Release notes article -> https://www.asyncapi.com/blog/release-notes-2.5.0

Features

• Server Variables can be now referenced from inside the Server Object (#776) (5deef1e), resolves #775 by @char0n
• Decorating Server Object with tags (#809) (b0c2f9c), resolves #654, resolves #465 by @smoya
• Added new Google Cloud Pub/Sub Bindings (#836) (babc3be) (binding definition) by @whitlockjc
• Added schema registry infos to Kafka binding (#115) (binding definition) by @lbroudoux
• Other enhancements
  • Clarified ChannelItem.$ref resolution rules (#779) (9a293c7), resolves #612 by @char0n
  • Clarification around URL resolution rules (#782) (fc324ef), resolves #674 by @char0n
  • Align wording with RFC 2119 (#818) (5580a9c) by @char0n

Fixes

• Added missing IBM MQ Operation Binding (#840) (68d85d1) (binding definition), refs #605 by @magicmatatjahu

Full Changelog: https://github.com/asyncapi/spec/compare/v2.4.0...v2.5.0

Changelog

Overview

• Unified events, stream, and topics into the channels object.
• Added a way to describe protocol-specific information, using the bindings object.
• Added support for multiple message schemas.
• Added optional id property to make it clear that an AsyncAPI document represents a single application.
• Added support for RAML-like traits in the Operation and Message objects.
• Added support for correlation IDS. Kudos to @SensibleWood.

Changes

• Added top-level property id.
• Changed topics to channels.
• Changed topics (now channels) format to URI template.
• Removed events and stream in favor of channels.
• Removed top-level property baseTopic.
• Added top-level property defaultContentType.
• Moved top-level property security to the Server object.
• Renamed Server object scheme as protocol.
• Renamed Server object schemeVersion as protocolVersion.
• Removed the restriction on supported protocols.
• Added examples property to the Server Variable object.
• Added support for correlation IDs. Kudos to @SensibleWood.
• Added support for RAML-like traits in the Operation and Message objects.
• Added examples property to the Schema object.
• Added bindings property to the Server, Channel, Operation, and Message objects.
• Added message property to the Operation object.
• Added schemaFormat property to the Message object.
• Added contentType property to the Message object.
• Added title property to the Message object.
• Added name property to the Message object.
• Changed the purpose of Message object headers to be only application-related headers.
• Removed constraints on Message object payload property. Its content can be anything now.
• Changed the example property in the Message object to examples.
• Fixed Server Variable object so it's not mandatory to provide at least one field. Kudos to @MikeRalphson.
• Improved the definitions section. Kudos to @jschabowsky.
• Changed schema.json from JSON Schema Draft 04 to Draft 07.
• Fixed specification extensions regular expression.
• Changed Schema object. It's now a superset of JSON Schema Draft 07.
• Added property location to Parameter object.
• Added missing security scheme types.
• Changed Parameters object. It's now an object/map instead of an array.
• Changed Servers object. It's now an object/map instead of an array

This release biggest —and possibly breaking— changes are:

• Schema Object is now a superset of JSON Schema Draft 07: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#schemaObject.
• Rename protocolInfo to bindings.
• Add bindings to Server Object: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#serverObject.
• Restricts most common protocols in the Bindings Object.
• Fixes Security Requirement Object definition.
• Add parameter location: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#parameterObject.
• Add missing security scheme types (they were on the JSON Schema definition but not on the Markdown one).
• Now parameters is an object/map instead of an array: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#parametersObject.
• Now servers is an object/map instead of an array: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#serversObject.
• Remove variables support from traits and simplifies syntax: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#messageTraitObject and https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#operationTraitObject.
• Remove baseChannel from the Server Object.
• Remove support for non-JSON schemas, like Protobuf and XSD.
• Message headers are a JSON Schema object again: https://github.com/asyncapi/asyncapi/blob/2.0.0-rc2/versions/next/asyncapi.md#messageObject.
• Id is now optional.