Breaking change in Streaming API in the next Height Coordinated Upgrade

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Hello,

Please note - there will be a breaking change to streaming Access API in the next height co-ordinated upgrade (11th Feb on Testnet and 13th Feb on Mainnet). However, these streaming APIs are fairly recent, therefore most apps will not be impacted.

Several AccessAPI and ExecutionDataAPI streaming endpoints include a message_index field in the response which indicates the order of messages sent by the server so the client can detect if they missed processing any. Previously, some endpoints used 1 as the first index in a stream while others used 0. After the HCU, all endpoints will be consistent regarding message_index and start from index 0.

APIs that will affected (Protobuf definition) -

  1. SubscribeEvents - Field message_index
  2. SendAndSubscribeTransactionStatuses - Field message_index
  3. SubscribeAccountStatuses - Field message_index

Thank you,
Flow Team

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