diff --git a/crates/engine/src/cmd/text.rs b/crates/engine/src/cmd/text.rs
index 48be3a5..856f7ab 100644
--- a/crates/engine/src/cmd/text.rs
+++ b/crates/engine/src/cmd/text.rs
@@ -17,6 +17,27 @@ pub fn specs() -> Vec<CommandSpec> {
         cmd!(noundo "text.exit", "Stop Editing Text", [], None, "{}", has_doc, exit),
         cmd!("text.insert", "Type Text", [], None, "{text} (\\n = new paragraph, \\u000b = line break)", has_text, insert),
         cmd!("text.delete", "Delete Text", [], Some("Backspace"), "{dir?: backward|forward|wordBackward|wordForward}", has_text, delete),
+        // The input method's composition: shown in place, an undo step only once committed.
+        CommandSpec {
+            id: "text.compose",
+            label: "Compose Text",
+            menu: &[],
+            shortcut: None,
+            params: "{text, active?: [start, end]} — an input method's composition (preedit) at the insertion point; empty text cancels it",
+            enabled: has_text,
+            run: compose,
+            journal: false,
+            undoable: false,
+        },
+        cmd!(
+            noundo "text.commit",
+            "Commit Composition",
+            [],
+            None,
+            "{text} — the input method's result replaces its composition, as one undo step",
+            has_text,
+            commit
+        ),
         cmd!(noundo "text.move", "Move Insertion Point", [], None, "{to: left|right|up|down|wordLeft|wordRight|lineStart|lineEnd|paraStart|paraEnd|start|end, extend?: bool}", has_text, move_caret),
         cmd!(noundo "text.select", "Select Text", [], None, "{anchor: [p, c], caret: [p, c]}", has_text, select),
         cmd!(noundo "text.selectAll", "Select All Text", [], None, "{}", has_text, select_all),
@@ -144,6 +165,33 @@ pub fn layout_for(st: &DocState, t: &TextSel) -> Option<deckcraft_text::TextLayo
     ))
 }
 
+/// The insertion point on the slide: its line from top to bottom, in slide coordinates (flips and
+/// vertical text as drawn). Text with no paragraph yet (a placeholder about to be typed in) is
+/// measured as one empty paragraph, so the caret shows where typing begins. `None` for notes and
+/// table cells, which aren't laid out on the slide here.
+pub fn caret_line(st: &DocState, t: &TextSel) -> Option<(deckcraft_geom::Point, deckcraft_geom::Point)> {
+    if t.notes || t.cell.is_some() {
+        return None;
+    }
+    let sh = st.shape(t.shape)?;
+    let ctx = ctx_for(&st.doc, &st.selection)?;
+    let x = xfrm_of(&st.doc, &st.selection, sh);
+    let geo = deckcraft_render::shape_geometry(sh, x.w, x.h);
+    let mut body = sh.text.clone().unwrap_or_default();
+    if body.paragraphs.is_empty() {
+        body.paragraphs.push(deckcraft_model::text::Paragraph::default());
+    }
+    let l = deckcraft_text::layout(
+        &ctx,
+        sh,
+        &body,
+        &deckcraft_text::Opts { rect: geo.text_rect, fields: &deckcraft_text::NoFields, prompt_color: None, no_shrink: false },
+    );
+    let (cx, top, bot) = l.caret(deckcraft_text::Pos { para: t.caret.0, ch: t.caret.1 })?;
+    let m = deckcraft_render::text_transform(x.affine(), geo.text_rect, l.rotation);
+    Some((m * deckcraft_geom::Point::new(cx, top), m * deckcraft_geom::Point::new(cx, bot)))
+}
+
 fn pos_param(p: &Value, key: &str) -> Option<Pos> {
     let a = p.get(key)?.as_array()?;
     Some((a.first()?.as_u64()? as usize, a.get(1)?.as_u64()? as usize))
@@ -340,6 +388,112 @@ pub(crate) fn insert_field(s: &mut Session, field: &str, text: &str) -> Result<V
     ok()
 }
 
+/// Text an input method sends: no paragraph or line breaks (Enter is a key of its own).
