Merge branch 'worktree-agent-a549a3d1a8812e372'

# Conflicts:
#	apps/effectcraft-cli/src/main.rs
#	crates/host/src/lib.rs
#	crates/render/src/lib.rs

crates/engine/src/commands/anim.rs

@@ -0,0 +1,414 @@
+//! Keyframe clipboard, selection, nudging, direct key/ease edits (Graph Editor handles) and key
+//! inspection for the Keyframe Velocity / Keyframe Interpolation dialogs.
+
+use effectcraft_keyframe::{Ease, Interp, Keyframe, key_at, retime_roving, side_ease};
+use effectcraft_project::{LayerId, Property, Uid};
+use effectcraft_time::Tick;
+use serde_json::{Value, json};
+
+use super::prop::{edit_keys, prop_ref};
+use super::{CommandSpec, bad, comp_id, f_p, has_comp, has_keys, layers_p, merge_p, str_p, time_p};
+use crate::{EngineError, KeyClip, KeyRef, Result, Session, cmd, query};
+
+fn has_key_clip(s: &Session) -> std::result::Result<(), String> {
+    has_comp(s)?;
+    if s.state.key_clipboard.is_empty() { Err("no keyframes have been copied".into()) } else { Ok(()) }
+}
+
+/// Copy the selected keyframes (Edit ▸ Copy with keys selected).
+fn copy(s: &mut Session, _: &Value) -> Result<Value> {
+    let comp = s.active_comp().ok_or(EngineError::NoComp)?;
+    let mut groups: std::collections::BTreeMap<(LayerId, Uid), Vec<Tick>> = Default::default();
+    for k in &s.state.selected_keys {
+        groups.entry((k.layer, k.prop)).or_default().push(k.time);
+    }
+    // Earliest selected key in comp time: pasted keys keep their offsets from it.
+    let mut earliest: Option<Tick> = None;
+    for ((lid, _), times) in &groups {
+        if let Some(l) = comp.layer(*lid) {
+            for t in times {
+                let ct = l.comp_time(*t);
+                earliest = Some(earliest.map_or(ct, |e: Tick| e.min(ct)));
+            }
+        }
+    }
+    let earliest = earliest.ok_or_else(|| bad("keys.copy", "select keyframes first"))?;
+    let mut clip = vec![];
+    for ((lid, uid), times) in groups {
+        let Some(l) = comp.layer(lid) else { continue };
+        let Some(pr) = l.props.find(uid) else { continue };
+        let Some(path) = l.props.match_path_of(uid) else { continue };
+        let mut keys: Vec<Keyframe> = pr.keys.iter().filter(|k| times.contains(&k.time)).cloned().collect();
+        for k in &mut keys {
+            k.time = l.comp_time(k.time) - earliest;
+        }
+        clip.push(KeyClip { layer: lid, path, keys });
+    }
+    let n: usize = clip.iter().map(|c| c.keys.len()).sum();
+    s.state.key_clipboard = clip;
+    s.state.clip_is_keys = true;
+    Ok(json!(n))
+}
+
+/// Values of the same kind (and dimensionality) can receive each other's keys.
+fn compatible(a: &Property, b: &effectcraft_keyframe::Value) -> bool {
+    a.value.kind_name() == b.kind_name() && a.value.components().len() == b.components().len()
+}
+
+/// Paste copied keyframes at the current time into the target layers' properties.
+fn paste(s: &mut Session, p: &Value) -> Result<Value> {
+    let clip = s.state.key_clipboard.clone();
+    if clip.is_empty() {
+        return Err(bad("keys.paste", "no keyframes have been copied"));
+    }
+    let cid = comp_id(s, p)?;
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    let t = time_p(s, p, Some(comp));
+    let (_, mut targets) = layers_p(s, p)?;
+    if targets.is_empty() {
+        targets = clip.iter().map(|c| c.layer).collect();
+        targets.dedup();
+    }
+    let explicit = p.get("prop").and_then(Value::as_u64).or_else(|| {
+        let path = str_p(p, "path")?;
+        comp.layer(*targets.first()?)?.props.prop(path).map(|pr| pr.uid)
+    });
+    // (layer, prop uid, clip index)
+    let mut plan: Vec<(LayerId, Uid, usize)> = vec![];
+    for lid in &targets {
+        let Some(l) = comp.layer(*lid) else { continue };
+        for (ci, c) in clip.iter().enumerate() {
+            let Some(sample) = c.keys.first().map(|k| &k.value) else { continue };
+            let target = if clip.len() == 1 {
+                explicit
+                    .and_then(|u| l.props.find(u))
+                    .or_else(|| {
+                        s.state.selected_props.iter().filter(|(sl, _)| sl == lid).filter_map(|(_, u)| l.props.find(*u)).find(|pr| compatible(pr, sample))
+                    })
+                    .or_else(|| l.props.prop(&c.path))
+            } else {
+                l.props.prop(&c.path)
+            };
+            if let Some(pr) = target.filter(|pr| compatible(pr, sample) && !pr.static_only) {
+                plan.push((*lid, pr.uid, ci));
+            }
+        }
+    }
+    if plan.is_empty() {
+        return Err(bad("keys.paste", "no compatible property to paste into (select a property of the same type)"));
+    }
+    s.edit("Paste Keyframes", None, |proj, st| {
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        let mut sel = vec![];
+        for (lid, uid, ci) in &plan {
+            let Some(l) = comp.layer_mut(*lid) else { continue };
+            let times: Vec<Tick> = clip[*ci].keys.iter().map(|k| l.layer_time(t + k.time)).collect();
+            let Some(pr) = l.props.find_mut(*uid) else { continue };
+            for (k, lt) in clip[*ci].keys.iter().zip(times) {
+                let mut k = k.clone();
+                k.time = lt;
+                if let Some(v) = pr.value.coerce_json(&k.value.to_json()) {
+                    k.value = v;
+                }
+                if pr.hold_only {
+                    k = k.hold();
+                }
+                match pr.keys.binary_search_by(|x| x.time.cmp(&k.time)) {
+                    Ok(i) => pr.keys[i] = k,
+                    Err(i) => pr.keys.insert(i, k),
+                }
+                sel.push(KeyRef { layer: *lid, prop: *uid, time: lt });
+            }
+            retime_roving(&mut pr.keys, pr.spatial);
+        }
+        st.selected_keys = sel;
+        Ok(json!(st.selected_keys.len()))
+    })
+}
+
+/// Select every keyframe of the selected properties, or of the given / selected layers.
+fn select_all(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, mut layers) = layers_p(s, p)?;
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    let mut sel = vec![];
+    if p.get("layers").is_none() && p.get("layer").is_none() && !s.state.selected_props.is_empty() {
+        for (lid, uid) in &s.state.selected_props {
+            if let Some(pr) = comp.layer(*lid).and_then(|l| l.props.find(*uid)) {
+                sel.extend(pr.keys.iter().map(|k| KeyRef { layer: *lid, prop: *uid, time: k.time }));
+            }
+        }
+    } else {
+        if layers.is_empty() {
+            layers = comp.layers.iter().map(|l| l.id).collect();
+        }
+        for l in comp.layers.iter().filter(|l| layers.contains(&l.id)) {
+            l.props.walk("", &mut |_, pr| sel.extend(pr.keys.iter().map(|k| KeyRef { layer: l.id, prop: pr.uid, time: k.time })));
+        }
+    }
+    s.state.selected_keys = sel;
+    Ok(json!(s.state.selected_keys.len()))
+}
+
+/// Move the selected keys by whole frames (Alt+→ / Alt+←, Shift for 10 frames).
+fn nudge(s: &mut Session, p: &Value) -> Result<Value> {
+    let frames = p.get("frames").and_then(Value::as_i64).ok_or_else(|| bad("keys.nudge", "missing `frames`"))?;
+    let comp = s.active_comp().ok_or(EngineError::NoComp)?;
+    let d = Tick(comp.frame_duration().0 * frames);
+    edit_keys(s, "Nudge Keyframes", merge_p(p), move |_, _, t| {
+        *t += d;
+        true
+    })
+}
+
+/// Edit one key directly: move it in time and/or set its value (Graph Editor drags).
+fn set_key(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid, uid) = prop_ref(s, p, "keys.set")?;
+    let t = Tick::from_seconds_f64(f_p(p, "time").ok_or_else(|| bad("keys.set", "missing `time` (layer time of the key)"))?);
+    let new_t = f_p(p, "newTime").map(Tick::from_seconds_f64);
+    let value = p.get("value").cloned();
+    let fr = s.project.comp(cid).map(|c| c.frame_rate);
+    s.edit("Edit Keyframe", merge_p(p), |proj, st| {
+        let l = super::layer_mut(proj, cid, lid)?;
+        let pr = l.props.find_mut(uid).ok_or_else(|| bad("keys.set", "no property"))?;
+        let i = nearest_key(&pr.keys, t).ok_or_else(|| bad("keys.set", "the property has no keyframes"))?;
+        let old_t = pr.keys[i].time;
+        if let Some(v) = &value {
+            let nv = pr.keys[i].value.coerce_json(v).ok_or_else(|| bad("keys.set", format!("can't use {v} here")))?;
+            pr.keys[i].value = nv;
+        }
+        let mut nt = old_t;
+        if let Some(n) = new_t {
+            nt = fr.map(|r| r.snap_nearest(n)).unwrap_or(n);
+            // Keys can't pass their neighbours or share a time.
+            let lo = if i > 0 { pr.keys[i - 1].time.0 + 1 } else { i64::MIN };
+            let hi = if i + 1 < pr.keys.len() { pr.keys[i + 1].time.0 - 1 } else { i64::MAX };
+            nt = Tick(nt.0.clamp(lo, hi));
+            pr.keys[i].time = nt;
+        }
+        retime_roving(&mut pr.keys, pr.spatial);
+        let nt = pr.keys.get(i).map(|k| k.time).unwrap_or(nt);
+        for k in st.selected_keys.iter_mut().filter(|k| k.layer == lid && k.prop == uid && k.time == old_t) {
+            k.time = nt;
+        }
+        Ok(json!({"time": nt.seconds()}))
+    })
+}
+
+fn nearest_key(keys: &[Keyframe], t: Tick) -> Option<usize> {
+    if let Some(i) = key_at(keys, t) {
+        return Some(i);
+    }
+    keys.iter().enumerate().min_by_key(|(_, k)| (k.time.0 - t.0).abs()).map(|(i, _)| i)
+}
+
+/// Set one side's temporal ease of a key (Graph Editor handle drags, scripting).
+fn set_ease(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid, uid) = prop_ref(s, p, "keys.setEase")?;
+    let t = Tick::from_seconds_f64(f_p(p, "time").ok_or_else(|| bad("keys.setEase", "missing `time`"))?);
+    let out = match str_p(p, "side") {
+        Some("in") => false,
+        Some("out") => true,
+        _ => return Err(bad("keys.setEase", "`side` must be in or out")),
+    };
+    let dim = p.get("dim").and_then(Value::as_u64).map(|d| d as usize);
+    let speed = f_p(p, "speed");
+    let influence = f_p(p, "influence").map(|v| (v / 100.0).clamp(0.001, 1.0));
+    s.edit("Keyframe Velocity", merge_p(p), |proj, _| {
+        let l = super::layer_mut(proj, cid, lid)?;
+        let pr = l.props.find_mut(uid).ok_or_else(|| bad("keys.setEase", "no property"))?;
+        let i = nearest_key(&pr.keys, t).ok_or_else(|| bad("keys.setEase", "no keyframes"))?;
+        let spatial = pr.spatial;
+        let n = if spatial && matches!(pr.keys[i].value, effectcraft_keyframe::Value::Vec2(_) | effectcraft_keyframe::Value::Vec3(_)) {
+            1
+        } else {
+            pr.keys[i].value.dims().max(1)
+        };
+        // Start from what the side presents now so untouched dimensions keep their shape.
+        let cur: Vec<Ease> = (0..n).map(|d| side_ease(&pr.keys, i, d, spatial, out).unwrap_or_default()).collect();
+        let k = &mut pr.keys[i];
+        let list = if out { &mut k.out_ease } else { &mut k.in_ease };
+        if list.len() != n {
+            *list = cur.clone();
+        }
+        for (d, e) in list.iter_mut().enumerate() {
+            if dim.is_some_and(|x| x != d) && n > 1 {
+                continue;
+            }
+            if let Some(v) = speed {
+                e.speed = v;
+            }
+            if let Some(v) = influence {
+                e.influence = v;
+            }
+        }
+        if out {
+            k.out_interp = Interp::Bezier;
+        } else {
+            k.in_interp = Interp::Bezier;
+        }
+        k.auto_bezier = false;
+        // Continuous Bezier keys keep matching speeds on both sides.
+        if k.continuous {
+            let src = if out { k.out_ease.clone() } else { k.in_ease.clone() };
+            let other = if out { &mut k.in_ease } else { &mut k.out_ease };
+            if other.len() != src.len() {
+                *other = src.clone();
+            }
+            for (o, sv) in other.iter_mut().zip(&src) {
+                o.speed = sv.speed;
+            }
+            k.in_interp = Interp::Bezier;
+            k.out_interp = Interp::Bezier;
+        }
+        Ok(Value::Null)
+    })
+}
+
+/// Speed units for a property (Keyframe Velocity dialog).
+fn units(pr: &Property) -> &'static str {
+    use effectcraft_project::ParamUi;
+    if pr.spatial {
+        return "pixels/sec";
+    }
+    match pr.ui {
+        ParamUi::Angle => "degrees/sec",
+        ParamUi::Percent => "%/sec",
+        ParamUi::Slider { .. } if pr.match_id == "opacity" => "%/sec",
+        _ if pr.match_id == "opacity" => "%/sec",
+        ParamUi::Pixels => "pixels/sec",
+        _ => "units/sec",
+    }
+}
+
+fn interp_name(i: Interp) -> &'static str {
+    match i {
+        Interp::Linear => "linear",
+        Interp::Bezier => "bezier",
+        Interp::Hold => "hold",
+    }
+}
+
+/// Describe the selected (or given) keys: interpolation, eases per side and dimension, units.
+fn info(s: &mut Session, p: &Value) -> Result<Value> {
+    let comp = s.active_comp().ok_or(EngineError::NoComp)?;
+    let refs: Vec<KeyRef> = match p.get("keys") {
+        Some(Value::Array(a)) => a
+            .iter()
+            .filter_map(|k| {
+                let l = super::resolve_layer(comp, k.get("layer")?)?;
+                Some(KeyRef { layer: l, prop: k.get("prop")?.as_u64()?, time: Tick::from_seconds_f64(k.get("time")?.as_f64()?) })
+            })
+            .collect(),
+        _ => s.state.selected_keys.clone(),
+    };
+    let mut out = vec![];
+    for r in refs {
+        let Some(l) = comp.layer(r.layer) else { continue };
+        let Some(pr) = l.props.find(r.prop) else { continue };
+        let Some(i) = nearest_key(&pr.keys, r.time) else { continue };
+        let k = &pr.keys[i];
+        let spatial = pr.spatial && matches!(k.value, effectcraft_keyframe::Value::Vec2(_) | effectcraft_keyframe::Value::Vec3(_));
+        let dims = if spatial { 1 } else { k.value.dims().max(1).min(if pr.shown_dims > 0 && !l.is_3d() { pr.shown_dims as usize } else { 4 }) };
+        let side = |out: bool| -> Value {
+            json!(
+                (0..dims)
+                    .map(|d| side_ease(&pr.keys, i, d, pr.spatial, out)
+                        .map(|e| json!({"speed": e.speed, "influence": e.influence * 100.0}))
+                        .unwrap_or(Value::Null))
+                    .collect::<Vec<_>>()
+            )
+        };
+        let temporal = if k.auto_bezier {
+            "autoBezier"
+        } else if k.continuous {
+            "continuousBezier"
+        } else if k.in_interp == k.out_interp {
+            interp_name(k.in_interp)
+        } else {
+            "mixed"
+        };
+        let spatial_kind = if !spatial {
+            Value::Null
+        } else if k.spatial_auto {
+            json!("autoBezier")
+        } else if k.spatial_continuous {
+            json!("continuousBezier")
+        } else if k.spatial_in == [0.0; 3] && k.spatial_out == [0.0; 3] {
+            json!("linear")
+        } else {
+            json!("bezier")
+        };
+        out.push(json!({
+            "layer": l.id.0, "prop": pr.uid, "name": pr.name, "path": l.props.match_path_of(pr.uid),
+            "time": k.time.seconds(), "compTime": l.comp_time(k.time).seconds(), "value": k.value.to_json(),
+            "in": interp_name(k.in_interp), "out": interp_name(k.out_interp), "temporal": temporal,
+            "autoBezier": k.auto_bezier, "continuous": k.continuous, "roving": k.roving, "spatial": spatial_kind,
+            "dims": dims, "units": units(pr), "inEase": side(false), "outEase": side(true),
+        }));
+    }
+    Ok(json!(out))
+}
+
+/// Keyframe Assistant ▸ Time-Reverse Keyframes: mirror the selected keys of each property.
+fn time_reverse(s: &mut Session, _: &Value) -> Result<Value> {
+    let cid = s.active_comp_id().ok_or(EngineError::NoComp)?;
+    let sel = s.state.selected_keys.clone();
+    s.edit("Time-Reverse Keyframes", None, |proj, st| {
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        let mut groups: std::collections::BTreeMap<(LayerId, Uid), Vec<Tick>> = Default::default();
+        for k in &sel {
+            groups.entry((k.layer, k.prop)).or_default().push(k.time);
+        }
+        let mut new_sel = vec![];
+        for ((lid, uid), times) in groups {
+            let Some(pr) = comp.layer_mut(lid).and_then(|l| l.props.find_mut(uid)) else { continue };
+            let (mut picked, rest): (Vec<Keyframe>, Vec<Keyframe>) = pr.keys.drain(..).partition(|k| times.contains(&k.time));
+            effectcraft_keyframe::time_reverse(&mut picked);
+            new_sel.extend(picked.iter().map(|k| KeyRef { layer: lid, prop: uid, time: k.time }));
+            pr.keys = rest;
+            for k in picked {
+                match pr.keys.binary_search_by(|x| x.time.cmp(&k.time)) {
+                    Ok(i) => pr.keys[i] = k,
+                    Err(i) => pr.keys.insert(i, k),
+                }
+            }
+        }
+        st.selected_keys = new_sel;
+        Ok(json!(st.selected_keys.len()))
+    })
+}
+
+fn keys_or_layers(s: &Session) -> std::result::Result<(), String> {
+    has_comp(s)
+}
+
+pub fn specs() -> Vec<CommandSpec> {
+    vec![
+        cmd!("keys.copy", "Copy Keyframes", [], None, "{}", has_keys, copy),
+        cmd!("keys.paste", "Paste Keyframes", [], None, "{layers?, prop?|path?, time?}", has_key_clip, paste),
+        cmd!("keys.selectAll", "Select All Keyframes", ["Edit"], Some("Cmd+Alt+A"), "{layers?}", keys_or_layers, select_all),
+        cmd!("keys.nudge", "Nudge Keyframes", [], None, "{frames, merge?}", has_keys, nudge),
+        cmd!("keys.nudgeForward", "Move Keyframes 1 Frame Later", [], Some("Alt+ArrowRight"), "{}", has_keys, |s, _| nudge(s, &json!({"frames": 1}))),
+        cmd!("keys.nudgeBackward", "Move Keyframes 1 Frame Earlier", [], Some("Alt+ArrowLeft"), "{}", has_keys, |s, _| nudge(s, &json!({"frames": -1}))),
+        cmd!("keys.nudgeForward10", "Move Keyframes 10 Frames Later", [], Some("Alt+Shift+ArrowRight"), "{}", has_keys, |s, _| nudge(
+            s,
+            &json!({"frames": 10})
+        )),
+        cmd!("keys.nudgeBackward10", "Move Keyframes 10 Frames Earlier", [], Some("Alt+Shift+ArrowLeft"), "{}", has_keys, |s, _| nudge(
+            s,
+            &json!({"frames": -10})
+        )),
+        cmd!("keys.set", "Edit Keyframe", [], None, "{layer?, path|prop, time (layer s), newTime?, value?, merge?}", has_comp, set_key),
+        cmd!(
+            "keys.setEase",
+            "Set Keyframe Ease",
+            [],
+            None,
+            "{layer?, path|prop, time (layer s), side: in|out, dim?, speed?, influence? %, merge?}",
+            has_comp,
+            set_ease
+        ),
+        cmd!("keys.timeReverse", "Time-Reverse Keyframes", ["Animation", "Keyframe Assistant"], None, "{}", has_keys, time_reverse),
+        query!("keys.info", "Keyframe Info", "{keys?: [{layer, prop, time}]}", info),
+    ]
+}

