diff --git a/crates/engine/src/commands/file.rs b/crates/engine/src/commands/file.rs
index 74ec861e..5825eac2 100644
--- a/crates/engine/src/commands/file.rs
+++ b/crates/engine/src/commands/file.rs
@@ -245,6 +245,8 @@ struct PendingImport {
     comps: Vec<u64>,
     items: Vec<u64>,
     errors: Vec<String>,
+    /// EffectCraft projects merged in (`file.importProject` results); never added to a comp.
+    projects: Vec<Value>,
 }
 
 /// Everything probing a file needs, apart from the session (it can run on a background thread).
@@ -370,10 +372,18 @@ fn prepare_import(s: &mut Session, p: &Value) -> Result<PendingImport> {
             _ => return Err(bad("file.import", "page: a page number from 1")),
         },
     };
-    let mut paths = paths;
     let mut comps = vec![];
     let mut items = vec![];
     let mut errors = vec![];
+    // EffectCraft projects import as projects, as After Effects imports an .aep.
+    let (project_paths, mut paths): (Vec<String>, Vec<String>) = paths.into_iter().partition(|x| super::import_project::is_project_path(x));
+    let mut projects = vec![];
+    for path in project_paths {
+        match s.execute("file.importProject", json!({"path": path})) {
+            Ok(r) => projects.push(r),
+            Err(e) => errors.push(format!("{path}: {e}")),
+        }
+    }
     if let Some(retain) = retain {
         let mut rest = vec![];
         for path in paths {
@@ -424,13 +434,13 @@ fn prepare_import(s: &mut Session, p: &Value) -> Result<PendingImport> {
         page,
         psd_layer: p.get("layer").cloned(),
     };
-    Ok(PendingImport { sources, prober, comps, items, errors })
+    Ok(PendingImport { sources, prober, comps, items, errors, projects })
 }
 
 /// The last part of an import: add the probed files to the project (one undo step) and select
 /// everything the import made, so the Project panel shows it.
 fn add_footage(s: &mut Session, pending: PendingImport, probed: Vec<std::result::Result<Probed, String>>) -> Result<Value> {
-    let PendingImport { comps, mut items, mut errors, .. } = pending;
+    let PendingImport { comps, mut items, mut errors, projects, .. } = pending;
     let mut found = vec![];
     let mut warnings = vec![];
     for r in probed {
@@ -482,7 +492,11 @@ fn add_footage(s: &mut Session, pending: PendingImport, probed: Vec<std::result:
     if let Some(first) = asked.first() {
         s.events.push(crate::Event::Frontend { command: "file.interpretFootage".into(), params: json!({"item": first, "reason": "unlabeledAlpha"}) });
     }
-    Ok(json!({"items": items, "comps": comps, "errors": errors, "warnings": warnings, "unlabeledAlpha": asked}))
+    let mut out = json!({"items": items, "comps": comps, "errors": errors, "warnings": warnings, "unlabeledAlpha": asked});
+    if !projects.is_empty() {
+        out["projects"] = Value::Array(projects);
+    }
+    Ok(out)
 }
 
 /// Whether a file format states how its alpha is stored (PNG, GIF, WebP and PSD are straight by
diff --git a/crates/engine/src/commands/import_project.rs b/crates/engine/src/commands/import_project.rs
new file mode 100644
index 00000000..f0474ee8
--- /dev/null
+++ b/crates/engine/src/commands/import_project.rs
@@ -0,0 +1,143 @@
+//! File ▸ Import ▸ EffectCraft Project: merge another `.ecproj` (or its XML copy) into the
+//! current project, as After Effects imports an `.aep` into the open project. The imported
+//! items land in a folder named after the file; every id is shifted past the current project's
+//! so nothing collides, and the whole import is one undo step.
+
+use effectcraft_color::Label;
+use effectcraft_project::{ItemId, ItemKind, LayerSource, Project, essential};
+use serde_json::{Value, json};
+
+use super::{CommandSpec, always, bad, str_p};
+use crate::{EngineError, Result, Session, cmd};
+
+const C: &str = "file.importProject";
+
+/// Whether `path` names a project EffectCraft imports as a project (not as footage).
