diff --git a/contributors/people.toml b/contributors/people.toml
index c5ec7060..705feb25 100644
--- a/contributors/people.toml
+++ b/contributors/people.toml
@@ -74,3 +74,7 @@ sync_github_name = true
 [people.dotCooCoo]
 real_name = "Robert Lee"
 sync_github_name = true
+
+[people.moecr7]
+real_name = "Moein Saharkhiz"
+display_name = "onlymoein"
diff --git a/crates/engine/src/commands/effect.rs b/crates/engine/src/commands/effect.rs
index 30237ede..ce773e54 100644
--- a/crates/engine/src/commands/effect.rs
+++ b/crates/engine/src/commands/effect.rs
@@ -1,7 +1,8 @@
 //! Effect menu and Effect Controls gestures.
 
 use effectcraft_project::build::Ids;
-use effectcraft_project::{GroupKind, LayerId, PropGroup, Uid};
+use effectcraft_project::{GroupKind, Layer, LayerId, PropGroup, Uid};
+use effectcraft_time::Tick;
 use serde_json::{Value, json};
 
 use super::{CommandSpec, b_p, bad, f_p, has_layers, layer_mut, layers_p, str_p};
@@ -319,12 +320,108 @@ fn effects_p(s: &Session, p: &Value, cmd: &str) -> Result<Vec<(LayerId, Uid)>> {
     Ok(sel)
 }
 
-/// Edit ▸ Copy with effects selected: puts the effect instances on the effect clipboard.
+fn effect_time_error(cmd: &str) -> EngineError {
+    bad(cmd, "an effect keyframe converts outside the supported time range")
+}
+
+/// Validate before Layer's saturating conversions, so a bad stretch or time never silently
+/// moves a copied key to another frame. Normal-speed layers keep their exact integer ticks.
+fn effect_time(layer: &Layer, time: Tick, to_comp: bool, cmd: &str) -> Result<Tick> {
+    if !layer.stretch.is_finite() || layer.stretch == 0.0 {
+        return Err(bad(cmd, "the layer has an invalid time stretch"));
+    }
+    let in_range = |t: i64| (Tick::MIN.0..=Tick::MAX.0).contains(&t);
+    if !in_range(time.0) {
+        return Err(effect_time_error(cmd));
+    }
+    let offset = if to_comp { time.0 } else { time.0.checked_sub(layer.start_time.0).ok_or_else(|| effect_time_error(cmd))? };
+    let scaled = if (layer.stretch - 100.0).abs() < 1e-9 {
+        offset
+    } else {
+        let scaled = if to_comp { offset as f64 * layer.stretch / 100.0 } else { offset as f64 * 100.0 / layer.stretch };
+        if !scaled.is_finite() || scaled < Tick::MIN.0 as f64 || scaled > Tick::MAX.0 as f64 {
+            return Err(effect_time_error(cmd));
+        }
+        scaled as i64
+    };
+    if !in_range(scaled) {
+        return Err(effect_time_error(cmd));
+    }
+    let time = if to_comp { layer.start_time.0.checked_add(scaled).ok_or_else(|| effect_time_error(cmd))? } else { scaled };
+    if !in_range(time) {
+        return Err(effect_time_error(cmd));
+    }
+    Ok(Tick(time))
+}
+
+/// Change the key time coordinate system throughout an effect, including nested controls.
+/// Ease speeds are per second in that coordinate system; reversed time swaps the key sides.
+fn retime_effect(group: &mut PropGroup, scale: f64, cmd: &str, mut time: impl FnMut(Tick) -> Result<Tick>) -> Result<()> {
+    let mut result = Ok(());
+    group.walk_mut(&mut |pr| {
+        if result.is_err() {
+            return;
+        }
+        for key in &mut pr.keys {
+            let mapped = time(key.time).and_then(|t| {
+                if !scale.is_finite() || scale == 0.0 {
+                    return Err(effect_time_error(cmd));
+                }
+                // Spatial paths and non-numeric values ease along positive progress;
+                // numeric components instead store a signed value derivative.