crates/engine/src/commands/comp.rs

@@ -62,7 +62,8 @@ fn apply_settings(c: &mut Comp, p: &Value) {
     }
     if let Some(d) = f_p(p, "duration") {
         let old = c.duration;
-        c.duration = Tick::from_seconds_f64(d.max(c.frame_rate.frame_duration().seconds()));
+        // Whole frames, at least one.
+        c.duration = c.frame_rate.snap_nearest(Tick::from_seconds_f64(d)).max(c.frame_rate.frame_duration());
         if c.work_area.1 == old {
             c.work_area.1 = c.duration;
         }
@@ -91,7 +92,7 @@ fn apply_settings(c: &mut Comp, p: &Value) {
 fn new_comp(s: &mut Session, p: &Value) -> Result<Value> {
     let name = str_p(p, "name").unwrap_or("Comp 1").to_string();
     let rate = rate_p(p).unwrap_or(FrameRate::FPS_29_97);
-    let mut c = Comp::new(1920, 1080, rate, Tick::from_seconds_f64(10.0));
+    let mut c = Comp::new(1920, 1080, rate, rate.snap_nearest(Tick::from_seconds_f64(10.0)));
     apply_settings(&mut c, p);
     let id = s.edit("New Composition", None, |proj, st| {
         let mut name = name.clone();

crates/engine/src/commands/edit.rs

@@ -15,7 +15,7 @@ fn can_redo(s: &Session) -> std::result::Result<(), String> {
 }
 fn has_clip(s: &Session) -> std::result::Result<(), String> {
     has_comp(s)?;
-    if s.state.clipboard.is_empty() { Err("the clipboard is empty".into()) } else { Ok(()) }
+    if s.state.clipboard.is_empty() && s.state.key_clipboard.is_empty() { Err("the clipboard is empty".into()) } else { Ok(()) }
 }
 
 fn undo(s: &mut Session, _: &Value) -> Result<Value> {
@@ -39,6 +39,7 @@ fn deselect_all(s: &mut Session, _: &Value) -> Result<Value> {
     s.state.selected_layers.clear();
     s.state.selected_props.clear();
     s.state.selected_keys.clear();
+    s.state.selected_vertices.clear();
     Ok(Value::Null)
 }
 
@@ -72,10 +73,13 @@ fn duplicate(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn delete(s: &mut Session, p: &Value) -> Result<Value> {
-    // Keyframes selected → delete keys; else layers.
+    // Keyframes selected → delete keys; mask vertices → delete them; else layers.
     if !s.state.selected_keys.is_empty() && p.get("layers").is_none() {
         return s.execute("keys.delete", json!({}));
     }
+    if !s.state.selected_vertices.is_empty() && p.get("layers").is_none() {
+        return s.execute("mask.deleteVertices", json!({}));
+    }
     let (cid, ids) = layers_p(s, p)?;
     s.edit("Clear", None, |proj, st| {
         let comp = proj.comp_mut(cid).ok_or(crate::EngineError::NoComp)?;
@@ -97,18 +101,30 @@ fn delete(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn copy(s: &mut Session, p: &Value) -> Result<Value> {
+    // Keyframes selected → copy keys (pasted at the CTI).
+    if !s.state.selected_keys.is_empty() && p.get("layers").is_none() {
+        return s.execute("keys.copy", json!({}));
+    }
     let (cid, ids) = layers_p(s, p)?;
+    s.state.clip_is_keys = false;
     let comp = s.project.comp(cid).ok_or(crate::EngineError::NoComp)?;
     s.state.clipboard = comp.layers.iter().filter(|l| ids.contains(&l.id)).cloned().collect();
     Ok(json!(s.state.clipboard.len()))
 }
 
 fn cut(s: &mut Session, p: &Value) -> Result<Value> {
+    if !s.state.selected_keys.is_empty() && p.get("layers").is_none() {
+        s.execute("keys.copy", json!({}))?;
+        return s.execute("keys.delete", json!({}));
+    }
     copy(s, p)?;
     delete(s, p)
 }
 
 fn paste(s: &mut Session, p: &Value) -> Result<Value> {
+    if s.state.clip_is_keys && !s.state.key_clipboard.is_empty() {
+        return s.execute("keys.paste", p.clone());
+    }
     let cid = super::comp_id(s, p)?;
     let clip = s.state.clipboard.clone();
     let new = s.edit("Paste", None, |proj, st| {
@@ -191,10 +207,10 @@ pub fn specs() -> Vec<CommandSpec> {
     vec![
         cmd!("edit.undo", "Undo", ["Edit"], Some("Cmd+Z"), "{}", can_undo, undo),
         cmd!("edit.redo", "Redo", ["Edit"], Some("Cmd+Shift+Z"), "{}", can_redo, redo),
-        cmd!("edit.cut", "Cut", ["Edit"], Some("Cmd+X"), "{layers?}", has_layers, cut),
-        cmd!("edit.copy", "Copy", ["Edit"], Some("Cmd+C"), "{layers?}", has_layers, copy),
+        cmd!("edit.cut", "Cut", ["Edit"], Some("Cmd+X"), "{layers?} (keyframes when keys are selected)", layers_or_keys, cut),
+        cmd!("edit.copy", "Copy", ["Edit"], Some("Cmd+C"), "{layers?} (keyframes when keys are selected)", layers_or_keys, copy),
         cmd!("edit.paste", "Paste", ["Edit"], Some("Cmd+V"), "{}", has_clip, paste),
-        cmd!("edit.clear", "Clear", ["Edit"], Some("Delete"), "{layers?}", has_layers, delete),
+        cmd!("edit.clear", "Clear", ["Edit"], Some("Delete"), "{layers?}", layers_or_keys, delete),
         cmd!("edit.duplicate", "Duplicate", ["Edit"], Some("Cmd+D"), "{layers?}", has_layers, duplicate),
         cmd!("edit.splitLayer", "Split Layer", ["Edit"], Some("Cmd+Shift+D"), "{layers?}", has_layers, split),
         cmd!("edit.selectAll", "Select All", ["Edit"], Some("Cmd+A"), "{}", has_comp, select_all),
@@ -204,6 +220,10 @@ pub fn specs() -> Vec<CommandSpec> {
     ]
 }
 
+fn layers_or_keys(s: &Session) -> std::result::Result<(), String> {
+    if !s.state.selected_keys.is_empty() || !s.state.selected_vertices.is_empty() { super::has_comp(s) } else { has_layers(s) }
+}
+
 fn always_ok(_: &Session) -> std::result::Result<(), String> {
     Ok(())
 }

crates/engine/src/commands/layer.rs

@@ -263,12 +263,13 @@ fn add_item(s: &mut Session, p: &Value) -> Result<Value> {
         ItemKind::Solid(so) => (LayerSource::Solid { item }, (so.width, so.height), None),
         ItemKind::Folder => return Err(bad("layer.addItem", "folders can't be layers")),
     };
-    let start = f_p(p, "time").map(Tick::from_seconds_f64).unwrap_or(Tick::ZERO);
+    let fr = comp.frame_rate;
+    let start = fr.snap_nearest(f_p(p, "time").map(Tick::from_seconds_f64).unwrap_or(Tick::ZERO));
     let id = s.edit("Add Footage to Comp", None, |proj, st| {
         let mut l = build::layer(proj, &comp, &it.name, src, size, dur);
         l.start_time = start;
         l.in_point = start;
-        l.out_point = (start + dur.unwrap_or(comp.duration)).min(comp.duration);
+        l.out_point = fr.snap_nearest((start + dur.unwrap_or(comp.duration)).min(comp.duration)).max(start + fr.frame_duration());
         insert_layer(proj, st, cid, l)
     })?;
     Ok(json!({"layer": id.0}))
@@ -302,6 +303,8 @@ fn select(s: &mut Session, p: &Value) -> Result<Value> {
         s.state.selected_layers = ids;
         s.state.selected_props.clear();
         s.state.selected_keys.clear();
+        let keep = s.state.selected_layers.clone();
+        s.state.selected_vertices.retain(|v| keep.contains(&v.layer));
     }
     Ok(json!(s.state.selected_layers.iter().map(|l| l.0).collect::<Vec<_>>()))
 }
@@ -484,10 +487,62 @@ fn set_parent(s: &mut Session, p: &Value) -> Result<Value> {
             cur = comp.layer(c).and_then(|l| l.parent);
         }
     }
+    // Like AE's pick-whip, parenting keeps the layer where it is: its transform is re-expressed
+    // in the new parent's space (Position, Rotation, Scale), unless `compensate: false`.
+    let compensate = b_p(p, "compensate").unwrap_or(true);
+    let ectx = effectcraft_render::EvalCtx { project: &s.project, comp_id: cid, comp, time: s.time(), expr: s.expr.as_deref() };
+    let space = |id: Option<LayerId>| -> effectcraft_geom::Mat3 {
+        id.and_then(|i| comp.layer(i)).filter(|l| !l.is_3d()).map(|l| ectx.layer_to_comp(l).0).unwrap_or(effectcraft_geom::Mat3::IDENTITY)
+    };
+    let decompose = |m: &effectcraft_geom::Mat3| {
+        let a = m.0;
+        let sx = (a[0][0] * a[0][0] + a[1][0] * a[1][0]).sqrt();
+        let det = a[0][0] * a[1][1] - a[0][1] * a[1][0];
+        (a[1][0].atan2(a[0][0]).to_degrees(), sx, if sx > 1e-12 { det / sx } else { 0.0 })
+    };
+    // Per layer: (id, position transform, rotation delta, scale factors).
+    let mut fixes: Vec<(LayerId, effectcraft_geom::Mat3, f64, [f64; 2])> = vec![];
+    if compensate {
+        let new_m = space(parent);
+        for l in comp.layers.iter().filter(|l| ids.contains(&l.id) && !l.is_3d() && l.parent != parent) {
+            let old_m = space(l.parent);
+            let Some(inv) = new_m.inverse() else { continue };
+            let (ro, sxo, syo) = decompose(&old_m);
+            let (rn, sxn, syn) = decompose(&new_m);
+            let k = [if sxn.abs() > 1e-12 { sxo / sxn } else { 1.0 }, if syn.abs() > 1e-12 { syo / syn } else { 1.0 }];
+            fixes.push((l.id, inv * old_m, ro - rn, k));
+        }
+    }
     s.edit("Parent", None, |proj, _| {
         let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
         for l in comp.layers.iter_mut().filter(|l| ids.contains(&l.id)) {
             l.parent = parent;
+            let Some((_, m, dr, k)) = fixes.iter().find(|f| f.0 == l.id) else { continue };
+            let Some(tr) = l.props.sub_mut("transform") else { continue };
+            let map = |pr: &mut effectcraft_project::Property, f: &dyn Fn(&KV) -> KV| {
+                pr.value = f(&pr.value);
+                for key in &mut pr.keys {
+                    key.value = f(&key.value);
+                }
+            };
+            if tr.get("positionX").is_none()
+                && let Some(pr) = tr.get_mut("position")
+            {
+                map(pr, &|v| {
+                    let c = v.as_vec3();
+                    let q = m.apply(effectcraft_geom::vec2(c[0], c[1]));
+                    KV::Vec3([q.x, q.y, c[2]])
+                });
+            }
+            if let Some(pr) = tr.get_mut("rotation") {
+                map(pr, &|v| KV::Scalar(v.as_f64() + dr));
+            }
+            if let Some(pr) = tr.get_mut("scale") {
+                map(pr, &|v| {
+                    let c = v.as_vec3();
+                    KV::Vec3([c[0] * k[0], c[1] * k[1], c[2]])
+                });
+            }
         }
         Ok(())
     })?;
@@ -498,10 +553,10 @@ fn timing(s: &mut Session, p: &Value) -> Result<Value> {
     let (cid, ids) = layers_p(s, p)?;
     let t = s.time();
     let op = str_p(p, "op").unwrap_or("set").to_string();
-    let delta = f_p(p, "delta").map(Tick::from_seconds_f64);
-    let start = f_p(p, "start").map(Tick::from_seconds_f64);
-    let inp = f_p(p, "in").map(Tick::from_seconds_f64);
-    let outp = f_p(p, "out").map(Tick::from_seconds_f64);
+    // Layer times stay on frame boundaries of the comp (as in AE).
+    let fr = s.project.comp(cid).ok_or(EngineError::NoComp)?.frame_rate;
+    let snap = |k: &str| f_p(p, k).map(|v| fr.snap_nearest(Tick::from_seconds_f64(v)));
+    let (delta, start, inp, outp) = (snap("delta"), snap("start"), snap("in"), snap("out"));
     s.edit("Layer Timing", merge_p(p), |proj, _| {
         let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
         let fd = comp.frame_duration();
@@ -818,34 +873,6 @@ fn transform_op(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(Value::Null)
 }
 