+pub(crate) fn is_project_path(path: &str) -> bool {
+    let lower = path.to_ascii_lowercase();
+    lower.ends_with(".ecproj") || lower.ends_with(".ecprojx")
+}
+
+/// Read a project file (JSON or its XML copy), as File ▸ Open does.
+fn read_project(s: &Session, path: &str) -> Result<(Project, Option<String>)> {
+    let bytes = s.services.read_file(path).map_err(|e| EngineError::Other(format!("cannot read {path}: {e}")))?;
+    let text = String::from_utf8(bytes).map_err(|_| bad(C, format!("{path} is not a text project file")))?;
+    let text = if crate::xml_project::is_xml(&text) { crate::xml_project::from_xml(&text).map_err(EngineError::Other)? } else { text };
+    let project = Project::from_json(&text).map_err(|e| bad(C, format!("{path} is not a project EffectCraft can open: {e}")))?;
+    Ok((project, effectcraft_project::saved_by(&text)))
+}
+
+/// Footage paths relative to the imported project's folder become absolute when the file is
+/// there; returns the footage paths that are missing.
+fn resolve_footage(s: &Session, project: &mut Project, dir: &std::path::Path) -> Vec<String> {
+    let services = s.services.clone();
+    let resolve = |raw: &mut String| -> bool {
+        if raw.is_empty() || services.exists(raw) {
+            return true;
+        }
+        if std::path::Path::new(raw.as_str()).is_absolute() {
+            return false;
+        }
+        let joined = dir.join(raw.as_str()).to_string_lossy().to_string();
+        if services.exists(&joined) {
+            *raw = joined;
+            true
+        } else {
+            false
+        }
+    };
+    let mut missing = vec![];
+    for it in project.items.values_mut() {
+        if let ItemKind::Footage(f) = &mut it.kind {
+            if f.sequence.is_empty() {
+                if !resolve(&mut f.path) {
+                    missing.push(f.path.clone());
+                }
+            } else {
+                let mut all = true;
+                for frame in &mut f.sequence {
+                    all &= resolve(frame);
+                }
+                if !all {
+                    missing.push(f.path.clone());
+                }
+            }
+        }
+    }
+    missing
+}
+
+/// The comps no other comp of `project` nests: the ones to open or place.
+fn root_comps(project: &Project) -> Vec<ItemId> {
+    let nested: std::collections::HashSet<ItemId> =
+        project.comps().flat_map(|(_, c)| c.layers.iter().filter_map(|l| if let LayerSource::Comp { item } = l.source { Some(item) } else { None })).collect();
+    project.comps().map(|(id, _)| *id).filter(|id| !nested.contains(id)).collect()
+}
+
+fn import_project(s: &mut Session, p: &Value) -> Result<Value> {
+    let path = str_p(p, "path").ok_or_else(|| bad(C, "missing `path` (.ecproj)"))?.to_string();
+    let (mut sub, saved_by) = read_project(s, &path)?;
+    crate::upgrade_effects(&mut sub);
+    let file = std::path::Path::new(&path);
+    let dir = file.parent().map(|d| d.to_path_buf()).unwrap_or_default();
+    let missing = resolve_footage(s, &mut sub, &dir);
+    // The imported project's own render queue stays behind (as for templates).