+                let speed_scale = if pr.spatial || key.value.dims() == 0 { scale.abs() } else { scale };
+                for ease in key.in_ease.iter_mut().chain(&mut key.out_ease) {
+                    ease.speed /= speed_scale;
+                    if !ease.speed.is_finite() {
+                        return Err(bad(cmd, "an effect keyframe ease converts outside the supported range"));
+                    }
+                }
+                if scale < 0.0 {
+                    std::mem::swap(&mut key.in_interp, &mut key.out_interp);
+                    std::mem::swap(&mut key.in_ease, &mut key.out_ease);
+                    std::mem::swap(&mut key.spatial_in, &mut key.spatial_out);
+                }
+                Ok(t)
+            });
+            match mapped {
+                Ok(t) => key.time = t,
+                Err(e) => {
+                    result = Err(e);
+                    return;
+                }
+            }
+        }
+        pr.keys.sort_by_key(|key| key.time);
+        if pr.keys.windows(2).any(|pair| pair[0].time == pair[1].time) {
+            result = Err(bad(cmd, "the layer's time stretch maps effect keyframes to the same tick"));
+        }
+    });
+    result
+}
+
+/// Edit ▸ Copy with effects selected: times on the clipboard are comp-time offsets from the
+/// earliest copied key, shared by all copied effects and their parameters (#989).
 fn copy(s: &mut Session, p: &Value) -> Result<Value> {
+    const CMD: &str = "effect.copy";
     let fx = effects_p(s, p, "effect.copy")?;
     let comp = s.active_comp().ok_or(EngineError::NoComp)?;
-    let groups: Vec<PropGroup> =
-        fx.iter().filter_map(|(l, u)| comp.layer(*l).and_then(|l| l.effects()).and_then(|e| e.groups().find(|g| g.uid == *u)).cloned()).collect();
+    let mut groups = Vec::new();
+    let mut earliest: Option<Tick> = None;
+    for (lid, uid) in fx {
+        let layer = comp.layer(lid).ok_or(EngineError::NoComp)?;
+        let mut group = layer.effects().and_then(|fx| fx.groups().find(|g| g.uid == uid)).cloned().ok_or_else(|| bad(CMD, "the effect no longer exists"))?;
+        retime_effect(&mut group, layer.stretch / 100.0, CMD, |t| {
+            let t = effect_time(layer, t, true, CMD)?;
+            earliest = Some(earliest.map_or(t, |first| first.min(t)));
+            Ok(t)
+        })?;
+        groups.push(group);
+    }
+    if let Some(first) = earliest {
+        for group in &mut groups {
+            retime_effect(group, 1.0, CMD, |t| Ok(Tick(t.0.checked_sub(first.0).ok_or_else(|| effect_time_error(CMD))?)))?;
+        }
+    }
     s.state.clipboard.clear();
     s.state.key_clipboard.clear();
     s.state.contents_clipboard.clear();
@@ -345,8 +442,10 @@ pub(crate) fn unique_name(fx: &PropGroup, base: &str) -> String {
 }
 
 /// Edit ▸ Paste with effects on the clipboard: adds copies to every target layer, after the
-/// layer's selected effect when it has one, else at the end of its stack.
+/// layer's selected effect when it has one, else at the end of its stack. The earliest copied
+/// key lands at the destination comp's CTI; all other keys keep their comp-time offsets.