+fn ime_text(s: &str) -> String {
+    s.chars().filter(|c| !c.is_control()).collect()
+}
+
+/// Is the composition still where it was put (the paragraph holds all of it)?
+fn composition_fits(st: &DocState, c: &crate::Composition) -> bool {
+    let Some(t) = &st.selection.text else { return false };
+    let Some(body) = body_of(st, t) else { return false };
+    body.paragraphs.get(c.start.0).is_some_and(|p| c.start.1.saturating_add(c.len) <= p.char_len())
+}
+
+/// `text.compose`: put an input method's preedit at the insertion point (replacing the selection)
+/// or replace the composition with the new preedit. An empty preedit cancels: the presentation
+/// goes back to how it was before the composition began.
+fn compose(s: &mut Session, p: &Value) -> Result<Value> {
+    let text = ime_text(str_param(p, "text").ok_or_else(|| bad("text.compose", "missing `text`"))?);
+    let n = text.chars().count();
+    let active = p.get("active").and_then(Value::as_array).and_then(|a| {
+        let (x, y) = (a.first()?.as_u64()? as usize, a.get(1)?.as_u64()? as usize);
+        (x < y).then_some((x.min(n), y.min(n)))
+    });
+    let current = s.doc()?.composition.clone();
+    // A composition whose text was changed under it is kept as it is; a new one starts.
+    let current = match current {
+        Some(c) if !composition_fits(s.doc()?, &c) => {
+            s.end_composition();
+            None
+        }
+        c => c,
+    };
+    match current {
+        None if text.is_empty() => Ok(json!({"composing": false})),
+        None => {
+            let st = s.doc()?;
+            let (before, before_selection) = (st.doc.clone(), st.selection.clone());
+            let (start, props) = edit_text(s, |body, t| {
+                let (a, b) = t.ordered();
+                let at = ed::delete(body, a, b);
+                let props = if a != b { Some(ed::props_at(body, at)) } else { unlinked_at_link_end(body, at) };
+                let c = ed::insert(body, at, &text, props.clone());
+                t.anchor = c;
+                t.caret = c;
+                (at, props)
+            })?;
+            s.doc_mut()?.composition = Some(crate::Composition { start, len: n, active, props, before, before_selection });
+            Ok(json!({"composing": true, "start": [start.0, start.1], "len": n}))
+        }
+        Some(c) if text.is_empty() => {
+            let st = s.doc_mut()?;
+            st.doc = c.before;
+            st.selection = c.before_selection;
+            st.composition = None;
+            st.revision += 1;
+            Ok(json!({"composing": false}))
+        }
+        Some(c) => {
+            let (start, len, props) = (c.start, c.len, c.props.clone());
+            edit_text(s, |body, t| {
+                ed::delete(body, start, (start.0, start.1 + len));
+                let e = ed::insert(body, start, &text, props);
+                t.anchor = e;
+                t.caret = e;
+            })?;
+            s.doc_mut()?.composition = Some(crate::Composition { len: n, active, ..c });
+            Ok(json!({"composing": true, "start": [start.0, start.1], "len": n}))
+        }
+    }
+}
+
+/// `text.commit`: the input method's result replaces the composition (or is typed at the
+/// insertion point when there is none) and the whole composition becomes one undo step.
+fn commit(s: &mut Session, p: &Value) -> Result<Value> {
+    let text = ime_text(str_param(p, "text").ok_or_else(|| bad("text.commit", "missing `text`"))?);
+    if s.doc()?.composition.is_some() || !text.is_empty() {
+        compose(s, &json!({"text": text}))?;
+    }
+    s.end_composition();
+    let caret = s.doc()?.selection.text.as_ref().map(|t| t.caret).unwrap_or_default();
+    Ok(json!({"caret": [caret.0, caret.1]}))
+}
+
+/// Underlines under an input method's composition (#101), in slide coordinates: `(from, to,
+/// thick)` per line, thick under the part being converted. Empty without a composition or when
+/// the edited text isn't laid out on the slide (notes, table cells).
