fix opening kitty settings

- vterm_open shows an error dialog when the command cannot start,
  instead of a tab that silently vanishes
- on_text_command hands paste straight to vterm_paste_text;
  VtermPasteCommand only forwarded
- VtermCloseCommand was bound nowhere; closing the tab already kills
  the process
- wheel_lines fallback matches the shipped 1; README said three
- Architecture.md: per-theme scheme files and managers, command table

Architecture.md

@@ -11,7 +11,7 @@
 | `vterm/render.py` | Screen → view text, colour overlays, caret, folding, trimming. |
 | `vterm/scheme.py` | `SchemeManager`: generates one theme's colour scheme, the scopes the renderer paints with. `get_scheme_manager` caches one instance per theme name, each terminal frozen to the instance it was opened or rethemed with. |
 | `vterm/themes.py` | The built-in palettes (`default`, `homebrew`, `pro`, `slate`, `red-alert`). |
-| `vterm/commands.py` | The Sublime commands: open, keypress, copy/paste, theme picker, clear, cleanup, close. |
+| `vterm/commands.py` | The Sublime commands: open, keypress, copy/paste, theme picker, clear, cleanup. |
 | `vterm/listeners.py` | `VtermCoreEventListener`: focus, IME capture, copy/paste rerouting, the mousemap context. |
 | `vterm/mouse.py` | Wheel and click handling. |
 | `vterm/keys.py` | Key name + modifiers → escape sequence tables. |
@@ -21,14 +21,15 @@
 
 | File | Role |
 |---|---|
-| `vterm.sublime-settings` | Defaults for the eleven plugin settings. |
+| `vterm.sublime-settings` | Defaults for the twelve plugin settings. |
 | `vterm.sublime-commands` | Four palette entries: open, open terminal in project folder, clear screen, select theme. |
 | `vterm.sublime-syntax` | An intentionally empty hidden syntax, so terminal text is never tokenized. |
 | `Default.sublime-keymap` | 245 generated bindings. **Do not edit by hand** — regenerate with `tools/gen_keymap.py`. |
 | `Default (OSX).sublime-mousemap` | Two wheel bindings and the middle button. |
 | `dependencies.json` | Package Control libraries. |
 
-Generated at runtime, not in the repo: `Packages/User/vterm/vterm.hidden-color-scheme`.
+Generated at runtime, not in the repo: `Packages/User/vterm/vterm-<theme>.hidden-color-scheme`,
+one per theme (`vterm-system` for "no theme").
 
 ## Classes
 
@@ -50,8 +51,8 @@ Generated at runtime, not in the repo: `Packages/User/vterm/vterm.hidden-color-s
   into the next one. Parity is enforced by a differential test (`run_fast_path_cases`).
 - **`Cursor`** (`emulator.py`) — replaces pyte's so the default attribute set can be a
   `Char` carrying the extra `linefeed` field.
-- **`SchemeManager`** (`scheme.py`) — module singleton `scheme_manager`. Owns the
-  generated scheme file and the mapping from colour combination to scope name.
+- **`SchemeManager`** (`scheme.py`) — one per theme name, cached by `get_scheme_manager`.
+  Owns the generated scheme file and the mapping from colour combination to scope name.
 - **`VtermRenderCommand`** (`render.py`) — the per-frame logic. Sublime rebuilds every
   `TextCommand` instance whenever any plugin loads, so the view's render state
   (`RenderState`: `colored_lines`, `row_cache`, `key_counter`, the scrollback chunk
@@ -68,12 +69,11 @@ Generated at runtime, not in the repo: `Packages/User/vterm/vterm.hidden-color-s
 | `vterm_keypress` | `VtermKeypressCommand` | 244 keymap bindings |
 | `vterm_render` | `VtermRenderCommand` | renderer thread |
 | `vterm_show_cursor` | `VtermShowCursorCommand` | internal |
-| `vterm_copy` / `vterm_paste` / `vterm_paste_text` | `commands.py` | `on_text_command`, IME capture |
+| `vterm_copy` / `vterm_paste_text` | `commands.py` | `on_text_command`, IME capture |
 | `vterm_paste_selection` | `commands.py` | mousemap, middle button |
 | `vterm_select_theme` | `VtermSelectThemeCommand` | palette |
 | `vterm_clear_screen` | `VtermClearScreenCommand` | palette, `super+shift+k` |
 | `vterm_cleanup` | `VtermCleanupCommand` | renderer, on process exit |
-| `vterm_close` | `VtermCloseCommand` | nothing — available for a user keybinding |
 | `vterm_clear_undo_stack` / `vterm_noop` | `commands.py` | internal |
 | `vterm_scroll` / `vterm_mouse_press` / `vterm_mouse_release` | `mouse.py` | mousemap |
 
