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+Internet Engineering Task Force (IETF)                         C. Smith
+Internet-Draft                                                    Fastmail
+Intended status: Standards Track                          August 15, 2025
+Expires: February 16, 2026
+
+
+                  The JSON Chat Application Protocol (JCHAT)
+                              draft-jchat-00
+
+Abstract
+
+   This document specifies a protocol for real-time chat messaging
+   built on top of the JSON Meta Application Protocol (JMAP) [RFC8620].
+   JCHAT provides a standardized way to exchange chat messages,
+   manage conversations, handle user presence, and synchronize chat
+   state across multiple devices efficiently.
+
+Status of This Memo
+
+   This Internet-Draft is submitted in full conformance with the
+   provisions of BCP 78 and BCP 79.
+
+   Internet-Drafts are working documents of the Internet Engineering
+   Task Force (IETF).  Note that other groups may also distribute
+   working documents as Internet-Drafts.  The list of current Internet-
+   Drafts is at https://datatracker.ietf.org/drafts/current/.
+
+   Internet-Drafts are draft documents valid for a maximum of six months
+   and may be updated, replaced, or obsoleted by other documents at any
+   time.  It is inappropriate to use Internet-Drafts as reference
+   material or to cite them other than as "work in progress."
+
+   This Internet-Draft will expire on February 16, 2026.
+
+Copyright Notice
+
+   Copyright (c) 2025 IETF Trust and the persons identified as the
+   document authors.  All rights reserved.
+
+   This document is subject to BCP 78 and the IETF Trust's Legal
+   Provisions Relating to IETF Documents
+   (https://trustee.ietf.org/license-info) in effect on the date of
+   publication of this document.  Please review these documents
+   carefully, as they describe your rights and restrictions with respect
+   to this document.
+
+Table of Contents
+
+   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
+     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
+     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
+   2.  JCHAT Capability  . . . . . . . . . . . . . . . . . . . . . .   4
+   3.  Data Types  . . . . . . . . . . . . . . . . . . . . . . . . .   5
+     3.1.  Conversation  . . . . . . . . . . . . . . . . . . . . . .   5
+     3.2.  Message . . . . . . . . . . . . . . . . . . . . . . . . .   7
+     3.3.  Participant . . . . . . . . . . . . . . . . . . . . . . .  10
+     3.4.  Presence . . . . . . . . . . . . . . . . . . . . . . . .  11
+   4.  Methods . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
+     4.1.  Conversation Methods . . . . . . . . . . . . . . . . . . .  12
+       4.1.1.  Conversation/get . . . . . . . . . . . . . . . . . . .  12
+       4.1.2.  Conversation/set . . . . . . . . . . . . . . . . . . .  13
+       4.1.3.  Conversation/changes . . . . . . . . . . . . . . . . .  15
+       4.1.4.  Conversation/query . . . . . . . . . . . . . . . . . .  15
+     4.2.  Message Methods . . . . . . . . . . . . . . . . . . . . .  17
+       4.2.1.  Message/get  . . . . . . . . . . . . . . . . . . . . .  17
+       4.2.2.  Message/set  . . . . . . . . . . . . . . . . . . . . .  18
+       4.2.3.  Message/changes . . . . . . . . . . . . . . . . . . .  20
+       4.2.4.  Message/query  . . . . . . . . . . . . . . . . . . . .  20
+     4.3.  Participant Methods . . . . . . . . . . . . . . . . . . .  22
+       4.3.1.  Participant/get  . . . . . . . . . . . . . . . . . . .  22
+       4.3.2.  Participant/set  . . . . . . . . . . . . . . . . . . .  23
+       4.3.3.  Participant/changes  . . . . . . . . . . . . . . . . .  24
+     4.4.  Presence Methods . . . . . . . . . . . . . . . . . . . . .  25
+       4.4.1.  Presence/get . . . . . . . . . . . . . . . . . . . . .  25
+       4.4.2.  Presence/set . . . . . . . . . . . . . . . . . . . . .  26
+   5.  Push Notifications  . . . . . . . . . . . . . . . . . . . . .  27
+   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
+   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  29
+   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  29
+     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  29
+     8.2.  Informative References . . . . . . . . . . . . . . . . . .  30
+   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  30
+
+1.  Introduction
+
+   Modern chat applications require real-time message delivery, 
+   efficient synchronization across multiple devices, and robust
+   handling of conversations with multiple participants. The JSON
+   Meta Application Protocol (JMAP) [RFC8620] provides an excellent
+   foundation for building such applications with its efficient
+   delta synchronization, push notifications, and batched operations.
