fix(cli): preserve renderer state on resize

cli.py

@@ -2827,6 +2827,53 @@ def _strip_leaked_terminal_responses(text: str) -> str:
     return cleaned
 
 
+def _estimate_tui_input_height(
+    lines: list[str] | tuple[str, ...],
+    prompt_text: str,
+    terminal_columns: int,
+    *,
+    max_height: int = 8,
+) -> int:
+    """Estimate classic prompt_toolkit input rows using live terminal cells.
+
+    The TextArea prompt is injected with prompt_toolkit's BeforeInput
+    processor, which means it consumes cells only on logical line 0. After a
+    narrow resize, that first row can leave only one input cell beside an icon
+    prompt such as ``⚔ ``, while continuation rows use the full terminal width.
+    Never substitute a fake wide fallback here: under- or over-allocating the
+    TextArea height leaves stale prompt/input cells visible at the bottom of the
+    terminal.
+    """
+    try:
+        from prompt_toolkit.utils import get_cwidth
+    except Exception:
+        get_cwidth = lambda value: len(value or "")  # type: ignore[assignment]
+
+    try:
+        columns = int(terminal_columns or 0)
+    except (TypeError, ValueError):
+        columns = 0
+
+    columns = max(1, columns)
+    prompt_width = max(0, get_cwidth(prompt_text or ""))
+
+    visual_lines = 0
+    for index, line in enumerate(lines or [""]):
+        # prompt_toolkit's TextArea injects ``prompt`` via BeforeInput, which
+        # applies only to logical line 0. Wrapped continuation rows, and later
+        # logical lines, use the full terminal width. Count the display cells
+        # after that same transformation rather than subtracting the prompt from
+        # every wrapped row.
+        line_width = get_cwidth(line or "")
+        display_width = line_width + (prompt_width if index == 0 else 0)
+        if display_width <= 0:
+            visual_lines += 1
+        else:
+            visual_lines += max(1, -(-display_width // columns))
+
+    return min(max(visual_lines, 1), max(1, int(max_height or 1)))
+
+
 def _collect_query_images(query: str | None, image_arg: str | None = None) -> tuple[str, list[Path]]:
     """Collect local image attachments for single-query CLI flows."""
     message = query or ""
@@ -3689,9 +3736,12 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
         startup UI and ``_replay_output_history`` cannot reconstruct it
         (the banner was never added to ``_OUTPUT_HISTORY``).
 
-        Instead we just reset prompt_toolkit's renderer cache so the next
-        incremental redraw starts from a clean slate, then let
-        ``original_on_resize`` recalculate layout for the new size.
+        Let prompt_toolkit's own resize path run with its renderer cursor
+        cache intact. Its Application._on_resize() starts with
+        renderer.erase(leave_alternate_screen=False), which needs the cached
+        cursor position to move back to the live prompt origin before
+        erase_down(). Resetting the renderer before that erase loses the
+        origin and can leave stale prompt glyphs after a narrow resize.
 
         We also flag ``_status_bar_suppressed_after_resize`` so the dynamic
         status bar and input separator rules stay hidden until the next user
@@ -3702,14 +3752,6 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
         next prompt restores the bar cleanly.
         """
         self._status_bar_suppressed_after_resize = True
-        try:
-            app.renderer.reset(leave_alternate_screen=False)
-        except Exception:
-            pass
-        try:
-            app.invalidate()
-        except Exception:
-            pass
         original_on_resize()
 
     def _schedule_resize_recovery(self, app, original_on_resize, delay: float = 0.12) -> None:
@@ -12004,26 +12046,17 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
         def _input_height():
             try:
                 from prompt_toolkit.application import get_app
-                from prompt_toolkit.utils import get_cwidth
 