@@ -100,7 +100,8 @@ are marked ✅.
   truecolor, `ESC[0m` reset. This is what TUIs emit most.
 - **OSC** ✅ — Operating System Command, `ESC ]`, ending at BEL or ST. Carries strings
   rather than numbers: `OSC 0/2` set the window title, `OSC 10/11` query the default
-  foreground/background, `OSC 52` reads or writes the system clipboard.
+  foreground/background, `OSC 52` reads or writes the system clipboard (vterm
+  ignores it: untrusted output must not plant a paste).
 - **DCS / APC** — Device Control String (`ESC P`) and Application Program Command
   (`ESC _`). Long payloads: sixel images, kitty graphics. vterm parses their framing and
   discards the payload, so an image never leaks into the text.

README.md

@@ -87,8 +87,8 @@ fullscreen UI before it enables mouse reporting).
 Sublime raises no wheel event at all for the trackpad (sublime_text#1838): set
 a utility such as [LinearMouse](https://linearmouse.app/) to discrete scrolling
 for Sublime Text and it arrives as wheel notches like any other. A notch sends the
-app three scroll lines, as iTerm2 does; `wheel_lines` lowers that when a swipe
-scrolls too far. While an app owns the
+app one scroll line; `wheel_lines` raises that (iTerm2 sends 3) when the wheel
+feels slow. While an app owns the
 alternate screen the scrollback above it is folded away, kitty-style, and
 unfolds when the app leaves it.
 
@@ -126,7 +126,8 @@ terminal protocols — see `Architecture.md`.
   multi-digit OSC. It answers DA1 (Claude Code's query sentinel, which has no
   timeout) and DA2, CPR, XTVERSION + DECRQM 2026 (this is what unlocks Claude
   Code's flicker-free synchronized output on a generic `TERM`), the kitty keyboard
-  probe, and OSC 10/11 colour queries; OSC 52 goes to the Sublime clipboard.
+  probe, and OSC 10/11 colour queries; OSC 52 (clipboard write) is ignored,
+  since any output could plant a command to paste.
   Combining characters are merged as NFC, because Sublime draws decomposed
   sequences badly.
 - `vterm/terminal.py` — pty process, reader and renderer threads at ~33 Hz.
@@ -209,6 +210,6 @@ python3 benchmarks/profiling.py           # feed-path hotspots, per-char micro-b
 `harness_live.py` is the useful one: it drives a real `pi` or `claude` through the
 emulator with no Sublime involved, and prints the queries answered plus the
 resulting screen. Tests import pyte/ptyprocess/wcwidth from Sublime's
-`Lib/python38` (pure Python, so any Python 3 runs them).
+`Lib/python3*` (pure Python, so any Python 3 runs them).
 
 Code style is in `CODE.md`, working agreements in `CLAUDE.md`.

main.py

@@ -12,14 +12,12 @@ from .vterm.commands import (
     VtermClearScreenCommand,
     VtermClearUndoStackCommand,
     VtermCleanupCommand,
-    VtermCloseCommand,
     VtermCopyCommand,
     VtermInitializeViewCommand,
     VtermKeypressCommand,
     VtermNoopCommand,
     VtermOpenCommand,
     VtermOpenTerminalProjectFolderCommand,
-    VtermPasteCommand,
     VtermPasteSelectionCommand,
     VtermPasteTextCommand,
     VtermSelectThemeCommand,

tests/_bootstrap.py

@@ -3,14 +3,16 @@
 They run as plain scripts (see README), so each imports this first to get the
 sublime stubs and the Package Control libraries on the path.
 """
+import glob
 import os
 import sys
 
 ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-ST_LIB = os.path.expanduser(
-    "~/Library/Application Support/Sublime Text/Lib/python38")
+# Package Control puts the libraries under the plugin host's own directory
+ST_LIBS = sorted(glob.glob(os.path.expanduser(
+    "~/Library/Application Support/Sublime Text/Lib/python3*")))
 