+
+   JCHAT builds upon JMAP to provide:
+
+   o  Structured conversation management with metadata
+   o  Real-time message delivery and synchronization
+   o  Participant management and permissions
+   o  User presence information
+   o  Message threading and replies
+   o  Rich message content including attachments
+   o  Message delivery receipts and read status
+
+   This specification defines the data model and methods for a 
+   chat system that can scale from simple one-on-one messaging
+   to large group conversations while maintaining the efficiency
+   benefits of JMAP.
+
+1.1.  Notational Conventions
+
+   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
+   "OPTIONAL" in this document are to be interpreted as described in
+   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
+   capitals, as shown here.
+
+   The underlying format used for this specification is JSON.
+   Consequently, the terms "object" and "array" as well as the four
+   primitive types (strings, numbers, booleans, and null) are to be
+   interpreted as described in Section 1 of [RFC8259].
+
+   Type signatures follow the conventions established in [RFC8620].
+
+1.2.  Terminology
+
+   Conversation: A container for messages between one or more
+   participants. Conversations have metadata such as a title,
+   creation time, and participant list.
+
+   Message: A single communication within a conversation, containing
+   text content, metadata, and optionally attachments or replies
+   to other messages.
+
+   Participant: A user who is a member of a conversation and can
+   send and receive messages within that conversation.
+
+   Presence: Information about a user's current availability status
+   and activity.
+
+2.  JCHAT Capability
+
+   The JCHAT capability is identified by the URI:
+
+      "urn:ietf:params:jmap:chat"
+
+   This capability is advertised in the "capabilities" object of
+   the JMAP Session response. The value of this capability in the
+   capabilities object MUST be an object with the following properties:
+
+   o  maxConversationsPerAccount: "UnsignedInt|null"
+      The maximum number of conversations allowed per account.
+      If null, there is no limit.
+
+   o  maxParticipantsPerConversation: "UnsignedInt|null"
+      The maximum number of participants allowed in a single
+      conversation. If null, there is no limit.
+
+   o  maxMessageLength: "UnsignedInt|null"
+      The maximum length in UTF-8 octets of a message body.
+      If null, there is no limit.
+
+   o  supportedMessageTypes: "String[]"
+      A list of message content types supported by the server.
+      MUST include "text/plain". MAY include "text/html",
+      "text/markdown", and others.
+
+   o  maxAttachmentSize: "UnsignedInt|null"
+      The maximum size in octets of a single attachment.
+      If null, attachments are not supported.
+
+3.  Data Types
+
+3.1.  Conversation
+
+   A *Conversation* object represents a chat conversation between
+   one or more participants. It has the following properties:
+
+   o  id: "Id" (immutable; server-set)
+      The id of the conversation.
+
+   o  title: "String|null"
+      A user-defined title for the conversation. If null, clients
+      SHOULD generate a title from participant names.
+
+   o  description: "String|null"
+      An optional description of the conversation purpose.
+
+   o  createdAt: "UTCDate" (immutable; server-set)
+      The date and time the conversation was created.
+
+   o  updatedAt: "UTCDate" (server-set)
+      The date and time the conversation was last modified.
+
+   o  isArchived: "Boolean" (default: false)
+      Whether this conversation has been archived by the user.
+
+   o  isMuted: "Boolean" (default: false)
+      Whether notifications for this conversation are muted.
+
+   o  participantIds: "Id[]"
+      The list of participant IDs who are members of this
+      conversation. The order MAY be significant for display purposes.
