Here's the issue again when running test_pdb.py for 3.11 (repository main). The same problem now occurs twice, and only inside the `screen` environment.

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~/Temp/cpython> ./python Lib/test/test_pdb.py
.....F.........F........................................
======================================================================
FAIL: test_errors_in_command (__main__.PdbTestCase)
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Traceback (most recent call last):
  File "/home/leon/Temp/cpython/Lib/test/test_pdb.py", line 1847, in test_errors_in_command
    self.assertEqual(stdout.splitlines()[1:], [
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Lists differ: ['-> [278 chars]efined", 'LEAVING RECURSIVE DEBUGGER', '(Pdb) ', '\x1b[?1034h'] != ['-> [278 chars]efined", 'LEAVING RECURSIVE DEBUGGER', '(Pdb) ']

First list contains 1 additional elements.
First extra element 10:
'\x1b[?1034h'

  ['-> pass',
   "(Pdb) *** SyntaxError: '(' was never closed",
   '(Pdb) ENTERING RECURSIVE DEBUGGER',
   "*** SyntaxError: '(' was never closed",
   'LEAVING RECURSIVE DEBUGGER',
   '(Pdb) ENTERING RECURSIVE DEBUGGER',
   '> <string>(1)<module>()',
   "((Pdb)) *** NameError: name 'doesnotexist' is not defined",
   'LEAVING RECURSIVE DEBUGGER',
-  '(Pdb) ',
?          ^

+  '(Pdb) ']
?          ^

-  '\x1b[?1034h']

======================================================================
FAIL: test_issue34266 (__main__.PdbTestCase)
do_run handles exceptions from parsing its arg
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Traceback (most recent call last):
  File "/home/leon/Temp/cpython/Lib/test/test_pdb.py", line 1875, in test_issue34266
    check('\\', 'No escaped character')
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/leon/Temp/cpython/Lib/test/test_pdb.py", line 1870, in check
    self.assertEqual(stdout.splitlines()[1:], [
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Lists differ: ['-> [13 chars] *** Cannot run \\: No escaped character', '(Pdb) \x1b[?1034h'] != ['-> [13 chars] *** Cannot run \\: No escaped character', '(Pdb) ']

First differing element 2:
'(Pdb) \x1b[?1034h'
'(Pdb) '

- ['-> pass',
-  '(Pdb) *** Cannot run \\: No escaped character',
+ ['-> pass', '(Pdb) *** Cannot run \\: No escaped character', '(Pdb) ']
? +++++++++++                                                 ++++++++++

-  '(Pdb) \x1b[?1034h']

----------------------------------------------------------------------
Ran 56 tests in 2.850s

FAILED (failures=2)