TOSQUASH 3a45dbd5, sync proctitle tests+doc to `_def_prefix`

Same trio 0.29 → 0.33 cancel-cascade slowdown that hit
`test_nested_multierrors` (ea67f1b6) — bumps the
`trio`-backend (non-debug, non-forking) budget in
`test_echoserver_detailed_mechanics` from 1s → 4s.

- The 1s budget raced the ~1s teardown deadline. On a
  deadline-fire trio 0.33 injects
  `Cancelled(source='deadline')` (cancel-reason
  metadata) that wraps the mid-stream KBI in a
  `BaseExceptionGroup`, breaking the bare
  `pytest.raises(KeyboardInterrupt)` below.
- Bump matches the forking-spawner branch (4s).
- Inline NOTE references the tracking issue
  `ai/conc-anal/trio_033_cancel_cascade_slowdown_depth3_issue.md`.

(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

ai/conc-anal/trio_033_cancel_cascade_slowdown_depth3_issue.md

@@ -0,0 +1,102 @@
+# `trio` 0.29 -> 0.33 slows the depth=3 cancel-cascade
+
+## Symptom
+
+After locking to `trio==0.33.0` (commit `c7741bba`, was
+`0.29.0`), this test reliably trips its `fail_after`
+deadline on the **`trio`** backend:
+
+```
+FAILED tests/test_cancellation.py::test_nested_multierrors[start_method=trio-depth=3]
+  - AssertionError: assert False
+    where False = isinstance(
+      Cancelled(source='deadline', source_task=None, reason=None),
+      tractor.RemoteActorError,
+    )
+```
+
+A `fail_after_w_trace` hang-snapshot is captured for the
+test each run (deadline-injected `Cancelled` wrapped into
+the actor-nursery `BaseExceptionGroup`).
+
+## Root cause (immediate)
+
+The test budgets `fail_after(6)` for the `trio` backend.
+That 6s was chosen (commit `32955db0`, while `trio==0.29`)
+with the assertion that trio finishes "well under" 6s.
+The `trio` 0.29 -> 0.33 bump slowed the depth=3 cascade
+past that budget, so the 6s deadline now fires mid-cascade.
+
+trio 0.33 added **cancel-reason tracking** — every
+`Cancelled` now carries `(source=, reason=, source_task=)`.
+The injected exc is `Cancelled(source='deadline')`, i.e.
+trio itself naming our `fail_after(6)` scope as the cancel
+origin. When that `Cancelled` collapses one branch of the
+nursery BEG, the test's `isinstance(subexc,
+RemoteActorError)` assertion fails. The healthy outcome is
+`BEG = [RemoteActorError, RemoteActorError]`; the
+`Cancelled` is purely an artifact of the deadline cutting
+the cascade short.
+
+## Measurements (standalone, this machine)
+
+```
+depth=1  trio   ~3.15s   PASS  (keeps 6s budget)
+depth=3  trio   ~6.8-8.2s  FAIL @ 6s  (now bumped to 12s)
+```
+
+depth=1 still fits comfortably; only depth=3 (deeper
+recursive spawn-and-error tree => more actors to reap)
+exceeds the old budget. The ~2s/depth-level cost looks
+like serialized per-actor reap / `terminate_after` waits.
+
+## Mitigation applied
+
+`test_nested_multierrors` now splits the `trio` budget:
+
+```python
+case ('trio', 1):
+    timeout = 6
+case ('trio', 3):
+    timeout = 12   # was 6; see this doc
+```
+
+This stops the deadline from firing so the cascade
+completes naturally to `[RAE, RAE]`.
+
+## Also affected — same root cause, different test
+
+`test_echoserver_detailed_mechanics[trio-raise_error=KeyboardInterrupt]`
+(`tests/test_infected_asyncio.py`) tripped the *same*
+slowdown via its much tighter `trio` budget of `1s`. The
+single-aio-subactor teardown now takes ~1s, so the `1s`
+`fail_after` raced the deadline (PASS at 0.99s / FAIL at
+1.03s across back-to-back standalone runs). On a deadline-
+fire the injected `Cancelled(source='deadline')` wraps the
+mid-stream `KeyboardInterrupt` into a `BaseExceptionGroup`,
+which is NOT a `KeyboardInterrupt` so the bare
+`pytest.raises(KeyboardInterrupt)` fails. (The sibling
+`raise_error=Exception` variant only "passes" by accident:
+an `ExceptionGroup` *is-a* `Exception`, so its
+`pytest.raises(Exception)` still matches even when wrapped.)
+
+Mitigation: bump that `trio` budget `1 -> 4s` (matching the
+forking-spawner case). Without a deadline-fire the KBI
+propagates bare and the assertion passes.
+
+## Open follow-up (the actual regression)
+
+The budget bump is a band-aid — the underlying question is
+**why** the depth=3 `trio` cancel-cascade went from <6s to
+~7-8s across `trio` 0.29 -> 0.33. Candidate avenues:
+
+- which scope owns the per-actor `terminate_after` wait,
+  and are the tree's reaps concurrent or serialized?
+- did trio 0.33's abort/reschedule or cancel-reason
+  bookkeeping change checkpoint timing on the cancel path?
+
+If/when the cascade speeds back up under-budget, depth=3
+will start completing well under 12s — at which point the
+budget can be tightened back toward 6s as a regression
+tripwire. Related (different backend, same cascade class):
+`cancel_cascade_too_slow_under_main_thread_forkserver_issue.md`.