+
+   o  lastMessageId: "Id|null" (server-set)
+      The ID of the most recent message in this conversation.
+      null if the conversation has no messages.
+
+   o  lastMessageAt: "UTCDate|null" (server-set)
+      The timestamp of the most recent message in this conversation.
+      null if the conversation has no messages.
+
+   o  unreadCount: "UnsignedInt" (server-set)
+      The number of unread messages in this conversation for
+      this user.
+
+   o  messageCount: "UnsignedInt" (server-set)
+      The total number of messages in this conversation.
+
+   o  metadata: "String[String]|null"
+      Application-specific metadata as key-value pairs.
+
+3.2.  Message
+
+   A *Message* object represents a single message within a conversation.
+   It has the following properties:
+
+   o  id: "Id" (immutable; server-set)
+      The id of the message.
+
+   o  conversationId: "Id" (immutable)
+      The id of the conversation this message belongs to.
+
+   o  senderId: "Id" (immutable)
+      The id of the participant who sent this message.
+
+   o  sentAt: "UTCDate" (immutable; server-set)
+      The date and time the message was sent.
+
+   o  receivedAt: "UTCDate" (immutable; server-set)
+      The date and time the message was received by the server.
+
+   o  editedAt: "UTCDate|null" (server-set)
+      The date and time the message was last edited. null if
+      never edited.
+
+   o  body: "String"
+      The main content of the message.
+
+   o  bodyType: "String" (default: "text/plain")
+      The MIME type of the message body. Servers MUST support
+      "text/plain". MAY support "text/html", "text/markdown".
+
+   o  attachments: "Attachment[]|null"
+      A list of file attachments associated with this message.
+      null if no attachments.
+
+   o  replyToMessageId: "Id|null"
+      The id of the message this message is replying to.
+      null if not a reply.
+
+   o  isSystemMessage: "Boolean" (immutable; default: false)
+      Whether this is a system-generated message (e.g., user
+      joined/left conversation).
+
+   o  isDeleted: "Boolean" (default: false)
+      Whether this message has been marked as deleted.
+
+   o  reactions: "Reaction[]|null" (server-set)
+      A list of emoji reactions to this message. null if no reactions.
+
+   o  deliveryStatus: "DeliveryStatus" (server-set)
+      The delivery status of this message.
+
+   o  readBy: "MessageRead[]" (server-set)
+      A list of participants who have read this message.
+
+   o  metadata: "String[String]|null"
+      Application-specific metadata as key-value pairs.
+
+   An *Attachment* object has the following properties:
+
+   o  blobId: "Id"
+      The blob id of the attachment data.
+
+   o  name: "String"
+      The filename of the attachment.
+
+   o  type: "String"
+      The MIME type of the attachment.
+
+   o  size: "UnsignedInt"
+      The size of the attachment in octets.
+
+   A *Reaction* object has the following properties:
+
+   o  emoji: "String"
+      The Unicode emoji character(s) for the reaction.
+
+   o  participantIds: "Id[]"
+      The list of participant IDs who added this reaction.
+
+   A *DeliveryStatus* is a string with one of the following values:
+
+   o  "sending": The message is being sent to the server.
+   o  "sent": The message has been accepted by the server.
+   o  "delivered": The message has been delivered to all online
+      participants.
+   o  "failed": The message failed to send.
+
+   A *MessageRead* object has the following properties:
+
+   o  participantId: "Id"
+      The id of the participant who read the message.
+
+   o  readAt: "UTCDate"
+      When the participant read the message.
+
+3.3.  Participant
+
+   A *Participant* object represents a user's membership in a
+   conversation. It has the following properties:
+
+   o  id: "Id" (immutable; server-set)
+      The id of the participant record.
+
+   o  conversationId: "Id" (immutable)
+      The id of the conversation.
+
+   o  userId: "Id" (immutable)
+      The id of the user account.
+
+   o  displayName: "String"
+      The display name for this participant in this conversation.
+
+   o  avatarBlobId: "Id|null"
+      The blob id of the participant's avatar image. null if
+      no custom avatar.