-fn time_stretch(s: &mut Session, p: &Value) -> Result<Value> {
-    let (cid, ids) = layers_p(s, p)?;
-    let reverse = str_p(p, "op") == Some("reverse");
-    let pct = f_p(p, "percent");
-    s.edit(if reverse { "Time-Reverse Layer" } else { "Time Stretch" }, None, |proj, _| {
-        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
-        for l in comp.layers.iter_mut().filter(|l| ids.contains(&l.id)) {
-            let old = l.stretch;
-            let new = if reverse { -old } else { pct.unwrap_or(old) };
-            if new.abs() < 1.0 {
-                continue;
-            }
-            // Keep the in point fixed: the layer's source span scales around it.
-            let lin = l.layer_time(l.in_point);
-            let lout = l.layer_time(l.out_point);
-            l.stretch = new;
-            if reverse {
-                l.start_time = l.in_point + Tick((lout.0 as f64 * new.abs() / 100.0) as i64);
-            } else {
-                l.start_time = l.in_point - Tick((lin.0 as f64 * new / 100.0) as i64);
-                l.out_point = l.comp_time(lout);
-            }
-        }
-        Ok(())
-    })?;
-    Ok(Value::Null)
-}
-
 fn layer_settings(s: &mut Session, p: &Value) -> Result<Value> {
     let (cid, lid) = layer_p(s, p, "layer.settings")?;
     let color = color_p(p, "color");
@@ -977,7 +1004,6 @@ pub fn specs() -> Vec<CommandSpec> {
             has_layers,
             transform_op
         ),
-        cmd!("layer.timeStretch", "Time Stretch…", ["Layer", "Time"], None, "{layers?, percent?, op?: reverse}", has_layers, time_stretch),
     ]
 }
 

crates/engine/src/commands/layer_time.rs

@@ -0,0 +1,188 @@
+//! Layer ▸ Time: Time Stretch, Time-Reverse Layer, Enable Time Remapping, Freeze Frame and
+//! Freeze on Last Frame.
+//!
+//! Time Remap is a `timeRemap` property at the top of the layer's tree whose value is the
+//! source time (seconds) to show; its keys live in layer time like every other property.
+
+use effectcraft_keyframe::{Keyframe, Value as KV};
+use effectcraft_project::build::Ids;
+use effectcraft_project::{Layer, LayerSource, Node, ParamUi, Property};
+use effectcraft_time::Tick;
+use serde_json::{Value, json};
+
+use super::{CommandSpec, b_p, bad, f_p, has_layers, layers_p, str_p};
+use crate::{EngineError, Result, Session, cmd};
+
+/// Layers whose source has its own time (precomps and footage) can be remapped.
+fn remappable(l: &Layer) -> bool {
+    matches!(l.source, LayerSource::Comp { .. } | LayerSource::Footage { .. })
+}
+
+fn time_stretch(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, ids) = layers_p(s, p)?;
+    let reverse = str_p(p, "op") == Some("reverse");
+    let pct = f_p(p, "percent");
+    let dur = f_p(p, "duration");
+    let hold = str_p(p, "hold").unwrap_or("in").to_string();
+    let cti = s.time();
+    let comp_rate = s.project.comp(cid).ok_or(EngineError::NoComp)?.frame_rate;
+    let fd = comp_rate.frame_duration();
+    s.edit(if reverse { "Time-Reverse Layer" } else { "Time Stretch" }, None, |proj, _| {
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        for l in comp.layers.iter_mut().filter(|l| ids.contains(&l.id)) {
+            let old = l.stretch;
+            if reverse {
+                // Keep the in/out points; play the visible span backwards.
+                let last = l.layer_time(l.out_point - fd);
+                l.stretch = -old;
+                l.start_time = l.in_point - Tick((last.0 as f64 * l.stretch / 100.0).round() as i64);
+                continue;
+            }
+            let span = (l.out_point - l.in_point).seconds();
+            let new = match (pct, dur) {
+                (Some(v), _) => v,
+                (None, Some(d)) if span > 0.0 => old * d / span,
+                _ => old,
+            };
+            if new.abs() < 1.0 {
+                return Err(bad("layer.timeStretch", "the stretch factor must be at least 1 %"));
+            }
+            // The hold point keeps showing the same layer time.
+            let h = match hold.as_str() {
+                "current" => cti,
+                "out" => l.out_point,
+                _ => l.in_point,
+            };
+            let lt_h = l.layer_time(h);
+            let (lin, lout) = (l.layer_time(l.in_point), l.layer_time(l.out_point));
+            l.stretch = new;
+            l.start_time = h - Tick((lt_h.0 as f64 * new / 100.0).round() as i64);
+            let (a, b) = (l.comp_time(lin), l.comp_time(lout));
+            let fr = comp_rate;
+            l.in_point = fr.snap_nearest(a.min(b));
+            l.out_point = fr.snap_nearest(a.max(b)).max(l.in_point + fr.frame_duration());
+        }
+        Ok(())
+    })?;
+    Ok(Value::Null)
+}
+
+fn remap_prop(ids: &mut Ids) -> Property {
+    let mut p = ids.prop("timeRemap", "Time Remap", KV::Scalar(0.0)).with_ui(ParamUi::Number);
+    p.ui = ParamUi::Number;
+    p
+}
+
+/// Source time (seconds) a layer shows at comp time `t` without remapping.
+fn source_secs(l: &Layer, t: Tick) -> f64 {
+    l.layer_time(t).seconds()
+}
+
+fn enable_time_remap(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, ids) = layers_p(s, p)?;
+    let want = b_p(p, "value");
+    let fd = s.project.comp(cid).ok_or(EngineError::NoComp)?.frame_duration();
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    if !comp.layers.iter().filter(|l| ids.contains(&l.id)).any(remappable) {
+        return Err(bad("layer.enableTimeRemap", "time remapping needs a footage or composition layer"));
+    }
+    let on = s.edit("Enable Time Remapping", None, |proj, _| {
+        let mut next = proj.next_id;
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        let mut on = false;
+        for l in comp.layers.iter_mut().filter(|l| ids.contains(&l.id) && remappable(l)) {
+            let has = l.props.get("timeRemap").is_some();
+            let target = want.unwrap_or(!has);
+            on |= target;
+            if target && !has {
+                let mut pr = remap_prop(&mut Ids(&mut next));
+                let (lin, lout) = (l.layer_time(l.in_point), l.layer_time(l.out_point));
+                let (a, b) = (lin.min(lout), lin.max(lout));
+                pr.value = KV::Scalar(source_secs(l, l.in_point));
+                pr.keys = vec![Keyframe::new(a, KV::Scalar(a.seconds())), Keyframe::new(b, KV::Scalar(b.seconds()))];
+                if lin > lout {
+                    // Reversed layers keep showing what they showed.
+                    pr.keys[0].value = KV::Scalar(source_secs(l, l.out_point - fd));
+                    pr.keys[1].value = KV::Scalar(source_secs(l, l.in_point));
+                }
+                l.props.children.insert(0, Node::Prop(pr));
+            } else if !target && has {
+                l.props.children.retain(|c| c.match_id() != "timeRemap");
+            }
+        }
+        proj.next_id = next;
+        Ok(on)
+    })?;
+    Ok(json!(on))
+}
+
+/// Freeze Frame: time remapping holding the current source frame for the whole layer.
+fn freeze(s: &mut Session, p: &Value, last: bool) -> Result<Value> {
+    let (cid, ids) = layers_p(s, p)?;
+    let cti = s.time();
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    let (fd, cdur) = (comp.frame_duration(), comp.duration);
+    if !comp.layers.iter().filter(|l| ids.contains(&l.id)).any(remappable) {
+        return Err(bad("layer.freezeFrame", "freezing needs a footage or composition layer"));
+    }
+    // What each layer shows now (honouring an existing remap) — evaluated before the edit.
+    let ectx = effectcraft_render::EvalCtx { project: &s.project, comp_id: cid, comp, time: cti, expr: s.expr.as_deref() };
+    let now: Vec<(effectcraft_project::LayerId, f64)> = comp
+        .layers
+        .iter()
+        .filter(|l| ids.contains(&l.id) && remappable(l))
+        .map(|l| {
+            let at = if last { ectx.at(l.out_point - fd) } else { ectx };
+            (l.id, at.source_time(l).seconds())
+        })
+        .collect();
+    s.edit(if last { "Freeze on Last Frame" } else { "Freeze Frame" }, None, |proj, _| {
+        let mut next = proj.next_id;
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        for (lid, src) in &now {
+            let Some(l) = comp.layer_mut(*lid) else { continue };
+            if l.props.get("timeRemap").is_none() {
+                l.props.children.insert(0, Node::Prop(remap_prop(&mut Ids(&mut next))));
+            }
+            let lt = if last { l.layer_time(l.out_point - fd) } else { l.layer_time(cti) };
+            let lin = l.layer_time(l.in_point);
+            let pr = l.props.get_mut("timeRemap").ok_or(EngineError::NoComp)?;
+            pr.value = KV::Scalar(*src);
+            if last {
+                // Play normally up to the last frame, then hold it to the end of the comp.
+                let mut end = Keyframe::new(lt.max(lin), KV::Scalar(*src));
+                end.out_interp = effectcraft_keyframe::Interp::Hold;
+                pr.keys = vec![Keyframe::new(lin.min(lt), KV::Scalar(lin.min(lt).seconds())), end];
+                pr.keys.dedup_by_key(|k| k.time);
+                l.out_point = cdur;
+            } else {
+                pr.keys = vec![Keyframe::new(lt, KV::Scalar(*src)).hold()];
+            }
+        }
+        proj.next_id = next;
+        Ok(())
+    })?;
+    Ok(Value::Null)
+}
+
+pub fn specs() -> Vec<CommandSpec> {
+    vec![
+        cmd!(
+            "layer.timeStretch",
+            "Time Stretch…",
+            ["Layer", "Time"],
+            None,
+            "{layers?, percent?|duration? (s), hold?: in|current|out, op?: reverse}",
+            has_layers,
+            time_stretch
+        ),
+        cmd!("layer.timeReverse", "Time-Reverse Layer", ["Layer", "Time"], Some("Cmd+Alt+R"), "{layers?}", has_layers, |s, p| {
+            let mut p = p.clone();
+            p["op"] = json!("reverse");
+            time_stretch(s, &p)
+        }),
+        cmd!("layer.enableTimeRemap", "Enable Time Remapping", ["Layer", "Time"], Some("Cmd+Alt+T"), "{layers?, value?}", has_layers, enable_time_remap),
+        cmd!("layer.freezeFrame", "Freeze Frame", ["Layer", "Time"], None, "{layers?}", has_layers, |s, p| freeze(s, p, false)),
+        cmd!("layer.freezeOnLastFrame", "Freeze on Last Frame", ["Layer", "Time"], None, "{layers?}", has_layers, |s, p| freeze(s, p, true)),
+    ]
+}