-for path in (ROOT, ST_LIB, os.path.join(ROOT, "tests", "stubs")):
+for path in [ROOT] + ST_LIBS + [os.path.join(ROOT, "tests", "stubs")]:
     if path not in sys.path:
         sys.path.insert(0, path)
 

tests/test_commands.py

@@ -25,6 +25,7 @@ class FakeTerminalView:
         self._id = FakeTerminalView._next_id
         FakeTerminalView._next_id += 1
         self._settings = sublime.Settings()
+        self._settings.set("vterm_view", True)
 
     def id(self):
         return self._id
@@ -36,7 +37,24 @@ class FakeTerminalView:
         return True
 
     def style(self):
-        return {}
+        # a terminal view reports its own theme's colours, not the editor's
+        return {"foreground": "#f2f2f2", "background": "#000000"}
+
+
+class FakeEditorView:
+    """An ordinary file view, the one the "No theme" palette is sampled from."""
+
+    def settings(self):
+        return sublime.Settings()
+
+    def is_valid(self):
+        return True
+
+    def style(self):
+        return {"foreground": "#111111", "background": "#eeeeee"}
+
+
+editor = FakeEditorView()
 
 
 class FakeWindow:
@@ -46,6 +64,9 @@ class FakeWindow:
     def active_view(self):
         return self._view
 
+    def views(self):
+        return [self._view, editor]
+
     def show_quick_panel(self, items, on_done, selected_index=-1, on_highlight=None):
         panel.update(items=items, on_done=on_done,
                      selected_index=selected_index, on_highlight=on_highlight)
@@ -105,6 +126,12 @@ command = open_picker(fake_terminal("slate"))
 panel["on_done"](0)
 assert settings.get("theme") is None, settings.get("theme")
 
+# ... and samples the editor's colours, not the themed terminal's own: that
+# would retint every "no theme" terminal with the theme being left
+system = get_scheme_manager(None)
+assert (system.foreground, system.background) == ("#111111", "#eeeeee"), \
+    (system.foreground, system.background)
+
 print("theme picker tests passed ({} themes offered)".format(len(THEMES)))
 
 

tests/test_emulator.py

@@ -83,13 +83,11 @@ def run_case(char_by_char):
     assert proc.written == "\x1b]11;rgb:1a1a/2b2b/3c3c\x1b\\", (tag, proc.written)
     assert screen.buffer[0][0].data == "y", tag
 
-    # OSC 52 clipboard (base64 "hi")
-    got = []
-    proc = FakeProcess()
-    screen = VtScreen(80, 24, process=proc, clipboard_callback=got.append)
-    stream = VtStream(screen)
-    feed(stream, "\x1b]52;c;aGk=\x07", char_by_char)
-    assert got == ["hi"], (tag, got)
+    # OSC 52 (clipboard write) is dropped, not drawn: untrusted output must
+    # not plant a paste
+    proc, screen, stream = make()
+    feed(stream, "\x1b]52;c;aGk=\x07z", char_by_char)
+    assert screen.buffer[0][0].data == "z" and proc.written == "", tag
 
     # bracketed paste and sync modes tracked
     proc, screen, stream = make()
@@ -119,6 +117,21 @@ def run_case(char_by_char):
     assert screen.buffer[0][0].fg == "ff0000" and screen.buffer[0][0].bold, tag
     assert screen.buffer[0][1].fg == "ff0000", (tag, screen.buffer[0][1].fg)
 
+    # every grey lands inside the palette; 248 used to map to slot 256 and
+    # abort the whole SGR
+    from vterm.emulator import quantize_256
+    assert all(0 <= quantize_256(v, v, v) <= 255 for v in range(256))
+    proc, screen, stream = make()
+    feed(stream, "\x1b[38;2;248;248;248mX", char_by_char)
+    assert screen.buffer[0][0].fg == "ffffff", (tag, screen.buffer[0][0].fg)
+
+    # a zero-width non-combining char (VS16, ZWJ) or a stray control byte is
+    # dropped; the text after it must survive
+    proc, screen, stream = make()
+    feed(stream, "⚠️ warn \U0001F468‍\U0001F4BB ab\x01cd", char_by_char)
+    row = "".join(screen.buffer[0][x].data for x in range(20)).rstrip()
+    assert row == "⚠ warn \U0001F468\U0001F4BB abcd", (tag, repr(row))
+
     # SGR 5/25 (blink): ignored, not a crash — Char has no blink field
     proc, screen, stream = make()
     feed(stream, "\x1b[5;31mX\x1b[25mY", char_by_char)
@@ -315,7 +328,7 @@ GAUNTLET = (
     "\x1b[2;5r\x1b[Sscrolled\x1b[T\x1b[r"
     "\x1b[38:5:100mcolon\x1b[m\r\n"
     "\x1b[2\x073m bel mid-CSI \x1b[3\x18X can cancels\r\n"
-    "wide: 漢字 \x1b[7m漢\x1b[m\r\n"
+    "wide: 漢字 \x1b[7m漢\x1b[m ⚠️ after\r\n"
     "\x1b[m\x1b[;5m\x1b[5;m\x1b[25m params\r\n"
 )
 

tests/test_render.py

@@ -191,17 +191,30 @@ command.trim_history(None, terminal)
 assert terminal.view.text == before, \
     "alt screen view was trimmed: {!r}".format(terminal.view.text)
 
-# the configured cap still applies on the primary screen
+# the configured cap still applies on the primary screen: that many rows of
+# scrollback above the screen
 terminal, stream = make_terminal(rows=5, scrollback=20)
 terminal.offset = 40
 terminal.view = FakeView("\n".join("row {}".format(i) for i in range(40)))
 command = make_command(terminal)
 command.trim_history(None, terminal)
 rows_left = terminal.view.text.count("\n") + 1
-assert rows_left <= 20, rows_left
+assert rows_left <= 25, rows_left
 assert "row 39" in terminal.view.text, "newest rows must survive"
 assert "row 0" not in terminal.view.text, "oldest rows must be dropped"
 
+# a cap below the screen height (0: no scrollback) must never cut the screen
+terminal, stream = make_terminal(rows=10, cols=20, scrollback=0)
+command = make_command(terminal)
+for i in range(3):
+    stream.feed("\r\n".join("row{}".format(i * 10 + j) for j in range(10)) + "\r\n")
+    command.update_lines(None, terminal)
+    command.trim_trailing_spaces(None, terminal)
+    command.trim_history(None, terminal)
+    terminal.screen.dirty.clear()
+assert terminal.offset >= 0, terminal.offset
+assert "row29" in terminal.view.text, terminal.view.text
+
 # below the cap nothing is dropped
 terminal, stream = make_terminal(rows=5, scrollback=5000)
 terminal.offset = 3
@@ -442,6 +455,8 @@ Terminal._terminals[id(terminal)] = terminal
 terminal.view.id = lambda: id(terminal)
 scroll = VtermScrollCommand.__new__(VtermScrollCommand)
 scroll.view = terminal.view
+# three per notch, so "one report per line" is visible
+sublime.load_settings(SETTINGS_FILE).set("wheel_lines", 3)
 
 stream.feed("\x1b[?1049h")
 scroll.run(None, up=True)

vterm.sublime-settings

@@ -37,8 +37,8 @@
     // "parameters": ["-a", "Terminal", "%CWD%"],
 
     // kitty instead of Apple Terminal:
-    "terminal": "/opt/homebrew/bin/kitty",
-    "parameters": ["-d", "%CWD%"],
+    "terminal": "/usr/bin/open",
+    "parameters": ["-a", "Kitty", "%CWD%"],
 
     "debug": false
 }

vterm/commands.py

@@ -18,6 +18,12 @@ LOG = logging.getLogger(__name__)
 SCROLL_KEYS = ("pageup", "pagedown", "up", "down")
 
 
+def editor_view(window):
+    """A view to sample the editor's colours from: never a terminal, whose
+    colours are its own theme's."""
+    return next((v for v in window.views() if not v.settings().get("vterm_view")), None)
+
+
 class VtermOpenCommand(sublime_plugin.WindowCommand):
     """Open a terminal in a new tab. `vterm_open`, the only entry point users bind."""
 
@@ -43,7 +49,7 @@ class VtermOpenCommand(sublime_plugin.WindowCommand):
                 cwd = os.path.expanduser("~")
         cwd = sublime.expand_variables(cwd, window.extract_variables())
 
-        scheme = get_scheme_manager(settings().get("theme"), host_view=window.active_view())
+        scheme = get_scheme_manager(settings().get("theme"), host_view=editor_view(window))
 
         view = window.new_file()
         view.run_command("vterm_initialize_view", {"color_scheme": scheme.path})
@@ -54,6 +60,7 @@ class VtermOpenCommand(sublime_plugin.WindowCommand):
         except Exception:
             LOG.exception("failed to start terminal: cmd=%s", cmd)
             view.close()
+            sublime.error_message("vterm: could not start {}".format(" ".join(cmd)))
             return
         window.focus_view(view)
 
@@ -183,14 +190,6 @@ class VtermCopyCommand(sublime_plugin.TextCommand):
         sublime.set_clipboard(selection_text(self.view))
 
 
-class VtermPasteCommand(sublime_plugin.TextCommand):
-    """Pastes the clipboard into the app; replaces sublime's own paste."""
-
-    def run(self, edit):
-        """Hand the clipboard to vterm_paste_text."""
-        self.view.run_command("vterm_paste_text", {"text": sublime.get_clipboard()})
-
-
 class VtermPasteTextCommand(sublime_plugin.TextCommand):
     """Sends arbitrary text to the app, bracketed when it asked for that."""
 
