diff --git a/pollen/setup.rkt b/pollen/setup.rkt
index fc76f78..125398a 100644
--- a/pollen/setup.rkt
+++ b/pollen/setup.rkt
@@ -48,16 +48,28 @@
                                 'NAME
                                 (λ () DEFAULT-NAME))))))]))
 
+(define-syntax (define-nonsettable stx)
+  (syntax-case stx ()
+    [(_ NAME DEFAULT-VALUE)
+     (with-syntax ([DEFAULT-NAME (format-id stx "default-~a" #'NAME)]
+                   [NAME-THUNKED (format-id stx "~a" #'NAME)]
+                   [NAME-FAIL-THUNKED (format-id stx "fail-thunk-~a" #'NAME)] )
+       #'(begin
+           (provide (prefix-out setup: NAME-THUNKED) DEFAULT-NAME)
+           (define DEFAULT-NAME DEFAULT-VALUE)
+           ;; can take a dir argument that sets start point for (get-path-to-override) search.
+           (define (NAME-THUNKED [dir #false]) DEFAULT-VALUE)))]))
+
 (define-settable cache-watchlist null)
 (define-settable envvar-watchlist null)
 
-(define-settable preproc-source-ext 'pp)
-(define-settable markup-source-ext 'pm)
-(define-settable markdown-source-ext 'pmd)
-(define-settable null-source-ext 'p)
-(define-settable pagetree-source-ext 'ptree)
-(define-settable template-source-ext 'pt)
-(define-settable scribble-source-ext 'scrbl)
+(define-nonsettable preproc-source-ext 'pp)
+(define-nonsettable markup-source-ext 'pm)
+(define-nonsettable markdown-source-ext 'pmd)
+(define-nonsettable null-source-ext 'p)
+(define-nonsettable pagetree-source-ext 'ptree)
+(define-nonsettable template-source-ext 'pt)
+(define-nonsettable scribble-source-ext 'scrbl)
 
 ;; these are deliberately not settable because they're just internal signalers, no effect on external interface
 (define+provide default-mode-auto 'auto)
@@ -67,9 +79,9 @@
 (define+provide default-mode-pagetree 'ptree)
 (define+provide default-mode-template 'template)
 
-(define-settable old-cache-names '("pollen.cache" "pollen-cache"))
-(define-settable cache-dir-name "compiled")
-(define-settable cache-subdir-name "pollen")
+(define-nonsettable old-cache-names '("pollen.cache" "pollen-cache"))
+(define-nonsettable cache-dir-name "compiled")
+(define-nonsettable cache-subdir-name "pollen")
 (define+provide default-cache-names (list* (cache-dir-name) (old-cache-names)))
 
 (define-settable decodable-extensions (list (markup-source-ext) (pagetree-source-ext)))
@@ -81,14 +93,14 @@
 (define-settable command-char #\◊)
 (define-settable template-command-char #\∂)
 
-(define-settable template-prefix "template")
-(define-settable fallback-template-prefix "fallback")
-(define-settable template-meta-key "template")
+(define-nonsettable template-prefix "template")
+(define-nonsettable fallback-template-prefix "fallback")
+(define-nonsettable template-meta-key "template")
 
-(define-settable main-export 'doc) ; don't forget to change fallback template too
-(define-settable meta-export 'metas)
-(define-settable meta-tag-name 'meta)
-(define-settable define-meta-name 'define-meta)
+(define-nonsettable main-export 'doc) ; don't forget to change fallback template too
+(define-nonsettable meta-export 'metas)
+(define-nonsettable meta-tag-name 'meta)
+(define-nonsettable define-meta-name 'define-meta)
 
 ;; tags from https://developer.mozilla.org/en-US/docs/Web/HTML/Block-level_elements
 (define-settable block-tags (cons (main-root-node) '(address article aside blockquote body canvas dd div dl fieldset figcaption figure footer form  h1 h2 h3 h4 h5 h6 header hgroup hr li main nav noscript ol output p pre section table tfoot ul video)))