+    let base = s.project.next_id;
+    if sub.next_id.checked_add(base).is_none() {
+        return Err(bad(C, format!("{path} has ids out of range")));
+    }
+    essential::offset_ids(&mut sub, base);
+    let roots: Vec<ItemId> = root_comps(&sub);
+    let folder_name = file.file_name().map(|n| n.to_string_lossy().to_string()).unwrap_or_else(|| "Imported Project".into());
+    let (folder, items) = s.edit("Import Project", None, |proj, st| {
+        let folder = proj.add_item(&folder_name, Label::Yellow, None, ItemKind::Folder);
+        let mut items = vec![];
+        for (id, mut it) in std::mem::take(&mut sub.items) {
+            if it.parent.is_none() {
+                it.parent = Some(folder);
+            }
+            items.push(id.0);
+            proj.items.insert(id, it);
+        }
+        proj.next_id = proj.next_id.max(sub.next_id);
+        proj.fix_next_id();
+        st.project_selection = vec![folder];
+        Ok((folder, items))
+    })?;
+    let comps: Vec<Value> = s
+        .project
+        .comps()
+        .filter(|(id, _)| items.contains(&id.0))
+        .map(|(id, _)| json!({"id": id.0, "name": s.project.item(*id).map(|i| i.name.clone()).unwrap_or_default()}))
+        .collect();
+    let primary = if let [one] = roots.as_slice() { Some(one.0) } else { None };
+    let mut warnings = vec![];
+    if let Some(v) = saved_by.as_deref().filter(|v| effectcraft_project::is_newer_version(v, effectcraft_project::APP_VERSION)) {
+        warnings.push(format!("saved by EffectCraft {v}, newer than this version ({})", effectcraft_project::APP_VERSION));
+    }
+    if !missing.is_empty() {
+        warnings.push(format!("{} footage file{} missing", missing.len(), if missing.len() == 1 { " is" } else { "s are" }));
+    }
+    s.toast(if warnings.is_empty() { format!("Imported {folder_name}") } else { format!("Imported {folder_name}: {}", warnings.join("; ")) });
+    Ok(json!({
+        "folder": folder.0,
+        "items": items,
+        "comps": comps,
+        "rootComps": roots.iter().map(|id| id.0).collect::<Vec<_>>(),
+        "primaryComp": primary,
+        "missingMedia": missing,
+        "warnings": warnings,
+    }))
+}
+
+pub fn specs() -> Vec<CommandSpec> {
+    vec![cmd!(
+        "file.importProject",
+        "EffectCraft Project...",
+        ["File", "Import"],
+        None,
+        "{path (.ecproj or .ecprojx)} — merges the project into a folder named after the file; returns {folder, items, comps, rootComps, primaryComp (the only root comp, else null), missingMedia, warnings}",
+        always,
+        import_project
+    )]
+}
diff --git a/crates/engine/src/commands/mod.rs b/crates/engine/src/commands/mod.rs
index 99b2d642..d3873e47 100644
--- a/crates/engine/src/commands/mod.rs
+++ b/crates/engine/src/commands/mod.rs
@@ -26,6 +26,7 @@ pub mod footage_panel;
 pub(crate) mod frame_export;
 mod frontend;
 mod help;
+mod import_project;
 mod key_labels;
 mod key_transform;
 mod keys_more;
@@ -193,6 +194,7 @@ pub fn command_specs() -> &'static [CommandSpec] {
         v.extend(file_more::specs());
         v.extend(relink::specs());
         v.extend(lottie::specs());
+        v.extend(import_project::specs());
         v.extend(timeline::specs());
         v.extend(comp_more::specs());
         v.extend(frame_export::specs());
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index a6243e44..c59bad27 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -1132,6 +1132,8 @@ mod tests_frame_export;
 #[cfg(test)]
 mod tests_fuzz_open;
 #[cfg(test)]
+mod tests_import_project;
+#[cfg(test)]
 mod tests_key_metadata_order;
 #[cfg(test)]
 mod tests_keylight;
diff --git a/crates/engine/src/menus.rs b/crates/engine/src/menus.rs
index bd1cffb0..e28b92e5 100644
--- a/crates/engine/src/menus.rs
+++ b/crates/engine/src/menus.rs
@@ -528,6 +528,7 @@ File
     File... | file.import
     Multiple Files... | file.importMultiple
     Adobe Premiere Pro Project... | file.importTimeline
+    EffectCraft Project... | file.importProject
     Placeholder... | file.importPlaceholder
     Solid... | file.importSolid
     Lottie... | file.importLottie
diff --git a/crates/engine/src/tests_import_project.rs b/crates/engine/src/tests_import_project.rs
new file mode 100644
index 00000000..6aa52b41
--- /dev/null
+++ b/crates/engine/src/tests_import_project.rs
@@ -0,0 +1,158 @@
+//! File ▸ Import ▸ EffectCraft Project: another project merges into the open one with fresh ids,
+//! its references intact, in one undo step.
+
+use std::collections::HashSet;
+
+use effectcraft_project::{Footage, FootageKind, ItemId, ItemKind, LayerSource, Project};
+use serde_json::json;
+
+use crate::Session;
+
+fn out_dir(name: &str) -> std::path::PathBuf {
+    let d = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("../../target/test-out").join(name);
+    let _ = std::fs::remove_dir_all(&d);
+    std::fs::create_dir_all(&d).unwrap();
+    d
+}
+
+/// Every item, layer and property uid of `p` (they share one counter).
