Nostr Relay Protocol

asyncapi: '2.6.0'
info:
  title: Nostr Relay Protocol
  version: '1.0.0'
  description: |
    AsyncAPI definition of the canonical Nostr relay-client protocol as
    specified by NIP-01 (basic protocol) and NIP-42 (authentication).

    Nostr relays expose a single WebSocket endpoint that exchanges JSON
    arrays as messages. Clients publish signed events and open filtered
    subscriptions; relays acknowledge publishes, stream matching events,
    signal end-of-stored-events, terminate subscriptions, and optionally
    challenge for authentication.

    Each message on the wire is a JSON array whose first element is a
    string label (EVENT, REQ, CLOSE, OK, EOSE, CLOSED, NOTICE, AUTH)
    identifying the message type. This spec models each label as a
    distinct AsyncAPI message and groups them under publish/subscribe
    operations on the single relay channel.

    Sources:
      - https://github.com/nostr-protocol/nips/blob/master/01.md
      - https://github.com/nostr-protocol/nips/blob/master/42.md
      - https://github.com/nostr-protocol/nips/blob/master/11.md
  contact:
    name: API Evangelist
    url: https://apievangelist.com
    email: [email protected]
  license:
    name: Public Domain
    url: https://github.com/nostr-protocol/nips/blob/master/LICENSE
  tags:
    - name: Nostr
    - name: NIP-01
    - name: NIP-42
    - name: Relay
    - name: WebSocket
servers:
  production:
    url: relay.example
    protocol: wss
    description: |
      Any Nostr relay implementing NIP-01. There is no canonical relay;
      clients typically connect to several relays in parallel. Public
      examples include wss://relay.damus.io, wss://nos.lol, and
      wss://relay.nostr.band. Relay metadata (supported NIPs, limits,
      payment requirements) is published via NIP-11 over HTTPS with the
      `Accept: application/nostr+json` header.
defaultContentType: application/json
channels:
  /:
    description: |
      The single WebSocket channel exposed by a Nostr relay. All
      client-to-relay and relay-to-client messages flow over this
      connection as JSON arrays. From the client's perspective,
      `publish` operations send messages to the relay and `subscribe`
      operations receive messages from the relay.
    bindings:
      ws:
        bindingVersion: '0.1.0'
    publish:
      operationId: sendToRelay
      summary: Messages a client sends to a relay.
      description: |
        Client-to-relay messages defined by NIP-01 and NIP-42. A client
        may publish an EVENT, open or update a subscription with REQ,
        terminate a subscription with CLOSE, or respond to an
        authentication challenge with AUTH.
      message:
        oneOf:
          - $ref: '#/components/messages/ClientEvent'
          - $ref: '#/components/messages/ClientReq'
          - $ref: '#/components/messages/ClientClose'
          - $ref: '#/components/messages/ClientAuth'
    subscribe:
      operationId: receiveFromRelay
      summary: Messages a relay sends to a client.
      description: |
        Relay-to-client messages defined by NIP-01 and NIP-42. The relay
        streams matching EVENTs for each open subscription, acknowledges
        published events with OK, signals end of stored events with
        EOSE, terminates subscriptions with CLOSED, surfaces human
        readable messages via NOTICE, and may challenge for
        authentication with AUTH.
      message:
        oneOf:
          - $ref: '#/components/messages/RelayEvent'
          - $ref: '#/components/messages/RelayOk'
          - $ref: '#/components/messages/RelayEose'
          - $ref: '#/components/messages/RelayClosed'
          - $ref: '#/components/messages/RelayNotice'
          - $ref: '#/components/messages/RelayAuthChallenge'
components:
  messages:
    ClientEvent:
      name: ClientEvent
      title: EVENT (client to relay)
      summary: Publish a signed event to the relay.
      description: |
        `["EVENT", <event>]` — submits a signed Nostr event for the
        relay to store and forward to matching subscriptions. The relay
        replies with an `OK` message keyed by the event id.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/ClientEventMessage'
    ClientReq:
      name: ClientReq
      title: REQ (client to relay)
      summary: Open or replace a subscription with one or more filters.