crates/engine/src/commands/link.rs

@@ -0,0 +1,182 @@
+//! Separate Dimensions and the property pick-whip (AE-style reference expressions).
+
+use effectcraft_keyframe::{Ease, Interp, Keyframe, Value as KV};
+use effectcraft_project::{Comp, Layer, Node, ParamUi, Property, Uid};
+use effectcraft_time::{TICKS_PER_SECOND, Tick};
+use serde_json::{Value, json};
+
+use super::prop::prop_ref;
+use super::{CommandSpec, b_p, bad, has_layers, layer_mut, layer_p};
+use crate::{EngineError, Result, Session, cmd};
+
+const AXES: [(&str, &str); 3] = [("positionX", "X Position"), ("positionY", "Y Position"), ("positionZ", "Z Position")];
+
+/// Per-dimension scalar keys from a (spatial) position key list: same times and interpolation;
+/// Bezier sides get the per-dimension velocity the combined property had at the key.
+fn split_keys(keys: &[Keyframe], spatial: bool, d: usize) -> Vec<Keyframe> {
+    let h = Tick(TICKS_PER_SECOND / 2000);
+    keys.iter()
+        .map(|k| {
+            let mut s = Keyframe::new(k.time, KV::Scalar(k.value.components().get(d).copied().unwrap_or(0.0)));
+            s.in_interp = k.in_interp;
+            s.out_interp = k.out_interp;
+            s.auto_bezier = k.auto_bezier;
+            s.continuous = k.continuous;
+            s.roving = false;
+            let vel = |t: Tick| effectcraft_keyframe::velocity(keys, t, spatial).get(d).copied().unwrap_or(0.0);
+            if k.in_interp == Interp::Bezier {
+                let inf = k.in_ease.first().map(|e| e.influence).unwrap_or(1.0 / 3.0);
+                s.in_ease = vec![Ease { speed: vel(k.time - h), influence: inf }];
+            }
+            if k.out_interp == Interp::Bezier {
+                let inf = k.out_ease.first().map(|e| e.influence).unwrap_or(1.0 / 3.0);
+                s.out_ease = vec![Ease { speed: vel(k.time + h), influence: inf }];
+            }
+            s
+        })
+        .collect()
+}
+
+fn separate(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid) = layer_p(s, p, "prop.separateDimensions")?;
+    let want = b_p(p, "value");
+    let on = s.edit("Separate Dimensions", None, |proj, _| {
+        let mut next = proj.next_id;
+        let l = layer_mut(proj, cid, lid)?;
+        let tr = l.props.sub_mut("transform").ok_or_else(|| bad("prop.separateDimensions", "this layer has no Transform"))?;
+        let has = tr.get("positionX").is_some();
+        let target = want.unwrap_or(!has);
+        if target && !has {
+            let pos = tr.get("position").ok_or_else(|| bad("prop.separateDimensions", "no Position"))?.clone();
+            let at = tr.children.iter().position(|c| c.uid() == pos.uid).map(|i| i + 1).unwrap_or(tr.children.len());
+            let comps = pos.value.components();
+            for (d, (m, name)) in AXES.iter().enumerate().rev() {
+                let mut pr = Property::new(next, m, name, KV::Scalar(comps.get(d).copied().unwrap_or(0.0))).with_ui(ParamUi::Number);
+                next += 1;
+                pr.three_d_only = d == 2;
+                pr.keys = split_keys(&pos.keys, pos.spatial, d);
+                tr.children.insert(at, Node::Prop(pr));
+            }
+        } else if !target && has {
+            let parts: Vec<Property> = AXES.iter().filter_map(|(m, _)| tr.get(m).cloned()).collect();
+            let mut times: Vec<Tick> = parts.iter().flat_map(|p| p.keys.iter().map(|k| k.time)).collect();
+            times.sort();
+            times.dedup();
+            let at = |t: Tick| KV::Vec3([0, 1, 2].map(|d| parts.get(d).map(|p| p.value_at(t).as_f64()).unwrap_or(0.0)));
+            let pos = tr.get_mut("position").ok_or_else(|| bad("prop.separateDimensions", "no Position"))?;
+            pos.value = at(Tick::ZERO);
+            pos.keys = times.iter().map(|t| Keyframe::new(*t, at(*t))).collect();
+            if pos.keys.is_empty() {
+                pos.value = KV::Vec3([0, 1, 2].map(|d| parts.get(d).map(|p| p.value.as_f64()).unwrap_or(0.0)));
+            }
+            tr.children.retain(|c| !AXES.iter().any(|(m, _)| c.match_id() == *m));
+        }
+        proj.next_id = next;
+        Ok(target)
+    })?;
+    Ok(json!(on))
+}
+
+// ---------------------------------------------------------------- pick-whip
+
+/// `X Position` → `xPosition`, `Mask Path` → `maskPath`.
+fn camel(name: &str) -> String {
+    let mut out = String::new();
+    for (i, w) in name.split(|c: char| !c.is_alphanumeric()).filter(|w| !w.is_empty()).enumerate() {
+        let mut cs = w.chars();
+        if let Some(f) = cs.next() {
+            if i == 0 {
+                out.extend(f.to_lowercase());
+            } else {
+                out.extend(f.to_uppercase());
+            }
+            out.push_str(cs.as_str());
+        }
+    }
+    out
+}
+
+fn quote(s: &str) -> String {
+    serde_json::to_string(s).unwrap_or_else(|_| format!("\"{s}\""))
+}
+
+/// The AE expression reference to property `uid` of `target` as seen from a property of `from`.
+pub(crate) fn reference(comp: &Comp, from: &Layer, target: &Layer, uid: Uid) -> Option<String> {
+    let chain = target.props.node_chain(uid)?;
+    let mut parts: Vec<String> = vec![];
+    let mut pending: Option<&str> = None;
+    let mut in_effect = false;
+    for n in chain {
+        if let Some(f) = pending.take() {
+            parts.push(format!("{f}({})", quote(n.name())));
+            in_effect |= f == "effect";
+            continue;
+        }
+        match (n, n.match_id()) {
+            (Node::Group(_), "masks") => pending = Some("mask"),
+            (Node::Group(_), "effects") => pending = Some("effect"),
+            (Node::Group(_), "contents") => pending = Some("content"),
+            (Node::Group(_), "transform") if !in_effect => parts.push("transform".into()),
+            (Node::Group(_), "text") if !in_effect => parts.push("text".into()),
+            (Node::Prop(_), "sourceText") => parts.push("sourceText".into()),
+            _ if in_effect => parts.push(format!("({})", quote(n.name()))),
+            _ => parts.push(camel(n.name())),
+        }
+    }
+    let mut out = if from.id == target.id { String::new() } else { format!("thisComp.layer({}).", quote(&target.name)) };
+    let _ = comp;
+    for (i, p) in parts.iter().enumerate() {
+        if i > 0 && !p.starts_with('(') {
+            out.push('.');
+        }
+        out.push_str(p);
+    }
+    Some(out)
+}
+
+/// Dimensions an expression sees (2D layers see 2D Position/Scale/Anchor).
+fn dims(l: &Layer, p: &Property) -> usize {
+    match &p.value {
+        KV::Vec3(_) if p.shown_dims == 2 && !l.is_3d() => 2,
+        v => v.components().len().max(1),
+    }
+}
+
+fn pick_whip(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid, uid) = prop_ref(s, p, "prop.pickWhip")?;
+    let t = p.get("target").ok_or_else(|| bad("prop.pickWhip", "missing `target` {layer, path|prop}"))?;
+    let (_, tl, tu) = prop_ref(s, t, "prop.pickWhip")?;
+    if (tl, tu) == (lid, uid) {
+        return Err(bad("prop.pickWhip", "a property can't reference itself"));
+    }
+    let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?;
+    let from = comp.layer(lid).ok_or(EngineError::NoComp)?;
+    let target = comp.layer(tl).ok_or(EngineError::NoComp)?;
+    let r = reference(comp, from, target, tu).ok_or_else(|| bad("prop.pickWhip", "no such target property"))?;
+    let (me, them) = (from.props.find(uid).ok_or(EngineError::NoComp)?, target.props.find(tu).ok_or(EngineError::NoComp)?);
+    let (dm, dt) = (dims(from, me), dims(target, them));
+    let text = if dt == 1 && dm > 1 {
+        format!("temp = {r};\n[{}]", vec!["temp"; dm].join(", "))
+    } else if dt > 1 && dm == 1 {
+        format!("{r}[0]")
+    } else {
+        r
+    };
+    s.execute("prop.setExpression", json!({"layer": lid.0, "prop": uid, "expression": text}))?;
+    Ok(json!(text))
+}
+
+pub fn specs() -> Vec<CommandSpec> {
+    vec![
+        cmd!("prop.separateDimensions", "Separate Dimensions", ["Animation"], None, "{layer?, value?}", has_layers, separate),
+        cmd!(
+            "prop.pickWhip",
+            "Pick Whip (Link Property)",
+            [],
+            None,
+            "{layer?, path|prop, target: {layer, path|prop}} → sets an AE reference expression",
+            has_layers,
+            pick_whip
+        ),
+    ]
+}

crates/engine/src/commands/mask.rs

@@ -0,0 +1,260 @@
+//! Masks drawn and edited in the viewer: Pen tool (new mask, add vertex, Bezier tangents, close
+//! path), vertex selection, moving and deleting vertices, and Layer ▸ Mask ▸ Remove (All).
+//!
+//! Coordinates are in layer space. Edits of an animated Mask Path set a key at the current time.
+
+use effectcraft_keyframe::{ShapePath, Value as KV};
+use effectcraft_project::build::{self, Ids};
+use effectcraft_project::{Layer, MaskMode, PropGroup, Uid};
+use serde_json::{Value, json};
+
+use super::{CommandSpec, b_p, bad, has_comp, has_layers, layer_mut, layer_p, merge_p, resolve_layer, str_p};
+use crate::{EngineError, Result, Session, VertexRef, cmd};
+
+fn pt(v: Option<&Value>) -> Option<[f64; 2]> {
+    let a = v?.as_array()?;
+    Some([a.first()?.as_f64()?, a.get(1)?.as_f64()?])
+}
+
+fn pts(v: Option<&Value>) -> Vec<[f64; 2]> {
+    v.and_then(Value::as_array).map(|a| a.iter().filter_map(|p| pt(Some(p))).collect()).unwrap_or_default()
+}
+
+/// Find a mask group by uid, 1-based index or name.
+fn find_mask<'a>(masks: &'a mut PropGroup, key: &Value) -> Option<&'a mut PropGroup> {
+    let i = match key {
+        Value::Number(n) => {
+            let n = n.as_u64()?;
+            masks.children.iter().position(|c| c.uid() == n).or_else(|| (n as usize).checked_sub(1).filter(|i| *i < masks.children.len()))?
+        }
+        Value::String(s) => masks.children.iter().position(|c| c.name() == s)?,
+        _ => return None,
+    };
+    masks.children.get_mut(i)?.as_group_mut()
+}
+
+/// Edit the mask path of (layer, mask) at the current time.
+fn edit_path<T>(s: &mut Session, p: &Value, label: &str, f: impl FnOnce(&mut ShapePath) -> Result<T>) -> Result<(Uid, T)> {
+    let (cid, lid) = layer_p(s, p, label)?;
+    let key = p.get("mask").cloned().ok_or_else(|| bad(label, "missing `mask` (uid, index or name)"))?;
+    let t = s.time();
+    s.edit(label, merge_p(p), |proj, _| {
+        let l = layer_mut(proj, cid, lid)?;
+        let lt = l.layer_time(t);
+        let masks = l.props.sub_mut("masks").ok_or_else(|| bad(label, "this layer has no masks"))?;
+        let g = find_mask(masks, &key).ok_or_else(|| bad(label, "no such mask"))?;
+        let uid = g.uid;
+        let pr = g.get_mut("path").ok_or_else(|| bad(label, "mask has no path"))?;
+        let KV::Path(mut sp) = pr.value_at(lt) else { return Err(bad(label, "not a path")) };
+        let r = f(&mut sp)?;
+        pr.set_value_at(lt, KV::Path(sp));
+        Ok((uid, r))
+    })
+}
+
+/// Pen tool: a new (open by default) mask from points.
+fn new_mask(s: &mut Session, p: &Value) -> Result<Value> {
+    let (cid, lid) = layer_p(s, p, "mask.new")?;
+    let v = pts(p.get("vertices"));
+    if v.is_empty() {
+        return Err(bad("mask.new", "need `vertices` [[x,y], …] in layer space"));
+    }
+    let n = v.len();
+    let mut ins = pts(p.get("inTangents"));
+    let mut outs = pts(p.get("outTangents"));
+    ins.resize(n, [0.0; 2]);
+    outs.resize(n, [0.0; 2]);
+    let path = ShapePath { vertices: v, in_tangents: ins, out_tangents: outs, closed: b_p(p, "closed").unwrap_or(false) };
+    let mode = str_p(p, "mode").and_then(MaskMode::from_name).unwrap_or(MaskMode::Add);
+    let uid = s.edit("New Mask", None, |proj, st| {
+        let mut next = proj.next_id;
+        let l = layer_mut(proj, cid, lid)?;
+        let masks = l.props.sub_mut("masks").ok_or_else(|| bad("mask.new", "this layer can't have masks"))?;
+        let k = masks.children.len();
+        let g = build::mask(&mut Ids(&mut next), &format!("Mask {}", k + 1), path, mode, build::MASK_COLORS[k % build::MASK_COLORS.len()]);
+        let uid = g.uid;
+        masks.children.push(g.into());
+        proj.next_id = next;
+        st.selected_vertices = vec![VertexRef { layer: lid, mask: uid, index: n - 1 }];
+        Ok(uid)
+    })?;
+    Ok(json!({"mask": uid}))
+}
+
+fn add_vertex(s: &mut Session, p: &Value) -> Result<Value> {
+    let point = pt(p.get("point")).ok_or_else(|| bad("mask.addVertex", "missing `point` [x,y]"))?;
+    let tin = pt(p.get("in")).unwrap_or([0.0; 2]);
+    let tout = pt(p.get("out")).unwrap_or([0.0; 2]);
+    let at = p.get("index").and_then(Value::as_u64).map(|i| i as usize);
+    let (_, lid) = layer_p(s, p, "mask.addVertex")?;
+    let (uid, i) = edit_path(s, p, "mask.addVertex", |sp| {
+        let i = at.unwrap_or(sp.vertices.len()).min(sp.vertices.len());
+        sp.vertices.insert(i, point);
+        sp.in_tangents.insert(i, tin);
+        sp.out_tangents.insert(i, tout);
+        Ok(i)
+    })?;
+    s.state.selected_vertices = vec![VertexRef { layer: lid, mask: uid, index: i }];
+    Ok(json!(i))
+}
+
+fn set_vertex(s: &mut Session, p: &Value) -> Result<Value> {
+    let i = p.get("index").and_then(Value::as_u64).ok_or_else(|| bad("mask.setVertex", "missing `index`"))? as usize;
+    let (point, tin, tout) = (pt(p.get("point")), pt(p.get("in")), pt(p.get("out")));
+    edit_path(s, p, "mask.setVertex", |sp| {
+        if i >= sp.vertices.len() {
+            return Err(bad("mask.setVertex", "no such vertex"));
+        }
+        if let Some(v) = point {
+            sp.vertices[i] = v;
+        }
+        if let Some(v) = tin {
+            sp.in_tangents[i] = v;
+        }
+        if let Some(v) = tout {
+            sp.out_tangents[i] = v;
+        }
+        Ok(())
+    })?;
+    Ok(Value::Null)
+}
+
+fn set_closed(s: &mut Session, p: &Value) -> Result<Value> {
+    let c = b_p(p, "closed").unwrap_or(true);
+    edit_path(s, p, "mask.setClosed", |sp| {
+        sp.closed = c;
+        Ok(())
+    })?;
+    Ok(json!(c))
+}
+
+/// Selected (or given) vertices grouped per (layer, mask).
+fn vertex_groups(s: &Session, p: &Value) -> Result<std::collections::BTreeMap<(u64, Uid), Vec<usize>>> {
+    let comp = s.active_comp().ok_or(EngineError::NoComp)?;
+    let mut g: std::collections::BTreeMap<(u64, Uid), Vec<usize>> = Default::default();
+    if let Some(Value::Array(a)) = p.get("vertices") {
+        for v in a {
+            let l = v.get("layer").and_then(|x| resolve_layer(comp, x)).ok_or_else(|| bad("mask", "vertex needs `layer`"))?;
+            let m = v.get("mask").and_then(Value::as_u64).ok_or_else(|| bad("mask", "vertex needs `mask` uid"))?;
+            let i = v.get("index").and_then(Value::as_u64).ok_or_else(|| bad("mask", "vertex needs `index`"))?;
+            g.entry((l.0, m)).or_default().push(i as usize);
+        }
+    } else {
+        for v in &s.state.selected_vertices {
+            g.entry((v.layer.0, v.mask)).or_default().push(v.index);
+        }
+    }
+    Ok(g)
+}
+
+fn select_vertices(s: &mut Session, p: &Value) -> Result<Value> {
+    let g = vertex_groups(s, &json!({"vertices": p.get("vertices").cloned().unwrap_or(json!([]))}))?;
+    let sel: Vec<VertexRef> =
+        g.into_iter().flat_map(|((l, m), is)| is.into_iter().map(move |i| VertexRef { layer: effectcraft_project::LayerId(l), mask: m, index: i })).collect();
+    if b_p(p, "add").unwrap_or(false) {
+        for v in sel {
+            if let Some(i) = s.state.selected_vertices.iter().position(|x| *x == v) {
+                if b_p(p, "toggle").unwrap_or(false) {
+                    s.state.selected_vertices.remove(i);
+                }
+            } else {
+                s.state.selected_vertices.push(v);
+            }
+        }
+    } else {
+        s.state.selected_vertices = sel;
+    }
+    Ok(json!(s.state.selected_vertices.len()))
+}
+
+fn has_vertices(s: &Session) -> std::result::Result<(), String> {
+    has_comp(s)?;
+    if s.state.selected_vertices.is_empty() { Err("select mask vertices first".into()) } else { Ok(()) }
+}
+
+/// Apply `f` to the selected vertices' paths (each mask once).
+fn edit_vertices(s: &mut Session, p: &Value, label: &str, f: impl Fn(&mut ShapePath, &[usize])) -> Result<Value> {
+    let cid = s.active_comp_id().ok_or(EngineError::NoComp)?;
+    let groups = vertex_groups(s, p)?;
+    let t = s.time();
+    s.edit(label, merge_p(p), |proj, _| {
+        let comp = proj.comp_mut(cid).ok_or(EngineError::NoComp)?;
+        for ((l, m), idx) in &groups {
+            let Some(layer) = comp.layer_mut(effectcraft_project::LayerId(*l)) else { continue };
+            let lt = layer.layer_time(t);
+            let Some(pr) = layer.props.sub_mut("masks").and_then(|ms| ms.find_group_mut(*m)).and_then(|g| g.get_mut("path")) else { continue };
+            let KV::Path(mut sp) = pr.value_at(lt) else { continue };
+            f(&mut sp, idx);
+            pr.set_value_at(lt, KV::Path(sp));
+        }
+        Ok(())
+    })?;
+    Ok(json!(groups.values().map(Vec::len).sum::<usize>()))
+}
+
+fn move_vertices(s: &mut Session, p: &Value) -> Result<Value> {
+    let d = pt(p.get("delta")).ok_or_else(|| bad("mask.moveVertices", "missing `delta` [dx,dy] (layer space)"))?;
+    edit_vertices(s, p, "Move Mask Vertices", |sp, idx| {
+        for &i in idx {
+            if let Some(v) = sp.vertices.get_mut(i) {
+                v[0] += d[0];
+                v[1] += d[1];
+            }
+        }
+    })
+}
+
+fn delete_vertices(s: &mut Session, p: &Value) -> Result<Value> {
+    let n = edit_vertices(s, p, "Delete Mask Vertices", |sp, idx| {
+        let mut idx = idx.to_vec();
+        idx.sort_unstable();
+        idx.dedup();
+        for &i in idx.iter().rev() {
+            if i < sp.vertices.len() {
+                sp.vertices.remove(i);
+                sp.in_tangents.remove(i);
+                sp.out_tangents.remove(i);
+            }
+        }
+        if sp.vertices.len() < 3 {
+            sp.closed = false;
+        }
+    })?;
+    s.state.selected_vertices.clear();
+    Ok(n)
+}
+
+fn remove_masks(s: &mut Session, p: &Value, all: bool) -> Result<Value> {
+    let (cid, lid) = layer_p(s, p, "mask.remove")?;
+    let key = p.get("mask").cloned();
+    if !all && key.is_none() {
+        return Err(bad("mask.remove", "missing `mask`"));
+    }
+    s.edit(if all { "Remove All Masks" } else { "Remove Mask" }, None, |proj, st| {
+        let l: &mut Layer = layer_mut(proj, cid, lid)?;
+        let masks = l.props.sub_mut("masks").ok_or_else(|| bad("mask.remove", "this layer has no masks"))?;
+        if all {
+            masks.children.clear();
+        } else if let Some(k) = &key {
+            let uid = find_mask(masks, k).map(|g| g.uid).ok_or_else(|| bad("mask.remove", "no such mask"))?;
+            masks.children.retain(|c| c.uid() != uid);
+        }
+        st.selected_vertices.retain(|v| v.layer != lid);
+        Ok(())
+    })?;
+    Ok(Value::Null)
+}
+
+pub fn specs() -> Vec<CommandSpec> {
+    vec![
+        cmd!("mask.new", "New Mask from Points", [], None, "{layer?, vertices: [[x,y]…], inTangents?, outTangents?, closed?, mode?}", has_layers, new_mask),
+        cmd!("mask.addVertex", "Add Mask Vertex", [], None, "{layer?, mask, point: [x,y], in?, out?, index?}", has_layers, add_vertex),
+        cmd!("mask.setVertex", "Set Mask Vertex", [], None, "{layer?, mask, index, point?, in?, out?, merge?}", has_layers, set_vertex),
+        cmd!("mask.setClosed", "Closed", ["Layer", "Mask and Shape Path"], None, "{layer?, mask, closed?}", has_layers, set_closed),
+        cmd!("mask.selectVertices", "Select Mask Vertices", [], None, "{vertices: [{layer, mask, index}], add?, toggle?}", has_comp, select_vertices),
+        cmd!("mask.moveVertices", "Move Mask Vertices", [], None, "{vertices?: [{layer, mask, index}], delta: [dx,dy], merge?}", has_vertices, move_vertices),
+        cmd!("mask.deleteVertices", "Delete Mask Vertices", [], None, "{vertices?}", has_vertices, delete_vertices),
+        cmd!("mask.remove", "Remove Mask", ["Layer", "Mask"], None, "{layer?, mask}", has_layers, |s, p| remove_masks(s, p, false)),
+        cmd!("mask.removeAll", "Remove All Masks", ["Layer", "Mask"], None, "{layer?}", has_layers, |s, p| remove_masks(s, p, true)),
+    ]
+}

