v4: a deployment chooses which ways federated sign-in goes — every instance took users of the others and let its own sign in to them, with no way to turn either off. GERBEUR_FEDERATION_INCOMING=0 keeps users of other instances out: the login and register pages offer no other instance, /manage no list of instances, their sign-ins are refused, and those already in are signed out until it is on again, their homes' events still applied meanwhile. GERBEUR_FEDERATION_OUTGOING=0 keeps the instance's users from signing in elsewhere: its /authorize page lets no instance sign them in, its metadata says so (gerbeur_outgoing), which other instances check before sending anyone there, the settings page lists no instances, and at startup every grant is withdrawn, which signs them out there. Both are on by default and reach the client through index.html. The dev instance gerbeur (:3000) takes no users of the others, while its own still sign in to them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.env.example

@@ -71,6 +71,12 @@ GERBEUR_DEFAULT_STYLE=smooth
 # How often, in minutes, the /community page's figures are recomputed.
 GERBEUR_COMMUNITY_REFRESH_MINUTES=15
 
+# Set to 0 to keep users of other gerbeur instances from signing in here, which
+# also signs out those already in until it is set back, or to keep this
+# instance's users from signing in to others, which signs them out there.
+# GERBEUR_FEDERATION_INCOMING=1
+# GERBEUR_FEDERATION_OUTGOING=1
+
 # Set to 1 to let federated sign-in reach other instances on private addresses
 # (localhost included) and over plain http, so that two instances on one
 # machine can trust each other in development. Never in production.