diff --git a/frontend/src/arthur/db.cljs b/frontend/src/arthur/db.cljs
index c83fff4..8fe4358 100644
--- a/frontend/src/arthur/db.cljs
+++ b/frontend/src/arthur/db.cljs
@@ -162,6 +162,7 @@
         :time-view :timeline
         :tone      :skin-base
         :tool      nil
+        :auto-key? false
         :draft     []
         :knobs     {}
         :trace     {:faces #{} :opacity trace/opacity-default}
diff --git a/frontend/src/arthur/domain/gesture.cljs b/frontend/src/arthur/domain/gesture.cljs
index ec27248..1a52d69 100644
--- a/frontend/src/arthur/domain/gesture.cljs
+++ b/frontend/src/arthur/domain/gesture.cljs
@@ -7,10 +7,10 @@
   is in the placement's matrices, so a shape five symbols down moves under the
   pointer like one on top.
 
-  THE KEYING RULE IS `node/set-channel`, the inspector's: a channel with keys
-  gets one on the node's own frame, and one without has its one value changed.
-  After Effects' stopwatch — there is no mode to be in, and nothing snaps back
-  on the next frame as an unkeyed change does in Blender."
+  The normal keying rule is `node/set-channel`, the inspector's: a channel with
+  keys gets one on the node's own frame, and one without has its one value
+  changed. Auto-key deliberately replaces that rule with `set-keyed-channel`,
+  so touching an otherwise static transform starts its animation at this frame."
   (:require [arthur.domain.channel :as ch]
             [arthur.domain.node :as node]))
 
@@ -78,7 +78,10 @@
 
 (defn apply-values
   "Clip with channel values `vs`, `{path value}`, written into node `id` of
-  symbol `sid` on the node's own frame `f`, by the keying rule above."
-  [clip sid id f vs]
-  (update-in clip [:symbols sid :nodes id]
-             #(reduce-kv (fn [n path v] (node/set-channel n path f v)) % vs)))
+  symbol `sid` on the node's own frame `f`, by the keying rule above. The sixth
+  argument arms auto-key; the five-argument form retains the normal rule."
+  ([clip sid id f vs] (apply-values clip sid id f vs false))
+  ([clip sid id f vs auto-key?]
+   (let [put (if auto-key? node/set-keyed-channel node/set-channel)]
+     (update-in clip [:symbols sid :nodes id]
+                #(reduce-kv (fn [n path v] (put n path f v)) % vs)))))
diff --git a/frontend/src/arthur/domain/node.cljs b/frontend/src/arthur/domain/node.cljs
index 77694ad..1d5a474 100644
--- a/frontend/src/arthur/domain/node.cljs
+++ b/frontend/src/arthur/domain/node.cljs
@@ -104,6 +104,17 @@
     (assoc-in n [:channels path]
               (if (:keys c) (assoc-in c [:keys f] v) (ch/framed v)))))
 
+(defn set-keyed-channel
+  "Write `v` as a key at `f`, starting an animated channel when needed. This is
+  the auto-key counterpart to `set-channel`; an existing channel keeps its
+  interpolation and segment choices."
+  [n path f v]
+  (let [c (get (channels n) path)]
+    (assoc-in n [:channels path]
+              (if (:keys c)
+                (assoc-in c [:keys f] v)
+                (ch/keyed {f v} (if (boolean? v) :hold :linear))))))
+
 (defn toggle-key
   "Key channel `path` on the node's own frame `f` with the value it has there, or
   take the key there off. The first key starts the channel animating and taking
diff --git a/frontend/src/arthur/events/project.cljs b/frontend/src/arthur/events/project.cljs
index 3d33ada..ab6b630 100644
--- a/frontend/src/arthur/events/project.cljs
+++ b/frontend/src/arthur/events/project.cljs
@@ -635,7 +635,8 @@
  ::set-channel
  ;; `frame` is the node's own, as for a drawing key.
  (fn [db [_ sid id path frame value]]
-   (edit/edit db #(update-in % [:symbols sid :nodes id] node/set-channel path frame value))))
+   (let [put (if (get-in db [:ui :auto-key?]) node/set-keyed-channel node/set-channel)]
+     (edit/edit db #(update-in % [:symbols sid :nodes id] put path frame value)))))
 
 (rf/reg-event-db
  ::toggle-key
diff --git a/frontend/src/arthur/events/ui.cljs b/frontend/src/arthur/events/ui.cljs
index 6e6efd5..50575c7 100644
--- a/frontend/src/arthur/events/ui.cljs
+++ b/frontend/src/arthur/events/ui.cljs
@@ -621,6 +621,11 @@
  (fn [db [_ scope id knob value]]
    (assoc-in db [:ui :knobs [scope id knob]] value)))
 
