Launchers: skip a python3 older than the bootstrap needs

plugin/scripts/te

@@ -32,10 +32,27 @@ if [ "${OS:-}" = Windows_NT ]; then
     exec "$py" "$dir/te_bootstrap.py" cli "$@"
   done
 else
-  for py in "${TE_PYTHON:-}" python3 python; do
-    [ -n "$py" ] && command -v "$py" >/dev/null 2>&1 || continue
-    exec "$py" "$dir/te_bootstrap.py" cli "$@"
+  # TE_PYTHON is the person's own choice: it runs as named. Otherwise the first python3 on PATH
+  # can be older than the bootstrap's minimum (macOS /usr/bin/python3 is 3.9, and an agent's
+  # hook PATH is often not a login shell's), which would make the plugin a silent no-op with a
+  # newer Python installed: take the first one new enough. With none, run the first one too old
+  # (the probe exits 1), so the bootstrap still fails open / says what it needs; a name that
+  # runs no Python (a pyenv shim with no version set exits 127) is passed over. The probe
+  # skips `site` (-E -S).
+  if [ -n "${TE_PYTHON:-}" ] && command -v "$TE_PYTHON" >/dev/null 2>&1; then
+    exec "$TE_PYTHON" "$dir/te_bootstrap.py" cli "$@"
+  fi
+  probe='import sys; sys.exit(sys.version_info < (3, 10))'
+  old=
+  for py in python3 python3.15 python3.14 python3.13 python3.12 python3.11 python3.10 python; do
+    command -v "$py" >/dev/null 2>&1 || continue
+    "$py" -E -S -c "$probe" </dev/null >/dev/null 2>&1
+    case $? in
+      0) exec "$py" "$dir/te_bootstrap.py" cli "$@" ;;
+      1) [ -n "$old" ] || old=$py ;;
+    esac
   done
+  [ -n "$old" ] && exec "$old" "$dir/te_bootstrap.py" cli "$@"
 fi
 echo "te: no python3 on PATH (set TE_PYTHON)" >&2
 exit 1

plugin/scripts/te-hook

@@ -1,5 +1,6 @@
 #!/bin/sh
-# TokenEconomizer hook launcher: run the hook dispatcher under the first Python 3 on PATH.
+# TokenEconomizer hook launcher: run the hook dispatcher under TE_PYTHON, else the first Python
+# 3.10+ on PATH.
 # Fails open -- with no usable Python the hook prints an empty object, which changes nothing.
 # On Windows (Git Bash), $0 can arrive with backslashes. The Microsoft Store alias under WindowsApps
 # runs nothing, and every probe of it starts AppXSvc (python/pymanager#396), so a Python outside
@@ -35,10 +36,27 @@ if [ "${OS:-}" = Windows_NT ]; then
     exec "$py" "$dir/te_bootstrap.py" hook "$@"
   done
 else
-  for py in "${TE_PYTHON:-}" python3 python; do
-    [ -n "$py" ] && command -v "$py" >/dev/null 2>&1 || continue
-    exec "$py" "$dir/te_bootstrap.py" hook "$@"
+  # TE_PYTHON is the person's own choice: it runs as named. Otherwise the first python3 on PATH
+  # can be older than the bootstrap's minimum (macOS /usr/bin/python3 is 3.9, and an agent's
+  # hook PATH is often not a login shell's), which would make the plugin a silent no-op with a
+  # newer Python installed: take the first one new enough. With none, run the first one too old
+  # (the probe exits 1), so the bootstrap still fails open / says what it needs; a name that
+  # runs no Python (a pyenv shim with no version set exits 127) is passed over. The probe
+  # skips `site` (-E -S).
+  if [ -n "${TE_PYTHON:-}" ] && command -v "$TE_PYTHON" >/dev/null 2>&1; then
+    exec "$TE_PYTHON" "$dir/te_bootstrap.py" hook "$@"
+  fi
+  probe='import sys; sys.exit(sys.version_info < (3, 10))'
+  old=
+  for py in python3 python3.15 python3.14 python3.13 python3.12 python3.11 python3.10 python; do
+    command -v "$py" >/dev/null 2>&1 || continue
+    "$py" -E -S -c "$probe" </dev/null >/dev/null 2>&1
+    case $? in
+      0) exec "$py" "$dir/te_bootstrap.py" hook "$@" ;;
+      1) [ -n "$old" ] || old=$py ;;
+    esac
   done
+  [ -n "$old" ] && exec "$old" "$dir/te_bootstrap.py" hook "$@"
 fi
 # Drain stdin with a builtin (no `cat` when PATH is empty), then answer "no change".
 while IFS= read -r _line; do :; done

tests/test_plugin_package.py

@@ -198,6 +198,67 @@ def test_the_launcher_fails_open_without_python(tmp_path):
     assert code == 0 and json.loads(out) == {}
 