 fn paste(s: &mut Session, p: &Value) -> Result<Value> {
+    const CMD: &str = "effect.paste";
     let clip = s.state.effect_clipboard.clone();
     if clip.is_empty() {
         return Err(bad("effect.paste", "no effects on the clipboard"));
@@ -356,6 +455,7 @@ fn paste(s: &mut Session, p: &Value) -> Result<Value> {
         return Err(bad("effect.paste", "select a layer to paste effects onto"));
     }
     let sel = selected_effects(s);
+    let cti = s.time_of(cid);
     let label = if clip.len() == 1 { format!("Paste {}", clip[0].name) } else { "Paste Effects".to_string() };
     let uids = s.edit(&label, None, |proj, st| {
         let mut out = vec![];
@@ -363,6 +463,13 @@ fn paste(s: &mut Session, p: &Value) -> Result<Value> {
         let mut new_sel = vec![];
         for lid in &ids {
             let l = layer_mut(proj, cid, *lid)?;
+            let mut groups = clip.clone();
+            for group in &mut groups {
+                retime_effect(group, 100.0 / l.stretch, CMD, |offset| {
+                    let t = Tick(cti.0.checked_add(offset.0).ok_or_else(|| effect_time_error(CMD))?);
+                    effect_time(l, t, false, CMD)
+                })?;
+            }
             let Some(fx) = l.props.sub_mut("effects") else { continue };
             let at = sel
                 .iter()
@@ -371,8 +478,7 @@ fn paste(s: &mut Session, p: &Value) -> Result<Value> {
                 .max()
                 .map(|i| i + 1)
                 .unwrap_or(fx.children.len());
-            for (k, g) in clip.iter().enumerate() {
-                let mut g = g.clone();
+            for (k, mut g) in groups.into_iter().enumerate() {
                 g.reassign_uids(&mut next);
                 g.name = unique_name(fx, &g.name);
                 out.push(g.uid);
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index 44dd926f..80956687 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -243,8 +243,8 @@ pub struct EditorState {
     /// Paste sets the same properties of the selected layers.
     #[serde(skip)]
     pub value_clipboard: Vec<(String, effectcraft_keyframe::Value)>,
-    /// Copied effect instances (Edit ▸ Copy with effects selected); Paste adds them to the
-    /// selected layers.
+    /// Copied effect instances, with comp-time key offsets from the earliest copied key.
+    /// Paste adds them to the selected layers at the destination comp's CTI.
     #[serde(skip)]
     pub effect_clipboard: Vec<effectcraft_project::PropGroup>,
     /// Copied shape items (Edit ▸ Copy with groups, paths, paints or path operations selected in
diff --git a/crates/engine/src/tests_effects.rs b/crates/engine/src/tests_effects.rs
index 83ea9c04..6f87b4ae 100644
--- a/crates/engine/src/tests_effects.rs
+++ b/crates/engine/src/tests_effects.rs
@@ -1,8 +1,9 @@
 //! Effect Controls operations: copy/paste, duplicate, reorder, remove (Delete), reset, and the
 //! Edit menu routing to them when effects are selected, all with undo.
 
-use effectcraft_keyframe::Value as KV;
-use effectcraft_project::{Layer, LayerId};
+use effectcraft_keyframe::{Ease, Interp, Value as KV};
+use effectcraft_project::{Layer, LayerId, PropGroup};
+use effectcraft_time::Tick;
 use serde_json::json;
 
 use crate::Session;
@@ -32,6 +33,24 @@ fn select_effect(s: &mut Session, lid: u64, uid: u64) {
     s.state.selected_props = vec![(LayerId(lid), uid)];
 }
 
+fn effect_group(s: &Session, lid: u64, uid: u64) -> PropGroup {
+    layer(s, lid).effects().unwrap().groups().find(|g| g.uid == uid).unwrap().clone()
+}
+
+fn animate_effect(s: &mut Session, lid: u64, uid: u64, path: &str, keys: &[(f64, f64)]) {
+    let prop = effect_group(s, lid, uid).prop(path).unwrap().uid;
+    for &(time, value) in keys {
+        s.execute("prop.addKey", json!({"layer": lid, "prop": prop, "time": time, "timeBase": "comp", "value": value})).unwrap();
+    }
+}
+
+fn set_layer_clock(s: &mut Session, lid: u64, start: f64, stretch: f64) {
+    let cid = s.active_comp_id().unwrap();
+    let l = std::sync::Arc::make_mut(&mut s.project).comp_mut(cid).unwrap().layer_mut(LayerId(lid)).unwrap();
+    l.start_time = Tick::from_seconds_f64(start);
+    l.stretch = stretch;
+}
+
 #[test]
 fn copy_paste_effects_between_layers_with_undo() {
     let (mut s, a, b) = comp_with_two_solids();
@@ -62,6 +81,233 @@ fn copy_paste_effects_between_layers_with_undo() {
     assert_eq!(fx_names(&s, a), vec!["Gaussian Blur"]);
 }
 
+/// #989: copying an animated effect aligns its first key to the destination CTI.