                 doc = input_area.buffer.document
-                prompt_width = max(2, get_cwidth(self._get_tui_prompt_text()))
                 try:
-                    available_width = get_app().output.get_size().columns - prompt_width
+                    terminal_columns = get_app().output.get_size().columns
                 except Exception:
-                    available_width = shutil.get_terminal_size((80, 24)).columns - prompt_width
-                if available_width < 10:
-                    available_width = 40
-                visual_lines = 0
-                for line in doc.lines:
-                    # Each logical line takes at least 1 visual row; long lines wrap.
-                    # Use prompt_toolkit's cell width so CJK wide characters count as 2.
-                    line_width = get_cwidth(line)
-                    if line_width <= 0:
-                        visual_lines += 1
-                    else:
-                        visual_lines += max(1, -(-line_width // available_width))  # ceil division
-                return min(max(visual_lines, 1), 8)
+                    terminal_columns = shutil.get_terminal_size((80, 24)).columns
+                return _estimate_tui_input_height(
+                    doc.lines,
+                    self._get_tui_prompt_text(),
+                    terminal_columns,
+                )
             except Exception:
                 return 1
 

tests/cli/test_cli_force_redraw.py

@@ -71,18 +71,14 @@ class TestForceFullRedraw:
             "invalidate",
         ]
 
-    def test_resize_preserves_scrollback_and_resets_renderer(self, bare_cli, monkeypatch):
-        """Resize recovery must NOT erase screen or scrollback.
+    def test_resize_recovery_uses_prompt_toolkit_original_resize_before_reset(self, bare_cli, monkeypatch):
+        """Resize recovery must preserve prompt_toolkit's tracked cursor state.
 
-        The startup banner lives in normal terminal scrollback (printed
-        before prompt_toolkit owns the chrome).  Clearing scrollback on
-        SIGWINCH removes it and ``_replay_output_history`` cannot
-        reconstruct it.  The fix is to only reset the renderer cache and
-        let ``original_on_resize`` recalculate layout.
-
-        Additionally, ``_status_bar_suppressed_after_resize`` must be set
-        so the input rules and status bar hide until the next user input,
-        preventing duplicated-bar artifacts on column shrink (#19280).
+        prompt_toolkit's built-in Application._on_resize() starts with
+        renderer.erase(leave_alternate_screen=False), which uses the renderer's
+        cached cursor position to move back to the live prompt origin before
+        erase_down(). If Hermes resets the renderer first, that cursor position
+        is lost and stale prompt glyphs can remain after a narrow resize.
         """
         app = MagicMock()
         events = []
@@ -94,11 +90,9 @@ class TestForceFullRedraw:
         bare_cli._status_bar_suppressed_after_resize = False
         bare_cli._recover_after_resize(app, original_on_resize)
 
-        assert events == [
-            "renderer_reset",
-            "invalidate",
-            "original_resize",
-        ]
+        assert events == ["original_resize"]
+        app.renderer.reset.assert_not_called()
+        app.invalidate.assert_not_called()
         # Must NOT clear the screen or scrollback — those destroy the banner.
         app.renderer.output.erase_screen.assert_not_called()
         app.renderer.output.write_raw.assert_not_called()

tests/cli/test_cli_status_bar.py

@@ -3,6 +3,7 @@ from datetime import datetime, timedelta
 from types import SimpleNamespace
 from unittest.mock import MagicMock, patch
 
+import cli as cli_mod
 from cli import HermesCLI
 
 
@@ -104,91 +105,24 @@ class TestCLIStatusBar:
         assert "-1" not in text
         assert "0/200K" in text
 
