As of SAPUI5 1.6 there is a close coupling of SAPUI5 core/runtime and SAPUI5 tools: It is required that within a running system both have the same version, that is, have the same major and minor version.
For example, SAPUI5 core/runtime 1.x.1 works together with SAPUI5 tools 1.x.2, but not with SAPUI5 tools 1.y. For a future release it is planned to have a more loose coupling here with regards to the minor and micro version.
As of SAPUI5 1.6 we can only support customers who follow this rule in their system landscapes.
SAPUI5 uses a 3-digit version identifier, for example 1.26.4. These digits have the following meaning:
The version number for each new SAPUI5 release contains a major and minor version number. The patch version number is only used to identify patches within a release.
If you are using SAPUI5 or OpenUI5 from SAP BTP, you have the option to switch to a different version as described in Variant for Bootstrapping from Content Delivery Network.
Check the available versions with respective maintenance status at https://ui5.sap.com/versionoverview.html and https://sdk.openui5.org/versionoverview.html.
The SAPUI5 maintenance strategy for SAP BTP is available in this document.