The IRCv3 specifications are available at ircv3.net.

IRCv3.1

Capability negotiation (as specified by IRCv3.1) is supported since Communi version 3.0.

Base extensions
multi-prefix	✔ Since 3.3	IrcUser::prefix IrcUser::mode
sasl	✔ Since 3.0	IrcConnection::saslMechanism IrcConnection::supportedSaslMechanisms
Optional extensions
account-notify	✔ Since 3.3	IrcAccountMessage
away-notify	✔ Since 3.3	IrcAwayMessage::reply
extended-join	✔ Since 3.3	IrcJoinMessage::account IrcJoinMessage::realName
tls	✘

Note: Communi does not automatically request any IRCv3 capabilities. It is left up to client implementations to choose which capabilities are requested.

IRCv3.2

Capability negotiation (as specified by IRCv3.2) is supported since Communi version 3.4, and message tags are supported since Communi version 3.1.

Base extensions
metadata	✘
monitor	✔ Since 3.4	IrcBufferModel::monitorEnabled IrcCommand::createMonitor()
Optional extensions
account-tag	✔ Since 3.4	IrcMessage::account
batch	✘
cap-notify	✔ Since 3.4	IrcNetwork::availableCapabilities IrcCapabilityMessage
chghost	✔ Since 3.4	IrcHostChangeMessage
echo-message	N/A	Should be handled in the client implementation.
invite-notify	✔ Since 3.0	IrcInviteMessage::user
sasl	✘
server-time	✔ Since 3.4	IrcMessage::timeStamp
userhost-in-names	✔ Since 3.0	IrcNamesMessage

Note: Communi does not automatically request any IRCv3 capabilities. It is left up to client implementations to choose which capabilities are requested.