diff --git a/changes/ui-mounted.md b/changes/ui-mounted.md
new file mode 100644
index 00000000..d029d68f
--- /dev/null
+++ b/changes/ui-mounted.md
@@ -0,0 +1,6 @@
+bump: minor
+type: feature
+**`ui_mounted` and `ui_model_of`: an editor's questions of a running interface.** `ui_mounted(out)` fills the
+caller's list with the classes of the components the last frame showed, in tree order and each once;
+`ui_model_of(cls)` is the first mounted instance's model, read in place (the next frame fills it again), or
+null. For devlink's ui_screen and ui_model; asked on request, never a frame.
diff --git a/examples/library/ui_mounted.ludic b/examples/library/ui_mounted.ludic
new file mode 100644
index 00000000..083468b4
--- /dev/null
+++ b/examples/library/ui_mounted.ludic
@@ -0,0 +1,18 @@
+# ui_mounted.ludic - an editor's questions of a running interface: which components the last frame
+# showed (in tree order, each once) and one's model, read in place. App shows two Counters: the list
+# is App then Counter, a Counter has a model, and a class not shown has none. Prints `App|Counter| 1 1`.
+import "ludic.ui"
+import "ui_component_parts/Counter.ludic"
+import "ui_component_parts/App.ludic"
+program UiMounted {
+  numbers float
+  entry (ui_st: mut UiState) {
+    let root: UiNode = ui_nodes(ui_st, "App", null)
+    ui_place(ui_st, root, 0.0, 0.0, 400.0, 400.0)
+    let names = new []string
+    ui_mounted(ui_st, names)
+    var joined = ""
+    for i in 0 .. len(names) { joined = joined + names[i] + "|" }
+    print(`{joined} {ui_model_of(ui_st, "Counter") != null} {ui_model_of(ui_st, "Nothing") == null}`)
+  }
+}
diff --git a/packages/ludic.ui/index.ludic b/packages/ludic.ui/index.ludic
index 022c474d..39dcb84e 100644
--- a/packages/ludic.ui/index.ludic
+++ b/packages/ludic.ui/index.ludic
@@ -111,3 +111,4 @@ import "dump.ludic"
 import "inspect.ludic"
 import "held.ludic"
 import "override.ludic"
+import "mounted.ludic"
diff --git a/packages/ludic.ui/mounted.ludic b/packages/ludic.ui/mounted.ludic
new file mode 100644
index 00000000..e9324f7a
--- /dev/null
+++ b/packages/ludic.ui/mounted.ludic
@@ -0,0 +1,39 @@
+# mounted.ludic - which components the last frame showed, and one's model: an editor's questions of a
+# running game's interface (devlink's ui_screen and ui_model), asked on request and never a frame.
+
+# the class names of the components mounted in the last build, in tree order (every root the frame
+# drew, a node at a time) and each once, into the caller's list
+@alloc_ok("an inspector's question: the caller's list grows to the most classes shown at once")
+export function ui_mounted(ui_st: UiState, out: []string) -> void {
+  List.clear(out)
+  for r in 0 .. len(ui_st.fb_roots) { mt_walk(ui_st, ui_st.fb_roots[r], out) }
+  for i in 0 .. len(ui_st.in_list) {            # a mounted one the walk did not meet, in the order made
+    let it = ui_st.in_list[i]
+    if it.seen == ui_st.in_build { mt_add(out, it.cls.name) }
+  }
+}
+@alloc_ok("an inspector's question: the caller's list grows to the most classes shown at once")
+function mt_walk(ui_st: UiState, n: UiNode, out: []string) -> void {
+  if n == null { return }
+  for i in 0 .. len(ui_st.in_list) {
+    let it = ui_st.in_list[i]
+    if it.seen == ui_st.in_build and it.key == n.key { mt_add(out, it.cls.name) }
+  }
+  for c in 0 .. len(n.children) { mt_walk(ui_st, n.children[c], out) }
+}
+@alloc_ok("an inspector's question: the caller's list grows to the most classes shown at once")
+function mt_add(out: []string, name: string) -> void {
+  for i in 0 .. len(out) {
+    if out[i] == name { return }
+  }
+  push(out, name)
+}
+# the model of the first mounted instance of `cls` (the Val its class's model() fills), or null: read
+# it now, as the next frame fills the same object again
+export function ui_model_of(ui_st: UiState, cls: string) -> Val {
+  for i in 0 .. len(ui_st.in_list) {
+    let it = ui_st.in_list[i]
+    if it.seen == ui_st.in_build and it.cls != null and it.cls.name == cls { return it.model }
+  }
+  return null
+}
diff --git a/tools/ludic-cli/test.ludic b/tools/ludic-cli/test.ludic
index 7699683d..59440ba3 100644
--- a/tools/ludic-cli/test.ludic
+++ b/tools/ludic-cli/test.ludic
@@ -1296,6 +1296,7 @@ function cmd_dev_test() -> int {
   controller_case("library/ui_reload", "", "ui: templates reloaded note 1 | reloaded 0 then 1 | note again 1", "ui_reload.ludic (L11: a template changed on disk is read again, and its state kept)")
   controller_case("library/ui_component", "", "counters|a: 1 (2)|+|reset|b: 10 (20) big|+|reset|outside| b margin 9; b text 16711680; outside -1; button 30 b: 0 (0)", "ui_component.ludic (L11: components as NAME.ludic + .xml + .lss - props, state, fields, events, scoped styles, @import, class passed down)")
   controller_case("library/ui_override", "", "counters|a: 1 (2)|+|reset|b: 0 (0)|+|reset|outside| counters|[a=1]|+|[b=0]|+|outside| 1 counters|a: 1 (2)|+|reset|b: 0 (0)|+|reset|outside| 0", "ui_override.ludic (a template given from outside: shown with the state kept, and the file back when let go)")
+  controller_case("library/ui_mounted", "", "App|Counter| 1 1", "ui_mounted.ludic (the components the last frame showed, in tree order and each once, and one's model)")
   reject_case("rejected/component_no_template", "there is no Lonely.xml beside it", "a component needs its template beside it")
   controller_case("library/ui_remount", "", "c: 2 (4) | c: 0 (0) | heap 0", "ui_remount.ludic (a component unmounted and mounted again starts as new, and two thousand comings and goings hold the heap flat)")
   controller_case("library/ui_controls", "", "1 false 7 2 Adalove 70 1 false 8 2 Adalove 70; scrolled 40", "ui_controls.ludic (L11: focus and keys, the built-in controls, a range dragged, a box scrolled)")