      description: |
        `["REQ", <subscription_id>, <filter1>, <filter2>, ...]` — asks
        the relay to send all stored events matching any of the filters
        and to stream future matching events until the subscription is
        closed. `subscription_id` is an arbitrary non-empty string of
        up to 64 characters, scoped to the connection.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/ClientReqMessage'
    ClientClose:
      name: ClientClose
      title: CLOSE (client to relay)
      summary: Terminate a previously opened subscription.
      description: |
        `["CLOSE", <subscription_id>]` — instructs the relay to stop
        sending events for the given subscription. The relay does not
        need to acknowledge this message.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/ClientCloseMessage'
    ClientAuth:
      name: ClientAuth
      title: AUTH (client to relay, NIP-42)
      summary: Respond to a relay AUTH challenge with a signed kind 22242 event.
      description: |
        `["AUTH", <signed-event>]` — the client signs a kind 22242
        event whose tags include `["relay", <relay-url>]` and
        `["challenge", <challenge-string>]` from the most recent AUTH
        challenge, and sends it back. The relay replies with an `OK`
        message keyed by the event id.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/ClientAuthMessage'
    RelayEvent:
      name: RelayEvent
      title: EVENT (relay to client)
      summary: Stream a stored or live event matching an open subscription.
      description: |
        `["EVENT", <subscription_id>, <event>]` — the relay delivers an
        event that matches one of the filters in the named
        subscription. Stored events are sent first, followed by EOSE,
        then live events as they arrive.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayEventMessage'
    RelayOk:
      name: RelayOk
      title: OK (relay to client)
      summary: Acknowledge a published EVENT or AUTH event.
      description: |
        `["OK", <event_id>, <true|false>, <message>]` — the relay
        accepted (`true`) or rejected (`false`) an event submitted via
        EVENT or AUTH. The message string is always present and SHOULD
        be prefixed (`duplicate:`, `pow:`, `blocked:`, `rate-limited:`,
        `invalid:`, `restricted:`, `error:`) when rejecting.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayOkMessage'
    RelayEose:
      name: RelayEose
      title: EOSE (relay to client)
      summary: Mark the end of stored events for a subscription.
      description: |
        `["EOSE", <subscription_id>]` — signals that all stored events
        matching the subscription have been delivered. Any further
        EVENTs on this subscription are live updates.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayEoseMessage'
    RelayClosed:
      name: RelayClosed
      title: CLOSED (relay to client)
      summary: Indicate the relay has terminated a subscription.
      description: |
        `["CLOSED", <subscription_id>, <message>]` — the relay refused
        or ended a subscription. The message string uses the same
        prefix conventions as `OK` (`auth-required:`, `restricted:`,
        `rate-limited:`, `error:` and so on).
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayClosedMessage'
    RelayNotice:
      name: RelayNotice
      title: NOTICE (relay to client)
      summary: Surface a human readable message from the relay.
      description: |
        `["NOTICE", <message>]` — used by the relay to communicate
        errors or informational messages that are not tied to a
        specific event or subscription.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayNoticeMessage'
    RelayAuthChallenge:
      name: RelayAuthChallenge
      title: AUTH (relay to client, NIP-42)
      summary: Challenge the client to authenticate.
      description: |
        `["AUTH", <challenge-string>]` — initiates NIP-42
        authentication. The challenge is valid for the lifetime of the
        connection or until replaced. The client must reply with a
        client AUTH message containing a signed kind 22242 event.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/RelayAuthChallengeMessage'
  schemas:
    Event:
      type: object
      description: |
        A canonical Nostr event as defined by NIP-01. The `id` is the
        lowercase hex sha256 of the serialized event array
        `[0, pubkey, created_at, kind, tags, content]`. The `sig` is a
        64-byte Schnorr signature over `id`.
      required:
        - id
        - pubkey
        - created_at
        - kind
        - tags
        - content
        - sig
      properties:
        id:
          type: string
          pattern: '^[0-9a-f]{64}$'
          description: 32-byte lowercase hex-encoded sha256 of the serialized event.
        pubkey:
          type: string
          pattern: '^[0-9a-f]{64}$'
          description: 32-byte lowercase hex-encoded secp256k1 public key of the author.
