diff --git a/crates/js/src/formcalc.rs b/crates/js/src/formcalc.rs
index 7a3de5a70..4ff77b74c 100644
--- a/crates/js/src/formcalc.rs
+++ b/crates/js/src/formcalc.rs
@@ -1617,19 +1617,13 @@ impl Interp<'_> {
                     "presence" => {
                         let p = self.to_str(&v);
                         if matches!(p.as_str(), "visible" | "invisible" | "hidden" | "inactive") {
-                            if let Some(n) = self.h.nodes.get_mut(i) {
-                                n.presence = p.clone();
-                            }
-                            self.h.push(XfaEffect::SetPresence { som, presence: p });
+                            self.h.set_state(i, XfaEffect::SetPresence { som, presence: p });
                         }
                     }
                     "access" => {
                         let a = self.to_str(&v);
                         if matches!(a.as_str(), "open" | "readOnly" | "protected" | "nonInteractive") {
-                            if let Some(n) = self.h.nodes.get_mut(i) {
-                                n.access = a.clone();
-                            }
-                            self.h.push(XfaEffect::SetAccess { som, access: a });
+                            self.h.set_state(i, XfaEffect::SetAccess { som, access: a });
                         }
                     }
                     other => {
diff --git a/crates/js/src/tests.rs b/crates/js/src/tests.rs
index 5e9512789..07f04614d 100644
--- a/crates/js/src/tests.rs
+++ b/crates/js/src/tests.rs
@@ -702,6 +702,27 @@ mod xfa_model {
         assert_eq!(o.result.as_deref(), Some("true:2"));
     }
 
+    /// Past the effect cap, presence and access set on a new object are left out of the snapshot
+    /// as well as the effects; one set again on an object that already has its effect still lands.
+    #[test]
+    fn presence_and_access_past_the_effect_cap_are_left_out_of_the_snapshot_too() {
+        let read = "qty.presence + ':' + qty.access + ':' + price.presence";
+        let before = go(read, "form1[0].page1[0]", "click").result;
+        let o = go(
+            &format!(
+                "price.presence = 'invisible'; for (var i = 0; i < 20000; i++) xfa.host.beep(); qty.presence = 'hidden'; qty.access = 'readOnly'; price.presence = 'hidden'; {read}"
+            ),
+            "form1[0].page1[0]",
+            "click",
+        );
+        assert_eq!(o.error, None, "{o:?}");
+        assert_eq!(o.effects.len(), MAX_EFFECTS);
+        let unchanged = before.as_deref().and_then(|b| b.rsplit_once(':')).map(|(qty, _)| format!("{qty}:hidden"));
+        assert_eq!(o.result, unchanged);
+        assert!(o.effects.contains(&XfaEffect::SetPresence { som: "form1[0].page1[0].price[0]".into(), presence: "hidden".into() }));
+        assert!(!o.effects.iter().any(|e| matches!(e, XfaEffect::SetPresence { som, .. } | XfaEffect::SetAccess { som, .. } if som.contains("qty"))));
+    }
+
     #[test]
     fn urls_and_reset_lists_are_clipped_and_deduplicated() {
         let o = go(
@@ -803,6 +824,20 @@ mod formcalc {
         assert_eq!(names, 2);
     }
 
+    /// FormCalc presence and access past the effect cap are left out of the snapshot too.
+    #[test]
+    fn formcalc_presence_and_access_past_the_effect_cap_are_left_out_of_the_snapshot_too() {
+        let o = go(
+            "for i = 1 upto 20000 do $host.beep() endfor\nqty.presence = \"hidden\"\nqty.access = \"readOnly\"\nConcat(qty.presence, \":\", qty.access)",
+            "form1[0].page1[0]",
+            "click",
+        );
+        assert_eq!(o.error, None, "{o:?}");
+        assert_eq!(o.effects.len(), MAX_EFFECTS);
+        let before = go("Concat(qty.presence, \":\", qty.access)", "form1[0].page1[0]", "click");
+        assert_eq!(o.result, before.result);
+    }
+
     /// FormCalc reads `formattedValue` as the field's picture shows it too, until the script
     /// sets the value.
     #[test]
diff --git a/crates/js/src/xfa.rs b/crates/js/src/xfa.rs
index b8440454a..18013e001 100644
--- a/crates/js/src/xfa.rs
+++ b/crates/js/src/xfa.rs
@@ -199,6 +199,17 @@ pub(crate) fn reset_names(list: &str) -> Vec<String> {
     out
 }
 
+/// The (property, SOM) an effect setting a property of an object is merged by, see
+/// [`XHost::set_at`].
+fn effect_key(e: &XfaEffect) -> Option<(u8, String)> {
+    match e {
+        XfaEffect::SetValue { som, .. } => Some((0, som.clone())),
+        XfaEffect::SetPresence { som, .. } => Some((1, som.clone())),
+        XfaEffect::SetAccess { som, .. } => Some((2, som.clone())),
+        _ => None,
+    }
+}
+
 /// Bytes of text `e` holds.
 fn payload(e: &XfaEffect) -> usize {
     match e {
@@ -321,17 +332,35 @@ impl XHost {
         }
     }
 