+#[test]
+fn pasted_effect_keys_start_at_the_playhead() {
+    let (mut s, a, b) = comp_with_two_solids();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    let uid = layer(&s, a).effects().unwrap().groups().next().unwrap().get("blurriness").unwrap().uid;
+    for (time, value) in [(1.0, 10.0), (3.0, 30.0)] {
+        s.execute("prop.addKey", json!({"layer": a, "prop": uid, "time": time, "value": value})).unwrap();
+    }
+    let source = layer(&s, a);
+    select_effect(&mut s, a, blur);
+    s.execute("edit.copy", json!({})).unwrap();
+    s.execute("time.set", json!({"time": 5.0})).unwrap();
+    s.execute("layer.select", json!({"layers": [b]})).unwrap();
+    let undo = s.history.undo.len();
+    s.execute("edit.paste", json!({})).unwrap();
+    let pasted = layer(&s, b);
+    let keys = &pasted.effects().unwrap().groups().next().unwrap().get("blurriness").unwrap().keys;
+    assert_eq!(keys.iter().map(|k| pasted.comp_time(k.time).seconds()).collect::<Vec<_>>(), vec![5.0, 7.0]);
+    assert_eq!(keys.iter().map(|k| k.value.as_f64()).collect::<Vec<_>>(), vec![10.0, 30.0]);
+    assert_eq!(layer(&s, a), source, "copy and paste do not edit the source");
+    assert_eq!(s.history.undo.len(), undo + 1, "the whole paste is one undo step");
+    s.execute("edit.undo", json!({})).unwrap();
+    assert!(fx_names(&s, b).is_empty());
+    s.execute("edit.redo", json!({})).unwrap();
+    assert_eq!(layer(&s, b), pasted);
+}
+
+#[test]
+fn pasted_effects_share_one_anchor_including_nested_parameters() {
+    let (mut s, a, b) = comp_with_two_solids();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    let fractal = apply(&mut s, a, "Fractal");
+    animate_effect(&mut s, a, blur, "blurriness", &[(1.0, 10.0), (3.0, 30.0)]);
+    animate_effect(&mut s, a, fractal, "mandelbrot/mandelbrotX", &[(2.0, 1.25), (4.0, 2.5)]);
+    animate_effect(&mut s, a, fractal, "mandelbrot/mandelbrotY", &[(3.0, 0.5), (5.0, 2.0)]);
+    let static_value = effect_group(&s, a, fractal).get("setChoice").unwrap().value.clone();
+    s.state.selected_props = vec![(LayerId(a), blur), (LayerId(a), fractal)];
+    s.execute("edit.copy", json!({})).unwrap();
+    s.execute("time.set", json!({"time": 5.0})).unwrap();
+    let reply = s.execute("effect.paste", json!({"layers": [b]})).unwrap();
+    for (index, path, times) in
+        [(0, "blurriness", vec![5.0, 7.0]), (1, "mandelbrot/mandelbrotX", vec![6.0, 8.0]), (1, "mandelbrot/mandelbrotY", vec![7.0, 9.0])]
+    {
+        let group = effect_group(&s, b, reply["effects"][index].as_u64().unwrap());
+        assert_eq!(group.prop(path).unwrap().keys.iter().map(|k| k.time.seconds()).collect::<Vec<_>>(), times, "{path}");
+    }
+    let group = effect_group(&s, b, reply["effects"][1].as_u64().unwrap());
+    assert_eq!(group.get("setChoice").unwrap().value, static_value, "unanimated controls stay unchanged");
+}
+
+#[test]
+fn pasted_effects_preserve_comp_timing_and_eased_values_on_stretched_layers() {
+    for (source_start, source_stretch) in [(2.0, 100.0), (1.0, 200.0), (8.0, -200.0)] {
+        for (target_start, target_stretch) in [(0.0, 100.0), (3.0, 200.0), (8.0, -100.0)] {
+            let (mut s, a, b) = comp_with_two_solids();
+            set_layer_clock(&mut s, a, source_start, source_stretch);
+            set_layer_clock(&mut s, b, target_start, target_stretch);
+            let blur = apply(&mut s, a, "Gaussian Blur");
+            animate_effect(&mut s, a, blur, "blurriness", &[(3.0, 10.0), (5.0, 30.0)]);
