diff --git a/frontend/src/arthur/domain/history.cljs b/frontend/src/arthur/domain/history.cljs
index 8727624..2ff1dfa 100644
--- a/frontend/src/arthur/domain/history.cljs
+++ b/frontend/src/arthur/domain/history.cljs
@@ -69,17 +69,34 @@
 
 (defn record
   "History `h` with an edit from leaves `before` to `after` at time `now`."
-  [{:keys [done] :as h} before after now]
+  [{:keys [done held?] :as h} before after now]
   (let [[b a] (changes before after)
         top   (peek done)]
     (cond
       (empty? a) h
-      (and top (< (- now (:at top)) gap-ms) (= b (:after top)))
-      {:done (conj (pop done) (assoc top :after a :at now)) :undone []}
+      (and top (not (:closed? top)) (= b (:after top))
+           (or held? (< (- now (:at top)) gap-ms)))
+      (assoc h :done (conj (pop done) (assoc top :after a :at now)) :undone [])
       :else
-      {:done (conj (vec (take-last (dec depth) done))
-                   {:before b :after a :at now :label (label before after (keys a))})
-       :undone []})))
+      (assoc h
+             :done (conj (vec (take-last (dec depth) done))
+                         {:before b :after a :at now :label (label before after (keys a))})
+             :undone []))))
+
+(defn- close [{:keys [done] :as h}]
+  (cond-> h (seq done) (assoc :done (conj (pop done) (assoc (peek done) :closed? true)))))
+
+(defn hold
+  "While a field has focus, everything typed into it is one step, however slowly
+  — the digits of 45 are seen as 4 and then 45, and undone as one. It starts a
+  step of its own rather than joining whatever came before."
+  [h]
+  (assoc (close h) :held? true))
+
+(defn settle
+  "The field is done with: its step is finished, and nothing joins it."
+  [h]
+  (dissoc (close h) :held?))
 
 (defn steps
   "The labels, newest first: `:done` is what undo would take off, `:undone`
diff --git a/frontend/src/arthur/events/edit.cljs b/frontend/src/arthur/events/edit.cljs
index e53ddb6..1730285 100644
--- a/frontend/src/arthur/events/edit.cljs
+++ b/frontend/src/arthur/events/edit.cljs
@@ -61,6 +61,14 @@
     (not= (:fps clip) (get-in db [:clip :fps]))
     (update :clip merge {:fps (:fps clip) :display-fps (:fps clip)})))
 
+(defn history
+  "Apply `f` to the loaded entry's undo history, which is not an edit: nothing
+  is redrawn and nothing becomes unsaved."
+  [db f]
+  (if-let [id (store/edit-entry! (:clip/current db) #(update % :history f))]
+    (assoc db :clip/current id)
+    db))
+
 (defn edit
   "Apply `f` to the loaded clip and return the new db."
   [db f]
diff --git a/frontend/src/arthur/events/history.cljs b/frontend/src/arthur/events/history.cljs
index 106b17a..f137a85 100644
--- a/frontend/src/arthur/events/history.cljs
+++ b/frontend/src/arthur/events/history.cljs
@@ -55,6 +55,9 @@
 (rf/reg-event-fx ::undo (fn [{:keys [db]} [_ n]] (steps db history/undo "undone" (or n 1))))
 (rf/reg-event-fx ::redo (fn [{:keys [db]} [_ n]] (steps db history/redo "redone" (or n 1))))
 
+(rf/reg-event-db ::hold (fn [db _] (edit/history db history/hold)))
+(rf/reg-event-db ::settle (fn [db _] (edit/history db history/settle)))
+
 (rf/reg-sub
  ::steps
  ;; The history is on the entry, outside app-db; the revision is what moves
diff --git a/frontend/src/arthur/ui/params.cljs b/frontend/src/arthur/ui/params.cljs
index 674614c..85d74f7 100644
--- a/frontend/src/arthur/ui/params.cljs
+++ b/frontend/src/arthur/ui/params.cljs
@@ -13,6 +13,7 @@
             [arthur.domain.node :as node]
             [arthur.domain.paint :as paint]
             [arthur.domain.params :as params]
+            [arthur.events.history :as history]
             [arthur.events.paint :as paint-events]
             [arthur.events.playback :as pb]
             [arthur.events.project :as project]
@@ -20,7 +21,8 @@
             [arthur.subs.playback :as playback]
             [arthur.subs.render :as render]
             [arthur.subs.ui :as sub]
-            [re-frame.core :as rf]))
+            [re-frame.core :as rf]
+            [reagent.core :as r]))
 