crates/engine/src/commands/mod.rs

@@ -1,12 +1,16 @@
 //! The command registry. Ids follow After Effects' menu structure; every menu item, panel button,
 //! shortcut and viewer/timeline gesture maps to one of these.
 
+mod anim;
 mod comp;
 mod edit;
 mod effect;
 mod file;
 mod help;
 mod layer;
+mod layer_time;
+mod link;
+mod mask;
 mod prop;
 mod query;
 mod render_queue;
@@ -69,7 +73,11 @@ pub fn command_specs() -> &'static [CommandSpec] {
         v.extend(edit::specs());
         v.extend(comp::specs());
         v.extend(layer::specs());
+        v.extend(layer_time::specs());
         v.extend(prop::specs());
+        v.extend(anim::specs());
+        v.extend(link::specs());
+        v.extend(mask::specs());
         v.extend(effect::specs());
         v.extend(time::specs());
         v.extend(render_queue::specs());

crates/engine/src/commands/prop.rs

@@ -9,7 +9,7 @@ use super::{CommandSpec, b_p, bad, f_p, has_comp, has_keys, has_layers, layer_mu
 use crate::{EngineError, KeyRef, Result, Session, cmd, query};
 
 /// Resolve `{layer, path}` (or `{layer, prop: uid}`) to (comp, layer, prop uid).
-fn prop_ref(s: &Session, p: &Value, cmd: &str) -> Result<(ItemId, LayerId, Uid)> {
+pub(crate) fn prop_ref(s: &Session, p: &Value, cmd: &str) -> Result<(ItemId, LayerId, Uid)> {
     let (cid, lid) = layer_p(s, p, cmd)?;
     let layer = s.project.comp(cid).and_then(|c| c.layer(lid)).ok_or(EngineError::NoComp)?;
     if let Some(u) = p.get("prop").and_then(Value::as_u64) {
@@ -38,10 +38,44 @@ fn with_prop<T>(
     })
 }
 
+/// An explicit key time (layer seconds) moved onto the nearest comp frame.
+fn snapped_key_time(s: &Session, cid: ItemId, lid: LayerId, p: &Value) -> Option<Tick> {
+    let t = Tick::from_seconds_f64(f_p(p, "time")?);
+    let comp = s.project.comp(cid)?;
+    let l = comp.layer(lid)?;
+    Some(l.layer_time(comp.frame_rate.snap_nearest(l.comp_time(t))))
+}
+
 fn set(s: &mut Session, p: &Value) -> Result<Value> {
     let (cid, lid, uid) = prop_ref(s, p, "prop.set")?;
+    // Position with Separate Dimensions: write the X/Y/Z Position properties instead.
+    if let Some(l) = s.project.comp(cid).and_then(|c| c.layer(lid))
+        && let Some(tr) = l.transform()
+        && tr.get("position").is_some_and(|pr| pr.uid == uid)
+        && tr.get("positionX").is_some()
+        && let Some(Value::Array(a)) = p.get("value")
+    {
+        let mut out = vec![];
+        let three = l.is_3d();
+        for (d, m) in ["positionX", "positionY", "positionZ"].iter().enumerate() {
+            if d == 2 && (!three || a.len() < 3) {
+                continue;
+            }
+            if let Some(v) = a.get(d) {
+                let mut q = p.clone();
+                q["path"] = json!(format!("transform/{m}"));
+                q["layer"] = json!(lid.0);
+                if let Some(o) = q.as_object_mut() {
+                    o.remove("prop");
+                }
+                q["value"] = v.clone();
+                out.push(set(s, &q)?);
+            }
+        }
+        return Ok(json!(out));
+    }
     let v = p.get("value").ok_or_else(|| bad("prop.set", "missing `value`"))?.clone();
-    let at = f_p(p, "time").map(Tick::from_seconds_f64);
+    let at = snapped_key_time(s, cid, lid, p);
     let out = with_prop(s, "Change Property", merge_p(p), cid, lid, uid, |pr, lt| {
         let cur = pr.value_at(lt);
         let mut nv = cur.coerce_json(&v).ok_or_else(|| bad("prop.set", format!("can't use {v} for a {} property", cur.kind_name())))?;
@@ -87,7 +121,7 @@ fn toggle_anim(s: &mut Session, p: &Value) -> Result<Value> {
 
 fn add_key(s: &mut Session, p: &Value) -> Result<Value> {
     let (cid, lid, uid) = prop_ref(s, p, "prop.addKey")?;
-    let at = f_p(p, "time").map(Tick::from_seconds_f64);
+    let at = snapped_key_time(s, cid, lid, p);
     let value = p.get("value").cloned();
     with_prop(s, "Add Keyframe", None, cid, lid, uid, |pr, lt| {
         let t = at.unwrap_or(lt);
@@ -128,8 +162,18 @@ fn toggle_key(s: &mut Session, p: &Value) -> Result<Value> {
 fn set_expr(s: &mut Session, p: &Value) -> Result<Value> {
     let (cid, lid, uid) = prop_ref(s, p, "prop.setExpression")?;
     let text = p.get("expression").and_then(Value::as_str).map(str::to_string);
-    let enabled = b_p(p, "enabled");
-    with_prop(s, "Expression", merge_p(p), cid, lid, uid, |pr, _| {
+    let mut enabled = b_p(p, "enabled");
+    // A syntax error keeps the text but disables the expression (AE shows the warning bar).
+    let error = match (&text, s.expr_check) {
+        (Some(t), Some(check)) if !t.trim().is_empty() => check(t).err(),
+        _ => None,
+    };
+    if error.is_some() {
+        enabled = Some(false);
+    }
+    // Alt-click on a stopwatch starts with the property's own reference (`transform.opacity`).
+    let def = s.project.comp(cid).and_then(|c| c.layer(lid).and_then(|l| super::link::reference(c, l, l, uid))).unwrap_or_else(|| "value".into());
+    let r = with_prop(s, "Expression", merge_p(p), cid, lid, uid, |pr, _| {
         match (&text, enabled) {
             (Some(t), _) if t.trim().is_empty() => pr.expr = None,
             (Some(t), e) => pr.expr = Some(effectcraft_project::Expression { text: t.clone(), enabled: e.unwrap_or(true) }),
@@ -137,20 +181,20 @@ fn set_expr(s: &mut Session, p: &Value) -> Result<Value> {
                 if let Some(x) = &mut pr.expr {
                     x.enabled = e;
                 } else if e {
-                    pr.expr = Some(effectcraft_project::Expression { text: default_expr(pr), enabled: true });
+                    pr.expr = Some(effectcraft_project::Expression { text: def.clone(), enabled: true });
                 }
             }
             (None, None) => {
-                pr.expr = if pr.expr.is_some() { None } else { Some(effectcraft_project::Expression { text: default_expr(pr), enabled: true }) };
+                pr.expr = if pr.expr.is_some() { None } else { Some(effectcraft_project::Expression { text: def.clone(), enabled: true }) };
             }
         }
         Ok(json!(pr.expr.as_ref().map(|e| e.text.clone())))
-    })
-}
-
-fn default_expr(pr: &Property) -> String {
-    let _ = pr;
-    "value".to_string()
+    })?;
+    if let Some(e) = error {
+        s.toast(format!("Expression disabled: {e}"));
+        return Ok(json!({"expression": r, "error": e}));
+    }
+    Ok(r)
 }
 
 fn reset(s: &mut Session, p: &Value) -> Result<Value> {
@@ -225,7 +269,7 @@ fn select_keys(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 /// Apply `f` to every selected key; keeps the selection pointing at moved keys.
-fn edit_keys(s: &mut Session, label: &str, merge: Option<&str>, f: impl Fn(&mut Vec<Keyframe>, usize, &mut Tick) -> bool) -> Result<Value> {
+pub(crate) fn edit_keys(s: &mut Session, label: &str, merge: Option<&str>, f: impl Fn(&mut Vec<Keyframe>, usize, &mut Tick) -> bool) -> Result<Value> {
     let cid = s.active_comp_id().ok_or(EngineError::NoComp)?;
     let sel = s.state.selected_keys.clone();
     s.edit(label, merge, |proj, st| {
@@ -262,8 +306,14 @@ fn edit_keys(s: &mut Session, label: &str, merge: Option<&str>, f: impl Fn(&mut
             for t in keep_times {
                 new_sel.push(KeyRef { layer: lid, prop: uid, time: t });
             }
-            if pr.keys.is_empty() {
-                // Deleting every key leaves the value at the last key.
+            // Roving keys follow their neighbours: re-time and keep the selection on them.
+            let before: Vec<Tick> = pr.keys.iter().map(|k| k.time).collect();
+            if effectcraft_keyframe::retime_roving(&mut pr.keys, pr.spatial) {
+                for r in new_sel.iter_mut().filter(|r| r.layer == lid && r.prop == uid) {
+                    if let Some(i) = before.iter().position(|t| *t == r.time) {
+                        r.time = pr.keys[i].time;
+                    }
+                }
             }
         }
         st.selected_keys = new_sel;
@@ -319,8 +369,56 @@ fn interpolation(s: &mut Session, p: &Value) -> Result<Value> {
     let both = parse("interpolation");
     let inn = parse("in").or(both);
     let out = parse("out").or(both);
-    let auto = b_p(p, "autoBezier");
+    // Temporal interpolation by dialog name: linear|bezier|continuousBezier|autoBezier|hold.
+    let temporal = str_p(p, "interpolation").map(|v| v.to_ascii_lowercase());
+    let mut auto = b_p(p, "autoBezier");
+    let mut continuous = b_p(p, "continuous");
+    match temporal.as_deref() {
+        Some("autobezier" | "auto") => auto = Some(true),
+        Some("continuousbezier" | "continuous") => {
+            continuous = Some(true);
+            auto = Some(false);
+        }
+        Some("linear" | "bezier" | "hold") => {
+            auto = auto.or(Some(false));
+            continuous = continuous.or(Some(false));
+        }
+        _ => {}
+    }
+    let inn = if matches!(temporal.as_deref(), Some("autobezier" | "auto" | "continuousbezier" | "continuous")) { inn.or(Some(Interp::Bezier)) } else { inn };
+    let out = if matches!(temporal.as_deref(), Some("autobezier" | "auto" | "continuousbezier" | "continuous")) { out.or(Some(Interp::Bezier)) } else { out };
+    let spatial = str_p(p, "spatial").map(|v| v.to_ascii_lowercase());
+    let roving = b_p(p, "roving");
     edit_keys(s, "Keyframe Interpolation", None, move |keys, i, _| {
+        if let Some(sp) = spatial.as_deref() {
+            let (tin, tout) = effectcraft_keyframe::spatial_tangents(keys, i);
+            let k = &mut keys[i];
+            match sp {
+                "linear" => {
+                    k.spatial_auto = false;
+                    k.spatial_continuous = false;
+                    k.spatial_in = [0.0; 3];
+                    k.spatial_out = [0.0; 3];
+                }
+                "bezier" | "continuous" | "continuousbezier" => {
+                    k.spatial_auto = false;
+                    k.spatial_in = tin;
+                    k.spatial_out = tout;
+                    k.spatial_continuous = sp != "bezier";
+                }
+                "auto" | "autobezier" => {
+                    k.spatial_auto = true;
+                    k.spatial_continuous = false;
+                }
+                _ => {}
+            }
+        }
+        if let Some(r) = roving {
+            keys[i].roving = r;
+        }
+        if let Some(c) = continuous {
+            keys[i].continuous = c;
+        }
         let n = keys[i].value.dims().max(1);
         if let Some(x) = inn {
             keys[i].in_interp = x;
@@ -339,6 +437,24 @@ fn interpolation(s: &mut Session, p: &Value) -> Result<Value> {
             if a {
                 keys[i].in_interp = Interp::Bezier;
                 keys[i].out_interp = Interp::Bezier;
+                keys[i].continuous = false;
+            }
+        }
+        if keys[i].continuous && !keys[i].auto_bezier {
+            // Continuous Bezier: one speed through the key (average of both sides).
+            let k = &mut keys[i];
+            k.in_interp = Interp::Bezier;
+            k.out_interp = Interp::Bezier;
+            if k.in_ease.len() != n {
+                k.in_ease = vec![Ease::default(); n];
+            }
+            if k.out_ease.len() != n {
+                k.out_ease = vec![Ease::default(); n];
+            }
+            for d in 0..n {
+                let sp = (k.in_ease[d].speed + k.out_ease[d].speed) / 2.0;
+                k.in_ease[d].speed = sp;
+                k.out_ease[d].speed = sp;
             }
         }
         false
@@ -353,41 +469,67 @@ fn toggle_hold(s: &mut Session, _: &Value) -> Result<Value> {
     })
 }
 
