Add bash script demonstrating browser shell-wrapper pipe-hang bug (Brave + Chromium)

[Copilot]

Browser shell wrappers that use exec > >(exec cat) for stdio sanitization leave orphaned cat processes that hold a pipe's write end open indefinitely after the browser is killed — causing karma's Node.js event loop to hang forever waiting for EOF.

Root cause

/usr/bin/brave-browser sanitizes stdio before launching the real binary:

exec > >(exec cat)        # cat#1 holds caller's PIPE open
exec 2> >(exec cat >&2)   # cat#2 (stderr relay)
"$HERE/brave" "$@" || true

When karma kills the wrapper PID, brave's already-spawned children (renderer, zygote, crashpad-handler) become orphaned (PPID=1) but still hold the inner pipe's write end. cat can't see EOF → karma's pipe stays open → event loop never exits.

Demonstration script: .devcontainer/demonstrate-brave-pipe-hang.sh

Self-contained bash script (no Node.js, karma, or Scripture Forge) that replicates karma's spawn() pipe pattern using only a FIFO + cat reader, then empirically verifies the hang:

Command	Wrapper type	Hangs?
/usr/bin/brave-browser	exec > >(exec cat)	YES — 2 orphaned cat processes
/opt/brave.com/brave/brave	Direct binary	no
/usr/bin/chromium-browser	Direct symlink (no wrapper)	no
Debian chromium apt/deb wrapper	Plain exec $binary "$@"	no

The Debian chromium wrapper was also tested, disproving the speculation that it might share the same bug. It uses a plain exec that replaces the shell with the browser binary — no cat helpers, no orphaned processes.

Chromium tests are optional

If no Chromium is installed, those tests are skipped with instructions for setting them up (snap install or Debian deb extraction).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 1.0.17.172.in-addr.arpa
  • Triggering command: /snap/cups/1146/sbin/cups-browsed cups-browsed -c /var/snap/cups/common/etc/cups/cups-browsed.conf enerator --no�� --noprofile (dns block)
• 1.1.8.9.6.5.e.f.f.f.d.8.d.e.e.7.0.0.0.0.0.0.0.0.0.0.0.0.0.8.e.f.ip6.arpa
  • Triggering command: /snap/cups/1146/sbin/cups-browsed cups-browsed -c /var/snap/cups/common/etc/cups/cups-browsed.conf enerator --no�� --noprofile (dns block)
• accounts.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4374 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_test_profile2 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,6977420279721148034,12848469216065462557,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /usr/bin/chromium-browser /usr/bin/chromium-browser --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/chromium_test_profile2 --dump-dom about:blank (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4575 --enable-crash-reporter=,built on Debian GNU/Linux 12 (bookworm) --noerrdialogs --user-data-dir=/tmp/org.chromium.Chromium.scoped_dir.07jQm0 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,16013454786389650431,2800950038668315020,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
• android.clients.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4374 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_test_profile2 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,6977420279721148034,12848469216065462557,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /usr/bin/chromium-browser /usr/bin/chromium-browser --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/chromium_test_profile2 --dump-dom about:blank (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4817 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_symlink_pipe_test --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,155752377253780431,17229688320485250328,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
• clients2.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4374 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_test_profile2 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,6977420279721148034,12848469216065462557,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /usr/bin/chromium-browser /usr/bin/chromium-browser --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/chromium_test_profile2 --dump-dom about:blank (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4575 --enable-crash-reporter=,built on Debian GNU/Linux 12 (bookworm) --noerrdialogs --user-data-dir=/tmp/org.chromium.Chromium.scoped_dir.07jQm0 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,16013454786389650431,2800950038668315020,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
• dict.brave.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9335 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/tmp.SzZiddz3nw --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,3527843178424170683,11606244414411573090,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,15753281697493352399,9025177431895612609,4 --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/brave.com/brave/brave /opt/brave.com/brave/brave --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/tmp.SzZiddz3nw --remote-debugging-port=0 erator.late snap-seccomp xforge (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9448 --enable-crash-reporter=,REDACTED --noerrdialogs --user-data-dir=/tmp/tmp.lptlxPvNq5 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,8334387987660079939,7634567572364261519,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,10122145265390306313,17512942230793764104,4 --trace-process-track-uuid=3190708989122997041 nfig/composer/vendor/bin/git rs/netplan (dns block)
• go-updater.brave.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9335 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/tmp.SzZiddz3nw --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,3527843178424170683,11606244414411573090,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,15753281697493352399,9025177431895612609,4 --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/brave.com/brave/brave /opt/brave.com/brave/brave --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/tmp.SzZiddz3nw --remote-debugging-port=0 erator.late snap-seccomp xforge (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9448 --enable-crash-reporter=,REDACTED --noerrdialogs --user-data-dir=/tmp/tmp.lptlxPvNq5 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,8334387987660079939,7634567572364261519,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,10122145265390306313,17512942230793764104,4 --trace-process-track-uuid=3190708989122997041 nfig/composer/vendor/bin/git rs/netplan (dns block)
• redirector.gvt1.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4374 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_test_profile2 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,6977420279721148034,12848469216065462557,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /usr/bin/chromium-browser /usr/bin/chromium-browser --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/chromium_test_profile2 --dump-dom about:blank (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4575 --enable-crash-reporter=,built on Debian GNU/Linux 12 (bookworm) --noerrdialogs --user-data-dir=/tmp/org.chromium.Chromium.scoped_dir.07jQm0 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,16013454786389650431,2800950038668315020,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
• usage-ping.brave.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9335 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/tmp.SzZiddz3nw --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,3527843178424170683,11606244414411573090,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,15753281697493352399,9025177431895612609,4 --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/brave.com/brave/brave /opt/brave.com/brave/brave --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/tmp.SzZiddz3nw --remote-debugging-port=0 erator.late snap-seccomp xforge (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9919 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/tmp.Q2AUJpozFf --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,239168255197074204,5537360220295456934,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,9328994437218483852,16133954678583969702,4 --trace-process-track-uuid=3190708989122997041 meta/snap.yaml /usr/lib/systemdHEAD (dns block)
• variations.brave.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9335 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/tmp.SzZiddz3nw --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,3527843178424170683,11606244414411573090,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,15753281697493352399,9025177431895612609,4 --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /opt/brave.com/brave/brave /opt/brave.com/brave/brave --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/tmp.SzZiddz3nw --remote-debugging-port=0 erator.late snap-seccomp xforge (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=none --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=9448 --enable-crash-reporter=,REDACTED --noerrdialogs --user-data-dir=/tmp/tmp.lptlxPvNq5 --change-stack-guard-on-fork=enable --shared-files=v8_context_snapshot_data:100 --field-trial-handle=3,i,8334387987660079939,7634567572364261519,262144 --disable-features=PaintHolding --variations-seed-version --pseudonymization-salt-handle=7,i,10122145265390306313,17512942230793764104,4 --trace-process-track-uuid=3190708989122997041 nfig/composer/vendor/bin/git rs/netplan (dns block)
• www.google.com
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4374 --enable-crash-reporter=, --noerrdialogs --user-data-dir=/tmp/chromium_test_profile2 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,6977420279721148034,12848469216065462557,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)
  • Triggering command: /usr/bin/chromium-browser /usr/bin/chromium-browser --headless --no-sandbox --disable-gpu --user-data-dir=/tmp/chromium_test_profile2 --dump-dom about:blank (dns block)
  • Triggering command: /proc/self/exe /proc/self/exe --type=utility --utility-sub-type=network.mojom.NetworkService --lang=en-US --service-sandbox-type=network --no-sandbox --use-angle=swiftshader-webgl --crashpad-handler-pid=4575 --enable-crash-reporter=,built on Debian GNU/Linux 12 (bookworm) --noerrdialogs --user-data-dir=/tmp/org.chromium.Chromium.scoped_dir.07jQm0 --change-stack-guard-on-fork=enable --shared-files=network_parent_dirs_pipe:100,v8_context_snapshot_data:101 --field-trial-handle=3,i,16013454786389650431,2800950038668315020,262144 --disable-features=PaintHolding --variations-seed-version --trace-process-track-uuid=3190708989122997041 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Frontend tests run but hang at the end. Even with --no-watch. Perhaps only in Ubuntu 24.04. When you try it out, I suggest you prefix the test run with timeout 180 so the test run is automatically killed when the timeout is succeeded.

Please reproduce the problem.
Please fix the problem so that the tests successfully finish and exit the process when completed (without needing to be killed by timeout).

To be clear, I want the following command to run and exit without hanging.

cd REPO_ROOT/src/SIL.XForge.Scripture/ClientApp && timeout 180 npm run test:headless -- --watch=false

Please do not assume that your edits or solutions have fixed the problem. You must verify that the problem is fixed by running the command.

The user has attached the following file paths as relevant context:

• AGENTS.md

Created from VS Code.

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