+fn all_ids(p: &Project) -> Vec<u64> {
+    let mut v = vec![];
+    for (id, it) in &p.items {
+        v.push(id.0);
+        if let ItemKind::Comp(c) = &it.kind {
+            for l in &c.layers {
+                v.push(l.id.0);
+                fn uids(g: &effectcraft_project::PropGroup, v: &mut Vec<u64>) {
+                    v.push(g.uid);
+                    for c in &g.children {
+                        match c {
+                            effectcraft_project::Node::Prop(p) => v.push(p.uid),
+                            effectcraft_project::Node::Group(g) => uids(g, v),
+                        }
+                    }
+                }
+                uids(&l.props, &mut v);
+            }
+        }
+    }
+    v
+}
+
+/// A project with "Main" nesting "Inner" under a parented null, a data file next to it by a
+/// relative path and a footage file that's gone. Saved as `<dir>/Library Card.ecproj`.
+fn source_project(dir: &std::path::Path) -> String {
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"name": "Inner", "width": 64, "height": 64, "frameRate": 30, "duration": 2})).unwrap();
+    let inner = s.active_comp_id().unwrap();
+    s.execute("layer.newSolid", json!({"name": "Fill", "color": "#ff0000"})).unwrap();
+    s.execute("comp.new", json!({"name": "Main", "width": 64, "height": 64, "frameRate": 30, "duration": 2})).unwrap();
+    let main = s.active_comp_id().unwrap();
+    let nest = s.execute("layer.addItem", json!({"comp": main.0, "item": inner.0, "time": 0.0})).unwrap()["layer"].as_u64().unwrap();
+    let rig = s.execute("layer.newNull", json!({"name": "Rig"})).unwrap()["layer"].as_u64().unwrap();
+    s.execute("layer.setParent", json!({"layers": [nest], "parent": rig})).unwrap();
+    std::fs::write(dir.join("data.json"), b"{\"v\": 1}").unwrap();
+    let p = std::sync::Arc::make_mut(&mut s.project);
+    p.add_item("data.json", Default::default(), None, ItemKind::Footage(Footage { path: "data.json".into(), kind: FootageKind::Data, ..Default::default() }));
+    p.add_item(
+        "gone.mov",
+        Default::default(),
+        None,
+        ItemKind::Footage(Footage { path: "/offline/gone.mov".into(), kind: FootageKind::Video, ..Default::default() }),
+    );
+    let path = dir.join("Library Card.ecproj").to_string_lossy().to_string();
+    s.execute("file.saveAs", json!({"path": path})).unwrap();
+    path
+}
+
+#[test]
+fn import_project_merges_with_fresh_ids_and_one_undo() {
+    let dir = out_dir("import-project");
+    let path = source_project(&dir);
+
+    let mut t = Session::default();
+    t.execute("comp.new", json!({"name": "Show", "width": 64, "height": 64, "frameRate": 30, "duration": 2})).unwrap();
+    t.execute("layer.newSolid", json!({"name": "Back", "color": "#00ff00"})).unwrap();
+    let before = t.project.items.len();
+    let before_ids: HashSet<u64> = all_ids(&t.project).into_iter().collect();
+
+    let r = t.execute("file.importProject", json!({"path": path})).unwrap();
+    let folder = ItemId(r["folder"].as_u64().unwrap());
+    assert_eq!(t.project.item(folder).unwrap().name, "Library Card.ecproj");
+    // Inner, Main, the Solids folder and its solid, two footage items, and the new folder.
+    assert_eq!(t.project.items.len(), before + 7);
+    let imported: Vec<ItemId> = r["items"].as_array().unwrap().iter().map(|v| ItemId(v.as_u64().unwrap())).collect();
+    // Everything lands in the folder (the Solids folder keeps its solid).
+    let top = |mut id: ItemId| {
+        while let Some(up) = t.project.item(id).and_then(|i| i.parent).filter(|p| *p != folder) {
+            id = up;
+        }
+        t.project.item(id).and_then(|i| i.parent)
+    };
+    assert!(imported.iter().all(|id| top(*id) == Some(folder)), "everything lands in the folder");
+
+    // No id is taken twice, and none of the open project's ids moved.
