From 0b2de17b126c9a68dfd160037d9a5e125a939f37 Mon Sep 17 00:00:00 2001
From: Byeonghoon Yoo <bhyoo@bhyoo.com>
Date: Tue, 21 Apr 2026 13:56:32 +0900
Subject: [PATCH] fix: use D-Bus auto-activation for AT-SPI bus in isolated
 sessions
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The hardcoded `/usr/lib/at-spi-bus-launcher` path is only correct on
Arch. Upstream at-spi2-core has migrated to `/usr/libexec/`, so on
Fedora, Debian sid, Ubuntu 24.04+, and Flatpak runtimes the AT-SPI
bus never starts and every AT-SPI tool (accessibility_tree,
find_ui_elements, wait_for_element, list_windows, focus_window)
fails with "Couldn't connect to accessibility bus".

Replace the manual launcher invocation with a D-Bus auto-activation
trigger (`gdbus call org.a11y.Bus.GetAddress`). dbus-daemon resolves
the service file and execs the launcher at whatever path the current
distro's package installed it to, so kwin-mcp no longer encodes any
binary path. at-spi2-registryd is auto-activated on first access by
the same mechanism, so no manual bootstrap is needed.

Also drop AT_SPI_PID from the cleanup trap — auto-activated processes
are torn down when dbus-run-session closes the session bus.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 CHANGELOG.md            |  1 +
 src/kwin_mcp/session.py | 31 ++++++++++++++++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66eaada..d395d90 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Segfault on Python 3.14 caused by missing `argtypes` on variadic `ei_seat_bind_capabilities` ctypes call
+- `accessibility_tree`, `find_ui_elements`, `wait_for_element`, `list_windows`, and `focus_window` now work in isolated virtual sessions on Fedora, Debian, Ubuntu, and any other distro that installs the AT-SPI bus launcher outside `/usr/lib` (e.g. `/usr/libexec`). Instead of executing a hardcoded path, the AT-SPI bus is now brought up via D-Bus auto-activation (`gdbus call org.a11y.Bus.GetAddress`), which defers binary-path resolution to `dbus-daemon` and the distro-provided service file. The registry daemon is auto-activated transparently when apps first touch the a11y bus, so no manual bootstrap is required. Thanks to @davidselassie for reporting the Fedora failure in [#8](https://github.com/isac322/kwin-mcp/pull/8).
 
 ## [0.7.0] - 2026-03-29
 
diff --git a/src/kwin_mcp/session.py b/src/kwin_mcp/session.py
index 8d0582b..84b0db3 100644
--- a/src/kwin_mcp/session.py
+++ b/src/kwin_mcp/session.py
@@ -333,19 +333,32 @@ def _build_wrapper_script(self, config: SessionConfig) -> str:
         return f"""\
 echo "DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS"
 
-# Ensure all child processes are cleaned up on exit
+# Ensure all child processes are cleaned up on exit.
+# The AT-SPI bus launcher and registryd are started via D-Bus
+# auto-activation below; they are terminated automatically when our
+# isolated session bus exits (dbus-run-session tears the bus down on
+# parent exit), so we only need to track KWin explicitly here.
 cleanup() {{
-    kill $KWIN_PID $AT_SPI_PID 2>/dev/null
-    wait $KWIN_PID $AT_SPI_PID 2>/dev/null
+    kill $KWIN_PID 2>/dev/null
+    wait $KWIN_PID 2>/dev/null
 }}
 trap cleanup EXIT TERM INT HUP
 
-# Start the AT-SPI accessibility bus.
-# ATSPI_DBUS_IMPLEMENTATION is set in _build_env() to force dbus-daemon
-# instead of dbus-broker (which reuses the host's AT-SPI bus).
-/usr/lib/at-spi-bus-launcher --launch-immediately &
-AT_SPI_PID=$!
-sleep 0.2
+# Bring up the AT-SPI accessibility bus via D-Bus auto-activation.
+# Calling org.a11y.Bus.GetAddress makes dbus-daemon resolve the
+# service file (/usr/share/dbus-1/services/org.a11y.Bus.service) and
+# exec the launcher at whatever path the current distro uses — Arch
+# /usr/lib, Fedora/Debian/Ubuntu /usr/libexec, Flatpak /app/libexec,
+# etc. Hardcoding a path breaks on everything except Arch.
+# ATSPI_DBUS_IMPLEMENTATION=dbus-daemon (set in _build_env) prevents
+# dbus-broker from sharing the host's a11y bus.
+# The registryd comes up on its own when apps first touch the a11y
+# bus, so no manual bootstrap is needed here.
+gdbus call --session \\
+    --dest=org.a11y.Bus \\
+    --object-path=/org/a11y/bus \\
+    --method=org.a11y.Bus.GetAddress >/dev/null 2>&1 || true
+sleep 0.3
 
 # Pre-set D-Bus activation environment BEFORE starting KWin.
 # When KWin triggers portal auto-activation, portal-kde will get