+
+   o  role: "String" (default: "member")
+      The participant's role in the conversation. Possible values:
+      "owner", "admin", "member", "observer".
+
+   o  joinedAt: "UTCDate" (immutable; server-set)
+      When the participant joined the conversation.
+
+   o  lastActiveAt: "UTCDate|null" (server-set)
+      When the participant was last active in this conversation.
+      null if never active.
+
+   o  isActive: "Boolean" (server-set)
+      Whether the participant is currently an active member
+      of the conversation.
+
+   o  permissions: "String[]"
+      The list of permissions this participant has in the
+      conversation. Possible values: "send", "edit", "delete",
+      "invite", "remove", "manage".
+
+   o  metadata: "String[String]|null"
+      Application-specific metadata as key-value pairs.
+
+3.4.  Presence
+
+   A *Presence* object represents a user's current availability
+   status. It has the following properties:
+
+   o  userId: "Id" (immutable)
+      The id of the user account.
+
+   o  status: "String"
+      The user's current status. Possible values: "online",
+      "away", "busy", "offline".
+
+   o  statusMessage: "String|null"
+      An optional custom status message.
+
+   o  lastSeenAt: "UTCDate|null" (server-set)
+      When the user was last seen online. null if currently online
+      or privacy settings prevent sharing.
+
+   o  updatedAt: "UTCDate" (server-set)
+      When the presence information was last updated.
+
+4.  Methods
+
+4.1.  Conversation Methods
+
+4.1.1.  Conversation/get
+
+   Standard "/get" method as described in [RFC8620], Section 5.1.
+
+   The following additional properties are supported in the response:
+
+   Additional errors:
+
+   None specific to this method.
+
+4.1.2.  Conversation/set
+
+   Standard "/set" method as described in [RFC8620], Section 5.3.
+
+   When creating a new conversation, the following properties are
+   required in the create object:
+
+   o  participantIds: Must include at least the creating user.
+
+   The following properties MUST NOT be included when creating
+   a conversation:
+
+   o  id, createdAt, updatedAt, lastMessageId, lastMessageAt,
+      unreadCount, messageCount
+
+   When updating a conversation, the following properties are
+   immutable and MUST NOT be changed:
+
+   o  id, createdAt
+
+   Additional SetErrors:
+
+   o  "invalidParticipants": The participantIds list is invalid
+      (empty, contains non-existent users, etc.).
+
+   o  "maxParticipantsExceeded": The conversation would exceed
+      the maximum number of participants allowed.
+
+   o  "insufficientPermissions": The user does not have permission
+      to perform the requested action on this conversation.
+
+4.1.3.  Conversation/changes
+
+   Standard "/changes" method as described in [RFC8620], Section 5.2.
+
+4.1.4.  Conversation/query
+
+   Standard "/query" method as described in [RFC8620], Section 5.5.
+
+   Supported filter conditions:
+
+   o  hasParticipant: "Id"
+      Matches conversations where the specified user is a participant.
+
+   o  isArchived: "Boolean"
+      Matches conversations with the specified archived status.
+
+   o  after: "UTCDate"
+      Matches conversations with lastMessageAt after this date.
+
+   o  before: "UTCDate" 
+      Matches conversations with lastMessageAt before this date.
+
+   o  hasUnread: "Boolean"
+      If true, matches conversations with unreadCount > 0.
+      If false, matches conversations with unreadCount = 0.
+
+   Supported sort options:
+
+   o  "lastMessageAt": Sort by the timestamp of the last message.
+   o  "createdAt": Sort by conversation creation time.
+   o  "title": Sort by conversation title (case-insensitive).
+   o  "unreadCount": Sort by number of unread messages.
+
+   Default sort is "lastMessageAt desc".
+
+4.2.  Message Methods
+
+4.2.1.  Message/get
+
+   Standard "/get" method as described in [RFC8620], Section 5.1.
+
+   Additional errors:
+
+   None specific to this method.