+pub fn composition_underlines(st: &DocState) -> Vec<(deckcraft_geom::Point, deckcraft_geom::Point, bool)> {
+    let (Some(c), Some(t)) = (&st.composition, &st.selection.text) else { return vec![] };
+    let Some(sh) = st.shape(t.shape) else { return vec![] };
+    let Some(l) = layout_for(st, t) else { return vec![] };
+    let x = xfrm_of(&st.doc, &st.selection, sh);
+    let tr = deckcraft_render::shape_geometry(sh, x.w, x.h).text_rect;
+    let m = deckcraft_render::text_transform(x.affine(), tr, l.rotation);
+    let pos = |ch: usize| deckcraft_text::Pos { para: c.start.0, ch: c.start.1 + ch };
+    let mut out = vec![];
+    let mut add = |a: usize, b: usize, thick: bool| {
+        for (x0, x1, y) in l.composition_underlines(pos(a), pos(b)) {
+            out.push((m * deckcraft_geom::Point::new(x0, y), m * deckcraft_geom::Point::new(x1, y), thick));
+        }
+    };
+    add(0, c.len, false);
+    if let Some((a, b)) = c.active {
+        add(a, b.min(c.len), true);
+    }
+    out
+}
+
 fn insert(s: &mut Session, p: &Value) -> Result<Value> {
     let text = str_param(p, "text").ok_or_else(|| bad("text.insert", "missing `text`"))?.to_string();
     insert_text(s, &text, None)
diff --git a/crates/engine/src/keys.rs b/crates/engine/src/keys.rs
index 966a109..cbfc705 100644
--- a/crates/engine/src/keys.rs
+++ b/crates/engine/src/keys.rs
@@ -25,6 +25,7 @@ impl Session {
     /// `ArrowLeft`…, `Home`, `End`, `PageUp`, `PageDown`, `F5`) or a character (`b`, `]`).
     /// Returns `{handled: bool, …}`.
     pub fn key(&mut self, key: &str, mods: Mods) -> Result<Value> {
+        self.end_composition();
         let editing = self.active().is_some_and(|d| d.selection.text.is_some());
         let has_shapes = self.active().is_some_and(|d| !d.selection.shapes.is_empty());
         let k = key.to_ascii_lowercase();
@@ -151,6 +152,45 @@ impl Session {
         self.execute("text.insert", &json!({"text": text}))
     }
 
+    /// An input method's preedit (#101). On a selected shape that isn't being edited, the first
+    /// one starts editing its text and replaces it, as typing does ([`Session::type_text`]).
+    /// `active` is the part being converted, in characters of `text`.
+    pub fn compose_text(&mut self, text: &str, active: Option<(usize, usize)>) -> Result<Value> {
+        if !self.start_typing(text)? {
+            return Ok(json!({"handled": false}));
+        }
+        let mut p = json!({"text": text});
+        if let Some((a, b)) = active {
+            p["active"] = json!([a, b]);
+        }
+        self.execute("text.compose", &p)
+    }
+
+    /// An input method's result (#101): replaces the composition as one undo step.
+    pub fn commit_text(&mut self, text: &str) -> Result<Value> {
+        if !self.start_typing(text)? {
+            return Ok(json!({"handled": false}));
+        }
+        self.execute("text.commit", &json!({"text": text}))
+    }
+
+    /// Ready to take typed `text`: editing text already, or one selected shape whose text editing
+    /// starts with everything selected. False when there is nowhere to type (or nothing to type
+    /// and nothing being edited).