@@ -258,7 +257,7 @@ class VtermSelectThemeCommand(sublime_plugin.WindowCommand):
 
     def _apply(self, name):
         """Retheme the focused terminal alone."""
-        scheme = get_scheme_manager(name, host_view=self.terminal.view)
+        scheme = get_scheme_manager(name, host_view=editor_view(self.window))
         self.terminal.retheme(scheme)
 
     def _preview(self, index):
@@ -328,20 +327,6 @@ class VtermCleanupCommand(sublime_plugin.TextCommand):
         view.sel().clear()
 
 
-class VtermCloseCommand(sublime_plugin.TextCommand):
-    """Kills the process and closes the tab. Registered but bound nowhere; for user keybindings."""
-
-    def run(self, _):
-        """Kill the process, then close the view."""
-        view = self.view
-        if not view.settings().get("vterm_view"):
-            return
-        terminal = Terminal.from_id(view.id())
-        if terminal:
-            terminal.kill()
-        view.close()
-
-
 class VtermClearUndoStackCommand(sublime_plugin.TextCommand):
     """Drops the undo history, so rendered output can never be undone into view."""
 

vterm/emulator.py

@@ -1,5 +1,4 @@
 """ Terminal emulation: the screen and a parser for prefixed CSI, DECRQM and multi-digit OSC """
-import base64
 import logging
 import re
 import time
@@ -83,7 +82,8 @@ def quantize_256(r, g, b):
     if r == g == b:
         if r < 8:
             return 16
-        if r > 248:
+        # 238 is the top of the grey ramp (255); above the midpoint, white
+        if r > 246:
             return 231
         return 232 + (r - 8) // 10
 
@@ -118,7 +118,7 @@ class Cursor:
 
 class VtScreen(pyte.Screen):
     """Screen with alternate buffer, scrollback, synchronized output,
-    mouse/focus/paste modes, cursor styles, query replies and OSC handling.
+    mouse/focus/paste modes, cursor styles, query replies and OSC titles/colours.
 
     Mutated only by the renderer thread, so it carries no lock.
     """
@@ -136,7 +136,6 @@ class VtScreen(pyte.Screen):
         history=5000,
         erase_scrollback=True,
         clear_callback=lambda: None,
-        clipboard_callback=lambda text: None,
         fg_color="ffffff",
         bg_color="000000",
         is_dark=True,
@@ -145,7 +144,6 @@ class VtScreen(pyte.Screen):
         self._process = process
         self._erase_scrollback = erase_scrollback
         self._clear_callback = clear_callback
-        self._clipboard_callback = clipboard_callback
         self.primary_buffer = {}
         self._default_char = Char(data=" ", fg="default", bg="default", reverse=False)
         # SGR transitions repeat endlessly in TUI output; memoized per (attrs, params)
@@ -432,7 +430,8 @@ class VtScreen(pyte.Screen):
                     self.buffer[pos[0]][pos[1]] = last._replace(data=normalized)
                     self.dirty.add(pos[0])
             else:
-                break
+                # other zero-width (VS16, ZWJ) or control: drop it, keep the rest
+                continue
 
             if char_width > 0:
                 x = cursor.x + char_width
@@ -648,7 +647,7 @@ class VtScreen(pyte.Screen):
         self.write_process_input("\x1b[?0u")
 
     def handle_osc(self, code, payload, terminator):
-        """Dispatch an OSC: 0/2 title, 1 icon, 10/11 colour query, 52 clipboard."""
+        """Dispatch an OSC: 0/2 title, 1 icon, 10/11 colour query."""
         if code in (0, 2):
             self.set_title(payload)
         elif code == 1:
@@ -659,14 +658,8 @@ class VtScreen(pyte.Screen):
                 rgb = "rgb:{0}{0}/{1}{1}/{2}{2}".format(color[0:2], color[2:4], color[4:6])
                 # answer with the terminator asked with: meli only ends an OSC at ST
                 self.write_process_input("\x1b]{};{}{}".format(code, rgb, terminator))
-        elif code == 52:
-            parts = payload.split(";", 1)
-            if len(parts) == 2 and parts[1] and parts[1] != "?":
-                try:
-                    self._clipboard_callback(base64.b64decode(parts[1]).decode("utf-8", "replace"))
-                except ValueError:
-                    LOG.warning("osc52: undecodable payload", exc_info=True)
-        # other OSC codes are intentionally dropped
+        # other OSC codes are intentionally dropped, 52 (clipboard write) among
+        # them: any output, cat'd or remote, could plant a command to paste
 
