diff --git a/crates/engine/src/analysis/models.rs b/crates/engine/src/analysis/models.rs
index 9ff8a5ca7..8d45b5473 100644
--- a/crates/engine/src/analysis/models.rs
+++ b/crates/engine/src/analysis/models.rs
@@ -449,9 +449,17 @@ fn install_bytes(dir: &Path, m: &ModelInfo, bytes: &[u8]) -> std::result::Result
     Ok(path)
 }
 
+fn models_for_platform(task: Task, wasm: bool) -> impl Iterator<Item = &'static ModelInfo> {
+    seg::models(task).filter(move |m| !wasm || !m.id.starts_with("sam2.1-hiera-"))
+}
+
+fn target_models(task: Task) -> impl Iterator<Item = &'static ModelInfo> {
+    models_for_platform(task, cfg!(target_arch = "wasm32"))
+}
+
 fn model_p(p: &Value, cmd: &str, task: Task) -> Result<&'static ModelInfo> {
     let id = str_p(p, "id").ok_or_else(|| bad(cmd, "missing `id`"))?;
-    seg::info(id).filter(|m| m.task == task).ok_or_else(|| bad(cmd, format!("unknown model `{id}` (see {}.models)", kind(task).prefix)))
+    target_models(task).find(|m| m.id == id).ok_or_else(|| bad(cmd, format!("unknown model `{id}` (see {}.models)", kind(task).prefix)))
 }
 
 fn list(s: &mut Session, task: Task) -> Result<Value> {
@@ -467,7 +475,7 @@ fn list(s: &mut Session, task: Task) -> Result<Value> {
         "selected": chosen == seg::CLASSICAL,
         "active": st.active.is_none(),
     })];
-    for m in seg::models(task) {
+    for m in target_models(task) {
         #[cfg(not(target_arch = "wasm32"))]
         let (recommended, hint) = (effectcraft_sam2::mask::recommended().id == m.id, effectcraft_sam2::mask::hint(m.id));
         #[cfg(target_arch = "wasm32")]
@@ -528,7 +536,9 @@ fn install(s: &mut Session, p: &Value, task: Task) -> Result<Value> {
         Some(_) => model_p(p, &cmd, task)?,
         None => {
             let h = seg::sha256::hex(&bytes);
-            seg::models(task).find(|m| m.sha256 == h).ok_or_else(|| bad(&cmd, "this file is not a published model in the registry (SHA-256 differs)"))?
+            target_models(task)
+                .find(|m| m.sha256 == h)
+                .ok_or_else(|| bad(&cmd, "this file is not a supported published model in the registry (SHA-256 differs)"))?
         }
     };
     let dest = install_bytes(&dir, m, &bytes).map_err(|e| bad(&cmd, e))?;
@@ -652,3 +662,19 @@ pub fn specs() -> Vec<CommandSpec> {
         cmd!("face.model.remove", "Remove Face Tracking Model", [], None, "{id}", always, |s, p| remove(s, p, Task::Face)),
     ]
 }
+
+#[cfg(test)]
+mod availability_tests {
+    use super::*;
+
+    #[test]
+    fn browser_models_exclude_native_trackers_and_keep_portable_models() {
+        let browser: Vec<_> = models_for_platform(Task::Mask, true).map(|m| m.id).collect();
+        assert_eq!(browser, ["mobilesam"]);
+        let desktop: Vec<_> = models_for_platform(Task::Mask, false).map(|m| m.id).collect();
+        assert_eq!(desktop, ["mobilesam", "sam2.1-hiera-tiny", "sam2.1-hiera-small", "sam2.1-hiera-base-plus", "sam2.1-hiera-large"]);
+        for wasm in [false, true] {
+            assert_eq!(models_for_platform(Task::Face, wasm).map(|m| m.id).collect::<Vec<_>>(), ["mediapipe-face"]);
+        }
+    }
+}
diff --git a/crates/engine/src/tests/models.rs b/crates/engine/src/tests/models.rs
index 567b51666..28ddebf55 100644
--- a/crates/engine/src/tests/models.rs
+++ b/crates/engine/src/tests/models.rs
@@ -15,6 +15,32 @@ fn session(tag: &str) -> (Session, std::path::PathBuf) {
     (Session { config: Some(store), ..Default::default() }, d)
 }
 
+#[test]
+fn model_list_and_direct_selection_agree_on_target_availability() {
+    super::roto::hold_roto_cache_test_lock();
+    let mut s = Session::default();
+    let list = s.execute_checked("roto.models", json!({})).unwrap();
+    let models = list["models"].as_array().unwrap();
+    for id in ["sam2.1-hiera-tiny", "sam2.1-hiera-small", "sam2.1-hiera-base-plus", "sam2.1-hiera-large"] {
+        let chosen = s.chosen_model(Task::Mask).to_string();
+        let generation = s.models.status(Task::Mask).generation;
+        let selected = s.execute_checked("roto.model.select", json!({"id": id}));
+        if cfg!(target_arch = "wasm32") {
+            assert!(!models.iter().any(|m| m["id"] == id));
+            assert!(selected.is_err());
+            assert_eq!(s.chosen_model(Task::Mask), chosen);
+            assert_eq!(s.models.status(Task::Mask).generation, generation, "rejection must not alter model state");
+        } else {
+            assert!(models.iter().any(|m| m["id"] == id));
+            selected.unwrap();
+            assert_eq!(s.chosen_model(Task::Mask), id);
+        }
+    }
+    s.execute_checked("roto.model.select", json!({"id": "classical"})).unwrap();
+    assert_eq!(s.chosen_model(Task::Mask), "classical");
+    assert!(models.iter().any(|m| m["id"] == "mobilesam"));
+}
+
 /// Poll until `task`'s model is in use (or a few seconds pass).
 fn wait_loaded(s: &mut Session, task: Task) {
     for _ in 0..400 {
@@ -37,7 +63,7 @@ fn models_are_listed_chosen_and_verified() {
         let list = s.execute_checked(&format!("{prefix}.models"), json!({})).unwrap();
         let ids: Vec<&str> = list["models"].as_array().unwrap().iter().map(|m| m["id"].as_str().unwrap()).collect();
         // Roto Brush also offers SAM 2.1 in four sizes (video trackers; see crates/sam2).
-        let expect: Vec<&str> = if task == Task::Mask {
+        let expect: Vec<&str> = if task == Task::Mask && !cfg!(target_arch = "wasm32") {
             vec!["classical", model, "sam2.1-hiera-tiny", "sam2.1-hiera-small", "sam2.1-hiera-base-plus", "sam2.1-hiera-large"]
         } else {
             vec!["classical", model]