+/// A number or a per-dimension array of numbers.
+fn nums_p(p: &Value, k: &str, scale: f64) -> Option<Vec<f64>> {
+    match p.get(k)? {
+        Value::Array(a) => Some(a.iter().filter_map(Value::as_f64).map(|v| v * scale).collect()),
+        v => v.as_f64().map(|v| vec![v * scale]),
+    }
+}
+
 fn velocity(s: &mut Session, p: &Value) -> Result<Value> {
-    let in_speed = f_p(p, "inSpeed");
-    let in_inf = f_p(p, "inInfluence").map(|v| v / 100.0);
-    let out_speed = f_p(p, "outSpeed");
-    let out_inf = f_p(p, "outInfluence").map(|v| v / 100.0);
+    let mut in_speed = nums_p(p, "inSpeed", 1.0);
+    let mut in_inf = nums_p(p, "inInfluence", 0.01);
+    let mut out_speed = nums_p(p, "outSpeed", 1.0);
+    let mut out_inf = nums_p(p, "outInfluence", 0.01);
+    // "Continuous" in the dialog: outgoing velocity follows incoming.
+    let continuous = b_p(p, "continuous");
+    if continuous == Some(true) {
+        if out_speed.is_none() {
+            out_speed = in_speed.clone();
+        }
+        if in_speed.is_none() {
+            in_speed = out_speed.clone();
+        }
+        if out_inf.is_none() {
+            out_inf = in_inf.clone();
+        }
+        if in_inf.is_none() {
+            in_inf = out_inf.clone();
+        }
+    }
     edit_keys(s, "Keyframe Velocity", merge_p(p), move |keys, i, _| {
         let n = keys[i].value.dims().max(1);
+        // Current presentation of each side, so unspecified parts keep their values.
+        let cur = |keys: &[Keyframe], out: bool| -> Vec<Ease> {
+            (0..n).map(|d| effectcraft_keyframe::side_ease(keys, i, d, false, out).unwrap_or(Ease::EASY)).collect()
+        };
+        let cur_in = cur(keys, false);
+        let cur_out = cur(keys, true);
         let k = &mut keys[i];
-        if in_speed.is_some() || in_inf.is_some() {
-            k.in_interp = Interp::Bezier;
-            if k.in_ease.is_empty() {
-                k.in_ease = vec![Ease::default(); n];
+        let apply = |list: &mut Vec<Ease>, base: Vec<Ease>, sp: &Option<Vec<f64>>, inf: &Option<Vec<f64>>| {
+            if list.len() != n {
+                *list = base;
             }
-            for e in &mut k.in_ease {
-                if let Some(v) = in_speed {
-                    e.speed = v;
+            for (d, e) in list.iter_mut().enumerate() {
+                if let Some(v) = sp.as_ref().and_then(|v| v.get(d).or(v.first())) {
+                    e.speed = *v;
                 }
-                if let Some(v) = in_inf {
+                if let Some(v) = inf.as_ref().and_then(|v| v.get(d).or(v.first())) {
                     e.influence = v.clamp(0.001, 1.0);
                 }
             }
+        };
+        if in_speed.is_some() || in_inf.is_some() {
+            k.in_interp = Interp::Bezier;
+            apply(&mut k.in_ease, cur_in, &in_speed, &in_inf);
         }
         if out_speed.is_some() || out_inf.is_some() {
             k.out_interp = Interp::Bezier;
-            if k.out_ease.is_empty() {
-                k.out_ease = vec![Ease::default(); n];
-            }
-            for e in &mut k.out_ease {
-                if let Some(v) = out_speed {
-                    e.speed = v;
-                }
-                if let Some(v) = out_inf {
-                    e.influence = v.clamp(0.001, 1.0);
-                }
-            }
+            apply(&mut k.out_ease, cur_out, &out_speed, &out_inf);
+        }
+        if let Some(c) = continuous {
+            k.continuous = c;
         }
         k.auto_bezier = false;
         false
@@ -451,7 +593,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Keyframe Interpolation…",
             ["Animation"],
             Some("Cmd+Alt+K"),
-            "{interpolation?|in?|out?: linear|bezier|hold, autoBezier?}",
+            "{interpolation?: linear|bezier|continuousBezier|autoBezier|hold, in?|out?: linear|bezier|hold, autoBezier?, continuous?, spatial?: linear|bezier|continuousBezier|autoBezier, roving?}",
             has_keys,
             interpolation
         ),
@@ -460,7 +602,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Keyframe Velocity…",
             ["Animation"],
             Some("Cmd+Shift+K"),
-            "{inSpeed?, inInfluence? %, outSpeed?, outInfluence? %}",
+            "{inSpeed?, inInfluence? %, outSpeed?, outInfluence? % (numbers or per-dimension arrays), continuous?}",
             has_keys,
             velocity
         ),

crates/engine/src/demo.rs

@@ -11,8 +11,9 @@ use effectcraft_time::{FrameRate, Tick};
 
 pub const MAIN_COMP: &str = "EffectCraft Intro";
 
+/// Seconds → the nearest frame of the demo's 29.97 fps comps (AE keeps times frame-aligned).
 fn t(s: f64) -> Tick {
-    Tick::from_seconds_f64(s)
+    FrameRate::FPS_29_97.snap_nearest(Tick::from_seconds_f64(s))
 }
 
 fn hex(h: &str) -> [f64; 4] {

crates/engine/src/lib.rs

@@ -93,6 +93,24 @@ pub struct KeyRef {
     pub time: Tick,
 }
 
+/// Keyframes of one property on the keyframe clipboard.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct KeyClip {
+    pub layer: LayerId,
+    /// Match-id path relative to the layer (`transform/position`), portable between layers.
+    pub path: String,
+    /// Keys with times relative to the earliest copied key (layer time).
+    pub keys: Vec<effectcraft_keyframe::Keyframe>,
+}
+
+/// A selected mask vertex: layer, mask group uid, vertex index.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct VertexRef {
+    pub layer: LayerId,
+    pub mask: Uid,
+    pub index: usize,
+}
+
 /// Editing state that commands depend on (headless-relevant, serde for agents).
 #[derive(Clone, Debug, Default, Serialize, Deserialize)]
 pub struct EditorState {
@@ -109,6 +127,15 @@ pub struct EditorState {
     /// Layer clipboard (serialized layers) and keyframe clipboard.
     #[serde(skip)]
     pub clipboard: Vec<Layer>,
+    /// Copied keyframes (times relative to the earliest copied key).
+    #[serde(skip)]
+    pub key_clipboard: Vec<KeyClip>,
+    /// The last copy was keyframes (Paste pastes keys at the CTI).
+    #[serde(skip)]
+    pub clip_is_keys: bool,
+    /// Selected mask vertices (viewer Selection tool / pen).
+    #[serde(default)]
+    pub selected_vertices: Vec<VertexRef>,
     pub snapping: bool,
     /// Last applied effect id (Effect ▸ last effect).
     pub last_effect: Option<String>,
@@ -133,6 +160,8 @@ pub struct Session {
     pub services: Arc<dyn Services>,
     pub footage: Arc<dyn FootageSource>,
     pub expr: Option<Arc<dyn ExprHost>>,
+    /// Expression syntax checker (set by the host that links the expression engine).
+    pub expr_check: Option<fn(&str) -> std::result::Result<(), String>>,
     pub importer: Option<Arc<dyn Importer>>,
     /// Render Queue encoder (the export layer); `None` = export unavailable.
     pub exporter: Option<Arc<dyn Exporter>>,
@@ -157,6 +186,7 @@ impl Default for Session {
             services: Arc::new(FsServices),
             footage: Arc::new(NoFootage),
             expr: None,
+            expr_check: None,
             importer: None,
             exporter: None,
             render_job: None,
@@ -262,6 +292,7 @@ impl Session {
             self.state.selected_layers.retain(|l| ids.contains(l));
             self.state.selected_props.retain(|(l, _)| ids.contains(l));
             self.state.selected_keys.retain(|k| ids.contains(&k.layer));
+            self.state.selected_vertices.retain(|v| ids.contains(&v.layer));
         }
         self.state.project_selection.retain(|i| p.item(*i).is_some());
     }
@@ -286,7 +317,7 @@ impl Session {
         if let Some(c) = self.state.active_comp {
             let comp = self.project.comp(c);
             let t = match comp {
-                Some(comp) => comp.frame_rate.snap(t.clamp(Tick::ZERO, comp.duration - comp.frame_duration())),
+                Some(comp) => comp.frame_rate.snap_nearest(t.clamp(Tick::ZERO, comp.duration - comp.frame_duration())),
                 None => t,
             };
             self.state.times.insert(c, t);
@@ -306,6 +337,7 @@ impl Session {
             self.state.selected_layers.clear();
             self.state.selected_props.clear();
             self.state.selected_keys.clear();
+            self.state.selected_vertices.clear();
         }
         self.events.push(Event::OpenComp(id));
     }
@@ -372,6 +404,8 @@ impl Session {
 mod rq_tests;
 #[cfg(test)]
 mod tests;
+#[cfg(test)]
+mod tests_timeline;
 
 /// Font families available to text layers (bundled + scanned system fonts).
 pub fn text_families() -> Vec<String> {

crates/engine/src/tests.rs

@@ -205,7 +205,7 @@ fn set_text_paragraph_fill_and_leading() {
 #[test]
 fn prop_get_and_render_rgba8() {
     let mut s = Session::default();
-    s.execute("comp.new", json!({"name": "T", "width": 320, "height": 180, "duration": 2.0})).unwrap();
+    s.execute("comp.new", json!({"name": "T", "width": 320, "height": 180, "duration": 2.0, "frameRate": 30})).unwrap();
     let l = s.execute("layer.newSolid", json!({"color": "#ff0000"})).unwrap()["layer"].as_u64().unwrap();
     s.execute("prop.addKey", json!({"layer": l, "path": "transform/position", "time": 0.0, "value": [0, 0]})).unwrap();
     s.execute("prop.addKey", json!({"layer": l, "path": "transform/position", "time": 1.0, "value": [100, 50]})).unwrap();