+    let ids = all_ids(&t.project);
+    let unique: HashSet<u64> = ids.iter().copied().collect();
+    assert_eq!(ids.len(), unique.len(), "ids collide");
+    assert!(before_ids.is_subset(&unique));
+    assert!(t.project.next_id > *ids.iter().max().unwrap());
+
+    // References follow the new ids: Main nests the imported Inner, under the imported null.
+    let main = ItemId(r["primaryComp"].as_u64().unwrap());
+    assert_eq!(t.project.item(main).unwrap().name, "Main");
+    assert_eq!(r["rootComps"], json!([main.0]));
+    let comp = t.project.comp(main).unwrap();
+    let nest = comp.layers.iter().find(|l| matches!(l.source, LayerSource::Comp { .. })).unwrap();
+    let LayerSource::Comp { item } = nest.source else { panic!("a precomp layer") };
+    assert_eq!(t.project.item(item).unwrap().name, "Inner");
+    assert!(imported.contains(&item));
+    let parent = nest.parent.unwrap();
+    assert_eq!(comp.layer(parent).unwrap().name, "Rig");
+
+    // A relative footage path resolves next to the imported project; a missing one is reported.
+    let data = t.project.items.values().find(|i| i.name == "data.json").unwrap();
+    let ItemKind::Footage(f) = &data.kind else { panic!("footage") };
+    assert_eq!(std::path::Path::new(&f.path), dir.join("data.json"));
+    assert_eq!(r["missingMedia"], json!(["/offline/gone.mov"]));
+
+    // One undo step removes all of it; redo brings it back.
+    t.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(t.project.items.len(), before);
+    t.execute("edit.redo", json!({})).unwrap();
+    assert_eq!(t.project.items.len(), before + 7);
+
+    // Importing again keeps the copies apart, and File ▸ Import routes .ecproj here.
+    let r2 = t.execute("file.import", json!({"paths": [path]})).unwrap();
+    let again = &r2["projects"][0];
+    assert_ne!(again["primaryComp"], r["primaryComp"]);
+    assert!(r2["items"].as_array().unwrap().is_empty(), "a project is not footage");
+    let ids = all_ids(&t.project);
+    assert_eq!(ids.len(), ids.iter().copied().collect::<HashSet<_>>().len());
+}
+
+#[test]
+fn import_project_rejects_bad_files_and_leaves_the_project() {
+    let dir = out_dir("import-project-bad");
+    let mut t = Session::default();
+    t.execute("comp.new", json!({"name": "Show", "width": 64, "height": 64, "frameRate": 30, "duration": 2})).unwrap();
+    let before = t.project.items.len();
+
+    std::fs::write(dir.join("junk.ecproj"), b"not a project").unwrap();
+    assert!(t.execute("file.importProject", json!({"path": dir.join("junk.ecproj").to_string_lossy()})).is_err());
+    assert!(t.execute("file.importProject", json!({"path": dir.join("absent.ecproj").to_string_lossy()})).is_err());
+
+    // Regression: an id at the top of the range saturated instead of overflowing (opening and
+    // importing must not panic), and the import refuses it.
+    let mut p = Project::default();
+    let id = p.add_item("Huge", Default::default(), None, ItemKind::Folder);
+    let mut it = p.items.remove(&id).unwrap();
+    it.id = ItemId(u64::MAX);
+    p.items.insert(it.id, it);
+    let huge = dir.join("huge.ecproj");
+    std::fs::write(&huge, p.to_json()).unwrap();
+    assert_eq!(Project::from_json(&p.to_json()).unwrap().next_id, u64::MAX);
+    let e = t.execute("file.importProject", json!({"path": huge.to_string_lossy()})).unwrap_err();
+    assert!(e.to_string().contains("out of range"), "{e}");
+    assert_eq!(t.project.items.len(), before);
+}
diff --git a/crates/project/src/essential.rs b/crates/project/src/essential.rs
index fcf2cfb3..77859c63 100644
--- a/crates/project/src/essential.rs
+++ b/crates/project/src/essential.rs
@@ -701,13 +701,13 @@ pub fn with_overrides(project: &Project, comp: ItemId, overrides: &[Override]) -
 // ------------------------------------------------------------------------------ id remapping
 
 /// Shift every id (items, layers, property uids, Essential Graphics controls) of `p` by
-/// `offset`, keeping all references consistent: used when merging a template project into
-/// another project.