+
+4.2.2.  Message/set
+
+   Standard "/set" method as described in [RFC8620], Section 5.3.
+
+   When creating a new message, the following properties are
+   required in the create object:
+
+   o  conversationId: Must reference an existing conversation.
+   o  body: The message content.
+
+   The following properties MUST NOT be included when creating
+   a message:
+
+   o  id, sentAt, receivedAt, editedAt, reactions, deliveryStatus,
+      readBy
+
+   The following properties are set by the server when creating:
+
+   o  senderId: Set to the authenticated user's participant ID
+      in the specified conversation.
+
+   When updating a message, the following properties are
+   immutable and MUST NOT be changed:
+
+   o  id, conversationId, senderId, sentAt, receivedAt, 
+      isSystemMessage
+
+   Only the message sender can edit these properties:
+
+   o  body, bodyType, attachments
+
+   The server MUST set editedAt when any editable property
+   is modified.
+
+   Message deletion is handled by setting isDeleted to true.
+   Servers MAY permanently delete message content after a
+   retention period.
+
+   Additional SetErrors:
+
+   o  "conversationNotFound": The specified conversationId
+      does not exist.
+
+   o  "notParticipant": The user is not a participant in
+      the specified conversation.
+
+   o  "messageNotFound": The message to update does not exist.
+
+   o  "cannotEditMessage": The user does not have permission
+      to edit this message (not the sender, message too old, etc.).
+
+   o  "invalidReplyTo": The replyToMessageId references a
+      non-existent message or a message in a different conversation.
+
+   o  "messageTooLarge": The message body exceeds maxMessageLength.
+
+4.2.3.  Message/changes
+
+   Standard "/changes" method as described in [RFC8620], Section 5.2.
+
+4.2.4.  Message/query
+
+   Standard "/query" method as described in [RFC8620], Section 5.5.
+
+   Supported filter conditions:
+
+   o  inConversation: "Id"
+      Matches messages in the specified conversation.
+
+   o  from: "Id"
+      Matches messages sent by the specified participant.
+
+   o  after: "UTCDate"
+      Matches messages sent after this date.
+
+   o  before: "UTCDate"
+      Matches messages sent before this date.
+
+   o  hasAttachment: "Boolean"
+      If true, matches messages with attachments.
+
+   o  text: "String"
+      Matches messages containing this text in the body
+      (case-insensitive substring search).
+
+   o  isUnread: "Boolean"
+      If true, matches unread messages for this user.
+
+   o  replyTo: "Id"
+      Matches messages that are replies to the specified message.
+
+   Supported sort options:
+
+   o  "sentAt": Sort by message timestamp.
+   o  "receivedAt": Sort by server receive timestamp.
+
+   Default sort is "sentAt asc".
+
+4.3.  Participant Methods
+
+4.3.1.  Participant/get
+
+   Standard "/get" method as described in [RFC8620], Section 5.1.
+
+4.3.2.  Participant/set
+
+   Standard "/set" method as described in [RFC8620], Section 5.3.
+
+   When creating a new participant, the following properties are
+   required in the create object:
+
+   o  conversationId: Must reference an existing conversation.
+   o  userId: Must reference an existing user account.
+
+   The following properties MUST NOT be included when creating
+   a participant:
+
+   o  id, joinedAt, lastActiveAt, isActive
+
+   When updating a participant, the following properties are
+   immutable and MUST NOT be changed:
+
+   o  id, conversationId, userId, joinedAt
+
+   Only conversation owners/admins can modify:
+
+   o  role, permissions
+
+   Additional SetErrors:
+
+   o  "conversationNotFound": The specified conversationId
+      does not exist.
+
+   o  "userNotFound": The specified userId does not exist.
+
+   o  "alreadyParticipant": The user is already a participant
+      in this conversation.
+
+   o  "cannotModifyParticipant": The user does not have
+      permission to modify participants in this conversation.
+
+   o  "cannotRemoveSelf": The user cannot remove themselves
+      from the conversation (use conversation archiving instead).
+
+4.3.3.  Participant/changes
+
+   Standard "/changes" method as described in [RFC8620], Section 5.2.
