Drop OSC 52 clipboard writes, force-kill on close, bound the reader, find the ST libs for tests

- OSC 52 is ignored: any output, cat'd or remote, could plant a command
  on the clipboard to paste
- kill(): terminate(force=True), so a child ignoring HUP and INT does
  not outlive its tab with the pty open
- reader pauses once 64 unparsed reads wait, so a large dump blocks the
  child at the pty instead of being buffered whole in memory
- tests/_bootstrap.py: add every Lib/python3* directory; Package Control
  puts the libraries under the active plugin host's own directory

Architecture.md

@@ -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

@@ -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`.

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_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()

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
@@ -119,7 +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.
     """
@@ -137,7 +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,
@@ -146,7 +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)
@@ -650,7 +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:
@@ -661,14 +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/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