+    fn start_typing(&mut self, text: &str) -> Result<bool> {
+        let st = self.doc()?;
+        if st.selection.text.is_some() {
+            return Ok(true);
+        }
+        let Some(id) = st.selection.shapes.first().copied() else { return Ok(false) };
+        if st.selection.shapes.len() != 1 || text.is_empty() {
+            return Ok(false);
+        }
+        self.execute("text.edit", &json!({"id": id}))?;
+        self.execute("text.selectAll", &json!({}))?;
+        Ok(true)
+    }
+
     fn cycle_selection(&mut self, forward: bool) -> Result<()> {
         let st = self.doc()?;
         let ids: Vec<_> = st.shapes().iter().filter(|s| !s.hidden).map(|s| s.id).collect();
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index b1775c2..f6f1598 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -131,6 +131,24 @@ pub struct Interaction {
     pub selection: Selection,
 }
 
+/// Text an input method is composing (#101): its preedit sits in the edited text body, at `start`
+/// for `len` characters, until it is committed, replaced or cancelled. The presentation from
+/// before it began makes the whole composition one undo step.
+#[derive(Clone, Debug)]
+pub struct Composition {
+    /// Where the composed text starts: (paragraph, char).
+    pub start: (usize, usize),
+    /// Its length in characters (it never spans paragraphs).
+    pub len: usize,
+    /// The part the input method is converting, relative to `start` (drawn with a thicker line).
+    pub active: Option<(usize, usize)>,
+    /// The formatting the composed text is typed with (as `text.insert` would choose).
+    pub props: Option<deckcraft_model::text::RunProps>,
+    /// The presentation and selection before the composition began.
+    pub before: Arc<Presentation>,
+    pub before_selection: Selection,
+}
+
 #[derive(Clone, Debug)]
 pub struct DocState {
     pub doc: Arc<Presentation>,
@@ -145,6 +163,8 @@ pub struct DocState {
     /// Fonts the file's text uses that aren't installed, found when it was opened (empty for new
     /// documents); the app mentions them once.
     pub missing_fonts: Vec<String>,
+    /// An input method's composition in progress ([`Composition`]).
+    pub composition: Option<Composition>,
 }
 
 static NEXT_UID: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(1);
@@ -163,6 +183,7 @@ impl DocState {
             uid: NEXT_UID.fetch_add(1, std::sync::atomic::Ordering::Relaxed),
             title,
             missing_fonts: Vec::new(),
+            composition: None,
         }
     }
     pub fn is_dirty(&self) -> bool {
@@ -403,6 +424,10 @@ impl Session {
 
     fn execute_unguarded(&mut self, id: &str, params: &Value) -> Result<Value> {
         let spec = find_command(id).ok_or_else(|| EngineError::UnknownCommand(id.into()))?;
+        // Any other edit (or a click, a key, undo) settles an input method's composition first.
+        if self.depth == 0 && (spec.journal || spec.undoable) && !matches!(id, "text.compose" | "text.commit") {
+            self.end_composition();
+        }
         if let Err(e) = (spec.enabled)(self) {
             let named = (e == cmd::NOTHING_SELECTED || e == cmd::SELECT_TWO) && (params.get("ids").is_some() || params.get("id").is_some());
             if !named {
@@ -453,6 +478,16 @@ impl Session {
         Ok(r)
     }
 
+    /// Keep an input method's composition as it stands (#101): its text stays and the whole
+    /// composition becomes one undo step. Nothing happens without one.
