diff --git a/src/nextjournal/clerk/render.cljs b/src/nextjournal/clerk/render.cljs
index 59f890b47..71ba532f3 100644
--- a/src/nextjournal/clerk/render.cljs
+++ b/src/nextjournal/clerk/render.cljs
@@ -302,7 +302,10 @@
          [:div.relative
           [:div.overflow-x-auto
            {:ref ref-fn}
-           [inspect-presented {:!expanded-at !expanded-at :swap-sync-state! swap-sync-state! :!sync-state viewer/!sync-state} @!desc]]]]]])))
+           [inspect-presented {:!expanded-at !expanded-at
+                               :swap-sync-state! swap-sync-state!
+                               :!sync-state viewer/!sync-state}
+            @!desc]]]]]])))
 
 (defn toggle-expanded [!expanded-at path event]
   (.preventDefault event)
@@ -547,25 +550,27 @@
      x
      (let [{:nextjournal/keys [value viewer] :keys [path]} x
            hash (str (:hash viewer) "@" (peek (:path opts)))]
-       #_(prn :inspect-presented value :valid-element? (react/isValidElement value) :viewer viewer)
        ;; each view function must be called in its own 'functional component' so that it gets its own hook state.
        ^{:key hash}
        [:> ErrorBoundary {:hash hash}
-        [(:render-fn viewer) value (merge opts
-                                          (:nextjournal/render-opts x)
-                                          {:viewer viewer :path path})]]))))
+        [(:f (:render-fn viewer)) value (merge opts
+                                               (:nextjournal/render-opts x)
+                                               {:viewer viewer :path path})]]))))
 
 (defn inspect [value]
-  (r/with-let [!state (r/atom nil)]
+  (r/with-let [!state   (r/atom nil)
+               fetch-fn (fn [fetch-opts]
+                          (let [{:keys [present-elision-fn]} (-> !state deref :desc meta)]
+                            (-> js/Promise
+                                (.resolve (present-elision-fn fetch-opts))
+                                (.then
+                                 (fn [more]
+                                   (swap! !state update :desc viewer/merge-presentations more fetch-opts))))))]
     (when (not= (:value @!state ::not-found) value)
       (swap! !state assoc
              :value value
              :desc (viewer/present value)))
-    [view-context/provide {:fetch-fn (fn [fetch-opts]
-                                       (.then (let [{:keys [present-elision-fn]} (-> !state deref :desc meta)]
-                                                (.resolve js/Promise (present-elision-fn fetch-opts)))
-                                              (fn [more]
-                                                (swap! !state update :desc viewer/merge-presentations more fetch-opts))))}
+    [view-context/provide {:fetch-fn fetch-fn}
      [inspect-presented (:desc @!state)]]))
 
 (defn show-panel [panel-id panel]
@@ -576,11 +581,14 @@
 (defn with-fetch-fn [{:nextjournal/keys [presented blob-id]} body-fn]
   ;; TODO: unify with result-viewer
   (let [!presented-value (hooks/use-state presented)
-        body-fn* (hooks/use-callback body-fn)]
+        body-fn* (hooks/use-callback body-fn)
+        fetch-fn (hooks/use-callback
+                  (fn [elision]
+                    (-> (fetch! {:blob-id blob-id} elision)
+                        (.then (fn [more]
+                                 (swap! !presented-value viewer/merge-presentations more elision))))))]
     [view-context/provide
-     {:fetch-fn (fn [elision]
-                  (.then (fetch! {:blob-id blob-id} elision)
-                         (fn [more] (swap! !presented-value viewer/merge-presentations more elision))))}
+     {:fetch-fn fetch-fn}
      [body-fn* @!presented-value]]))
 
 (defn exception-overlay [title & content]
diff --git a/src/nextjournal/clerk/viewer.cljc b/src/nextjournal/clerk/viewer.cljc
index 672d3cd0c..1c45601b5 100644
--- a/src/nextjournal/clerk/viewer.cljc
+++ b/src/nextjournal/clerk/viewer.cljc
@@ -36,8 +36,8 @@
 
 (defrecord ViewerFn [form #?(:cljs f)]
   #?@(:cljs [IFn
-             (-invoke [this x] ((:f this) x))
-             (-invoke [this x y] ((:f this) x y))]))
+             (-invoke [this x] (f x))
+             (-invoke [this x y] (f x y))]))
 
 ;; Make sure `ViewerFn` and `ViewerEval` is changed atomically
 #?(:clj
@@ -65,10 +65,11 @@
   #?(:clj ([form] (resolve-aliases (ns-aliases *ns*) form)))
   ([aliases form] (w/postwalk #(cond->> % (qualified-symbol? %) (resolve-symbol-alias aliases)) form)))
 
-(defn ->viewer-fn
-  [form]
-  (map->ViewerFn {:form form
-                  #?@(:cljs [:f (*eval* form)])}))
+(def ->viewer-fn
+  (memoize
+   (fn [form]
+     (map->ViewerFn {:form form
+                     #?@(:cljs [:f (*eval* form)])}))))
 
 (defn ->viewer-eval [form]
   (map->ViewerEval {:form form}))
@@ -1829,11 +1830,24 @@
 #_(desc->values (present (table (mapv vector (range 30)))))
 #_(desc->values (present (with-viewer `table-viewer (normalize-table-data (repeat 60 ["Adelie" "Biscoe" 50 30 200 5000 :female])))))
 
+(defn- postwalk-colls
+  "A variant of postwalk that doesn’t go into records"
+  [f form]
+  (cond
+    (list? form)      (f (apply list (map #(postwalk-colls f %) form)))
+    (map-entry? form) (f #?(:clj (clojure.lang.MapEntry/create (postwalk-colls f (key form)) (postwalk-colls (val form)))
+                            :cljs (cljs.core.MapEntry. (postwalk-colls f (key form)) (postwalk-colls f (val form)) nil)))
+    (seq? form)       (f (doall (map #(postwalk-colls f %) form)))
+    (record? form)    (f form)
+    (coll? form)      (f (into (empty form) (map #(postwalk-colls f %) form)))
+    :else             (f form)))
+
 (defn merge-presentations [root more elision]
-  (clojure.walk/postwalk (fn [x] (if (some #(= elision (:nextjournal/value %)) (when (coll? x) x))
-                                   (into (pop x) (:nextjournal/value more))
-                                   x))
-                         root))
+  (postwalk-colls
+   (fn [x] (if (some #(= elision (:nextjournal/value %)) (when (coll? x) x))
+             (into (pop x) (:nextjournal/value more))
+             x))
+   root))
 
 (defn assign-closing-parens
   ([node] (assign-closing-parens '() node))