# Major engine version behavior and compatibility differences with Valkey
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Valkey 7.2.6 has similar compatibility differences with previous versions of Redis OSS 7.2.4. For the most recent supported version of Valkey, see [Supported engines and versions](VersionManagement.md#supported-engine-versions).

For more information on the Valkey 7.2 release, see [Redis OSS 7.2.4 Release Notes](https://github.com/valkey-io/valkey/blob/d2c8a4b91e8c0e6aefd1f5bc0bf582cddbe046b7/00-RELEASENOTES) (Valkey 7.2 includes all changes from Redis OSS up to version 7.2.4) and [Valkey 7.2 release notes](https://github.com/valkey-io/valkey/blob/7.2/00-RELEASENOTES) at Valkey on GitHub.

Here are the potentially breaking behavior changes between Valkey 7.2 and Redis OSS 7.1 (or 7.0):
+ Freeze time sampling occurs during command execution and in scripts.
+ A blocked stream command that's released when key no longer exists carries a different error code (-NOGROUP or -WRONGTYPE instead of -UNBLOCKED). 
+ Client side tracking for scripts now tracks the keys that are read by the script, instead of the keys that are declared by the caller of EVAL / FCALL.