 (defn- brief
   "A value that fits the column. The `facts` list puts the whole thing in a
@@ -39,14 +41,37 @@
 (defn- section [title & body]
   (into [:section.section [:h2 title]] body))
 
+(defn- number-input
+  "A number box that edits as it is typed in or stepped, and is one undo step
+  from focus to blur. What is typed is kept while it has focus — \"-\" or
+  \"4.\" is no number yet, and the value it would round-trip to must not
+  replace it under the caret."
+  [_]
+  (let [draft (r/atom nil)]
+    (fn [{:keys [value parse on-number] :as attrs}]
+      [:input (merge (dissoc attrs :value :parse :on-number)
+                     {:type "number"
+                      :value (or @draft value "")
+                      :on-focus (fn [e]
+                                  (reset! draft (.. e -target -value))
+                                  (rf/dispatch [::history/hold]))
+                      :on-blur (fn [_]
+                                 (reset! draft nil)
+                                 (rf/dispatch [::history/settle]))
+                      :on-key-down #(when (= "Enter" (.-key %)) (.. % -target blur))
+                      :on-change (fn [e]
+                                   (let [s (.. e -target -value)
+                                         n (parse s)]
+                                     (when @draft (reset! draft s))
+                                     (when-not (js/isNaN n) (on-number n))))})])))
+
 (defn- number-field [label value on-change & [placeholder disabled?]]
   [:label.inspector-field label
-   [:input {:type "number" :min 1 :step 1 :value (or value "")
-            :placeholder placeholder
-            :disabled disabled?
-            :on-change (fn [e]
-                         (let [v (.. e -target -value)]
-                           (on-change (when (seq v) (js/parseInt v 10)))))}]])
+   [number-input {:min 1 :step 1 :value value
+                  :placeholder placeholder
+                  :disabled disabled?
+                  :parse #(if (seq %) (js/parseInt % 10) nil)
+                  :on-number on-change}]])
 
 ;; ---------------------------------------------------------------------------
 ;; the clip
@@ -151,19 +176,12 @@
         off?   (and keyed? (nil? frame))
         deg?   (= path [:xform :rot])
         put    #(rf/dispatch [::project/set-channel sid id path frame %])
-        ;; Written on blur or Enter rather than per keystroke, so a typed
-        ;; number is one edit. Keyed by what it shows, so a seek or an undo
-        ;; that changes the value puts the new one in the box.
         field  (fn [i x on-number]
-                 (let [shown (if deg? (/ (js/Math.round (* x (/ 18000 js/Math.PI))) 100) x)]
-                   ^{:key (str i " " shown)}
-                   [:input {:type "number" :step "any" :disabled off?
-                            :default-value shown
-                            :on-key-down #(when (= "Enter" (.-key %)) (.. % -target blur))
-                            :on-blur (fn [e]
-                                       (let [n (js/parseFloat (.. e -target -value))]
-                                         (when-not (or (js/isNaN n) (= n shown))
-                                           (on-number (if deg? (* n (/ js/Math.PI 180)) n)))))}]))]
+                 ^{:key i}
+                 [number-input {:step "any" :disabled off?
+                                :value (if deg? (/ (js/Math.round (* x (/ 18000 js/Math.PI))) 100) x)
+                                :parse js/parseFloat
+                                :on-number #(on-number (if deg? (* % (/ js/Math.PI 180)) %))}])]
     [:dd.channel
      [:button.key {:class    (cond (contains? (:keys ch) frame) "on" keyed? "keyed")
                    :disabled (nil? frame)
diff --git a/frontend/test/arthur/domain/history_test.cljs b/frontend/test/arthur/domain/history_test.cljs
index 7acc6ec..deefb2e 100644
--- a/frontend/test/arthur/domain/history_test.cljs
+++ b/frontend/test/arthur/domain/history_test.cljs
@@ -23,6 +23,17 @@
     (is (= 1 (count (:done h))))
     (is (= {"v" 0} (:leaves (history/undo h {"v" 3}))))))
 
+(deftest typing-into-a-field-is-one-step-however-slow
+  (let [h (-> nil
+              (history/record {"w" 1} {"w" 2} 0)
+              history/hold
+              (history/record {"w" 2} {"w" 4} 100)
+              (history/record {"w" 4} {"w" 45} 9000)
+              history/settle
+              (history/record {"w" 45} {"w" 46} 9100))]
+    (is (= 3 (count (:done h))) "the edit before focus and the one after blur stand apart")
+    (is (= {"w" 2} (:leaves (history/undo (:history (history/undo h {"w" 46})) {"w" 45}))))))
+
 (deftest their-write-between-two-of-mine-keeps-them-apart
   (let [h (-> nil
               (history/record {"fps" 30} {"fps" 12} 0)