perf: reduce live Markdown re-render churn while streaming

gcode/ui.py

@@ -5,6 +5,8 @@
 display, a permission gate, and status/error output.
 """
 
+import time
+
 import questionary
 from prompt_toolkit import PromptSession
 from prompt_toolkit.formatted_text import HTML
@@ -16,7 +18,8 @@
 from rich.spinner import Spinner
 from rich.text import Text
 
-_TRUNCATE_STEP = 80  # re-render Markdown only after this many new characters
+_TRUNCATE_STEP = 160  # re-render Markdown only after this many new characters
+_TRUNCATE_MIN_INTERVAL = 0.10  # seconds between live updates (max ~10 fps)
 
 # Slash commands available in the interactive menu
 _SLASH_COMMANDS = [
@@ -148,6 +151,7 @@ def prompt(self) -> str:
     def assistant_start(self) -> None:
         self._buffer = ""
         self._last_len = 0
+        self._last_update = 0.0
         self._live = Live(
             Spinner("dots", text="Thinking…"),
             console=self.console,
@@ -160,9 +164,14 @@ def token(self, text: str) -> None:
         if self._live is None:
             return
         self._buffer += text
-        if len(self._buffer) - self._last_len >= _TRUNCATE_STEP:
+        now = time.monotonic()
+        if (
+            len(self._buffer) - self._last_len >= _TRUNCATE_STEP
+            and now - self._last_update >= _TRUNCATE_MIN_INTERVAL
+        ):
             self._live.update(Markdown(self._buffer))
             self._last_len = len(self._buffer)
+            self._last_update = now
 
     def assistant_end(self) -> None:
         if self._live is None:

tests/test_ui.py

@@ -133,16 +133,17 @@ def test_token_renders_markdown_after_threshold(monkeypatch):
 
     fake = _FakeLive()
     monkeypatch.setattr(ui_module, "Live", lambda *args, **kwargs: fake)
+    monkeypatch.setattr(ui_module, "_TRUNCATE_MIN_INTERVAL", 0.0)
 
     ui = RichUI()
     ui.assistant_start()
 
-    # Below the 80-char re-render threshold: no update yet.
+    # Below the 160-char re-render threshold: no update yet.
     ui.token("x" * 40)
     assert fake.updates == []
 
     # Crossing the threshold triggers one Markdown update.
-    ui.token("y" * 50)  # total 90 >= 80
+    ui.token("y" * 150)  # total 190 >= 160
     assert len(fake.updates) == 1
 
     # Ending the stream renders the final text and stops the live region.
@@ -151,6 +152,31 @@ def test_token_renders_markdown_after_threshold(monkeypatch):
     assert len(fake.updates) == 2
 
 
+def test_token_throttled_by_time_interval(monkeypatch):
+    from gcode import ui as ui_module
+
+    fake = _FakeLive()
+    monkeypatch.setattr(ui_module, "Live", lambda *args, **kwargs: fake)
+    monkeypatch.setattr(ui_module, "_TRUNCATE_STEP", 1)
+    monkeypatch.setattr(ui_module, "_TRUNCATE_MIN_INTERVAL", 60.0)
+
+    clock = iter([10.0, 10.05, 70.0])
+    monkeypatch.setattr(ui_module.time, "monotonic", lambda: next(clock))
+
+    ui = RichUI()
+    ui.assistant_start()
+
+    ui.token("a")  # 1 char but only 10s elapsed since 0.0 -> throttled
+    ui.token("b")  # still < 60s elapsed -> throttled
+    assert len(fake.updates) == 0
+
+    ui.token("c")  # 70s elapsed -> update fires
+    assert len(fake.updates) == 1
+
+    ui.assistant_end()
+    assert fake.stopped
+
+
 # -- tool display ----------------------------------------------------------