+    pub fn end_composition(&mut self) {
+        let Some(st) = self.active_mut() else { return };
+        let Some(c) = st.composition.take() else { return };
+        if !Arc::ptr_eq(&c.before, &st.doc) {
+            push_undo(st, HistoryEntry { label: "Type Text".into(), doc: c.before, selection: c.before_selection });
+        }
+    }
+
     /// Change only the selection (no undo step).
     pub fn select(&mut self, f: impl FnOnce(&Presentation, &mut Selection)) -> Result<()> {
         let st = self.doc_mut()?;
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 2693853..673f8ec 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -606,3 +606,171 @@ fn shapes_off_the_slide_can_be_selected_and_moved() {
     s.pointer(ev(PointerKind::Up, 80.0, 420.0)).unwrap();
     assert_eq!(s.doc().unwrap().selection.shapes.iter().map(|i| i.0 as u64).collect::<Vec<_>>(), vec![half]);
 }
+
+fn title_text(s: &Session) -> String {
+    let sh = &s.doc().unwrap().current_slide().unwrap().shapes[0];
+    sh.text.as_ref().map(|t| t.paragraphs.iter().map(|p| p.text()).collect::<Vec<_>>().join("\n")).unwrap_or_default()
+}
+
+/// #101: Korean typed through an input method arrives as preedit updates (ㅎ → 하 → 한 → 한ㄱ →
+/// 한그 → 한글) and a commit. The preedit is shown in place and replaced on each update; the
+/// committed text is one undo step, and nothing on the way is an undo step of its own.
+#[test]
+fn ime_composition_replaces_its_preedit_and_commits_as_one_undo_step() {
+    let mut s = session();
+    let title = s.doc().unwrap().current_slide().unwrap().shapes[0].id.0;
+    s.execute("text.edit", &json!({"id": title})).unwrap();
+    s.execute("text.insert", &json!({"text": "A "})).unwrap();
+    let undo0 = s.doc().unwrap().history.undo.len();
+    for pre in ["ㅎ", "하", "한", "한ㄱ", "한그", "한글"] {
+        s.compose_text(pre, None).unwrap();
+        assert_eq!(title_text(&s), format!("A {pre}"), "the preedit is shown in place");
+        let c = s.doc().unwrap().composition.clone().unwrap();
+        assert_eq!((c.start, c.len), ((0, 2), pre.chars().count()));
+        assert_eq!(s.doc().unwrap().selection.text.as_ref().unwrap().caret, (0, 2 + pre.chars().count()), "caret after the preedit");
+        assert_eq!(s.doc().unwrap().history.undo.len(), undo0, "no undo step while composing");
+    }
+    s.commit_text("한글").unwrap();
+    assert_eq!(title_text(&s), "A 한글");
+    assert!(s.doc().unwrap().composition.is_none());
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo0 + 1, "one undo step for the composition");
+    assert_eq!(s.doc().unwrap().history.undo.last().unwrap().label, "Type Text");
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(title_text(&s), "A ");
+    s.execute("edit.redo", &json!({})).unwrap();
+    assert_eq!(title_text(&s), "A 한글");
+
+    // Windows' Korean IME commits a syllable when the next begins: an empty preedit, the commit,
+    // then a new preedit.
+    s.compose_text("ㄴ", None).unwrap();
+    s.compose_text("", None).unwrap();
+    s.commit_text("ㄴ").unwrap();
+    s.compose_text("ㅁ", None).unwrap();
+    assert_eq!(title_text(&s), "A 한글ㄴㅁ");
+    s.commit_text("마").unwrap();
+    assert_eq!(title_text(&s), "A 한글ㄴ마");
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(title_text(&s), "A 한글ㄴ");
+}
+
+/// #101: an empty preedit cancels the composition (Escape, or Backspace over its last jamo):
+/// the text and the selection it replaced are as they were, with no undo step.