+(rf/reg-event-db
+ ::toggle-auto-key
+ (fn [db _]
+   (update-in db [:ui :auto-key?] not)))
+
 ;; ---------------------------------------------------------------------------
 ;; a new symbol
 
@@ -754,14 +759,19 @@
  ;; A transform in the middle of a drag on the stage, `{:sid :id :frame
  ;; :values}`, drawn by `::render/clip` as `::sliding` is; nil when abandoned.
  (fn [db [_ g]]
-   (if g (assoc-in db [:ui :gesture] g) (update db :ui dissoc :gesture))))
+   (if g
+     (assoc-in db [:ui :gesture]
+               (assoc g :auto-key? (boolean (get-in db [:ui :auto-key?]))))
+     (update db :ui dissoc :gesture))))
 
 (rf/reg-event-db
  ::transform
  ;; The drag let go: one edit, so one undo step and one write to collaborators.
  (fn [db [_ {:keys [sid id frame values]}]]
    (cond-> (update db :ui dissoc :gesture)
-     (seq values) (edit/edit #(gesture/apply-values % sid id frame values)))))
+     (seq values) (edit/edit #(gesture/apply-values
+                               % sid id frame values
+                               (boolean (get-in db [:ui :auto-key?])))))))
 
 (rf/reg-event-db
  ::delete-selected
diff --git a/frontend/src/arthur/subs/render.cljs b/frontend/src/arthur/subs/render.cljs
index 7f69a51..f76c45e 100644
--- a/frontend/src/arthur/subs/render.cljs
+++ b/frontend/src/arthur/subs/render.cljs
@@ -46,8 +46,8 @@
    (let [c (:clip (footage/entry id))]
      (or (when-let [{:keys [path df]} sliding]
            (:clip (nest/slide c open path df)))
-         (when-let [{:keys [sid id frame values]} gesture]
-           (when c (gesture/apply-values c sid id frame values)))
+         (when-let [{:keys [sid id frame values auto-key?]} gesture]
+           (when c (gesture/apply-values c sid id frame values auto-key?)))
          c))))
 
 (rf/reg-sub
diff --git a/frontend/src/arthur/subs/ui.cljs b/frontend/src/arthur/subs/ui.cljs
index 059e218..4086778 100644
--- a/frontend/src/arthur/subs/ui.cljs
+++ b/frontend/src/arthur/subs/ui.cljs
@@ -17,6 +17,7 @@
 (rf/reg-sub ::lane-retry (fn [db _] (get-in db [:ui :lane-retry])))
 (rf/reg-sub ::tone      (fn [db _] (get-in db [:ui :tone])))
 (rf/reg-sub ::tool      (fn [db _] (get-in db [:ui :tool])))
+(rf/reg-sub ::auto-key? (fn [db _] (boolean (get-in db [:ui :auto-key?]))))
 (rf/reg-sub ::draft     (fn [db _] (get-in db [:ui :draft])))
 (rf/reg-sub ::convert   (fn [db _] (get-in db [:ui :convert])))
 (rf/reg-sub ::drop      (fn [db _] (get-in db [:ui :drop])))
diff --git a/frontend/src/arthur/ui/palette.cljs b/frontend/src/arthur/ui/palette.cljs
index 2e59458..79cd841 100644
--- a/frontend/src/arthur/ui/palette.cljs
+++ b/frontend/src/arthur/ui/palette.cljs
@@ -42,11 +42,19 @@
 (defn bar []
   (let [tone  @(rf/subscribe [::sub/tone])
         tool  @(rf/subscribe [::sub/tool])
+        auto? @(rf/subscribe [::sub/auto-key?])
         draft @(rf/subscribe [::sub/draft])]
     [:div.palette-bar
      [:div.swatches (doall (map #(swatch % tone) (range slots)))]
      [:span.dim (name tone)]
      [:span {:style {:flex 1}}]
+     [:button.auto-key {:class (when auto? "on")
+                        :aria-pressed auto?
+                        :title (if auto?
+                                 "auto-key is on — edited parameters get a key at this frame"
+                                 "auto-key edited parameters at this frame")
+                        :on-click #(rf/dispatch [::ui/toggle-auto-key])}
+      "◆ auto key"]
      (if (= :polygon tool)
        [:<>
         [:span.dim (str (quot (count draft) 2) " points")]
diff --git a/frontend/src/arthur/ui/params.cljs b/frontend/src/arthur/ui/params.cljs
index 9bf21b1..cc67730 100644
--- a/frontend/src/arthur/ui/params.cljs
+++ b/frontend/src/arthur/ui/params.cljs
@@ -167,7 +167,7 @@
 ;; Rotation is shown in degrees. Between two keys, the gap after the one here
 ;; holds or tweens, as a drawing's does.
 
