personal memory agent
Recover desktop session env vars from systemd when missing
When the observer is launched from SSH or tmux, DISPLAY,
WAYLAND_DISPLAY, and DBUS_SESSION_BUS_ADDRESS may be missing from the
inherited environment. Before failing with EX_TEMPFAIL, query
`systemctl --user show-environment` to recover these vars from the
running GNOME session (which pushes them into the systemd user manager
on startup). Silently falls back to existing behavior if systemctl is
unavailable or the session isn't running.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
+228
+44
observe/linux/observer.py
+44
observe/linux/observer.py
···
829
829
logger.info("Callosum connection stopped")
830
830
831
831
832
+
def _recover_session_env() -> None:
833
+
"""Try to recover desktop session env vars from the systemd user manager.
834
+
835
+
On GNOME Wayland, gnome-shell pushes DISPLAY, WAYLAND_DISPLAY, and
836
+
DBUS_SESSION_BUS_ADDRESS into the systemd user environment on startup.
837
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When the observer is launched from SSH or tmux, these vars may be missing
838
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from the inherited environment — but systemctl --user show-environment
839
+
has them.
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+
"""
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needed = {"DISPLAY", "WAYLAND_DISPLAY", "DBUS_SESSION_BUS_ADDRESS"}
842
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missing = {v for v in needed if not os.environ.get(v)}
843
+
if not missing:
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return
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+
846
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# Ensure XDG_RUNTIME_DIR is set (required for systemctl --user to connect)
847
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if not os.environ.get("XDG_RUNTIME_DIR"):
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os.environ["XDG_RUNTIME_DIR"] = f"/run/user/{os.getuid()}"
849
+
850
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try:
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result = subprocess.run(
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["systemctl", "--user", "show-environment"],
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capture_output=True,
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text=True,
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timeout=5,
856
+
)
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if result.returncode != 0:
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return
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+
except (FileNotFoundError, subprocess.TimeoutExpired):
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return
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+
862
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recovered = []
863
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for line in result.stdout.splitlines():
864
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key, _, value = line.partition("=")
865
+
if key in missing and value:
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os.environ[key] = value
867
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recovered.append(f"{key}={value}")
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+
869
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if recovered:
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logger.info("Recovered session env from systemd: %s", ", ".join(recovered))
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+
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+
832
873
def check_session_ready() -> str | None:
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"""Check if the desktop session is ready for observation.
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875
835
876
Returns None if ready, or a description of what's missing.
836
877
"""
878
+
# Try to recover missing session vars from systemd user manager
879
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_recover_session_env()
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+
837
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# Display server
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if not os.environ.get("DISPLAY") and not os.environ.get("WAYLAND_DISPLAY"):
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return "no display server (DISPLAY/WAYLAND_DISPLAY not set)"
+184
tests/test_session_env.py
+184
tests/test_session_env.py
···
1
+
# SPDX-License-Identifier: AGPL-3.0-only
2
+
# Copyright (c) 2026 sol pbc
3
+
4
+
"""Tests for desktop session environment recovery."""
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+
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import os
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import subprocess
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from unittest.mock import patch
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+
10
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from observe.linux.observer import _recover_session_env, check_session_ready
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+
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+
13
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class TestRecoverSessionEnv:
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"""Tests for _recover_session_env()."""
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+
16
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def test_noop_when_vars_already_set(self, monkeypatch):
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"""Should not call systemctl when all vars are present."""
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monkeypatch.setenv("DISPLAY", ":1")
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monkeypatch.setenv("WAYLAND_DISPLAY", "wayland-0")
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monkeypatch.setenv("DBUS_SESSION_BUS_ADDRESS", "unix:path=/run/user/1000/bus")
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+
22
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with patch("observe.linux.observer.subprocess.run") as mock_run:
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_recover_session_env()
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mock_run.assert_not_called()
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+
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def test_recovers_missing_vars(self, monkeypatch):
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"""Should recover missing vars from systemctl output."""
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monkeypatch.delenv("DISPLAY", raising=False)
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monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
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monkeypatch.delenv("DBUS_SESSION_BUS_ADDRESS", raising=False)
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monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
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+
33
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systemctl_output = (
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"HOME=/home/user\n"
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"DISPLAY=:0\n"
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"WAYLAND_DISPLAY=wayland-0\n"
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"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus\n"
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"XDG_SESSION_TYPE=wayland\n"
39
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)
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mock_result = subprocess.CompletedProcess(
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args=[], returncode=0, stdout=systemctl_output, stderr=""
42
+
)
43
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with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
44
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_recover_session_env()
45
+
46
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assert os.environ.get("DISPLAY") == ":0"
47
+
assert os.environ.get("WAYLAND_DISPLAY") == "wayland-0"
48
+
assert (
49
+
os.environ.get("DBUS_SESSION_BUS_ADDRESS") == "unix:path=/run/user/1000/bus"
50
+
)
51
+
52
+
def test_recovers_only_missing_vars(self, monkeypatch):
53
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"""Should not overwrite vars that are already set."""