+            let uid = effect_group(&s, a, blur).get("blurriness").unwrap().uid;
+            let cid = s.active_comp_id().unwrap();
+            let pr = std::sync::Arc::make_mut(&mut s.project).comp_mut(cid).unwrap().layer_mut(LayerId(a)).unwrap().props.find_mut(uid).unwrap();
+            for key in &mut pr.keys {
+                key.in_interp = Interp::Bezier;
+                key.out_interp = Interp::Bezier;
+                key.in_ease = vec![Ease { speed: 7.0, influence: 0.25 }];
+                key.out_ease = vec![Ease { speed: 3.0, influence: 0.6 }];
+                key.label = 4;
+            }
+            let source = layer(&s, a);
+            let source_pr = source.props.find(uid).unwrap();
+            s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+            s.execute("time.set", json!({"time": 5.0})).unwrap();
+            let pasted = s.execute("effect.paste", json!({"layers": [b]})).unwrap()["effects"][0].as_u64().unwrap();
+            let target = layer(&s, b);
+            let target_group = target.effects().unwrap().groups().find(|g| g.uid == pasted).unwrap();
+            let target_pr = target_group.get("blurriness").unwrap();
+            let mut times: Vec<Tick> = target_pr.keys.iter().map(|k| target.comp_time(k.time)).collect();
+            times.sort();
+            assert_eq!(times, vec![Tick::from_seconds_f64(5.0), Tick::from_seconds_f64(7.0)]);
+            for offset in [0.0, 0.25, 0.75, 1.5, 2.0] {
+                let expected = source_pr.value_at(source.layer_time(Tick::from_seconds_f64(3.0 + offset))).as_f64();
+                let actual = target_pr.value_at(target.layer_time(Tick::from_seconds_f64(5.0 + offset))).as_f64();
+                assert!((expected - actual).abs() < 1e-8, "source {source_stretch} %, target {target_stretch} %, t={offset}: {expected} != {actual}");
+            }
+            assert!(target_pr.keys.iter().all(|k| k.label == 4));
+            assert_eq!(layer(&s, a), source);
+        }
+    }
+}
+
+#[test]
+fn pasted_spatial_effect_keys_preserve_the_eased_path_on_reversed_layers() {
+    for (source_stretch, target_stretch) in [(200.0, 100.0), (-200.0, 100.0), (100.0, -200.0)] {
+        let (mut s, a, b) = comp_with_two_solids();
+        set_layer_clock(&mut s, a, if source_stretch < 0.0 { 8.0 } else { 1.0 }, source_stretch);
+        set_layer_clock(&mut s, b, if target_stretch < 0.0 { 8.0 } else { 0.0 }, target_stretch);
+        let ramp = apply(&mut s, a, "Gradient Ramp");
+        let uid = effect_group(&s, a, ramp).get("start").unwrap().uid;
+        for (time, value) in [(3.0, [50.0, 25.0]), (5.0, [180.0, 75.0])] {
+            s.execute("prop.addKey", json!({"layer": a, "prop": uid, "time": time, "timeBase": "comp", "value": value})).unwrap();
+        }
+        let cid = s.active_comp_id().unwrap();
+        let pr = std::sync::Arc::make_mut(&mut s.project).comp_mut(cid).unwrap().layer_mut(LayerId(a)).unwrap().props.find_mut(uid).unwrap();
+        pr.spatial = true;
+        for key in &mut pr.keys {
+            key.in_interp = Interp::Bezier;
+            key.out_interp = Interp::Bezier;
+            key.in_ease = vec![Ease { speed: 15.0, influence: 0.25 }];
+            key.out_ease = vec![Ease { speed: 30.0, influence: 0.6 }];
+            key.spatial_auto = false;
+            key.spatial_in = [-10.0, -20.0, 0.0];
+            key.spatial_out = [20.0, 5.0, 0.0];
+        }
+        let source = layer(&s, a);
+        let source_pr = source.props.find(uid).unwrap();
