gh-145448: Fix REPL tab completion cursor position in pending wrap state

Lib/_pyrepl/unix_console.py

@@ -946,6 +946,14 @@ def __apply_line_update(
             self.__write(text)
             self.posxy = update.start_x + update.char_width, update.y
 
+        # When a write reaches the last column, the terminal enters the
+        # "pending wrap" state and the cursor physically stays at width - 1.
+        # Record that position so later relative moves (CUB) don't overshoot
+        # by one cell (gh-145448).
+        x, y = self.posxy
+        if x >= self.width:
+            self.posxy = self.width - 1, y
+
         if update.reset_to_margin:
             # Non-SGR terminal controls can affect the cursor position.
             self.move_cursor(0, update.y)

Lib/test/test_pyrepl/test_unix_console.py

@@ -259,6 +259,20 @@ def test_cursor_back_write(self, _os_write):
         _os_write.assert_any_call(ANY, b"2")
         con.restore()
 
+    def test_write_to_last_column_records_pending_wrap_position(self, _os_write):
+        # gh-145448: after writing into the last column the terminal is in
+        # "pending wrap" state and the cursor stays at width - 1.
+        from _pyrepl.render import LineUpdate, RenderCell
+        con = unix_console(iter([]), width=5)
+        cells = tuple(RenderCell(ch, 1) for ch in "abcde")
+        update = LineUpdate(
+            kind="replace_span", y=0, start_cell=0, start_x=0,
+            cells=cells, char_width=5,
+        )
+        con._UnixConsole__apply_line_update(update)
+        self.assertEqual(con.posxy, (4, 0))
+        con.restore()
+
     def test_multiline_function_move_up_short_terminal(self, _os_write):
         # fmt: off
         code = (

Misc/NEWS.d/next/Library/2026-03-09-00-00-02.gh-issue-145448.repl-cursor.rst

@@ -0,0 +1,3 @@
+Fixed REPL tab completion cursor moving backward by one cell in terminals
+that correctly handle CUB (Cursor Backward) in pending wrap state, such as
+xterm and Ghostty.