54
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monkeypatch.setenv("DISPLAY", ":5")
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monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
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monkeypatch.setenv("DBUS_SESSION_BUS_ADDRESS", "unix:path=/run/user/1000/bus")
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monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
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+
59
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systemctl_output = "DISPLAY=:0\nWAYLAND_DISPLAY=wayland-0\n"
60
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mock_result = subprocess.CompletedProcess(
61
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args=[], returncode=0, stdout=systemctl_output, stderr=""
62
+
)
63
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with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
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_recover_session_env()
65
+
66
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assert os.environ.get("DISPLAY") == ":5" # unchanged
67
+
assert os.environ.get("WAYLAND_DISPLAY") == "wayland-0" # recovered
68
+
69
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def test_sets_xdg_runtime_dir_if_missing(self, monkeypatch):
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"""Should set XDG_RUNTIME_DIR from uid when missing."""
71
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monkeypatch.delenv("DISPLAY", raising=False)
72
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monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
73
+
monkeypatch.delenv("DBUS_SESSION_BUS_ADDRESS", raising=False)
74
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monkeypatch.delenv("XDG_RUNTIME_DIR", raising=False)
75
+
76
+
mock_result = subprocess.CompletedProcess(
77
+
args=[], returncode=0, stdout="DISPLAY=:0\n", stderr=""
78
+
)
79
+
with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
80
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_recover_session_env()
81
+
82
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assert os.environ.get("XDG_RUNTIME_DIR") == f"/run/user/{os.getuid()}"
83
+
84
+
def test_handles_systemctl_failure(self, monkeypatch):
85
+
"""Should silently handle systemctl failure."""
86
+
monkeypatch.delenv("DISPLAY", raising=False)
87
+
monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
88
+
monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
89
+
90
+
mock_result = subprocess.CompletedProcess(
91
+
args=[], returncode=1, stdout="", stderr="error"
92
+
)
93
+
with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
94
+
_recover_session_env()
95
+
96
+
assert not os.environ.get("DISPLAY")
97
+
98
+
def test_handles_systemctl_not_found(self, monkeypatch):
99
+
"""Should silently handle missing systemctl binary."""
100
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monkeypatch.delenv("DISPLAY", raising=False)
101
+
monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
102
+
monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
103
+
104
+
with patch(
105
+
"observe.linux.observer.subprocess.run", side_effect=FileNotFoundError
106
+
):
107
+
_recover_session_env()
108
+
109
+
assert not os.environ.get("DISPLAY")
110
+
111
+
def test_handles_systemctl_timeout(self, monkeypatch):
112
+
"""Should silently handle systemctl timeout."""
113
+
monkeypatch.delenv("DISPLAY", raising=False)
114
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monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
115
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monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
116
+
117
+
with patch(
118
+
"observe.linux.observer.subprocess.run",
119
+
side_effect=subprocess.TimeoutExpired(cmd="systemctl", timeout=5),
120
+
):
121
+
_recover_session_env()
122
+
123
+
assert not os.environ.get("DISPLAY")
124
+
125
+
def test_ignores_empty_values(self, monkeypatch):
126
+
"""Should not set vars with empty values."""
127
+
monkeypatch.delenv("DISPLAY", raising=False)
128
+
monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
129
+
monkeypatch.setenv("DBUS_SESSION_BUS_ADDRESS", "unix:path=/run/user/1000/bus")
130
+
monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
131
+
132
+
systemctl_output = "DISPLAY=\nWAYLAND_DISPLAY=wayland-0\n"
133
+
mock_result = subprocess.CompletedProcess(
134
+
args=[], returncode=0, stdout=systemctl_output, stderr=""
135
+
)
136
+
with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
137
+
_recover_session_env()
138
+
139
+
assert not os.environ.get("DISPLAY")
140
+
assert os.environ.get("WAYLAND_DISPLAY") == "wayland-0"
141
+
142
+
143
+
class TestCheckSessionReady:
144
+
"""Tests for check_session_ready() with env recovery integration."""
145
+
146
+
def test_ready_after_recovery(self, monkeypatch):
147
+
"""Should pass after recovering vars from systemd."""
148
+
monkeypatch.delenv("DISPLAY", raising=False)
149
+
monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
150
+
monkeypatch.delenv("DBUS_SESSION_BUS_ADDRESS", raising=False)
151
+
monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
152
+
153
+
systemctl_output = (
154
+
"DISPLAY=:0\n"
155
+
"WAYLAND_DISPLAY=wayland-0\n"
156
+
"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus\n"
157
+
)
158
+
mock_result = subprocess.CompletedProcess(
159
+
args=[], returncode=0, stdout=systemctl_output, stderr=""
160
+
)
161
+
with (
162
+
patch("observe.linux.observer.subprocess.run", return_value=mock_result),
163
+
patch("observe.linux.observer.shutil.which", return_value=None),
164
+
):
165
+
result = check_session_ready()
166
+
167
+
assert result is None
168
+
169
+
def test_fails_when_recovery_incomplete(self, monkeypatch):
170
+
"""Should fail when recovery doesn't provide display vars."""
171
+
monkeypatch.delenv("DISPLAY", raising=False)
172
+
monkeypatch.delenv("WAYLAND_DISPLAY", raising=False)
173
+
monkeypatch.delenv("DBUS_SESSION_BUS_ADDRESS", raising=False)
174
+
monkeypatch.setenv("XDG_RUNTIME_DIR", "/run/user/1000")
175
+
176
+
# systemctl returns nothing useful
177
+
mock_result = subprocess.CompletedProcess(
178
+
args=[], returncode=0, stdout="HOME=/home/user\n", stderr=""
179
+
)
180
+
with patch("observe.linux.observer.subprocess.run", return_value=mock_result):
181
+
result = check_session_ready()
182
+
183
+
assert result is not None
184
+
assert "DISPLAY" in result