+        s.execute("effect.copy", json!({"layer": a, "effect": ramp})).unwrap();
+        s.execute("time.set", json!({"time": 5.0})).unwrap();
+        let pasted = s.execute("effect.paste", json!({"layers": [b]})).unwrap()["effects"][0].as_u64().unwrap();
+        let target = layer(&s, b);
+        let group = target.effects().unwrap().groups().find(|g| g.uid == pasted).unwrap();
+        let target_pr = group.get("start").unwrap();
+        for offset in [0.0, 0.25, 0.75, 1.5, 2.0] {
+            let expected = source_pr.value_at(source.layer_time(Tick::from_seconds_f64(3.0 + offset))).components();
+            let actual = target_pr.value_at(target.layer_time(Tick::from_seconds_f64(5.0 + offset))).components();
+            assert_eq!(expected.len(), actual.len());
+            assert!(expected.iter().zip(&actual).all(|(a, b)| (a - b).abs() < 0.05), "path at {offset}: {expected:?} != {actual:?}");
+        }
+    }
+}
+
+#[test]
+fn effect_clipboard_is_a_snapshot_and_repeated_paste_uses_the_target_comps_cti() {
+    let (mut s, a, _) = comp_with_two_solids();
+    let original_comp = s.active_comp_id().unwrap();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    animate_effect(&mut s, a, blur, "blurriness", &[(1.0, 10.0), (3.0, 30.0)]);
+    s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+    let clipboard = s.state.effect_clipboard.clone();
+    // Changing the source after Copy must not change what the clipboard will paste.
+    animate_effect(&mut s, a, blur, "blurriness", &[(4.0, 99.0)]);
+    s.execute("time.set", json!({"time": 9.0})).unwrap();
+    let destination = s.execute("comp.new", json!({"name": "Destination", "frameRate": 24, "duration": 10})).unwrap()["comp"].as_u64().unwrap();
+    let b = s.execute("layer.newSolid", json!({"color": "#ffffff"})).unwrap()["layer"].as_u64().unwrap();
+    s.execute("time.set", json!({"time": 4.0})).unwrap();
+    s.open_comp(original_comp);
+    for (cti, expected) in [(4.0, vec![4.0, 6.0]), (2.0, vec![2.0, 4.0])] {
+        s.state.times.insert(effectcraft_project::ItemId(destination), Tick::from_seconds_f64(cti));
+        let uid = s.execute("effect.paste", json!({"comp": destination, "layers": [b]})).unwrap()["effects"][0].as_u64().unwrap();
+        let l = s.project.comp(effectcraft_project::ItemId(destination)).unwrap().layer(LayerId(b)).unwrap();
+        let pr = l.effects().unwrap().groups().find(|g| g.uid == uid).unwrap().get("blurriness").unwrap();
+        assert_eq!(pr.keys.iter().map(|k| l.comp_time(k.time).seconds()).collect::<Vec<_>>(), expected);
+        assert_eq!(pr.keys.iter().map(|k| k.value.as_f64()).collect::<Vec<_>>(), vec![10.0, 30.0]);
+        assert_eq!(s.state.effect_clipboard, clipboard);
+    }
+}
+
+#[test]
+fn invalid_effect_paste_timing_leaves_every_target_and_history_unchanged() {
+    for stretch in [0.0, f64::NAN, f64::INFINITY, 1e-300, 1e300] {
+        let (mut s, a, b) = comp_with_two_solids();
+        let blur = apply(&mut s, a, "Gaussian Blur");
+        animate_effect(&mut s, a, blur, "blurriness", &[(1.0, 10.0), (3.0, 30.0)]);
+        s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+        set_layer_clock(&mut s, b, 0.0, stretch);
+        s.execute("time.set", json!({"time": 5.0})).unwrap();
+        let project = s.project.clone();
+        let clipboard = s.state.effect_clipboard.clone();
+        let undo = s.history.undo.len();
+        // A is valid and comes first; failure on B must roll back A's new effect too.