+#[test]
+fn ime_cancel_restores_the_text_and_selection() {
+    let mut s = session();
+    let title = s.doc().unwrap().current_slide().unwrap().shapes[0].id.0;
+    s.execute("text.edit", &json!({"id": title})).unwrap();
+    s.execute("text.insert", &json!({"text": "Hello world"})).unwrap();
+    s.execute("text.select", &json!({"anchor": [0, 6], "caret": [0, 11]})).unwrap();
+    let undo0 = s.doc().unwrap().history.undo.len();
+    let rev = s.doc().unwrap().revision;
+    s.compose_text("せかい", Some((0, 3))).unwrap();
+    assert_eq!(title_text(&s), "Hello せかい", "the preedit replaces the selection");
+    assert_eq!(s.doc().unwrap().composition.as_ref().unwrap().active, Some((0, 3)));
+    s.compose_text("世界", Some((0, 9))).unwrap();
+    assert_eq!(s.doc().unwrap().composition.as_ref().unwrap().active, Some((0, 2)), "clamped to the preedit");
+    s.compose_text("", None).unwrap();
+    assert_eq!(title_text(&s), "Hello world");
+    let t = s.doc().unwrap().selection.text.clone().unwrap();
+    assert_eq!((t.anchor, t.caret), ((0, 6), (0, 11)), "the selection is back");
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo0);
+    assert!(s.doc().unwrap().revision > rev, "redrawn");
+    // A commit of nothing without a composition is nothing.
+    s.commit_text("").unwrap();
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo0);
+    // A commit without a preedit (some input methods send only the result) is one step.
+    s.commit_text("世界").unwrap();
+    assert_eq!(title_text(&s), "Hello 世界");
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo0 + 1);
+}
+
+/// #101: anything else settles the composition first: its text stays and is its own undo step.
+#[test]
+fn ime_composition_is_kept_by_a_key_a_click_or_another_command() {
+    let mut s = session();
+    let title = s.doc().unwrap().current_slide().unwrap().shapes[0].id.0;
+    s.execute("text.edit", &json!({"id": title})).unwrap();
+    let undo0 = s.doc().unwrap().history.undo.len();
+    s.compose_text("안", None).unwrap();
+    s.key("Right", Mods::default()).unwrap();
+    assert!(s.doc().unwrap().composition.is_none());
+    assert_eq!(title_text(&s), "안");
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo0 + 1);
+
+    s.compose_text("녕", None).unwrap();
+    s.pointer(PointerEvent { kind: PointerKind::Move, x: 5.0, y: 5.0, mods: Mods::default(), tol: 4.0 }).unwrap();
+    assert!(s.doc().unwrap().composition.is_some(), "hovering keeps composing");
+    s.pointer(PointerEvent { kind: PointerKind::Down, x: 5.0, y: 5.0, mods: Mods::default(), tol: 4.0 }).unwrap();
+    assert!(s.doc().unwrap().composition.is_none(), "a click settles it");
+    assert_eq!(title_text(&s), "안녕");
+
+    s.execute("text.edit", &json!({"id": title})).unwrap();
+    s.compose_text("하", None).unwrap();
+    s.execute("text.get", &json!({"id": title})).unwrap();
+    assert!(s.doc().unwrap().composition.is_some(), "a query doesn't");
+    s.execute("text.insert", &json!({"text": "!"})).unwrap();
+    assert_eq!(title_text(&s), "안녕하!");
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(title_text(&s), "안녕하");
+    s.execute("edit.undo", &json!({})).unwrap();
+    assert_eq!(title_text(&s), "안녕");
+
+    // Text changed under the composition (here behind its back): a new one starts, no panic.
+    s.compose_text("ㄱ", None).unwrap();
+    s.doc_mut().unwrap().composition.as_mut().unwrap().len = 99;
+    s.compose_text("가", None).unwrap();
+    assert!(title_text(&s).ends_with('가'));
+    // Control characters (an Enter sent as text) never split the paragraph.
+    s.commit_text("가\n\r\u{b}").unwrap();
+    assert_eq!(s.doc().unwrap().current_slide().unwrap().shapes[0].text.as_ref().unwrap().paragraphs.len(), 1);
+}
+
+/// #101: the first preedit on a selected shape starts editing it and replaces its text, as typing
+/// does; with nothing selected there is nowhere to compose.