-(defn- channel-control [sid id path ch frame]
+(defn- channel-control [sid id path ch frame auto-key?]
   (let [keyed? (some? (:keys ch))
         ;; No store: the call site below hands this only channels that are not
         ;; `:dense`, which are the only ones with anything in tier 2 to read.
@@ -184,7 +184,7 @@
                                 :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
+    [:dd.channel {:class (when auto-key? "live")}
      [:button.key {:class    (cond (contains? (:keys ch) frame) "on" keyed? "keyed")
                    :disabled (nil? frame)
                    :title    (if keyed? (str (count (:keys ch)) " keys") "key this here")
@@ -199,7 +199,8 @@
      (when gap? [segment-select sid id path ch left])]))
 
 (defn- node-section [[sid id n]]
-  (let [[start end] (:span n)]
+  (let [[start end] (:span n)
+        auto-key? @(rf/subscribe [::sub/auto-key?])]
     [section (str (name (:kind n)) " · in " (name sid))
      [facts
       "name" (or (:name n) (brief id))
@@ -221,7 +222,7 @@
            [:<>
             [:dt (str/join " " (map name path))]
             (if (and (contains? (node/defaults-of n) path) (not (:dense ch)))
-              [channel-control sid id path ch frame]
+              [channel-control sid id path ch frame auto-key?]
               [:dd (channel-state ch)])]))])]))
 
 ;; ---------------------------------------------------------------------------
diff --git a/frontend/test/arthur/domain/node_test.cljs b/frontend/test/arthur/domain/node_test.cljs
index c7cc882..5c19862 100644
--- a/frontend/test/arthur/domain/node_test.cljs
+++ b/frontend/test/arthur/domain/node_test.cljs
@@ -216,3 +216,13 @@
     (let [d (node/toggle-key (node/set-segment-interp c [:xform :pos] 0 :hold) [:xform :pos] 0 nil)]
       (is (not (contains? (get-in d [:channels [:xform :pos] :segments]) 0))
           "taking a key off takes its gap's choice with it"))))
+
+(deftest auto-keying-a-channel-from-a-parameter-edit
+  (let [n {:id :x :kind :group}
+        keyed (node/set-keyed-channel n [:xform :rot] 7 1.25)
+        moved (node/set-keyed-channel keyed [:xform :rot] 11 2.5)
+        visible (node/set-keyed-channel n [:vis] 7 false)]
+    (is (= {7 1.25, 11 2.5} (get-in moved [:channels [:xform :rot] :keys])))
+    (is (= :linear (get-in moved [:channels [:xform :rot] :interp])))
+    (is (= :hold (get-in visible [:channels [:vis] :interp]))
+        "boolean parameters do not tween")))
diff --git a/static/arthur/app.css b/static/arthur/app.css
index 7c02fa8..3adc3c1 100644
--- a/static/arthur/app.css
+++ b/static/arthur/app.css
@@ -56,6 +56,10 @@
   --aim:       #8d4bd6;
   --aim-stage: #c79bf2;
 
+  /* Auto-key is a recording state, distinct from selection and aiming. */
+  --live:    #239447;
+  --live-bg: #e2f5e7;
+
   /* A keyframe is a dot and a dot is ink. Flash draws them black and so does
      this; the frames a node exists over are a pale tint behind them. */
   --key:      #1f1f1f;
@@ -748,6 +752,13 @@ button.share-button:hover, button.share-button.on { filter: brightness(1.1); }
   border-bottom: 1px solid var(--line);
 }
 
+.palette-bar .auto-key.on {
+  color: #145c2b;
+  background: var(--live-bg);
+  border-color: var(--live);
+  box-shadow: 0 0 7px rgba(35, 148, 71, .72), inset 0 0 0 1px rgba(255, 255, 255, .7);
+}
+
 .swatches { display: flex; gap: 3px; }
 
 /* Circles. A palette entry is one indivisible tone, not an area of coverage, and
@@ -1283,6 +1294,14 @@ button.share-button:hover, button.share-button.on { filter: brightness(1.1); }
 .facts dd.channel .key { padding: 0 3px; color: var(--dim); }
 .facts dd.channel .key.keyed { color: var(--fg); }
 .facts dd.channel .key.on { color: var(--sel); }
+.facts dd.channel.live {
+  margin: -2px;
+  padding: 2px;
+  border-radius: 3px;
+  background: var(--live-bg);
+  box-shadow: 0 0 0 1px rgba(35, 148, 71, .45), 0 0 6px rgba(35, 148, 71, .28);
+}
+.facts dd.channel.live input { border-color: var(--live); }
 
 /* The selected node's transform box, in stage pixels (the SVG's viewBox). */
 .paint-overlay .handles .box { fill: none; stroke: #e6ca8b; stroke-width: 0.5; stroke-dasharray: 2 1; pointer-events: none; }