tests/devx/conftest.py

@@ -5,6 +5,7 @@
 from __future__ import annotations
 import platform
 import os
+import re
 import signal
 import time
 from typing import (
@@ -294,6 +295,26 @@ def expect(
 PROMPT = r"\(Pdb\+\)"
 
 
+# Strip terminal color / ANSI-VT100 escape sequences so
+# substring matching against REPL + traceback output stays
+# robust to color leakage — Python 3.13's colored tracebacks,
+# `pdbp`'s pygments highlighting, etc. — even when
+# `PYTHON_COLORS=0` (set in the `spawn` fixture) isn't honored
+# by every renderer in the spawned subproc.
+# Regex per https://stackoverflow.com/a/14693789
+_ansi_re: re.Pattern = re.compile(
+    r'\x1B(?:[@-Z\\-_]|\[[0-?]*[ -/]*[@-~])'
+)
+
+
+def ansi_strip(text: str) -> str:
+    '''
+    Remove ANSI/VT100 escape sequences from `text`.
+
+    '''
+    return _ansi_re.sub('', text)
+
+
 def in_prompt_msg(
     child: SpawnBase,
     parts: list[str],
@@ -313,7 +334,7 @@ def in_prompt_msg(
     '''
     __tracebackhide__: bool = False
 
-    before: str = str(child.before.decode())
+    before: str = ansi_strip(str(child.before.decode()))
     for part in parts:
         if part not in before:
             if pause_on_false:
@@ -333,9 +354,9 @@ def in_prompt_msg(
     return True
 
 
-# TODO: todo support terminal color-chars stripping so we can match
-# against call stack frame output from the the 'll' command the like!
-# -[ ] SO answer for stipping ANSI codes: https://stackoverflow.com/a/14693789
+# NB: color-char stripping (so we can match against call-stack
+# frame output from the `ll` command and the like) is handled by
+# `ansi_strip()` applied inside `in_prompt_msg()` + below.
 def assert_before(
     child: SpawnBase,
     patts: list[str],
@@ -356,7 +377,7 @@ def assert_before(
         err_on_false=True,
         **kwargs
     )
-    before: str = str(child.before.decode())
+    before: str = ansi_strip(str(child.before.decode()))
     return before
 
 

tests/devx/test_debugger.py

@@ -1186,7 +1186,12 @@ def test_shield_pause(
             "('cancelled_before_pause'",  # actor name
             _repl_fail_msg,
             "trio.Cancelled",
-            "raise Cancelled._create()",
+            # trio >=0.30 raises via a multi-line
+            # `raise Cancelled._create(source=.., reason=..,
+            #  source_task=..)` (cancel-reason metadata), so
+            # match the open-paren form only, NOT the legacy
+            # bare `()`.
+            "raise Cancelled._create(",
 