        created_at:
          type: integer
          format: int64
          description: Unix timestamp in seconds.
        kind:
          type: integer
          minimum: 0
          maximum: 65535
          description: Event kind. Kind semantics are defined by individual NIPs.
        tags:
          type: array
          description: Array of tag arrays. Each tag is an array of strings; the first element is the tag name.
          items:
            type: array
            items:
              type: string
        content:
          type: string
          description: Arbitrary string payload whose meaning depends on the event kind.
        sig:
          type: string
          pattern: '^[0-9a-f]{128}$'
          description: 64-byte lowercase hex-encoded Schnorr signature of `id`.
    Filter:
      type: object
      description: |
        A NIP-01 subscription filter. A REQ message carries one or more
        filters and the relay returns events matching any of them.
        Tag filters are expressed as keys of the form `#<single-letter>`
        whose values are arrays of strings.
      additionalProperties: true
      properties:
        ids:
          type: array
          description: List of event ids (or id prefixes) to match.
          items:
            type: string
        authors:
          type: array
          description: List of pubkeys (or pubkey prefixes) to match.
          items:
            type: string
        kinds:
          type: array
          description: List of event kinds to match.
          items:
            type: integer
            minimum: 0
            maximum: 65535
        since:
          type: integer
          format: int64
          description: Match events with `created_at >= since`.
        until:
          type: integer
          format: int64
          description: Match events with `created_at <= until`.
        limit:
          type: integer
          minimum: 0
          description: Maximum number of stored events to return.
    ClientEventMessage:
      type: array
      description: '["EVENT", <event>]'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: EVENT
        - $ref: '#/components/schemas/Event'
    ClientReqMessage:
      type: array
      description: '["REQ", <subscription_id>, <filter>, ...]'
      minItems: 3
      items:
        - type: string
          const: REQ
        - type: string
          minLength: 1
          maxLength: 64
          description: Connection-scoped subscription identifier.
      additionalItems:
        $ref: '#/components/schemas/Filter'
    ClientCloseMessage:
      type: array
      description: '["CLOSE", <subscription_id>]'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: CLOSE
        - type: string
          minLength: 1
          maxLength: 64
          description: Subscription identifier to terminate.
    ClientAuthMessage:
      type: array
      description: '["AUTH", <signed kind 22242 event>] (NIP-42)'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: AUTH
        - $ref: '#/components/schemas/Event'
    RelayEventMessage:
      type: array
      description: '["EVENT", <subscription_id>, <event>]'
      minItems: 3
      maxItems: 3
      items:
        - type: string
          const: EVENT
        - type: string
          description: Subscription identifier the event is associated with.
        - $ref: '#/components/schemas/Event'
    RelayOkMessage:
      type: array
      description: '["OK", <event_id>, <accepted>, <message>]'
      minItems: 4
      maxItems: 4
      items:
        - type: string
          const: OK
        - type: string
          pattern: '^[0-9a-f]{64}$'
          description: Hex id of the EVENT or AUTH event being acknowledged.
        - type: boolean
          description: True if the event was accepted by the relay.
        - type: string
          description: Human readable message; MAY be empty when accepted.
    RelayEoseMessage:
      type: array
      description: '["EOSE", <subscription_id>]'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: EOSE
        - type: string
          description: Subscription identifier whose stored events have all been sent.
    RelayClosedMessage:
      type: array
      description: '["CLOSED", <subscription_id>, <message>]'
      minItems: 3
      maxItems: 3
      items:
        - type: string
          const: CLOSED
        - type: string
          description: Subscription identifier the relay is closing.
        - type: string
          description: Human readable reason; uses NIP-01 prefix conventions.
    RelayNoticeMessage:
      type: array
      description: '["NOTICE", <message>]'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: NOTICE
        - type: string
          description: Human readable message from the relay.
    RelayAuthChallengeMessage:
      type: array
      description: '["AUTH", <challenge-string>] (NIP-42)'
      minItems: 2
      maxItems: 2
      items:
        - type: string
          const: AUTH
        - type: string
          description: Opaque challenge string the client must sign into a kind 22242 event.