+/// `offset`, keeping all references consistent: used when merging a template or another project
+/// into a project. Ids from a damaged file saturate instead of overflowing.
 pub fn offset_ids(p: &mut Project, offset: u64) {
     let items = std::mem::take(&mut p.items);
     for (_, mut it) in items {
-        it.id = ItemId(it.id.0 + offset);
-        it.parent = it.parent.map(|f| ItemId(f.0 + offset));
+        it.id = ItemId(it.id.0.saturating_add(offset));
+        it.parent = it.parent.map(|f| ItemId(f.0.saturating_add(offset)));
         if let ItemKind::Comp(c) = &mut it.kind {
             let c = std::sync::Arc::make_mut(c);
             for l in &mut c.layers {
@@ -716,18 +716,18 @@ pub fn offset_ids(p: &mut Project, offset: u64) {
             if let Some(eg) = &mut c.essential {
                 fn go(v: &mut [EgControl], o: u64) {
                     for c in v {
-                        c.id += o;
+                        c.id = c.id.saturating_add(o);
                         match &mut c.kind {
                             EgKind::Property { layer, prop, links } => {
-                                *layer = LayerId(layer.0 + o);
-                                *prop += o;
+                                *layer = LayerId(layer.0.saturating_add(o));
+                                *prop = prop.saturating_add(o);
                                 for k in links {
-                                    k.layer = LayerId(k.layer.0 + o);
-                                    k.prop += o;
+                                    k.layer = LayerId(k.layer.0.saturating_add(o));
+                                    k.prop = k.prop.saturating_add(o);
                                 }
                             }
-                            EgKind::Mirror { of } => *of += o,
-                            EgKind::Media { layer } => *layer = LayerId(layer.0 + o),
+                            EgKind::Mirror { of } => *of = of.saturating_add(o),
+                            EgKind::Media { layer } => *layer = LayerId(layer.0.saturating_add(o)),
                             EgKind::Group { children } => go(children, o),
                             EgKind::Comment { .. } => {}
                         }
@@ -739,34 +739,43 @@ pub fn offset_ids(p: &mut Project, offset: u64) {
         p.items.insert(it.id, it);
     }
     p.render_queue.clear();
-    p.next_id += offset;
+    p.next_id = p.next_id.saturating_add(offset);
 }
 
 fn offset_layer(l: &mut Layer, o: u64) {
-    l.id = LayerId(l.id.0 + o);
-    l.parent = l.parent.map(|x| LayerId(x.0 + o));
+    l.id = LayerId(l.id.0.saturating_add(o));
+    l.parent = l.parent.map(|x| LayerId(x.0.saturating_add(o)));
     if let Some(tm) = &mut l.track_matte {
-        tm.layer = LayerId(tm.layer.0 + o);
+        tm.layer = LayerId(tm.layer.0.saturating_add(o));
     }
     match &mut l.source {
-        LayerSource::Footage { item } | LayerSource::Comp { item } | LayerSource::Solid { item } | LayerSource::Model { item } => *item = ItemId(item.0 + o),
+        LayerSource::Footage { item } | LayerSource::Comp { item } | LayerSource::Solid { item } | LayerSource::Model { item } => {
+            *item = ItemId(item.0.saturating_add(o))
+        }
         _ => {}
     }
     fn group(g: &mut PropGroup, o: u64, essential_parent: bool) {
-        g.uid += o;
-        if let GroupKind::Essential { overridden } = &mut g.kind {
-            for u in overridden.iter_mut() {
-                *u += o;
+        g.uid = g.uid.saturating_add(o);
+        match &mut g.kind {
+            GroupKind::Essential { overridden } => {
+                for u in overridden.iter_mut() {
+                    *u = u.saturating_add(o);
+                }
             }
+            // A tracker's Motion Target is a layer of the same comp.
