Abeey04 · Nov 8, 2026 · Nov 8, 2026 · isaaclab-review-bot · Nov 8, 2026 · Abeey04
diff --git a/source/isaaclab/changelog.d/fix-loading-screen-logo-encoding.fixed.rst b/source/isaaclab/changelog.d/fix-loading-screen-logo-encoding.fixed.rst
@@ -0,0 +1,4 @@
+* Fixed the startup loading screen crashing with ``UnicodeEncodeError`` on consoles that cannot encode
+  block or box-drawing characters, such as Windows output redirected to a file. The run summary drew a
+  greeting logo picked at random without checking the console encoding; logos the console cannot encode
+  are now left out.
@@ -338,14 +338,15 @@ def __init__(self, num_stages: int, *, enabled: bool | None = None, logo: bool =
                 output. Defaults to None, which enables both when standard
                 output is a terminal.
             logo: Whether :meth:`summary` shows a responsive greeting beside
-                the run summary. Defaults to True.
+                the run summary. Greetings the console cannot encode are left
+                out. Defaults to True.
         """
         self._num_stages = num_stages
-        self._logos = random.choice(_LOGO_PAIRS) if logo else ()
         self._remote_greetings: RemoteGreetings | None = None
         self._enabled = _console_is_interactive() if enabled is None else enabled
         self._console: IO[str] = sys.stdout
         self._ascii_only = not _supports_box_drawing(self._console)
+        self._logos = _bundled_logos(self._console) if logo else ()
         self._rich_console: Console | None = None
         self._live: Live | None = None
         self._display = self._Display(self)
@@ -645,10 +646,26 @@ def _console_is_interactive() -> bool:
         return False
 
 
-def _supports_box_drawing(stream: IO[str]) -> bool:
-    """Return whether *stream* can encode box-drawing characters."""
+def _can_encode(stream: IO[str], text: str) -> bool:
+    """Return whether *stream* can encode *text*."""
     try:
-        "".join(_BOX).encode(getattr(stream, "encoding", None) or "ascii")
+        text.encode(getattr(stream, "encoding", None) or "ascii")
     except (LookupError, UnicodeEncodeError):
         return False
     return True
+
+
+def _supports_box_drawing(stream: IO[str]) -> bool:
+    """Return whether *stream* can encode box-drawing characters."""
+    return _can_encode(stream, "".join(_BOX))
+
+
+def _bundled_logos(stream: IO[str]) -> tuple[str, ...]:
+    """Draw a bundled greeting pair, keeping only the logos *stream* can encode.
+
+    A console that cannot encode block or box-drawing characters, such as a
+    Windows code page, would otherwise fail on the first summary that draws them.
+    """
+    pairs = [tuple(logo for logo in pair if _can_encode(stream, logo)) for pair in _LOGO_PAIRS]
+    pairs = [pair for pair in pairs if pair]
+    return random.choice(pairs) if pairs else ()
@@ -13,7 +13,7 @@
 import sys
 import textwrap
 import time
-from io import StringIO
+from io import BytesIO, StringIO, TextIOWrapper
 from unittest.mock import Mock
 
 import pytest
@@ -151,6 +151,31 @@ def test_hidden_greetings_do_not_start_remote_loading(monkeypatch: pytest.Monkey
         screen.close()
 
 
+@pytest.mark.kitless
+@pytest.mark.parametrize(
+    ("drawn", "columns"),
+    [(-1, 100), (0, 130)],
+    ids=["standard-width-art", "wide-width-art"],
+)
+def test_summary_prints_on_console_that_cannot_encode_greeting_art(
+    monkeypatch: pytest.MonkeyPatch, drawn: int, columns: int
+):
+    # Output redirected to a file on Windows is encoded with the ANSI code page, which has no block or
+    # box-drawing characters, so a greeting drawn with them must give way to one the console can show.
+    console = TextIOWrapper(BytesIO(), encoding="cp1252")
+    monkeypatch.setattr(sys, "stdout", console)
+    monkeypatch.setenv("COLUMNS", str(columns))
+    monkeypatch.setattr(loading_screen.random, "choice", lambda options: options[drawn])
+    screen = loading_screen.LoadingScreen(1, enabled=False)
+
+    screen.summary("Run", {"Task": "Cartpole"})
+
+    console.flush()
+    shown = Text.from_ansi(console.buffer.getvalue().decode("cp1252")).plain
+    assert "Cartpole" in shown
+    assert "Welcome to Isaac Lab 3!" in shown
+
+
 @pytest.mark.skipif(sys.platform == "win32", reason="Pseudo-terminals require POSIX.")
 def test_interactive_input_shows_captured_context_before_waiting_for_answer():
     import pty