-    /// Room for one more effect holding `bytes` of text, charged now: a change to the snapshot
-    /// is made only when the effect that applies it will be kept, so a script never sees a change
-    /// its effects leave out. A drop is counted when there is no room.
-    fn reserve(&mut self, bytes: usize) -> bool {
-        if self.effects.len() >= MAX_EFFECTS {
+    /// Room for `e`, which holds `bytes` of text, charged now: a change to the snapshot is made
+    /// only when the effect that applies it will be kept, so a script never sees a change its
+    /// effects leave out. An effect that replaces an earlier one needs no new slot. A drop is
+    /// counted when there is no room.
+    fn reserve(&mut self, e: &XfaEffect, bytes: usize) -> bool {
+        let replaces = effect_key(e).and_then(|k| self.set_at.get(&k)).is_some_and(|&at| at >= self.barrier && at < self.effects.len());
+        if !replaces && self.effects.len() >= MAX_EFFECTS {
             self.dropped_effects += 1;
             return false;
         }
         self.room(bytes)
     }
 
+    /// Set the presence or access of node `i` to what `e` (a [`XfaEffect::SetPresence`] or
+    /// [`XfaEffect::SetAccess`]) says, in the snapshot only when the effect is kept.
+    pub(crate) fn set_state(&mut self, i: usize, e: XfaEffect) {
+        if !self.reserve(&e, payload(&e)) {
+            return;
+        }
+        if let Some(n) = self.nodes.get_mut(i) {
+            match &e {
+                XfaEffect::SetPresence { presence, .. } => n.presence = presence.clone(),
+                XfaEffect::SetAccess { access, .. } => n.access = access.clone(),
+                _ => {}
+            }
+        }
+        self.record(e);
+    }
+
     /// `e` with its text cut to the lengths an effect keeps.
     fn clip_effect(&mut self, e: XfaEffect) -> XfaEffect {
         match e {
@@ -352,13 +381,7 @@ impl XHost {
 
     /// Keep `e`, whose bytes are already charged, against the count limits.
     fn record(&mut self, e: XfaEffect) {
-        let key = match &e {
-            XfaEffect::SetValue { som, .. } => Some((0u8, som.clone())),
-            XfaEffect::SetPresence { som, .. } => Some((1, som.clone())),
-            XfaEffect::SetAccess { som, .. } => Some((2, som.clone())),
-            _ => None,
-        };
-        if let Some(key) = key {
+        if let Some(key) = effect_key(&e) {
             if let Some(&at) = self.set_at.get(&key)
                 && at >= self.barrier
                 && let Some(slot) = self.effects.get_mut(at)
@@ -773,7 +796,7 @@ impl XHost {
         let name = h.nodes.get(first).map(|n| n.name.clone()).unwrap_or_default();
         let parent_som = h.nodes.get(parent).map(|p| p.som.clone()).unwrap_or_default();
         let som = child_som(parent_som, &name, live.len());
-        if !h.reserve(som.len()) {
+        if !h.reserve(&XfaEffect::AddInstance { som: String::new() }, som.len()) {
             return None;
         }
         let new = clone_subtree(h, first, Some(parent), 0)?;
@@ -825,7 +848,7 @@ impl XHost {
             return;
         }
         let som = h.nodes.get(gone).map(|n| n.som.clone()).unwrap_or_default();
-        if !h.reserve(som.len()) {
+        if !h.reserve(&XfaEffect::RemoveInstance { som: String::new() }, som.len()) {
             return;
         }
         if let Some(n) = h.nodes.get_mut(gone) {
@@ -1061,20 +1084,14 @@ fn node_set(_: &JsValue, args: &[JsValue], ctx: &mut Context) -> JsResult<JsValu
                 "hidden" | "invisible" | "inactive" | "visible" => value.clone(),
                 _ => return Ok(JsValue::from(true)),
             };
-            if let Some(n) = h.nodes.get_mut(idx) {
-                n.presence = p.clone();
-            }
-            h.push(XfaEffect::SetPresence { som, presence: p });
+            h.set_state(idx, XfaEffect::SetPresence { som, presence: p });
         }
         "access" => {
             let a = match value.as_str() {
                 "open" | "readOnly" | "protected" | "nonInteractive" => value.clone(),
                 _ => return Ok(JsValue::from(true)),
             };
-            if let Some(n) = h.nodes.get_mut(idx) {
-                n.access = a.clone();
-            }
-            h.push(XfaEffect::SetAccess { som, access: a });
+            h.set_state(idx, XfaEffect::SetAccess { som, access: a });
         }
         _ => {}
     }