+            GroupKind::Tracker { settings } => {
+                settings.target = settings.target.map(|t| LayerId(t.0.saturating_add(o)));
+            }
+            _ => {}
         }
         let is_essential = matches!(g.kind, GroupKind::Essential { .. }) || essential_parent;
         for c in &mut g.children {
             match c {
                 Node::Prop(p) => {
-                    p.uid += o;
+                    p.uid = p.uid.saturating_add(o);
                     let fix = |v: &mut Value| {
                         if let Value::Layer(Some(id)) = v {
-                            *id += o;
+                            *id = id.saturating_add(o);
                         }
                     };
                     fix(&mut p.value);
@@ -774,7 +783,7 @@ fn offset_layer(l: &mut Layer, o: u64) {
                         fix(&mut k.value);
                     }
                     if is_essential && control_of(&p.match_id).is_some() {
-                        p.match_id = match_id(control_of(&p.match_id).unwrap_or(0) + o);
+                        p.match_id = match_id(control_of(&p.match_id).unwrap_or(0).saturating_add(o));
                         // Media replacement values are item ids.
                         if matches!(p.ui, ParamUi::Hidden)
                             && let Value::Scalar(x) = &mut p.value
@@ -785,7 +794,7 @@ fn offset_layer(l: &mut Layer, o: u64) {
                 }
                 Node::Group(sub) => {
                     if is_essential && let Some(id) = control_of(&sub.match_id) {
-                        sub.match_id = match_id(id + o);
+                        sub.match_id = match_id(id.saturating_add(o));
                     }
                     group(sub, o, is_essential);
                 }
diff --git a/crates/project/src/lib.rs b/crates/project/src/lib.rs
index fee3b8ce..aaf155f3 100644
--- a/crates/project/src/lib.rs
+++ b/crates/project/src/lib.rs
@@ -1394,10 +1394,11 @@ impl Project {
     pub fn fix_next_id(&mut self) {
         let mut m = self.next_id;
         for (id, it) in &self.items {
-            m = m.max(id.0 + 1);
+            // Saturating: a damaged file's ids must not overflow (the import then refuses it).
+            m = m.max(id.0.saturating_add(1));
             if let ItemKind::Comp(c) = &it.kind {
                 for l in &c.layers {
-                    m = m.max(l.id.0 + 1).max(l.props.max_uid() + 1);
+                    m = m.max(l.id.0.saturating_add(1)).max(l.props.max_uid().saturating_add(1));
                 }
             }
         }
diff --git a/crates/ui-egui/src/i18n.rs b/crates/ui-egui/src/i18n.rs
index 4e814ea2..b07ac4d7 100644
--- a/crates/ui-egui/src/i18n.rs
+++ b/crates/ui-egui/src/i18n.rs
@@ -303,6 +303,7 @@ const SIMPLIFIED_CHINESE: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "文件..."),
     ("file.importMultiple", "Multiple Files...", "多个文件..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Adobe Premiere Pro 项目..."),
+    ("file.importProject", "EffectCraft Project...", "EffectCraft 项目..."),
     ("file.importPlaceholder", "Placeholder...", "占位符..."),
     ("file.importSolid", "Solid...", "纯色..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -933,6 +934,7 @@ const TRADITIONAL_CHINESE: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "檔案..."),
     ("file.importMultiple", "Multiple Files...", "多個檔案..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Adobe Premiere Pro 專案..."),
+    ("file.importProject", "EffectCraft Project...", "EffectCraft 專案..."),
     ("file.importPlaceholder", "Placeholder...", "預留位置..."),
     ("file.importSolid", "Solid...", "純色..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -1563,6 +1565,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("file.importPlaceholder", "Placeholder...", "プレースホルダー..."),
     ("file.importSolid", "Solid...", "平面..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
+    ("file.importProject", "EffectCraft Project...", "EffectCraftプロジェクト..."),
     ("file.importVanishingPoint", "Vanishing Point (.vpe)...", "Vanishing Point (.vpe)..."),
     ("essential.importTemplate", "Essential Graphics Template...", "エッセンシャルグラフィックステンプレート..."),
     ("", "Import Recent Footage", "最近使用したフッテージを読み込み"),
@@ -2190,6 +2193,7 @@ const UKRAINIAN: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Файл..."),
     ("file.importMultiple", "Multiple Files...", "Кілька файлів..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Проєкт Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Проєкт EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Заповнювач..."),