             # we should be handling a taskc inside
             # the first `.port_mortem()` sin-shield!
@@ -1204,7 +1209,12 @@ def test_shield_pause(
             "('root'",  # actor name
             _repl_fail_msg,
             "trio.Cancelled",
-            "raise Cancelled._create()",
+            # trio >=0.30 raises via a multi-line
+            # `raise Cancelled._create(source=.., reason=..,
+            #  source_task=..)` (cancel-reason metadata), so
+            # match the open-paren form only, NOT the legacy
+            # bare `()`.
+            "raise Cancelled._create(",
 
             # handling a taskc inside the first unshielded
             # `.port_mortem()`.

tests/devx/test_proctitle.py

@@ -8,9 +8,9 @@ after `Actor` construction, so any spawned sub-actor process
 should:
 
   - have `argv[0]` (== `/proc/<pid>/cmdline`) start with
-    `tractor[<aid.reprol()>]`
-  - have `/proc/<pid>/comm` start with `tractor[` (kernel
-    truncates to ~15 bytes)
+    `<_def_prefix>[<aid.reprol()>]` (currently `_subactor[…]`)
+  - have `/proc/<pid>/comm` start with `<_def_prefix>[`
+    (kernel truncates to ~15 bytes)
   - be detected as a tractor sub-actor by
     `_is_tractor_subactor(pid)` via the cmdline marker.
 
@@ -27,7 +27,10 @@ import trio
 import tractor
 
 from tractor.runtime._runtime import Actor
-from tractor.devx._proctitle import set_actor_proctitle
+from tractor.devx._proctitle import (
+    set_actor_proctitle,
+    _def_prefix,
+)
 from tractor._testing._reap import (
     _is_tractor_subactor,
     _read_cmdline,
@@ -41,8 +44,9 @@ _non_linux: bool = platform.system() != 'Linux'
 def test_set_actor_proctitle_format():
     '''
     `set_actor_proctitle()` returns the canonical
-    `tractor[<aid.reprol()>]` form and actually mutates
-    the running proc's title.
+    `<_def_prefix>[<aid.reprol()>]` form (currently
+    `_subactor[…]`) and actually mutates the running
+    proc's title.
 
     '''
     pytest.importorskip(
@@ -60,12 +64,14 @@ def test_set_actor_proctitle_format():
         )
         title: str = set_actor_proctitle(actor)
 
-        # canonical wrapping: `tractor[<aid.reprol()>]`. We
-        # compare against the runtime-computed `reprol()`
-        # rather than a hard-coded value so the test stays
-        # decoupled from `Aid.reprol()`'s internal format
-        # (currently `<name>@<pid>`, but could evolve).
-        expected: str = f'tractor[{actor.aid.reprol()}]'
+        # canonical wrapping: `<_def_prefix>[<aid.reprol()>]`.
+        # We source BOTH the prefix (`_def_prefix`) and the
+        # runtime-computed `reprol()` rather than hard-coding,
+        # so the test stays decoupled from the prefix shape
+        # (flipped to `_subactor` in `3a45dbd5`) AND from
+        # `Aid.reprol()`'s internal format (currently
+        # `<name>@<pid>`, but could evolve).
+        expected: str = f'{_def_prefix}[{actor.aid.reprol()}]'
         assert title == expected
         # sanity: the actor's name must be in the title
         # somewhere (so a future `reprol()` change that
@@ -140,15 +146,17 @@ def test_subactor_proctitle_visible_via_proc():
     )
 