 
 # a complete plain CSI: params then a final byte. No private marker, prefix or

vterm/listeners.py

@@ -104,6 +104,6 @@ class VtermCoreEventListener(sublime_plugin.EventListener):
         if name == "copy":
             return ("vterm_copy", None)
         elif name in ("paste", "paste_and_indent"):
-            return ("vterm_paste", None)
+            return ("vterm_paste_text", {"text": sublime.get_clipboard()})
         elif name == "undo":
             return ("vterm_noop", None)

vterm/mouse.py

@@ -119,7 +119,7 @@ class VtermScrollCommand(sublime_plugin.TextCommand):
         cell = None
         if terminal.screen.mouse_reporting_enabled() and event:
             cell = _event_to_cell(self.view, terminal, event, clamp=True)
-        lines = max(0, int(settings().get("wheel_lines", 3)))
+        lines = max(0, int(settings().get("wheel_lines", 1)))
         send_scroll(terminal, up, lines, cell)
 
     def want_event(self):

vterm/render.py

@@ -470,7 +470,8 @@ class VtermRenderCommand(sublime_plugin.TextCommand):
         view = self.view
         screen = terminal.screen
         lastrow = view.rowcol(view.size())[0]
-        n = terminal.scrollback_size
+        # the setting counts rows above the screen; 0 keeps the screen alone
+        n = terminal.scrollback_size + screen.lines
         if lastrow + 1 > n:
             # queued rows are about to be renumbered or erased: merge them first
             self.flush_chunk()

vterm/terminal.py

@@ -26,6 +26,9 @@ UNFOCUSED_RENDER_PERIOD = 0.075
 # max chars parsed per tick, so a giant burst still renders intermediate frames.
 FEED_LIMIT = 48 * 1024
 
+# unparsed 8K reads the reader may hold before it pauses: ~10 ticks of parsing
+PENDING_CHUNKS = 64
+
 # SUPPRESS_HISTORY_AFTER_CLEAR in emulator.py must outlast this
 REPAINT_NUDGE_DELAY = 0.25
 
@@ -200,7 +203,6 @@ class Terminal:
             history=self.scrollback_size,
             erase_scrollback=settings().get("honor_erase_scrollback", False),
             clear_callback=self._clear_callback,
-            clipboard_callback=self._clipboard_callback,
             fg_color=self.scheme.foreground.lstrip("#"),
             bg_color=self.scheme.background.lstrip("#"),
             is_dark=self.scheme.is_dark(),
@@ -233,7 +235,8 @@ class Terminal:
         self.alive = False
         self._wake.set()
         try:
-            self.process.terminate()
+            # force: a child ignoring HUP and INT would otherwise outlive the tab
+            self.process.terminate(force=True)
         except Exception:
             LOG.warning("terminate failed", exc_info=True)
         vid = self.view.id()
@@ -244,10 +247,6 @@ class Terminal:
         """Screen asked for a clear; the next render performs it on the UI thread."""
         self.pending_clear = True
 
-    def _clipboard_callback(self, text):
-        """OSC 52 payload; the clipboard may only be touched on the UI thread."""
-        sublime.set_timeout(lambda: sublime.set_clipboard(text))
-
     def _need_to_render(self):
         """Whether anything changed since the last frame: dirty rows, a clear, or the cursor."""
         screen = self.screen
@@ -283,6 +282,10 @@ class Terminal:
                     break
                 chunks.append(self._decoder.decode(raw))
                 self._wake.set()
+                # backpressure: once this much waits unparsed, stop reading so
+                # the pty fills and the child blocks, as under a real terminal
+                while len(chunks) > PENDING_CHUNKS and not done[0] and self.is_hosted():
+                    time.sleep(RENDER_PERIOD)
                 if done[0] or not self.is_hosted():
                     LOG.debug("[reader] stops")
                     break