     ("file.importSolid", "Solid...", "Суцільний колір..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -2821,6 +2825,7 @@ const SPANISH: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Archivo..."),
     ("file.importMultiple", "Multiple Files...", "Varios archivos..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Proyecto de Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Proyecto de EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Marcador de posición..."),
     ("file.importSolid", "Solid...", "Sólido..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -3450,6 +3455,7 @@ const PORTUGUESE: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Arquivo..."),
     ("file.importMultiple", "Multiple Files...", "Vários arquivos..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Projeto do Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Projeto do EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Espaço reservado..."),
     ("file.importSolid", "Solid...", "Sólido..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -4087,6 +4093,7 @@ const RUSSIAN: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Файл..."),
     ("file.importMultiple", "Multiple Files...", "Несколько файлов..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Проект Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Проект EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Заполнитель..."),
     ("file.importSolid", "Solid...", "Сплошной цвет..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -4716,6 +4723,7 @@ const FRENCH: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Fichier..."),
     ("file.importMultiple", "Multiple Files...", "Plusieurs fichiers..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Projet Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Projet EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Espace réservé..."),
     ("file.importSolid", "Solid...", "Solide..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -5345,6 +5353,7 @@ const GERMAN: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Datei..."),
     ("file.importMultiple", "Multiple Files...", "Mehrere Dateien..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Adobe Premiere Pro-Projekt..."),
+    ("file.importProject", "EffectCraft Project...", "EffectCraft-Projekt..."),
     ("file.importPlaceholder", "Placeholder...", "Platzhalter..."),
     ("file.importSolid", "Solid...", "Farbfläche..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
@@ -5974,6 +5983,7 @@ const CZECH: &[(&str, &str, &str)] = &[
     ("file.import", "File...", "Soubor..."),
     ("file.importMultiple", "Multiple Files...", "Více souborů..."),
     ("file.importTimeline", "Adobe Premiere Pro Project...", "Projekt Adobe Premiere Pro..."),
+    ("file.importProject", "EffectCraft Project...", "Projekt EffectCraft..."),
     ("file.importPlaceholder", "Placeholder...", "Zástupný záznam..."),
     ("file.importSolid", "Solid...", "Plná vrstva..."),
     ("file.importLottie", "Lottie...", "Lottie..."),
diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index b10b0e31..c21f5595 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -1239,6 +1239,7 @@ fn file_dialog(app: &mut EffectcraftApp, id: &str, params: &Value) -> Option<Res
         "view.importGuides" => ("path", Ask::Open(&["json"])),
         "file.exportLottie" => ("path", Ask::Save("Animation.json")),
         "file.importLottie" => ("path", Ask::Open(&["json", "lottie"])),
+        "file.importProject" => ("path", Ask::Open(&["ecproj", "ecprojx"])),
         "file.importTimeline" => ("path", Ask::Open(&["xml", "fcpxml", "otio", "edl", "aaf", "omf"])),
         "render.saveCurrentPreview" => ("path", Ask::Save("Preview.mp4")),
         "file.runScript" if params.get("name").is_none() => ("path", Ask::Open(&["jsx", "js", "jsonl", "json", "txt"])),
diff --git a/docs/parity-log.md b/docs/parity-log.md
new file mode 100644
index 00000000..22319e6e
--- /dev/null
+++ b/docs/parity-log.md
@@ -0,0 +1,13 @@
+
+## Update: File ▸ Import ▸ EffectCraft Project
+
+- **Import a project into a project**, as After Effects imports an `.aep`:
+  `file.importProject {path}` (File ▸ Import ▸ EffectCraft Project..., and `.ecproj` /
+  `.ecprojx` files given to File ▸ Import) merges the project into a folder named after the
+  file. Every item, layer and property id moves past the open project's, so references
+  (precomps, parents, track mattes, Layer Control values, Essential Graphics, tracker
+  targets) stay intact. It's one undo step. Footage paths relative to the imported project
+  resolve next to it. The result lists the comps, the root comps, `primaryComp` (the only
+  root comp) and missing media.
+- Id shifting saturates instead of overflowing on damaged files, for both templates and
+  projects.