crates/engine/src/tests_timeline.rs

@@ -0,0 +1,573 @@
+//! Timeline depth: keyframe clipboard, easing, velocity/interpolation, roving, nudging, graph
+//! editor key edits, time remapping/stretch/reverse/freeze, separate dimensions, pick-whips,
+//! expressions and masks (pen tool). Every command is checked with undo/redo.
+
+use effectcraft_keyframe::{Interp, Value as KV};
+use effectcraft_project::Property;
+use serde_json::{Value, json};
+
+use crate::Session;
+
+/// A 4 s, 30 fps comp with one solid; returns (session, layer id).
+pub(crate) fn setup() -> (Session, u64) {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "T", "width": 400, "height": 300, "frameRate": 30, "duration": 4})).unwrap();
+    let r = s.execute("layer.newSolid", json!({"color": "#ffffff", "width": 100, "height": 100})).unwrap();
+    (s, r["layer"].as_u64().unwrap())
+}
+
+pub(crate) fn prop(s: &Session, layer: u64, path: &str) -> Property {
+    s.active_comp().unwrap().layer(effectcraft_project::LayerId(layer)).unwrap().props.prop(path).unwrap().clone()
+}
+
+/// Key `path` at the given (time, value) pairs.
+pub(crate) fn animate(s: &mut Session, layer: u64, path: &str, keys: &[(f64, Value)]) {
+    for (t, v) in keys {
+        s.execute("prop.addKey", json!({"layer": layer, "path": path, "time": t, "value": v})).unwrap();
+    }
+}
+
+fn select_prop_keys(s: &mut Session, layer: u64, path: &str) {
+    s.execute("prop.select", json!({"layer": layer, "path": path})).unwrap();
+}
+
+fn undo_redo_roundtrip(s: &mut Session, check_after: impl Fn(&Session), check_before: impl Fn(&Session)) {
+    check_after(s);
+    s.execute("edit.undo", json!({})).unwrap();
+    check_before(s);
+    s.execute("edit.redo", json!({})).unwrap();
+    check_after(s);
+}
+
+#[test]
+fn easy_ease_family_sets_influence_and_zero_speed() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/opacity", &[(0.0, json!(0)), (1.0, json!(100)), (2.0, json!(0))]);
+    select_prop_keys(&mut s, l, "transform/opacity");
+    s.execute("keys.easyEase", json!({})).unwrap();
+    undo_redo_roundtrip(
+        &mut s,
+        |s| {
+            let p = prop(s, l, "transform/opacity");
+            assert!(p.keys.iter().all(|k| k.in_interp == Interp::Bezier && k.out_interp == Interp::Bezier));
+            assert!((p.keys[1].in_ease[0].influence - 1.0 / 3.0).abs() < 1e-9 && p.keys[1].in_ease[0].speed == 0.0);
+        },
+        |s| assert!(prop(s, l, "transform/opacity").keys.iter().all(|k| k.in_interp == Interp::Linear)),
+    );
+    // Easy Ease In only touches the incoming side; Out only the outgoing side.
+    s.execute("keys.interpolation", json!({"interpolation": "linear"})).unwrap();
+    s.execute("keys.easyEaseIn", json!({})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    assert!(p.keys.iter().all(|k| k.in_interp == Interp::Bezier && k.out_interp == Interp::Linear));
+    s.execute("keys.interpolation", json!({"interpolation": "linear"})).unwrap();
+    s.execute("keys.easyEaseOut", json!({})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    assert!(p.keys.iter().all(|k| k.in_interp == Interp::Linear && k.out_interp == Interp::Bezier));
+    // Eased motion is slow near the key.
+    s.execute("keys.easyEase", json!({})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    let early = p.value_at(effectcraft_time::Tick::from_seconds_f64(0.1)).as_f64();
+    assert!(early < 5.0, "{early}");
+}
+
+#[test]
+fn keyframe_copy_paste_keeps_relative_timing_and_crosses_properties() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/rotation", &[(0.5, json!(0)), (1.0, json!(90)), (2.0, json!(45))]);
+    select_prop_keys(&mut s, l, "transform/rotation");
+    s.execute("keys.easyEase", json!({})).unwrap();
+    assert_eq!(s.execute("edit.copy", json!({})).unwrap(), json!(3));
+    assert!(s.state.clip_is_keys);
+    // Paste into the same property at 2.5 s: keys at 2.5, 3.0 and 4.0 (clamped by nothing).
+    s.execute("time.set", json!({"time": 2.5})).unwrap();
+    s.execute("keys.select", json!({"keys": []})).unwrap();
+    s.execute("edit.paste", json!({})).unwrap();
+    let after = |s: &Session| {
+        let p = prop(s, l, "transform/rotation");
+        let times: Vec<f64> = p.keys.iter().map(|k| (k.time.seconds() * 30.0).round() / 30.0).collect();
+        assert_eq!(times, vec![0.5, 1.0, 2.0, 2.5, 3.0, 4.0]);
+        assert_eq!(p.keys[4].value, KV::Scalar(90.0));
+        assert_eq!(p.keys[4].in_interp, Interp::Bezier, "interpolation travels with the keys");
+        assert_eq!(s.state.selected_keys.len(), 3, "pasted keys are selected");
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert_eq!(prop(s, l, "transform/rotation").keys.len(), 3));
+    // Cross-property paste of one property's keys into another of the same type (Scalar).
+    let r = s.execute("layer.newSolid", json!({"color": "#ff0000"})).unwrap();
+    let l2 = r["layer"].as_u64().unwrap();
+    select_prop_keys(&mut s, l, "transform/rotation");
+    s.execute("keys.select", json!({"keys": [{"layer": l, "prop": prop(&s, l, "transform/rotation").uid, "time": 1.0}]})).unwrap();
+    s.execute("keys.copy", json!({})).unwrap();
+    s.execute("time.set", json!({"time": 1.0})).unwrap();
+    s.execute("prop.select", json!({"layer": l2, "path": "transform/opacity", "selectKeys": false})).unwrap();
+    s.execute("keys.paste", json!({"layers": [l2]})).unwrap();
+    let op = prop(&s, l2, "transform/opacity");
+    assert_eq!(op.keys.len(), 1);
+    assert_eq!(op.keys[0].value, KV::Scalar(90.0));
+    // Incompatible target (Vec3 position) is refused when explicitly given.
+    let e = s.execute("keys.paste", json!({"layers": [l2], "path": "transform/position"}));
+    assert!(e.is_err() || prop(&s, l2, "transform/position").keys.is_empty());
+}
+
+#[test]
+fn cut_removes_keys_and_paste_restores_them() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/opacity", &[(0.0, json!(10)), (1.0, json!(20))]);
+    select_prop_keys(&mut s, l, "transform/opacity");
+    s.execute("edit.cut", json!({})).unwrap();
+    assert!(prop(&s, l, "transform/opacity").keys.is_empty());
+    s.execute("time.set", json!({"time": 0.0})).unwrap();
+    s.execute("layer.select", json!({"layers": [l]})).unwrap();
+    s.execute("edit.paste", json!({})).unwrap();
+    assert_eq!(prop(&s, l, "transform/opacity").keys.len(), 2);
+}
+
+#[test]
+fn select_all_and_nudge_keys() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/opacity", &[(0.0, json!(10)), (1.0, json!(20))]);
+    animate(&mut s, l, "transform/rotation", &[(0.5, json!(10))]);
+    s.state.selected_props.clear();
+    s.execute("layer.select", json!({"layers": [l]})).unwrap();
+    assert_eq!(s.execute("keys.selectAll", json!({})).unwrap(), json!(3));
+    s.execute("keys.nudgeForward", json!({})).unwrap();
+    let after = |s: &Session| {
+        let p = prop(s, l, "transform/opacity");
+        assert!((p.keys[0].time.seconds() - 1.0 / 30.0).abs() < 1e-6);
+        assert_eq!(s.state.selected_keys.len(), 3);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert_eq!(prop(s, l, "transform/opacity").keys[0].time.0, 0));
+    s.execute("keys.nudgeBackward10", json!({})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    assert!((p.keys[0].time.seconds() + 9.0 / 30.0).abs() < 1e-6, "{}", p.keys[0].time.seconds());
+}
+
+#[test]
+fn velocity_dialog_values_per_dimension_and_continuous() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/scale", &[(0.0, json!([100, 100])), (1.0, json!([200, 50])), (2.0, json!([100, 100]))]);
+    s.execute("keys.select", json!({"keys": [{"layer": l, "prop": prop(&s, l, "transform/scale").uid, "time": 1.0}]})).unwrap();
+    let info = s.execute("keys.info", json!({})).unwrap();
+    assert_eq!(info[0]["units"], "%/sec");
+    assert_eq!(info[0]["dims"], 2);
+    // Linear sides present the segment slope: +100 %/s in X on the incoming side.
+    assert!((info[0]["inEase"][0]["speed"].as_f64().unwrap() - 100.0).abs() < 1e-6, "{info}");
+    s.execute("keys.velocity", json!({"inSpeed": [10, -20], "inInfluence": 50, "continuous": true})).unwrap();
+    let after = |s: &Session| {
+        let k = &prop(s, l, "transform/scale").keys[1];
+        assert_eq!(k.in_ease[0].speed, 10.0);
+        assert_eq!(k.in_ease[1].speed, -20.0);
+        assert_eq!(k.out_ease[1].speed, -20.0, "continuous mirrors incoming");
+        assert!((k.out_ease[0].influence - 0.5).abs() < 1e-9);
+        assert!(k.continuous);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert_eq!(prop(s, l, "transform/scale").keys[1].in_interp, Interp::Linear));
+}
+
+#[test]
+fn interpolation_dialog_temporal_spatial_and_roving() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/position", &[(0.0, json!([0, 0])), (0.3, json!([300, 0])), (2.0, json!([400, 0]))]);
+    select_prop_keys(&mut s, l, "transform/position");
+    s.execute("keys.interpolation", json!({"interpolation": "hold"})).unwrap();
+    assert!(prop(&s, l, "transform/position").keys.iter().all(|k| k.out_interp == Interp::Hold));
+    s.execute("keys.interpolation", json!({"interpolation": "autoBezier"})).unwrap();
+    assert!(prop(&s, l, "transform/position").keys.iter().all(|k| k.auto_bezier));
+    s.execute("keys.interpolation", json!({"interpolation": "continuousBezier", "spatial": "linear"})).unwrap();
+    let p = prop(&s, l, "transform/position");
+    assert!(p.keys.iter().all(|k| k.continuous && !k.auto_bezier && !k.spatial_auto && k.spatial_out == [0.0; 3]));
+    // Rove the middle key: its time follows the path length (300 of 400 px → 1.5 s).
+    let uid = p.uid;
+    s.execute("keys.select", json!({"keys": [{"layer": l, "prop": uid, "time": 0.3}]})).unwrap();
+    s.execute("keys.interpolation", json!({"roving": true})).unwrap();
+    let after = |s: &Session| {
+        let p = prop(s, l, "transform/position");
+        assert!(p.keys[1].roving);
+        assert!((p.keys[1].time.seconds() - 1.5).abs() < 0.01, "{}", p.keys[1].time.seconds());
+        // The selection follows the roving key.
+        assert!((s.state.selected_keys[0].time.seconds() - 1.5).abs() < 0.01);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert!(!prop(s, l, "transform/position").keys[1].roving));
+    // Moving the last key re-times the roving key.
+    s.execute("keys.set", json!({"layer": l, "path": "transform/position", "time": 2.0, "newTime": 4.0})).unwrap();
+    let p = prop(&s, l, "transform/position");
+    assert!((p.keys[1].time.seconds() - 3.0).abs() < 0.02, "{}", p.keys[1].time.seconds());
+    // Toggle hold on a key and back.
+    s.execute("keys.select", json!({"keys": [{"layer": l, "prop": uid, "time": 0.0}]})).unwrap();
+    s.execute("keys.toggleHold", json!({})).unwrap();
+    assert_eq!(prop(&s, l, "transform/position").keys[0].out_interp, Interp::Hold);
+    s.execute("keys.toggleHold", json!({})).unwrap();
+    assert_ne!(prop(&s, l, "transform/position").keys[0].out_interp, Interp::Hold);
+}
+
+#[test]
+fn graph_editor_key_and_handle_edits() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/opacity", &[(0.0, json!(0)), (2.0, json!(100))]);
+    // Drag a key in the value graph: new time + value, merged into one undo step.
+    s.execute("keys.set", json!({"layer": l, "path": "transform/opacity", "time": 2.0, "newTime": 1.0, "value": 50, "merge": "g1"})).unwrap();
+    s.execute("keys.set", json!({"layer": l, "path": "transform/opacity", "time": 1.0, "newTime": 1.5, "value": 60, "merge": "g1"})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    assert!((p.keys[1].time.seconds() - 1.5).abs() < 1e-6);
+    assert_eq!(p.keys[1].value, KV::Scalar(60.0));
+    s.execute("edit.undo", json!({})).unwrap();
+    assert!((prop(&s, l, "transform/opacity").keys[1].time.seconds() - 2.0).abs() < 1e-6);
+    s.execute("edit.redo", json!({})).unwrap();
+    // A key can't be dragged past its neighbour.
+    s.execute("keys.set", json!({"layer": l, "path": "transform/opacity", "time": 1.5, "newTime": -1.0})).unwrap();
+    let p = prop(&s, l, "transform/opacity");
+    assert!(p.keys[1].time > p.keys[0].time);
+    // Handle drag: out side of key 0 → speed 200 %/s, 60 % influence.
+    s.execute("keys.setEase", json!({"layer": l, "path": "transform/opacity", "time": 0.0, "side": "out", "speed": 200, "influence": 60})).unwrap();
+    let k = &prop(&s, l, "transform/opacity").keys[0];
+    assert_eq!(k.out_interp, Interp::Bezier);
+    assert_eq!(k.out_ease[0].speed, 200.0);
+    assert!((k.out_ease[0].influence - 0.6).abs() < 1e-9);
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(prop(&s, l, "transform/opacity").keys[0].out_interp, Interp::Linear);
+}
+
+#[test]
+fn time_reverse_keyframes() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/opacity", &[(0.0, json!(0)), (1.0, json!(30)), (3.0, json!(100))]);
+    select_prop_keys(&mut s, l, "transform/opacity");
+    s.execute("keys.timeReverse", json!({})).unwrap();
+    let after = |s: &Session| {
+        let p = prop(s, l, "transform/opacity");
+        assert_eq!(p.keys[0].value, KV::Scalar(100.0));
+        assert!((p.keys[1].time.seconds() - 2.0).abs() < 1e-6);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert_eq!(prop(s, l, "transform/opacity").keys[0].value, KV::Scalar(0.0)));
+}
+
+#[test]
+fn pen_tool_draws_edits_and_closes_a_mask() {
+    let (mut s, l) = setup();
+    // Click (corner), click, drag (Bezier), click on the first vertex (close).
+    let r = s.execute("mask.new", json!({"layer": l, "vertices": [[10, 10]]})).unwrap();
+    let m = r["mask"].as_u64().unwrap();
+    s.execute("mask.addVertex", json!({"layer": l, "mask": m, "point": [90, 10]})).unwrap();
+    s.execute("mask.addVertex", json!({"layer": l, "mask": m, "point": [90, 90]})).unwrap();
+    s.execute("mask.setVertex", json!({"layer": l, "mask": m, "index": 2, "in": [0, -20], "out": [0, 20], "merge": "pen"})).unwrap();
+    s.execute("mask.addVertex", json!({"layer": l, "mask": m, "point": [10, 90]})).unwrap();
+    s.execute("mask.setClosed", json!({"layer": l, "mask": m, "closed": true})).unwrap();
+    let path = |s: &Session| prop(s, l, "masks/#1/path").value.as_path().unwrap().clone();
+    let p = path(&s);
+    assert_eq!(p.vertices, vec![[10.0, 10.0], [90.0, 10.0], [90.0, 90.0], [10.0, 90.0]]);
+    assert_eq!(p.out_tangents[2], [0.0, 20.0]);
+    assert!(p.closed);
+    assert_eq!(s.state.selected_vertices.last().unwrap().index, 3);
+    // The mask cuts the 100×100 solid (layer centred in the 400×300 comp at 150..250, 100..200).
+    let cid = s.active_comp_id().unwrap();
+    let img = s.render(cid, effectcraft_time::Tick::ZERO, effectcraft_render::RenderOpts { scale: 1.0, ..Default::default() });
+    assert!(img.get(200, 150)[3] > 0.99 && img.get(152, 102)[3] < 0.01);
+    // Undo removes the close, redo restores it.
+    s.execute("edit.undo", json!({})).unwrap();
+    assert!(!path(&s).closed);
+    s.execute("edit.redo", json!({})).unwrap();
+    // Select two vertices and drag them; Delete removes them.
+    s.execute("mask.selectVertices", json!({"vertices": [{"layer": l, "mask": m, "index": 0}, {"layer": l, "mask": m, "index": 1}]})).unwrap();
+    s.execute("mask.moveVertices", json!({"delta": [5, -5], "merge": "v1"})).unwrap();
+    s.execute("mask.moveVertices", json!({"delta": [5, -5], "merge": "v1"})).unwrap();
+    assert_eq!(path(&s).vertices[1], [100.0, 0.0]);
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(path(&s).vertices[1], [90.0, 10.0], "a drag is one undo step");
+    s.execute("edit.clear", json!({})).unwrap();
+    assert_eq!(path(&s).vertices.len(), 2);
+    assert!(!path(&s).closed);
+    // Animated mask paths get a key at the current time.
+    s.execute("prop.toggleAnimation", json!({"layer": l, "path": "masks/#1/path"})).unwrap();
+    s.execute("time.set", json!({"time": 1.0})).unwrap();
+    s.execute("mask.setVertex", json!({"layer": l, "mask": 1, "index": 0, "point": [0, 0]})).unwrap();
+    assert_eq!(prop(&s, l, "masks/#1/path").keys.len(), 2);
+    // Mode / feather / opacity / expansion through the timeline commands.
+    s.execute("layer.setMask", json!({"layer": l, "mask": m, "mode": "Subtract", "inverted": true})).unwrap();
+    s.execute("prop.set", json!({"layer": l, "path": "masks/#1/feather", "value": [4, 4]})).unwrap();
+    s.execute("prop.set", json!({"layer": l, "path": "masks/#1/expansion", "value": 3})).unwrap();
+    s.execute("prop.set", json!({"layer": l, "path": "masks/#1/opacity", "value": 50})).unwrap();