+        assert!(s.execute("effect.paste", json!({"layers": [a, b]})).is_err(), "{stretch}");
+        assert!(std::sync::Arc::ptr_eq(&s.project, &project));
+        assert_eq!(s.state.effect_clipboard, clipboard);
+        assert_eq!(s.history.undo.len(), undo);
+    }
+}
+
+#[test]
+fn invalid_effect_copy_keeps_the_previous_clipboard() {
+    let (mut s, a, _) = comp_with_two_solids();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    animate_effect(&mut s, a, blur, "blurriness", &[(1.0, 10.0), (3.0, 30.0)]);
+    s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+    let clipboard = s.state.effect_clipboard.clone();
+    set_layer_clock(&mut s, a, 0.0, 0.0);
+    assert!(s.execute("effect.copy", json!({"layer": a, "effect": blur})).is_err());
+    assert_eq!(s.state.effect_clipboard, clipboard);
+}
+
+#[test]
+fn effect_paste_keeps_exact_ntsc_frame_offsets() {
+    let (mut s, a, b) = comp_with_two_solids();
+    let cid = s.active_comp_id().unwrap();
+    let frame = effectcraft_time::FrameRate::new(30000, 1001).frame_duration();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    let uid = effect_group(&s, a, blur).get("blurriness").unwrap().uid;
+    let pr = std::sync::Arc::make_mut(&mut s.project).comp_mut(cid).unwrap().layer_mut(LayerId(a)).unwrap().props.find_mut(uid).unwrap();
+    pr.keys = vec![
+        effectcraft_keyframe::Keyframe::new(frame.mul_ratio(11, 1), KV::Scalar(10.0)),
+        effectcraft_keyframe::Keyframe::new(frame.mul_ratio(43, 1), KV::Scalar(30.0)),
+    ];
+    s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+    let cti = frame.mul_ratio(71, 1);
+    s.state.times.insert(cid, cti);
+    let pasted = s.execute("effect.paste", json!({"layers": [b]})).unwrap()["effects"][0].as_u64().unwrap();
+    let group = effect_group(&s, b, pasted);
+    assert_eq!(group.get("blurriness").unwrap().keys.iter().map(|k| k.time).collect::<Vec<_>>(), vec![cti, cti + frame.mul_ratio(32, 1)]);
+}
+
+#[test]
+fn overflowing_effect_paste_times_return_an_error_without_an_edit() {
+    let (mut s, a, b) = comp_with_two_solids();
+    let blur = apply(&mut s, a, "Gaussian Blur");
+    animate_effect(&mut s, a, blur, "blurriness", &[(1.0, 10.0), (3.0, 30.0)]);
+    s.execute("effect.copy", json!({"layer": a, "effect": blur})).unwrap();
+    let cid = s.active_comp_id().unwrap();
+    for cti in [Tick::MAX, Tick(i64::MAX)] {
+        s.state.times.insert(cid, cti);
+        let project = s.project.clone();
+        let undo = s.history.undo.len();
+        assert!(s.execute("effect.paste", json!({"layers": [b]})).is_err());
+        assert!(std::sync::Arc::ptr_eq(&s.project, &project));
+        assert_eq!(s.history.undo.len(), undo);
+    }
+}
+
 #[test]
 fn duplicate_reorder_and_delete_selected_effect() {
     let (mut s, a, _) = comp_with_two_solids();
diff --git a/docs/agents.md b/docs/agents.md
index 2eba652a..ccd7c57e 100644
--- a/docs/agents.md
+++ b/docs/agents.md
@@ -257,6 +257,9 @@ build real projects through these interfaces; they are worked examples of everyt
   the ones between by equal steps, onto subframes; `merge` + `fromStart: true` make `delta` the whole
   drag. Keys of locked layers can't be selected. Copy / paste: `keys.copy`, then `keys.paste`
   at the current time (keys copied from several layers go to as many selected layers in order).
+  Whole effects: `effect.copy`, then `effect.paste {layers}` places the earliest copied effect
+  key at the destination comp's current time, preserving the offsets between all copied
+  effects and parameters, including on offset or time-stretched layers.
   `time.nextKey` / `time.previousKey` / `keys.selectAll` take `visible: [{layer, prop}]` to act
   only on those properties (the Timeline passes its revealed ones, as J / K and Ctrl+Alt+A do).
 * **Easing with Keyframe Velocity**: select keys by path, `keys.select {"keys":[{"layer":"Ring","path":"contents/trim/end","time":0}]}`,