+    def test_input_height_counts_prompt_only_on_first_wrapped_row(self):
+        # Regression for prompt_toolkit classic CLI resize glitches: the prompt
+        # is inserted by BeforeInput only on logical line 0. At three terminal
+        # cells, "⚔ " leaves one cell for the first input character, but
+        # wrapped continuation rows use the full three cells. Estimating every
+        # wrapped row as one-cell wide over-allocates the TextArea and can leave
+        # stale prompt/input cells visible after resize.
+        assert cli_mod._estimate_tui_input_height(["abcdef"], "⚔ ", 3) == 3
+
     def test_input_height_counts_wide_characters_using_cell_width(self):
-        cli_obj = _make_cli()
+        # Prompt width (2 cells) + ten CJK chars (20 cells) = 22 display cells,
+        # which wraps to two rows at 14 terminal columns.
+        assert cli_mod._estimate_tui_input_height(["你" * 10], "❯ ", 14) == 2
 
-        class _Doc:
-            lines = ["你" * 10]
-
-        class _Buffer:
-            document = _Doc()
-
-        input_area = SimpleNamespace(buffer=_Buffer())
-
-        def _input_height():
-            try:
-                from prompt_toolkit.application import get_app
-                from prompt_toolkit.utils import get_cwidth
-
-                doc = input_area.buffer.document
-                prompt_width = max(2, get_cwidth(cli_obj._get_tui_prompt_text()))
-                try:
-                    available_width = get_app().output.get_size().columns - prompt_width
-                except Exception:
-                    import shutil
-                    available_width = shutil.get_terminal_size((80, 24)).columns - prompt_width
-                if available_width < 10:
-                    available_width = 40
-                visual_lines = 0
-                for line in doc.lines:
-                    line_width = get_cwidth(line)
-                    if line_width <= 0:
-                        visual_lines += 1
-                    else:
-                        visual_lines += max(1, -(-line_width // available_width))
-                return min(max(visual_lines, 1), 8)
-            except Exception:
-                return 1
-
-        mock_app = MagicMock()
-        mock_app.output.get_size.return_value = MagicMock(columns=14)
-        with patch.object(HermesCLI, "_get_tui_prompt_text", return_value="❯ "), \
-             patch("prompt_toolkit.application.get_app", return_value=mock_app):
-            assert _input_height() == 2
-
-    def test_input_height_uses_prompt_toolkit_width_over_shutil(self):
-        cli_obj = _make_cli()
-
-        class _Doc:
-            lines = ["你" * 10]
-
-        class _Buffer:
-            document = _Doc()
-
-        input_area = SimpleNamespace(buffer=_Buffer())
-
-        def _input_height():
-            try:
-                from prompt_toolkit.application import get_app
-                from prompt_toolkit.utils import get_cwidth
-
-                doc = input_area.buffer.document
-                prompt_width = max(2, get_cwidth(cli_obj._get_tui_prompt_text()))
-                try:
-                    available_width = get_app().output.get_size().columns - prompt_width
-                except Exception:
-                    import shutil
-                    available_width = shutil.get_terminal_size((80, 24)).columns - prompt_width
-                if available_width < 10:
-                    available_width = 40
-                visual_lines = 0
-                for line in doc.lines:
-                    line_width = get_cwidth(line)
-                    if line_width <= 0:
-                        visual_lines += 1
-                    else:
-                        visual_lines += max(1, -(-line_width // available_width))
-                return min(max(visual_lines, 1), 8)
-            except Exception:
-                return 1
-
-        mock_app = MagicMock()
-        mock_app.output.get_size.return_value = MagicMock(columns=14)
-        with patch.object(HermesCLI, "_get_tui_prompt_text", return_value="❯ "), \
-             patch("prompt_toolkit.application.get_app", return_value=mock_app), \
-             patch("shutil.get_terminal_size") as mock_shutil:
-            assert _input_height() == 2
-        mock_shutil.assert_not_called()
+    def test_input_height_clamps_zero_width_to_one_cell(self):
+        # Some terminals briefly report zero columns during resize. Treat that
+        # as a one-cell terminal rather than falling back to a fake wide width.
+        assert cli_mod._estimate_tui_input_height(["abcd"], "", 0) == 4
 
     def test_build_status_bar_text_no_cost_in_status_bar(self):
         cli_obj = _attach_agent(