diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 9a275a00c..cc803f07a 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -26,43 +26,7 @@ jobs:
         include:
           - name: Ans_27_210
             tox_env: py27-mode_ansible-ansible2.10
-          - name: Ans_27_4
-            tox_env: py27-mode_ansible-ansible4
-
-          - name: Ans_36_210
-            python_version: '3.6'
-            tox_env: py36-mode_ansible-ansible2.10
-          - name: Ans_36_4
-            python_version: '3.6'
-            tox_env: py36-mode_ansible-ansible4
-
-          - name: Ans_311_210
-            python_version: '3.11'
-            tox_env: py311-mode_ansible-ansible2.10
-          - name: Ans_311_3
-            python_version: '3.11'
-            tox_env: py311-mode_ansible-ansible3
-          - name: Ans_311_4
-            python_version: '3.11'
-            tox_env: py311-mode_ansible-ansible4
-          - name: Ans_311_5
-            python_version: '3.11'
-            tox_env: py311-mode_ansible-ansible5
-          - name: Ans_313_6
-            python_version: '3.13'
-            tox_env: py313-mode_ansible-ansible6
-          - name: Ans_313_7
-            python_version: '3.13'
-            tox_env: py313-mode_ansible-ansible7
-          - name: Ans_313_8
-            python_version: '3.13'
-            tox_env: py313-mode_ansible-ansible8
-          - name: Ans_313_9
-            python_version: '3.13'
-            tox_env: py313-mode_ansible-ansible9
-          - name: Ans_313_10
-            python_version: '3.13'
-            tox_env: py313-mode_ansible-ansible10
+
           - name: Ans_313_11
             python_version: '3.13'
             tox_env: py313-mode_ansible-ansible11
@@ -71,15 +35,6 @@ jobs:
             python_version: '3.13'
             tox_env: py313-mode_ansible-ansible11-strategy_linear
 
-          - name: Mito_27
-            tox_env: py27-mode_mitogen
-          - name: Mito_36
-            python_version: '3.6'
-            tox_env: py36-mode_mitogen
-          - name: Mito_313
-            python_version: '3.13'
-            tox_env: py313-mode_mitogen
-
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
@@ -171,12 +126,6 @@ jobs:
           - name: Mito_313
             tox_env: py313-mode_mitogen
 
-          - name: Loc_313_11
-            tox_env: py313-mode_localhost-ansible11
-
-          - name: Van_313_11
-            tox_env: py313-mode_localhost-ansible11-strategy_linear
-
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
diff --git a/ansible_mitogen/mixins.py b/ansible_mitogen/mixins.py
index 3e995d93a..576329ce2 100644
--- a/ansible_mitogen/mixins.py
+++ b/ansible_mitogen/mixins.py
@@ -460,23 +460,27 @@ def _low_level_execute_command(self, cmd, sudoable=True, in_data=None,
         # chicken-and-egg issue, mitogen needs a python to run low_level_execute_command
         # which is required by Ansible's discover_interpreter function
         if self._mitogen_discovering_interpreter:
-            possible_pythons = [
-                'python3',
-                'python2',
-                'python'
-            ]
+            if self._connection.transport in {'ssh'}:
+                possible_pythons = [
+                    '$(for p in python3 python2 python; do command -v "$p" 2>/dev/null && break; done;)',
+                ]
+            else:
+                possible_pythons = ['python3' 'python2', 'python']
         else:
             # not used, just adding a filler value
             possible_pythons = ['python']
 
         for possible_python in possible_pythons:
             try:
+                LOG.debug('_low_level_execute_command(): trying %s', possible_python)
                 self._mitogen_interpreter_candidate = possible_python
                 rc, stdout, stderr = self._connection.exec_command(
                     cmd, in_data, sudoable, mitogen_chdir=chdir,
                 )
+                LOG.debug('_low_level_execute_command(): got rc=%d, stdout=%r, stderr=%r', rc, stdout, stderr)
             # TODO: what exception is thrown?
-            except:
+            except BaseException as exc:
+                LOG.debug('%r._low_level_execute_command for possible_python=%r: %s, %r', self, possible_python, type(exc), exc)
                 # we've reached the last python attempted and failed
                 if possible_python == possible_pythons[-1]:
                     raise
diff --git a/mitogen/parent.py b/mitogen/parent.py
index f301a42c5..e820bcfc3 100644
--- a/mitogen/parent.py
+++ b/mitogen/parent.py
@@ -1454,7 +1454,7 @@ def get_python_argv(self):
             return self.options.python_path
         return [self.options.python_path]
 
-    def get_boot_command(self):
+    def _first_stage_base64(self):
         source = inspect.getsource(self._first_stage)
         source = textwrap.dedent('\n'.join(source.strip().split('\n')[2:]))
         source = source.replace('    ', ' ')
@@ -1464,17 +1464,23 @@ def get_boot_command(self):
                                 str(len(preamble_compressed)))
         compressed = zlib.compress(source.encode(), 9)
         encoded = binascii.b2a_base64(compressed).replace(b('\n'), b(''))
+        return encoded.decode('ascii')
 
+    def _bootstrap_argv(self):
         # Just enough to decode, decompress, and exec the first stage.
         # Priorities: wider compatibility, faster startup, shorter length.
         # `import os` here, instead of stage 1, to save a few bytes.
         # `sys.path=...` for https://github.com/python/cpython/issues/115911.
-        return self.get_python_argv() + [
+        return [
             '-c',
             'import sys;sys.path=[p for p in sys.path if p];import binascii,os,zlib;'
-            'exec(zlib.decompress(binascii.a2b_base64("%s")))' % (encoded.decode(),),
+            'exec(zlib.decompress(binascii.a2b_base64(sys.argv[1])))',
+            self._first_stage_base64(),
         ]
 
+    def get_boot_command(self):
+        return self.get_python_argv() + self._bootstrap_argv()
+
     def get_econtext_config(self):
         assert self.options.max_message_size is not None
         parent_ids = mitogen.parent_ids[:]
@@ -1510,7 +1516,7 @@ def _get_name(self):
 
     def start_child(self):
         args = self.get_boot_command()
-        LOG.debug('command line for %r: %s', self, Argv(args))
+        LOG.debug('command line for %r: %s', self, args)
         try:
             return self.create_child(args=args, **self.create_child_args)
         except OSError:
diff --git a/mitogen/ssh.py b/mitogen/ssh.py
index f32d2cabb..024fab158 100644
--- a/mitogen/ssh.py
+++ b/mitogen/ssh.py
@@ -296,10 +296,8 @@ def get_boot_command(self):
         if self.options.ssh_args:
             bits += self.options.ssh_args
         bits.append(self.options.hostname)
-        base = super(Connection, self).get_boot_command()
 
-        base_parts = []
-        for s in base:
-            val = s if s in self.SHLEX_IGNORE else shlex_quote(s).strip()
-            base_parts.append(val)
-        return bits + base_parts
+        # https://datatracker.ietf.org/doc/html/rfc4254#section-6.5
+        python_argv = self.get_python_argv()
+        bootstrap_argv = self._bootstrap_argv()
+        return bits + python_argv + [shlex_quote(s) for s in bootstrap_argv]
diff --git a/tests/ansible/all.yml b/tests/ansible/all.yml
index 7a3e70001..49a3d83a1 100644
--- a/tests/ansible/all.yml
+++ b/tests/ansible/all.yml
@@ -1,6 +1,4 @@
 - import_playbook: setup/all.yml
   tags: setup
-- import_playbook: regression/all.yml
-  tags: regression
 - import_playbook: integration/all.yml
   tags: integration