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fix: Prevent display freeze during tool call streaming #454

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Merged
evalstate merged 1 commit into from
Nov 6, 2025
Merged

fix: Prevent display freeze during tool call streaming #454

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42 changes: 22 additions & 20 deletions src/fast_agent/ui/streaming.py
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Original file line number Diff line number Diff line change
Expand Up @@ -447,14 +447,19 @@ def _render_current_buffer(self) -> None:
if not self._live:
return

# Consolidate buffer if it gets too large (preserves all content)
if len(self._buffer) > 10:
self._buffer = ["".join(self._buffer)]

text = "".join(self._buffer)

# Truncate for display only - don't modify the buffer with truncated content
display_text = text

if self._use_plain_text:
trimmed = self._trim_to_displayable(text)
if trimmed != text:
text = trimmed
self._buffer = [trimmed]
trailing_paragraph = self._extract_trailing_paragraph(text)
display_text = self._trim_to_displayable(display_text)

trailing_paragraph = self._extract_trailing_paragraph(display_text)
if trailing_paragraph and "\n" not in trailing_paragraph:
width = max(1, console.console.size.width)
target_ratio = (
Expand All @@ -463,35 +468,28 @@ def _render_current_buffer(self) -> None:
target_rows = max(1, int(console.console.size.height * target_ratio) - 1)
estimated_rows = math.ceil(len(trailing_paragraph.expandtabs()) / width)
if estimated_rows > target_rows:
trimmed_text = self._trim_to_displayable(text)
if trimmed_text != text:
text = trimmed_text
self._buffer = [trimmed_text]

if len(self._buffer) > 10:
text = self._trim_to_displayable(text)
self._buffer = [text]
display_text = self._trim_to_displayable(display_text)

header = self._build_header()
max_allowed_height = max(1, console.console.size.height - 2)
self._max_render_height = min(self._max_render_height, max_allowed_height)

if self._use_plain_text:
content_height = self._estimate_plain_render_height(text)
content_height = self._estimate_plain_render_height(display_text)
budget_height = min(content_height + PLAIN_STREAM_HEIGHT_FUDGE, max_allowed_height)

if budget_height > self._max_render_height:
self._max_render_height = budget_height

padding_lines = max(0, self._max_render_height - content_height)
display_text = text + ("\n" * padding_lines if padding_lines else "")
display_text_padded = display_text + ("\n" * padding_lines if padding_lines else "")
content = (
Text(display_text, style=self._plain_text_style)
Text(display_text_padded, style=self._plain_text_style)
if self._plain_text_style
else Text(display_text)
else Text(display_text_padded)
)
else:
prepared = prepare_markdown_content(text, self._display._escape_xml)
prepared = prepare_markdown_content(display_text, self._display._escape_xml)
prepared_for_display = self._close_incomplete_code_blocks(prepared)

content_height = self._truncator.measure_rendered_height(
Expand All @@ -515,8 +513,12 @@ def _render_current_buffer(self) -> None:
try:
self._live.update(combined)
self._last_render_time = time.monotonic()
except Exception:
pass
except Exception as exc:
logger.warning(
"Error updating live display during streaming",
exc_info=True,
data={"error": str(exc)},
)

async def _render_worker(self) -> None:
assert self._queue is not None
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