+#[test]
+fn ime_on_a_selected_shape_replaces_its_text() {
+    let mut s = session();
+    let r = s.execute("shape.insert", &json!({"preset": "rect", "rect": [100, 100, 200, 100], "text": "Old"})).unwrap();
+    let id = r["id"].as_u64().unwrap();
+    s.select(|_, sel| {
+        sel.text = None;
+        sel.shapes = vec![ShapeId(id as u32)];
+    })
+    .unwrap();
+    assert_eq!(s.compose_text("", None).unwrap()["handled"], false, "an empty preedit doesn't start editing");
+    s.compose_text("新", None).unwrap();
+    s.commit_text("新しい").unwrap();
+    let v = s.execute("text.get", &json!({"id": id})).unwrap();
+    assert_eq!(v["text"], "新しい");
+    s.select(|_, sel| {
+        sel.text = None;
+        sel.shapes.clear();
+    })
+    .unwrap();
+    assert_eq!(s.compose_text("x", None).unwrap()["handled"], false);
+    assert_eq!(s.commit_text("x").unwrap()["handled"], false);
+}
+
+/// #101: the composition is underlined in place, under the composed characters, with a thicker
+/// line under the part being converted.
+#[test]
+fn ime_composition_underlines_follow_the_text() {
+    let mut s = session();
+    let title = s.doc().unwrap().current_slide().unwrap().shapes[0].id.0;
+    s.execute("text.edit", &json!({"id": title})).unwrap();
+    assert!(cmd::text::composition_underlines(s.doc().unwrap()).is_empty());
+    s.compose_text("にほんご", Some((2, 4))).unwrap();
+    let u = cmd::text::composition_underlines(s.doc().unwrap());
+    let thin: Vec<_> = u.iter().filter(|x| !x.2).collect();
+    let thick: Vec<_> = u.iter().filter(|x| x.2).collect();
+    assert_eq!((thin.len(), thick.len()), (1, 1), "{u:?}");
+    let sh = s.doc().unwrap().current_slide().unwrap().shapes[0].clone();
+    let x = cmd::xfrm_of(&s.doc().unwrap().doc, &s.doc().unwrap().selection, &sh);
+    for (a, b, _) in &u {
+        assert!(b.x > a.x && (a.y - b.y).abs() < 1e-9, "a horizontal line: {a:?} {b:?}");
+        assert!(a.x >= x.x - 1.0 && b.x <= x.x + x.w + 1.0 && a.y > x.y && a.y < x.y + x.h, "inside the title box");
+    }
+    assert!(thick[0].0.x > thin[0].0.x && (thick[0].1.x - thin[0].1.x).abs() < 1e-6, "the converted part is the end");
+    s.commit_text("日本語").unwrap();
+    assert!(cmd::text::composition_underlines(s.doc().unwrap()).is_empty());
+}
diff --git a/crates/engine/src/tools.rs b/crates/engine/src/tools.rs
index 9a33933..876ea6e 100644
--- a/crates/engine/src/tools.rs
+++ b/crates/engine/src/tools.rs
@@ -265,6 +265,10 @@ impl Session {
         if !(p.x.is_finite() && p.y.is_finite()) {
             return Ok(Value::Null);
         }
+        // A press (not a hover) settles an input method's composition, as clicking does in PowerPoint.
+        if !matches!(ev.kind, PointerKind::Move) {
+            self.end_composition();
+        }
         match ev.kind {
             PointerKind::Move => {
                 if let Some(Drag::Freeform { points, mode, .. }) = &self.tool.drag {
diff --git a/crates/text/src/lib.rs b/crates/text/src/lib.rs
index 69e6599..791f257 100644
--- a/crates/text/src/lib.rs
+++ b/crates/text/src/lib.rs
@@ -1831,6 +1831,33 @@ impl TextLayout {
         }
         out
     }
+    /// Underlines for text an input method is composing, from `a` to `b` (#101): `(x0, x1, y)` per
+    /// visual span, a little below each line's baseline (PowerPoint underlines the composition
+    /// in place). A composition that wraps gets one underline per line.