 
+def _old_python(path, marker):
+    # Fails the launcher's version probe (`-E -S -c ...`); anything else it is asked to run, it
+    # records.
+    _script(path, f'for a in "$@"; do [ "$a" = -c ] && exit 1; done\n: > "{marker}"\n'
+                  'while IFS= read -r _l; do :; done\necho "{}"')
+
+
+@pytest.mark.skipif(os.name == "nt", reason="the POSIX launcher path")
+def test_the_launcher_skips_a_python3_older_than_the_bootstrap_needs(tmp_path):
+    old, new = tmp_path / "old" / "python3", tmp_path / "new" / "python3.12"
+    _old_python(old, tmp_path / "old_ran")
+    _script(new, f'exec "{sys.executable}" "$@"')
+    work = tmp_path / "work"
+    work.mkdir()
+    code, out, _ = _run_hook(os.path.join(PLUGIN, "scripts", "te-hook"),
+                             {"hook_event_name": "SessionStart", "session_id": "s",
+                              "cwd": str(work), "source": "startup"},
+                             _hook_env(tmp_path, PATH=f"{old.parent}:{new.parent}:/usr/bin:/bin"))
+    assert code == 0 and json.loads(out) == {}
+    assert os.path.isdir(tmp_path / "home" / "repos")      # the new Python ran the dispatcher
+    assert not (tmp_path / "old_ran").exists()
+
+
+@pytest.mark.skipif(os.name == "nt", reason="the POSIX launcher path")
+def test_with_only_an_old_python_the_launcher_still_hands_it_the_hook(tmp_path):
+    old = tmp_path / "old" / "python3"
+    _old_python(old, tmp_path / "old_ran")
+    code, out, _ = _run_hook(os.path.join(PLUGIN, "scripts", "te-hook"),
+                             {"hook_event_name": "SessionStart"},
+                             {"PATH": str(old.parent),
+                              "TOKENECONOMIZER_HOME": str(tmp_path / "home")})
+    assert code == 0 and json.loads(out) == {}
+    assert (tmp_path / "old_ran").exists()                 # so the bootstrap can fail open itself
+
+
+@pytest.mark.skipif(os.name == "nt", reason="the POSIX launcher path")
+def test_a_shim_that_runs_no_python_is_passed_over(tmp_path):
+    """A pyenv shim with no version set exits 127 and runs nothing: with no other Python on
+    PATH, the launcher answers no change itself."""
+    shim = tmp_path / "shims" / "python3"
+    _script(shim, 'echo "pyenv: python3: command not found" >&2\nexit 127')
+    code, out, _ = _run_hook(os.path.join(PLUGIN, "scripts", "te-hook"),
+                             {"hook_event_name": "SessionStart"}, {"PATH": str(shim.parent)})
+    assert code == 0 and json.loads(out) == {}
+
+
+@pytest.mark.skipif(os.name == "nt", reason="the POSIX launcher path")
+def test_te_python_runs_as_named_even_beside_a_newer_python(tmp_path):
+    """`TE_PYTHON` is the person's own choice: the launcher runs it without a probe, and the
+    bootstrap says what it needs if it is too old."""
+    old, new = tmp_path / "old" / "python3", tmp_path / "new" / "python3.12"
+    _old_python(old, tmp_path / "old_ran")
+    _script(new, f'exec "{sys.executable}" "$@"')
+    code, out, _ = _run_hook(os.path.join(PLUGIN, "scripts", "te-hook"),
+                             {"hook_event_name": "SessionStart"},
+                             {"PATH": str(new.parent), "TE_PYTHON": str(old),
+                              "TOKENECONOMIZER_HOME": str(tmp_path / "home")})
+    assert code == 0 and json.loads(out) == {}
+    assert (tmp_path / "old_ran").exists()
+
+
 def test_the_bootstrap_answers_no_change_on_an_old_python(tmp_path, monkeypatch):
     sys.path.insert(0, os.path.join(PLUGIN, "scripts"))
     try: