Restart the client once for a title mapped while it runs

The client reads config.vdf once, as it starts. A title installed during a
session got its per-app ARM64 Proton entry from the compat beat, but the
running client kept its own pick: native for a Linux build, which then sat
on "Downloading content (0%)" waiting for Steam Linux Runtime 2.0 and FEX
it can never run here (Left 4 Dead 2), or proton-stable for a Windows one.

The beat now runs the compat pass with --live, which notes titles it maps
while the client runs. Once each has finished installing and no game is
running, the session restarts the client through the existing restart-once
marker. Once per title and three times per session at most. The mapping is
re-applied before the client starts again, since it writes config.vdf back
from memory as it exits.

tools/linuxfs/overlay/usr/local/bin/bannerlator-session

@@ -498,6 +498,31 @@ case $mode in
         done
         return 1
       }
+      # A title the compat pass maps while the client runs only takes that mapping at the client's
+      # next start (see bannerlator-steam-compat): until then the client launches it its own way -
+      # a Linux build stuck on "Downloading content (0%)" for a Steam Linux Runtime and FEX that
+      # cannot run here (Left 4 Dead 2, 2026-10-02). So restart the client once for it, through the
+      # same marker and -shutdown as the ARM64 Proton's restart: only when every new title has
+      # finished installing (StateFlags 4) and no game is running; another download just resumes.
+      # Once per title and three times per session at most, so a client that rewrites config.vdf
+      # can never loop it.
+      compat_pending=$HOME/.bl-compat-pending
+      compat_restarted=$HOME/.bl-compat-restarted
+      rm -f "$compat_pending"
+      : > "$compat_restarted"
+      compat_restarts=0
+      compat_settled() {
+        local app m flags
+        while read -r app; do
+          [ -n "$app" ] || continue
+          m="$steam_root/steamapps/appmanifest_$app.acf"
+          [ -f "$m" ] || m="/mnt/droiddeck-sd/steamapps/appmanifest_$app.acf"
+          [ -f "$m" ] || return 1
+          flags=$(sed -n 's/^[[:space:]]*"StateFlags"[[:space:]]*"\([0-9]*\)".*/\1/p' "$m" | head -n 1)
+          [ "$flags" = 4 ] || return 1
+        done < "$compat_pending"
+        ! pgrep -f 'reaper SteamLaunch' >/dev/null 2>&1
+      }
       for ((_i = 0; _i < 720; _i++)); do
         nap 5
         beat=$((beat + 1))
@@ -505,7 +530,17 @@ case $mode in
         bannerlator-seed-redists "$steam_root" >/dev/null 2>&1 || true
         if compat_due; then
           : > "$compat_stamp"
-          bannerlator-steam-compat "$steam_root" >/dev/null 2>&1 || true
+          bannerlator-steam-compat "$steam_root" --live >/dev/null 2>&1 || true
+        fi
+        if [ -s "$compat_pending" ] && compat_settled; then
+          _bl_new=$(sort -u "$compat_pending" | grep -vxF -f "$compat_restarted" || true)
+          rm -f "$compat_pending"
+          [ -n "$_bl_new" ] && [ "$compat_restarts" -lt 3 ] || continue
+          compat_restarts=$((compat_restarts + 1))
+          printf '%s\n' $_bl_new >> "$compat_restarted"
+          step "newly installed title(s) $(echo $_bl_new) set to the ARM64 Proton: restarting the Steam client once so it takes effect"
+          : > "$HOME/.bl-restart-once"
+          "$steam_root/steamrtarm64/steam" -shutdown >/dev/null 2>&1 || true
         fi
       done
     ) &
@@ -719,6 +754,9 @@ BUSCONF
       # arguments, which were acted on. Not counted against the update cap.
       if [ -f "$HOME/.bl-restart-once" ]; then
         echo "== steam: restarting once so the new compatibility layer is in the client's lists"
+        # The client wrote config.vdf back from its own memory as it exited, which can drop the
+        # per-title entries written while it ran - the very ones this restart is for.
+        bannerlator-steam-compat "$steam_root" >/dev/null 2>&1 || true
         set --
         continue
       fi

tools/linuxfs/overlay/usr/local/bin/bannerlator-steam-compat

@@ -579,7 +579,8 @@ def installed_apps(steam_root):
 
 
 def register_default(config_path, apps=(), name=None, protect=()):
-    """Writes the mapping. `name` defaults to our own tool; the first-run seed passes Valve's."""
+    """Writes the mapping. `name` defaults to our own tool; the first-run seed passes Valve's.
+    Returns the app ids given a per-app entry by this call."""
     tool = name or TOOL
     # Tool names the user may deliberately have chosen (see adopt_extras); never repointed.
     keep = {n.lower() for n in protect}
@@ -588,7 +589,8 @@ def register_default(config_path, apps=(), name=None, protect=()):
     tokens = tokenize(original)
     steam = find_block(tokens, ["InstallConfigStore", "Software", "Valve", "Steam"])
     if steam is None:
-        return
+        return []
+    added = []
     mapping = find_block(tokens[steam + 1:], ["CompatToolMapping"])
     entry = ['"0"', "{", '"name"', '"%s"' % tool, '"config"', '""', '"priority"', '"75"', "}"]
     if mapping is None:
@@ -612,10 +614,12 @@ def register_default(config_path, apps=(), name=None, protect=()):
                 continue
             tokens[mapping + 1:mapping + 1] = [
                 '"%s"' % app, "{", '"name"', '"%s"' % tool, '"config"', '""', '"priority"', '"250"', "}"]
+            added.append(app)
     # Nothing to change is the usual case on the session's beat: the client's own file is left alone.
     text = serialize(tokens)
     if text != serialize(tokenize(original)):
         write_changed(config_path, text)
+    return added
 
 
 def depot_build(depot):
@@ -666,8 +670,18 @@ def main():
     config = os.path.join(steam_root, "config", "config.vdf")
     if os.path.isfile(config):
         apps = installed_apps(steam_root)
-        register_default(config, apps, protect=extras)
+        added = register_default(config, apps, protect=extras)
         print("bannerlator-steam-compat: default and %d installed title(s) set to %s" % (len(apps), TOOL))
+        # The client reads config.vdf once, as it starts, and keeps its own decisions in memory for
+        # the rest of its run: a title installed while it runs gets the client's own pick (native
+        # for a Linux build, which then waits for Steam Linux Runtime + FEX it can never run here;
+        # proton-stable for a Windows one), and the entry written here only counts from the next
+        # start. Run from the session's beat (--live), the new entries are noted for the session,
+        # which restarts the client once the install has settled (bannerlator-session).
+        if added and "--live" in sys.argv[2:]:
+            with open(os.path.join(os.path.expanduser("~"), ".bl-compat-pending"), "a") as f:
+                f.write("".join("%s\n" % a for a in added))
+            print("bannerlator-steam-compat: mapped while the client runs: %s" % " ".join(added))
 
 
 if __name__ == "__main__":