diff --git a/crates/engine/src/cmd/edit.rs b/crates/engine/src/cmd/edit.rs
index 3bba84748..f2972be5a 100644
--- a/crates/engine/src/cmd/edit.rs
+++ b/crates/engine/src/cmd/edit.rs
@@ -129,7 +129,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Replace…",
             ["Home", "Editing", "Find & Select"],
             Some("Ctrl+H"),
-            "{what, with, matchCase?, wholeCell?, all?: true, within?: sheet|workbook}",
+            "{what, with, matchCase?, wholeCell?, all?: true, within?: sheet|workbook} → {replaced, skipped?} (in a Python cell the code is edited; skipped counts Python cells whose code would no longer fit)",
             has_doc,
             replace
         ),
diff --git a/crates/engine/src/cmd/edit/find.rs b/crates/engine/src/cmd/edit/find.rs
index bce0ba728..06a908e14 100644
--- a/crates/engine/src/cmd/edit/find.rs
+++ b/crates/engine/src/cmd/edit/find.rs
@@ -115,6 +115,7 @@ pub(super) fn replace(s: &mut Session, p: &Json) -> Result<Json> {
     let all = bool_param(p, "all").unwrap_or(true);
     let workbook = str_param(p, "within") == Some("workbook");
     let active = s.doc()?.selection.active;
+    let mut skipped = 0usize;
     let n = edit(s, |cx| {
         let sheets: Vec<usize> = if workbook { (0..cx.wb.sheets.len()).collect() } else { vec![cx.wb.active_sheet()] };
         let mut n = 0;
@@ -135,6 +136,31 @@ pub(super) fn replace(s: &mut Session, p: &Json) -> Result<Json> {
                 } else {
                     replace_ci(&text, &what, &with)
                 };
+                // A Python cell's text is its code: the replacement edits the code and the cell
+                // stays a Python cell. Code that would no longer fit in a PY formula is left as it was.
+                let old_py = cx.wb.sheet(si).and_then(|sh| sh.cell(c)).and_then(|x| x.py.clone());
+                if let Some(old) = old_py {
+                    let py = gridcraft_model::PyCode { object: old.object, ..gridcraft_model::PyCode::new(&new) };
+                    if py.code == old.code {
+                        continue;
+                    }
+                    if !py.fits() {
+                        skipped += 1;
+                        continue;
+                    }
+                    let sh = cx.sheet_mut(si)?;
+                    if let Some(r) = sh.spill_ranges.remove(&c) {
+                        sh.clear_spill(r);
+                    }
+                    let style = sh.style_id(c);
+                    sh.set_cell(
+                        c,
+                        Cell { value: Value::Error(gridcraft_core::CellError::Blocked), formula: None, style, py: Some(std::sync::Arc::new(py)) },
+                    );
+                    cx.touch(si, c);
+                    n += 1;
+                    continue;
+                }
                 let cell = input_to_cell(&new, si, c, &mut cx.wb).unwrap_or_else(|_| Some(Cell::value(Value::text(new.as_str()))));
                 let sh = cx.sheet_mut(si)?;
                 match cell {
@@ -149,6 +175,9 @@ pub(super) fn replace(s: &mut Session, p: &Json) -> Result<Json> {
         }
         Ok(n)
     })?;
+    if skipped > 0 {
+        return Ok(json!({"replaced": n, "skipped": skipped}));
+    }
     Ok(json!({"replaced": n}))
 }
 
diff --git a/crates/engine/src/tests/python_cells.rs b/crates/engine/src/tests/python_cells.rs
index 417ed1e4a..ef1df605a 100644
--- a/crates/engine/src/tests/python_cells.rs
+++ b/crates/engine/src/tests/python_cells.rs
@@ -263,3 +263,36 @@ fn a_macro_counts_python_code_as_data_and_a_blocked_spill_as_no_write() {
     assert!(e.contains("F2") && e.contains("H2") && !e.contains("J2"), "{e}");
     assert_eq!(code(&s, 0, "F2").as_deref(), Some("1"), "nothing was changed");
 }
+
+#[test]
+fn replace_edits_a_python_cells_code_and_keeps_it_a_python_cell() {
+    let mut s = s();
+    plant(&mut s, 0, "A1", "x = 1\nx");
+    {
+        let d = s.doc_mut().unwrap();
+        let mut wb = (*d.wb).clone();
+        let cell = wb.sheet_mut(0).unwrap().cells.get_mut(CellRef::parse("A1").unwrap()).unwrap();
+        Arc::make_mut(cell.py.as_mut().unwrap()).object = true;
+        d.wb = Arc::new(wb);
+    }
+    let r = s.execute("edit.replace", json!({"what": "x", "with": "y"})).unwrap();
+    assert_eq!(r["replaced"], 1);
+    assert_eq!(code(&s, 0, "A1").as_deref(), Some("y = 1\ny"));
+    let d = s.doc().unwrap();
+    let cell = d.wb.sheet(0).unwrap().cell(CellRef::parse("A1").unwrap()).unwrap();
+    assert!(cell.py.as_ref().unwrap().object, "the return type is kept");
+    assert_eq!(cell.value, Value::Error(gridcraft_core::CellError::Blocked));
+    s.execute("edit.undo", json!({})).unwrap();
+    assert_eq!(code(&s, 0, "A1").as_deref(), Some("x = 1\nx"));
+}
+
+#[test]
+fn replace_leaves_python_code_that_would_no_longer_fit() {
+    let mut s = s();
+    let long = "a".repeat(gridcraft_model::python::MAX_FORMULA_CHARS / 2);
+    plant(&mut s, 0, "A1", &long);
+    let r = s.execute("edit.replace", json!({"what": "a", "with": "bb"})).unwrap();
+    assert_eq!(r["replaced"], 0);
+    assert_eq!(r["skipped"], 1);
+    assert_eq!(code(&s, 0, "A1").as_deref(), Some(long.as_str()));
+}