diff --git a/crates/edit/src/added.rs b/crates/edit/src/added.rs
index a603a37060..250f71a533 100644
--- a/crates/edit/src/added.rs
+++ b/crates/edit/src/added.rs
@@ -29,6 +29,8 @@ use draw::{GLYPHS_PER_FONT, LaidLine, draw_laid_shaped};
 use layout::Piece;
 #[cfg(test)]
 pub(crate) use layout::WRAP_CALLS;
+#[cfg(test)]
+pub(crate) use layout::shaped_width;
 pub use layout::{PASTE_STEP, first_undrawable, lines, paste_place, paste_rect, text_rect, text_width};
 pub use store::{add_content, delete_content, isolate_content, list_added, scan_markers, update_content};
 pub use types::{Added, AddedImage, AddedText, Align, CHAR_SPACING_LIMIT, Family, MarkerScan};
diff --git a/crates/edit/src/added/layout.rs b/crates/edit/src/added/layout.rs
index 62f24c5c4c..c76db6463a 100644
--- a/crates/edit/src/added/layout.rs
+++ b/crates/edit/src/added/layout.rs
@@ -107,7 +107,8 @@ fn thai_lines(t: &AddedText, para: &str, width: f64) -> Result<Vec<String>, Edit
             end_row(&mut lines, &mut line);
             used = 0.0;
         }
-        let too_wide = blank(&line) && ink > width;
+        // Too wide for what is left of the row, counting the spaces that open the paragraph.
+        let too_wide = blank(&line) && used + ink > width;
         for (text, advance) in word {
             if too_wide && !blank(&line) && !blank(&text) && used + advance > width {
                 end_row(&mut lines, &mut line);
@@ -319,7 +320,7 @@ pub(super) fn shaped_layout(t: &AddedText, line: &str, rtl: bool) -> Result<(Vec
 
 /// The width of `s` in a shaped-text item; the item's font's estimate if it can't be shaped (drawing
 /// then reports why).
-fn shaped_width(t: &AddedText, s: &str, rtl: bool) -> f64 {
+pub(crate) fn shaped_width(t: &AddedText, s: &str, rtl: bool) -> f64 {
     shaped_layout(t, s, rtl).map(|(_, w)| w).unwrap_or_else(|_| latin_width(t, s))
 }
 
diff --git a/crates/edit/src/tests.rs b/crates/edit/src/tests.rs
index d8ba0a8aeb..02378057b7 100644
--- a/crates/edit/src/tests.rs
+++ b/crates/edit/src/tests.rs
@@ -5826,6 +5826,19 @@ fn added_thai_text_wraps_between_dictionary_words() {
         assert!(rows[0].starts_with("      "), "the opening spaces are kept at width {width}: {rows:?}");
         assert_eq!(rows.concat().trim_start(), "ประปาสะอาด");
     }
+    // A first word that fits a row alone but not after the opening spaces breaks between clusters
+    // on the first row rather than running past its end.
+    let word = "ประปา";
+    let word_w = super::added::shaped_width(&t, word, false);
+    let indent_w = super::added::shaped_width(&t, "      ", false);
+    let width = word_w + indent_w / 2.0;
+    let indented = AddedText { rect: [0.0, 0.0, width, 400.0], text: format!("      {word}"), ..t.clone() };
+    let rows = super::added::lines(&indented);
+    for row in &rows {
+        assert!(super::added::shaped_width(&t, row, false) <= width + 0.5, "{row:?} overflows {width}: {rows:?}");
+    }
+    assert!(rows.len() > 1 && rows[0].starts_with("      "), "{rows:?}");
+    assert_eq!(rows.concat().trim_start(), word);
 }
 
 #[test]