+    assert_eq!(prop(&s, l, "masks/#1/opacity").value, KV::Scalar(50.0));
+    s.execute("mask.removeAll", json!({"layer": l})).unwrap();
+    assert!(s.active_comp().unwrap().layers[0].masks().unwrap().children.is_empty());
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(s.active_comp().unwrap().layers[0].masks().unwrap().children.len(), 1);
+}
+
+#[test]
+fn alt_click_stopwatch_toggles_a_self_reference_expression() {
+    let (mut s, l) = setup();
+    s.execute("prop.setExpression", json!({"layer": l, "path": "transform/opacity"})).unwrap();
+    assert_eq!(prop(&s, l, "transform/opacity").expr.unwrap().text, "transform.opacity");
+    s.execute("prop.setExpression", json!({"layer": l, "path": "transform/opacity", "enabled": false})).unwrap();
+    assert!(!prop(&s, l, "transform/opacity").expr.unwrap().enabled);
+    s.execute("prop.setExpression", json!({"layer": l, "path": "transform/opacity", "enabled": true})).unwrap();
+    s.execute("prop.setExpression", json!({"layer": l, "path": "transform/opacity"})).unwrap();
+    assert!(prop(&s, l, "transform/opacity").expr.is_none());
+    s.execute("edit.undo", json!({})).unwrap();
+    assert!(prop(&s, l, "transform/opacity").expr.unwrap().enabled);
+}
+
+#[test]
+fn layer_comp_and_key_times_stay_frame_aligned() {
+    let aligned = |fr: effectcraft_time::FrameRate, t: effectcraft_time::Tick| fr.snap(t) == t;
+    // The demo project: every comp duration, layer in/out/start and key time is on a frame.
+    let mut s = Session::default();
+    s.execute("file.openDemoProject", json!({})).unwrap();
+    for (_, c) in s.project.comps() {
+        let fr = c.frame_rate;
+        assert!(aligned(fr, c.duration), "duration {:?}", c.duration);
+        for l in &c.layers {
+            for t in [l.in_point, l.out_point, l.start_time] {
+                assert!(aligned(fr, t), "{} {t:?}", l.name);
+            }
+            l.props.walk("", &mut |_, pr| {
+                for k in &pr.keys {
+                    assert!(aligned(fr, l.comp_time(k.time)), "{} {}", l.name, pr.name);
+                }
+            });
+        }
+    }
+    let lower = s.active_comp().unwrap().layer_by_name("Lower Third").unwrap();
+    let fr = s.active_comp().unwrap().frame_rate;
+    assert_eq!(fr.frame_at(lower.in_point), 150, "5 s at 29.97 is frame 150 (0:00:05:00)");
+    // Commands snap: comp duration, layer timing, key times.
+    s.execute("comp.new", json!({"name": "F", "frameRate": 29.97, "duration": 10.0})).unwrap();
+    let c = s.active_comp().unwrap();
+    assert_eq!(c.frame_rate.frame_at(c.duration), 300);
+    assert!(aligned(c.frame_rate, c.duration));
+    let l = s.execute("layer.newSolid", json!({"color": "#fff"})).unwrap()["layer"].as_u64().unwrap();
+    s.execute("layer.timing", json!({"layers": [l], "in": 1.01, "out": 3.3333, "delta": 0.02})).unwrap();
+    let ly = s.active_comp().unwrap().layers[0].clone();
+    let fr = s.active_comp().unwrap().frame_rate;
+    for t in [ly.in_point, ly.out_point, ly.start_time] {
+        assert!(aligned(fr, t), "{t:?}");
+    }
+    s.execute("prop.addKey", json!({"layer": l, "path": "transform/opacity", "time": 1.2345, "value": 10})).unwrap();
+    let k = prop(&s, l, "transform/opacity").keys[0].time;
+    assert!(aligned(fr, ly.comp_time(k)));
+    // Layer shifted one frame (delta 0.02 s rounds to 1 frame): 1.2345 s + 1 frame -> frame 38.
+    assert_eq!(fr.frame_at(ly.comp_time(k)), 38);
+}
+
+#[test]
+fn time_set_snaps_to_the_nearest_frame_and_ae_timecode() {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "T", "width": 100, "height": 100, "frameRate": 29.97, "duration": 10})).unwrap();
+    let r = s.execute("time.set", json!({"time": 2.5})).unwrap();
+    assert_eq!(r["frame"], 75);
+    let fr = s.active_comp().unwrap().frame_rate;
+    assert_eq!(effectcraft_time::format_timecode_ae(75, fr, false), "0:00:02:15");
+    assert_eq!(effectcraft_time::format_timecode_ae(75, fr, true), "0;00;02;15");
+}
+
+#[test]
+fn separate_dimensions_split_and_rejoin() {
+    let (mut s, l) = setup();
+    animate(&mut s, l, "transform/position", &[(0.0, json!([0, 100])), (2.0, json!([200, 50]))]);
+    s.execute("prop.separateDimensions", json!({"layer": l})).unwrap();
+    let after = |s: &Session| {
+        let x = prop(s, l, "transform/positionX");
+        let y = prop(s, l, "transform/positionY");
+        assert_eq!(x.keys.len(), 2);
+        assert_eq!(y.keys[1].value, KV::Scalar(50.0));
+        // The layer still renders at the same place (render sees the separated values).
+        let cid = s.active_comp_id().unwrap();
+        let comp = s.project.comp(cid).unwrap();
+        let layer = &comp.layers[0];
+        let ctx = effectcraft_render::EvalCtx::new(&s.project, cid, comp, effectcraft_time::Tick::from_seconds_f64(1.0));
+        let p = ctx.value(layer, layer.transform().unwrap().get("position").unwrap()).as_vec3();
+        assert!((p[0] - 100.0).abs() < 1e-6 && (p[1] - 75.0).abs() < 1e-6, "{p:?}");
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert!(s.active_comp().unwrap().layers[0].transform().unwrap().get("positionX").is_none()));
+    // X and Y animate independently.
+    s.execute("keys.select", json!({"keys": []})).unwrap();
+    s.execute("prop.select", json!({"layer": l, "path": "transform/positionX"})).unwrap();
+    s.execute("keys.easyEase", json!({})).unwrap();
+    assert_eq!(prop(&s, l, "transform/positionY").keys[0].out_interp, Interp::Linear);
+    // Setting Position (viewer drags) writes X/Y.
+    s.execute("time.set", json!({"time": 3.0})).unwrap();
+    s.execute("prop.set", json!({"layer": l, "path": "transform/position", "value": [7, 8, 0]})).unwrap();
+    assert_eq!(prop(&s, l, "transform/positionX").keys.len(), 3);
+    // Re-join: one Position with keys at the union of times.
+    s.execute("prop.separateDimensions", json!({"layer": l})).unwrap();
+    let p = prop(&s, l, "transform/position");
+    assert_eq!(p.keys.len(), 3);
+    assert_eq!(p.keys[2].value, KV::Vec3([7.0, 8.0, 0.0]));
+    assert!(s.active_comp().unwrap().layers[0].transform().unwrap().get("positionX").is_none());
+}
+
+#[test]
+fn parenting_keeps_the_layer_in_place() {
+    let (mut s, child) = setup();
+    let r = s.execute("layer.newNull", json!({})).unwrap();
+    let par = r["layer"].as_u64().unwrap();
+    s.execute("prop.set", json!({"layer": par, "path": "transform/position", "value": [300, 200]})).unwrap();
+    s.execute("prop.set", json!({"layer": par, "path": "transform/rotation", "value": 90})).unwrap();
+    s.execute("prop.set", json!({"layer": par, "path": "transform/scale", "value": [200, 200]})).unwrap();
+    s.execute("prop.set", json!({"layer": child, "path": "transform/position", "value": [100, 50]})).unwrap();
+    let world = |s: &Session| {
+        let cid = s.active_comp_id().unwrap();
+        let comp = s.project.comp(cid).unwrap();
+        let l = comp.layer(effectcraft_project::LayerId(child)).unwrap();
+        let ctx = effectcraft_render::EvalCtx::new(&s.project, cid, comp, effectcraft_time::Tick::ZERO);
+        let (m, _) = ctx.layer_to_comp(l);
+        let a = m.apply(effectcraft_geom::vec2(50.0, 50.0));
+        let b = m.apply(effectcraft_geom::vec2(100.0, 50.0));
+        (a, (b.y - a.y).atan2(b.x - a.x).to_degrees(), (b.x - a.x).hypot(b.y - a.y))
+    };
+    let before = world(&s);
+    s.execute("layer.setParent", json!({"layers": [child], "parent": par})).unwrap();
+    let after = world(&s);
+    assert!((before.0.x - after.0.x).abs() < 1e-6 && (before.0.y - after.0.y).abs() < 1e-6, "{before:?} {after:?}");
+    assert!((before.1 - after.1).abs() < 1e-6 && (before.2 - after.2).abs() < 1e-6);
+    assert!((prop(&s, child, "transform/rotation").value.as_f64() + 90.0).abs() < 1e-9);
+    // Unparenting restores comp-space values.
+    s.execute("layer.setParent", json!({"layers": [child], "parent": null})).unwrap();
+    let p = prop(&s, child, "transform/position").value.as_vec3();
+    assert!((p[0] - 100.0).abs() < 1e-6 && (p[1] - 50.0).abs() < 1e-6, "{p:?}");
+    s.execute("edit.undo", json!({})).unwrap();
+    assert!(s.active_comp().unwrap().layer(effectcraft_project::LayerId(child)).unwrap().parent.is_some());
+}
+
+#[test]
+fn pick_whip_generates_ae_reference_expressions() {
+    let (mut s, l) = setup();
+    let r = s.execute("layer.newSolid", json!({"name": "Other", "color": "#00ff00"})).unwrap();
+    let o = r["layer"].as_u64().unwrap();
+    s.execute("effect.apply", json!({"layer": o, "effect": "Gaussian Blur"})).unwrap();
+    s.execute("layer.addMask", json!({"layer": o})).unwrap();
+    let cases = [
+        ("transform/opacity", json!({"layer": o, "path": "transform/opacity"}), "thisComp.layer(\"Other\").transform.opacity"),
+        ("transform/rotation", json!({"layer": l, "path": "transform/opacity"}), "transform.opacity"),
+        ("transform/rotation", json!({"layer": o, "path": "effects/#1/blurriness"}), "thisComp.layer(\"Other\").effect(\"Gaussian Blur\")(\"Blurriness\")"),
+        ("transform/opacity", json!({"layer": o, "path": "masks/#1/feather"}), "thisComp.layer(\"Other\").mask(\"Mask 1\").maskFeather[0]"),
+        ("transform/scale", json!({"layer": o, "path": "transform/rotation"}), "temp = thisComp.layer(\"Other\").transform.rotation;\n[temp, temp]"),
+        ("transform/position", json!({"layer": o, "path": "transform/position"}), "thisComp.layer(\"Other\").transform.position"),
+    ];
+    for (path, target, want) in cases {
+        let got = s.execute("prop.pickWhip", json!({"layer": l, "path": path, "target": target})).unwrap();
+        assert_eq!(got, json!(want));
+        assert_eq!(prop(&s, l, path).expr.unwrap().text, want);
+    }
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_ne!(prop(&s, l, "transform/position").expr.map(|e| e.text), Some("thisComp.layer(\"Other\").transform.position".into()));
+    assert!(s.execute("prop.pickWhip", json!({"layer": l, "path": "transform/opacity", "target": {"layer": l, "path": "transform/opacity"}})).is_err());
+}
+
+/// Outer comp (4 s) containing a precomp whose 10×10 white solid moves x = 10 + 20·t (t in s).
+/// Returns (session, precomp layer id in the outer comp).
+fn precomp_setup() -> (Session, u64) {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "Inner", "width": 100, "height": 100, "frameRate": 30, "duration": 4})).unwrap();
+    let r = s.execute("layer.newSolid", json!({"color": "#ffffff", "width": 10, "height": 10})).unwrap();
+    let l = r["layer"].as_u64().unwrap();
+    animate(&mut s, l, "transform/position", &[(0.0, json!([10, 50])), (4.0, json!([90, 50]))]);
+    s.execute("comp.new", json!({"name": "Outer", "width": 100, "height": 100, "frameRate": 30, "duration": 4})).unwrap();
+    let r = s.execute("layer.addItem", json!({"item": "Inner"})).unwrap();
+    let pl = r["layer"].as_u64().unwrap();
+    s.execute("layer.select", json!({"layers": [pl]})).unwrap();
+    (s, pl)
+}
+
+/// X of the moving square's centre in the outer comp at `t`.
+fn square_x(s: &Session, t: f64) -> f64 {
+    let cid = s.active_comp_id().unwrap();
+    let img = s.render(cid, effectcraft_time::Tick::from_seconds_f64(t), effectcraft_render::RenderOpts { scale: 1.0, ..Default::default() });
+    let xs: Vec<usize> = (0..img.width as usize).filter(|x| img.get(*x as i64, 50)[3] > 0.5).collect();
+    assert!(!xs.is_empty(), "nothing drawn at {t}");
+    (xs[0] + xs[xs.len() - 1]) as f64 / 2.0 + 0.5
+}
+
+#[test]
+fn time_remap_enable_freeze_and_disable() {
+    let (mut s, l) = precomp_setup();
+    assert!((square_x(&s, 1.0) - 30.0).abs() < 1.5);
+    s.execute("layer.enableTimeRemap", json!({})).unwrap();
+    let after = |s: &Session| {
+        let p = prop(s, l, "timeRemap");
+        assert_eq!(p.keys.len(), 2);
+        assert_eq!(p.keys[1].value, KV::Scalar(4.0));
+        // Remapping at identity shows the same frames.
+        assert!((square_x(s, 1.0) - 30.0).abs() < 1.5);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert!(s.active_comp().unwrap().layers[0].props.get("timeRemap").is_none()));
+    // Remap the first key to show source time 3 s at comp time 0.
+    s.execute("keys.set", json!({"layer": l, "path": "timeRemap", "time": 0.0, "value": 3.0})).unwrap();
+    assert!((square_x(&s, 0.0) - 70.0).abs() < 1.5, "{}", square_x(&s, 0.0));
+    // Freeze Frame at 2 s: one hold key; every frame shows source time 2 s.
+    s.execute("time.set", json!({"time": 2.0})).unwrap();
+    s.execute("keys.set", json!({"layer": l, "path": "timeRemap", "time": 0.0, "value": 0.0})).unwrap();
+    s.execute("layer.freezeFrame", json!({})).unwrap();
+    let p = prop(&s, l, "timeRemap");
+    assert_eq!(p.keys.len(), 1);
+    assert_eq!(p.keys[0].out_interp, Interp::Hold);
+    for t in [0.0, 1.0, 3.5] {
+        assert!((square_x(&s, t) - 50.0).abs() < 1.5, "{t}: {}", square_x(&s, t));
+    }
+    // Ctrl+Alt+T again disables remapping.
+    s.execute("layer.enableTimeRemap", json!({})).unwrap();
+    assert!((square_x(&s, 1.0) - 30.0).abs() < 1.5);
+    // Solids can't be remapped.
+    let r = s.execute("layer.newSolid", json!({"color": "#ff0000"})).unwrap();
+    assert!(s.execute("layer.enableTimeRemap", json!({"layers": [r["layer"]]})).is_err());
+}
+
+#[test]
+fn freeze_on_last_frame_extends_the_layer() {
+    let (mut s, l) = precomp_setup();
+    s.execute("layer.timing", json!({"layers": [l], "out": 2.0})).unwrap();
+    s.execute("layer.freezeOnLastFrame", json!({})).unwrap();
+    let layer = s.active_comp().unwrap().layers[0].clone();
+    assert_eq!(layer.out_point, s.active_comp().unwrap().duration);
+    // Plays normally, then holds the frame before the old out point.
+    assert!((square_x(&s, 1.0) - 30.0).abs() < 1.5);
+    let hold = 10.0 + 20.0 * (2.0 - 1.0 / 30.0);
+    assert!((square_x(&s, 3.5) - hold).abs() < 1.5, "{}", square_x(&s, 3.5));
+}
+
+#[test]
+fn time_reverse_layer_plays_backwards_and_round_trips() {
+    let (mut s, l) = precomp_setup();
+    let before = s.active_comp().unwrap().layers[0].clone();
+    s.execute("layer.timeReverse", json!({})).unwrap();
+    let after = |s: &Session| {
+        let ly = &s.active_comp().unwrap().layers[0];
+        assert_eq!(ly.stretch, -100.0);
+        assert_eq!((ly.in_point, ly.out_point), (before.in_point, before.out_point));
+        // First frame shows the last source frame; the end shows the start.
+        let last = 10.0 + 20.0 * (4.0 - 1.0 / 30.0);
+        assert!((square_x(s, 0.0) - last).abs() < 1.5, "{}", square_x(s, 0.0));
+        assert!((square_x(s, 4.0 - 1.0 / 30.0) - 10.0).abs() < 1.5);
+    };
+    undo_redo_roundtrip(&mut s, after, |s| assert_eq!(s.active_comp().unwrap().layers[0].stretch, 100.0));
+    // Reversing twice restores normal playback.
+    s.execute("layer.timeReverse", json!({"layers": [l]})).unwrap();
+    let ly = &s.active_comp().unwrap().layers[0];
+    assert_eq!(ly.stretch, 100.0);
+    assert_eq!(ly.start_time, before.start_time);
+    assert!((square_x(&s, 1.0) - 30.0).abs() < 1.5);
+}
+
+#[test]
+fn time_stretch_holds_in_current_or_out() {
+    let (mut s, l) = precomp_setup();
+    s.execute("layer.timeStretch", json!({"percent": 50})).unwrap();
+    let ly = s.active_comp().unwrap().layers[0].clone();
+    assert_eq!(ly.stretch, 50.0);
+    assert!((ly.out_point.seconds() - 2.0).abs() < 1e-6);
+    // Twice as fast: comp 1 s shows source 2 s.
+    assert!((square_x(&s, 1.0) - 50.0).abs() < 1.5);
+    s.execute("edit.undo", json!({})).unwrap();
+    // Hold the current frame (2 s) in place while doubling the duration.
+    s.execute("time.set", json!({"time": 2.0})).unwrap();
+    s.execute("layer.timeStretch", json!({"layers": [l], "duration": 8.0, "hold": "current"})).unwrap();
+    let ly = s.active_comp().unwrap().layers[0].clone();
+    assert!((ly.stretch - 200.0).abs() < 1e-6);
+    assert!((ly.in_point.seconds() + 2.0).abs() < 1e-6, "{}", ly.in_point.seconds());
+    assert!((square_x(&s, 2.0) - 50.0).abs() < 1.5);
+    // Hold the out point.
+    s.execute("edit.undo", json!({})).unwrap();
+    s.execute("layer.timeStretch", json!({"layers": [l], "percent": 50, "hold": "out"})).unwrap();
+    let ly = s.active_comp().unwrap().layers[0].clone();
+    assert!((ly.out_point.seconds() - 4.0).abs() < 1e-6 && (ly.in_point.seconds() - 2.0).abs() < 1e-6);
+    assert!(s.execute("layer.timeStretch", json!({"layers": [l], "percent": 0})).is_err());
+}