
+(if (treesit-available-p)
     (add-to-list 'auto-mode-alist '("\\.ya?ml\\'" . yaml-ts-mode)))
 
 (provide 'yaml-ts-mode)