+    pub fn composition_underlines(&self, a: Pos, b: Pos) -> Vec<(f64, f64, f64)> {
+        let (s, e) = if a <= b { (a, b) } else { (b, a) };
+        let mut out = vec![];
+        if s == e {
+            return out;
+        }
+        for l in &self.lines {
+            let lp = Pos { para: l.para, ch: l.start };
+            let le = Pos { para: l.para, ch: l.end };
+            if le <= s || lp >= e {
+                continue;
+            }
+            let from = if s > lp { s.ch } else { l.start };
+            let to = if e < le { e.ch } else { l.end };
+            // Under the baseline, in the descent, never below the line.
+            let y = (l.baseline + (l.bottom - l.baseline) * 0.35).min(l.bottom);
+            for (x0, x1) in l.spans(from, to) {
+                if x1 > x0 {
+                    out.push((x0, x1, y));
+                }
+            }
+        }
+        out
+    }
     /// Vertical caret movement: the position on the line above/below closest to `x`.
     pub fn vertical(&self, pos: Pos, down: bool, x: f64) -> Pos {
         let Some(li) = self.line_of(pos) else { return pos };
diff --git a/crates/text/src/tests.rs b/crates/text/src/tests.rs
index 724e63b..f3dd013 100644
--- a/crates/text/src/tests.rs
+++ b/crates/text/src/tests.rs
@@ -151,6 +151,36 @@ fn caret_and_hit_roundtrip() {
     assert_eq!(r.len(), 1);
 }
 
+/// #101: the text an input method is composing is underlined in place, under the baseline of each
+/// line it occupies, and only over the composed characters.
+#[test]
+fn composition_is_underlined_per_line() {
+    let (p, sh) = setup("Hello 한국어 world", 600.0, 100.0);
+    let l = lay(&p, &sh, 600.0, 100.0);
+    let (a, b) = (Pos { para: 0, ch: 6 }, Pos { para: 0, ch: 9 });
+    let u = l.composition_underlines(a, b);
+    assert_eq!(u.len(), 1, "{u:?}");
+    let (x0, x1, y) = u[0];
+    let (cx0, ..) = l.caret(a).unwrap();
+    let (cx1, ..) = l.caret(b).unwrap();
+    assert!((x0 - cx0).abs() < 0.01 && (x1 - cx1).abs() < 0.01, "{u:?} vs carets {cx0} {cx1}");
+    let line = &l.lines[0];
+    assert!(y > line.baseline && y <= line.bottom, "under the baseline: {y} ({} – {})", line.baseline, line.bottom);
+    // Reversed ends give the same; an empty composition, nothing.
+    assert_eq!(l.composition_underlines(b, a), u);
+    assert!(l.composition_underlines(a, a).is_empty());
+
+    // Wrapped: one underline per line.
+    let (p, sh) = setup("가나다라마바사아자차카타파하 가나다라마바사아자차카타파하 가나다라마바사", 120.0, 400.0);
+    let l = lay(&p, &sh, 120.0, 400.0);
+    assert!(l.lines.len() >= 2);
+    let u = l.composition_underlines(Pos { para: 0, ch: 0 }, Pos { para: 0, ch: 40 });
+    assert!(u.len() >= 2, "{u:?}");
+    assert!(u.windows(2).all(|w| w[1].2 > w[0].2), "each lower than the last: {u:?}");
+    // Positions past the text never panic.
+    let _ = l.composition_underlines(Pos { para: 3, ch: 0 }, Pos { para: 9, ch: 99 });
+}
+
 #[test]
 fn alignment_center_and_right() {
     let (p, mut sh) = setup("Hi", 400.0, 100.0);