fix(tui): strip ANSI/control sequences from diff card bodies

render_diff rendered untrusted file content and model-supplied edit text
verbatim, so a crafted edit could smuggle ANSI escapes (cursor movement,
color) into the terminal through Update/Write diff cards and the approval/
pager diffs that share the renderer. Sanitize diff_text once at the top of
render_diff; sanitize_ansi keeps newlines/tabs so +/- prefix and line-number
parsing are unaffected, and visible text is preserved.

Author: elkaix

CHANGELOG.md

@@ -15,6 +15,11 @@ GitHub Releases page; `0.8.0` is the new starting line.
 
 ## Unreleased
 
+- **TUI: diff cards strip terminal control sequences.** Inline file-diff bodies
+  (Update/Write cards, approval and pager diffs) now sanitize ANSI/control escapes
+  from the untrusted file and model-supplied edit content before rendering, so a
+  crafted edit can no longer smuggle cursor-movement or color escapes into the
+  terminal through a diff card. Visible text is preserved.
 - **TUI: interactive resize/handoff ghosting.** Scrollback handoffs in prompt mode
   now fully suppress the transient preamble (agent stream body, verb spinner, and
   tips) while ``run_in_terminal`` emits permanent scrollback, so stacked

src/pythinker_code/ui/shell/components/diff.py

@@ -25,6 +25,7 @@
 from rich.table import Table
 from rich.text import Text
 
+from pythinker_code.ui.shell.components.render_utils import sanitize_ansi
 from pythinker_code.ui.shell.render_constants import (
     DIFF_CONTEXT_LINES,
     DIFF_LINE_NUMBER_MIN_WIDTH,
@@ -403,6 +404,13 @@ def render_diff(diff_text: str, *, path: str | None = None) -> RenderableType:
     if not diff_text:
         return Text("")
 
+    # Diff bodies carry untrusted file content and model-supplied edit text. Strip
+    # ANSI/control sequences before rendering so a crafted edit can't smuggle
+    # cursor-movement or color escapes into the terminal through the diff card.
+    # sanitize_ansi keeps newlines and tabs, so +/- prefix and line-number parsing
+    # below is unaffected.
+    diff_text = sanitize_ansi(diff_text)
+
     colors = get_diff_colors()
     # Added/removed rows are distinguished by background tint only; line numbers,
     # +/- markers, and code content all use the terminal's default foreground

tests/ui_and_conv/test_tui_card_tool_renderers.py

@@ -1082,6 +1082,16 @@ def test_render_diff_colorizes_added_removed():
     assert "world" in plain
 
 
+def test_render_diff_strips_ansi_control_sequences():
+    """Diff bodies carry untrusted file/model content; a crafted edit must not
+    smuggle ANSI/control escapes into the terminal through the diff card."""
+    diff = "- safe\n+ \x1b[31mRED\x1b[0m\x07evil"
+    plain = render_plain(render_diff(diff, path="/x.py"), width=80)
+    assert "\x1b" not in plain  # CSI escape stripped
+    assert "\x07" not in plain  # BEL stripped
+    assert "RED" in plain and "evil" in plain  # visible text preserved
+
+
 def test_render_diff_spaces_marker_before_at_rule():
     old = "@keyframes drawer-fade-in { from { opacity: 0; } to { opacity: 1); } }\n"
     new = "@keyframes drawer-fade-in { from { opacity: 0; } to { opacity: 1; } }\n"