+
+4.4.  Presence Methods
+
+4.4.1.  Presence/get
+
+   Standard "/get" method as described in [RFC8620], Section 5.1.
+
+   Users can only retrieve presence information for users they
+   share conversations with, unless broader permissions are granted.
+
+   Additional errors:
+
+   o  "cannotAccessPresence": The user does not have permission
+      to view presence information for the requested users.
+
+4.4.2.  Presence/set
+
+   Standard "/set" method as described in [RFC8620], Section 5.3.
+
+   Users can only update their own presence information.
+
+   The following properties are immutable and MUST NOT be changed:
+
+   o  userId, lastSeenAt, updatedAt
+
+   Additional SetErrors:
+
+   o  "cannotSetOthersPresence": Attempted to set presence
+      for a user other than the authenticated user.
+
+5.  Push Notifications
+
+   JCHAT extends JMAP push notifications to provide real-time
+   updates for chat events. The following state changes trigger
+   push notifications:
+
+   o  New messages in conversations the user participates in
+   o  Changes to conversation metadata
+   o  Participant additions/removals
+   o  Presence updates for users the client is interested in
+
+   Push subscription setup follows the standard JMAP push model
+   described in [RFC8620], Section 7.
+
+   The push notification payload includes the standard JMAP
+   StateChange object with the following chat-specific type
+   changes:
+
+   o  "Conversation": Conversation state changes
+   o  "Message": Message state changes  
+   o  "Participant": Participant state changes
+   o  "Presence": Presence state changes
+
+   Clients SHOULD subscribe to push notifications for responsive
+   chat experience and battery efficiency on mobile devices.
+
+6.  Security Considerations
+
+   JCHAT inherits the security model of JMAP [RFC8620] and adds
+   the following chat-specific considerations:
+
+   o  Message Privacy: Messages are only accessible to conversation
+      participants. Servers MUST enforce participant membership
+      when processing requests.
+
+   o  Participant Management: Only users with appropriate permissions
+      can add/remove participants or modify conversation settings.
+
+   o  Presence Privacy: Presence information should only be shared
+      with users who share conversations or have explicit permission.
+
+   o  Message Retention: Servers SHOULD provide configurable message
+      retention policies and honor deletion requests.
+
+   o  Content Filtering: Servers MAY implement content filtering
+      for spam, abuse, or regulatory compliance.
+
+   o  Rate Limiting: Servers SHOULD implement rate limiting for
+      message sending to prevent abuse.
+
+7.  IANA Considerations
+
+   This document registers the JMAP Capability for chat as follows:
+
+   Capability Name: urn:ietf:params:jmap:chat
+   Specification document: This document
+   Intended use: COMMON
+   Change controller: IETF
+   Security and privacy considerations: See Section 6
+
+8.  References
+
+8.1.  Normative References
+
+   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
+              Requirement Levels", BCP 14, RFC 2119,
+              DOI 10.17487/RFC2119, March 1997,
+              <https://www.rfc-editor.org/info/rfc2119>.
+
+   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
+              2119 Key Words", BCP 14, RFC 8174,
+              DOI 10.17487/RFC8174, May 2017,
+              <https://www.rfc-editor.org/info/rfc8174>.
+
+   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON)
+              Data Interchange Format", STD 90, RFC 8259,
+              DOI 10.17487/RFC8259, December 2017,
+              <https://www.rfc-editor.org/info/rfc8259>.
+
+   [RFC8620]  Jenkins, N. and C. Newman, "The JSON Meta Application
+              Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620,
+              July 2019, <https://www.rfc-editor.org/info/rfc8620>.
+
+8.2.  Informative References
+
+   [RFC6901]  Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
+              "JavaScript Object Notation (JSON) Pointer", RFC 6901,
+              DOI 10.17487/RFC6901, April 2013,
+              <https://www.rfc-editor.org/info/rfc6901>.
+
+Author's Address
+
+   Calvin Smith
+   Fastmail
+   
+   Email: calvin@fastmail.com