Your system information

• Steam client version (build number or date): 1784669098
• Distribution: Fedora Linux 44, KDE Plasma 6.7.3 on Wayland
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• Steam Logs: Full archive not attached because it contains unrelated identifying information. The exact relevant log excerpt is included below. A narrowly scoped and redacted excerpt can be provided if additional context is required.
• GPU: NVIDIA GeForce RTX 4060 Laptop GPU and AMD Radeon 880M/890M
• Steam Runtime: steamrt3c_platform_3c.0.20260618.246540
• Bundled libatk-bridge2.0-0: 2.38.0-1
• Host at-spi2-core: 2.60.5-1.fc44

Please describe your issue in as much detail as possible

A single standard, read-only AT-SPI org.a11y.atspi.Action.GetActions call on Steam's Chromium AT-SPI application root causes steamwebhelper to terminate. Steam automatically starts a replacement helper while the main Steam process remains running.

GetActions is specified to return a(sss): an array of three-string structures containing the localized action name, localized description, and keybinding. Instead, the D-Bus connection is closed while the response is being marshalled. The caller observes that the remote D-Bus peer disconnected, followed by Steam starting a replacement steamwebhelper.

Expected behavior

• GetActions returns a valid a(sss) response.
• The D-Bus connection remains open.
• steamwebhelper continues running.

Actual behavior

• The D-Bus peer disconnects during the call.
• steamwebhelper terminates.
• Steam automatically starts a replacement helper.
• The main Steam process remains running.

The exact relevant Steam log excerpt is:

D-Bus: Array or variant type requires that type end_struct be written, but string was written.
The overall signature expected here was 'a(sss)' and we are on byte 5 of that signature.

The Steam Runtime listed above bundles libatk-bridge2.0-0 version 2.38.0-1. This matches a known upstream bug in the ATK-to-AT-SPI bridge: the affected GetActions implementation opens a three-string (sss) structure but attempts to append four strings. The upstream fix removes the extra unlocalized action name:

https://github.com/GNOME/at-spi2-core/commit/dc0dc3318171c824ba16cbb3e28780df2bda21cc

The host Fedora library is newer, but steamwebhelper loads the Steam Runtime copy at:

/usr/lib/x86_64-linux-gnu/libatk-bridge-2.0.so.0.0.0

Steps for reproducing this issue

1. Start the stable Steam client and leave its desktop UI running.

2. Resolve the AT-SPI bus address:

   AT_SPI_ADDRESS=$(gdbus call --session \
     --dest org.a11y.Bus \
     --object-path /org/a11y/bus \
     --method org.a11y.Bus.GetAddress | cut -d "'" -f 2)
   

3. List the registered AT-SPI application roots:

   gdbus call --address "$AT_SPI_ADDRESS" \
     --dest org.a11y.atspi.Registry \
     --object-path /org/a11y/atspi/accessible/root \
     --method org.a11y.atspi.Accessible.GetChildren
   

4. Identify the unique bus name for Steam's Chromium AT-SPI application root and assign it to STEAM_AT_SPI_BUS_NAME.

5. Run this single direct, read-only call:

   gdbus call --address "$AT_SPI_ADDRESS" \
     --dest "$STEAM_AT_SPI_BUS_NAME" \
     --object-path /org/a11y/atspi/accessible/root \
     --method org.a11y.atspi.Action.GetActions
   

6. Observe that the D-Bus peer disconnects and Steam automatically restarts steamwebhelper, while the main Steam process remains running.