     pid, info = matched[0]
-    # canonical proctitle prefix in cmdline (full form)
-    assert info['cmdline'].startswith('tractor[proctitle_boi@'), (
-        f'cmdline missing `tractor[proctitle_boi@…]` prefix: '
+    # canonical proctitle prefix in cmdline (full form);
+    # prefix sourced from `_def_prefix` so it tracks the
+    # `3a45dbd5` flip (`tractor[` -> `_subactor[`).
+    assert info['cmdline'].startswith(f'{_def_prefix}[proctitle_boi@'), (
+        f'cmdline missing `{_def_prefix}[proctitle_boi@…]` prefix: '
         f'{info["cmdline"]!r}'
     )
     # comm is kernel-truncated to ~15 bytes — just check the
-    # `tractor[` prefix made it.
-    assert info['comm'].startswith('tractor['), (
-        f'comm missing `tractor[` prefix: {info["comm"]!r}'
+    # `<_def_prefix>[` prefix made it.
+    assert info['comm'].startswith(f'{_def_prefix}['), (
+        f'comm missing `{_def_prefix}[` prefix: {info["comm"]!r}'
     )
     # intrinsic-signal detector should match.
     assert info['is_tractor'] is True

tests/test_cancellation.py

@@ -605,17 +605,28 @@ async def test_nested_multierrors(
             )
         )
 
-    # 6s budget: in the non-hang case (and on the trio
-    # backend) the whole spawn + cancel-cascade should
-    # complete in well under that. On the borderline hang
-    # case the `fail_after_w_trace` fires `TooSlowError`
-    # AND captures a ptree/wchan/py-spy snapshot to
+    # Per-backend/-depth budgets: in the non-hang case the
+    # whole spawn + cancel-cascade should complete in well
+    # under these. On the borderline hang case the
+    # `fail_after_w_trace` fires `TooSlowError` AND captures a
+    # ptree/wchan/py-spy snapshot to
     # `$XDG_CACHE_HOME/tractor/hung-dumps/` for offline
     # inspection. See
     # `ai/conc-anal/cancel_cascade_too_slow_under_main_thread_forkserver_issue.md`.
+    #
+    # NOTE: the `trio` depth=3 budget was bumped 6 -> 12s after
+    # the `trio` 0.29 -> 0.33 lock bump (commit c7741bba) slowed
+    # the depth-3 cancel-cascade from <6s to ~7-8s; the 6s
+    # deadline was firing and its `Cancelled(source='deadline')`
+    # (trio 0.33 cancel-reason metadata) collapsed a BEG branch,
+    # breaking the `RemoteActorError` assertion below. depth=1
+    # still finishes in ~3s so keeps the 6s budget. See
+    # `ai/conc-anal/trio_033_cancel_cascade_slowdown_depth3_issue.md`.
     match (start_method, depth):
-        case ('trio', _):
+        case ('trio', 1):
             timeout = 6
+        case ('trio', 3):
+            timeout = 12
         case ('main_thread_forkserver', 1):
             timeout = 16
         case ('main_thread_forkserver', 3):

tests/test_infected_asyncio.py

@@ -860,7 +860,14 @@ def test_echoserver_detailed_mechanics(
     timeout: float = (
         999 if tractor.debug_mode()
         else 4 if is_forking_spawner
-        else 1
+        # was 1; the `trio` 0.29 -> 0.33 bump slowed the
+        # cancel-cascade so a 1s budget raced the ~1s teardown
+        # deadline. On a deadline-fire the injected
+        # `Cancelled(source='deadline')` wraps the mid-stream
+        # KBI in a `BaseExceptionGroup`, breaking the bare
+        # `pytest.raises(KeyboardInterrupt)` below. See
+        # `ai/conc-anal/trio_033_cancel_cascade_slowdown_depth3_issue.md`.
+        else 4
     )
 
     # body factored out so the `fail_after_w_trace`-wrapping

tractor/devx/_proctitle.py

@@ -24,7 +24,10 @@ which" at a glance without needing to read full
 `/proc/<pid>/cmdline`.
 
 Format:
-  ``tractor[<aid.reprol()>]``    e.g. ``tractor[doggy@1027301b]``
+  ``<_def_prefix>[<aid.reprol()>]``  e.g. ``_subactor[doggy@1027301b]``
+(prefix from the `_def_prefix` const, flipped `tractor` ->
+`_subactor` so sub-actor procs are visually distinct from the
+root in `ps`/`htop` and the reap-recognition markers.)
 
 Uses the canonical `Aid.reprol()` form
 (``<name>@<uuid_short>``) so the proc-title matches the