Blender 5.0 is expected in less than one year now. According to our Compatibility Policy, this is the next opportunity to make changes in Blender that introduce severe forward compatibility breakages. Blender 4.5 will have to be compatible with these changes, and allow some level of conversion between blendfiles from 5.x releases and older Blenders.
There are two main categories of changes that should only happen when switching to a new major version.
- Blendfile Data: Changes to the blendfile format itself, or some of the stored data (e.g. heavy modifications to an existing ID type), that will make new blendfiles impossible to open in older releases.
- Non-essential API changes: Changes to the Blender Python API that can be delayed, but need to be done at some point. For example, cleanups (renaming or removal of deprecated items), or refactors leading to modifications of existing behaviors.
General Schedule
All modules that have plans to introduce such forward incompatibilities should start working on it now. The goal is to have finalized plans and designs agreed on by the end of 2024, and to start implementing them in the first quarter of 2025.
As the owner of the Blendfile I/O, RNA and DNA areas of Blender, the Core module will coordinate the process and validate the designs regarding their compatibility handling.
Third Quarter 2024 - Planning & Design
Module teams discuss their plans for the module, and create TODO and/or Design tasks. All tasks must be listed in one of these two parent TODO tasks:
These two tasks will be used a reference and ground truth for coordination purposes.
It’s the responsibility of each module to reach out and ask for feedback from other affected/related modules during the design phase. They should ensure that all aspects of the proposed changes are well understood and accepted.
Modules should also update the main releases compatibility page with any planned significant user-level change as soon as possible.
First Semester 2025 - Implementation
Implementation work should start early in 2025. Especially regarding Blendfile breakages, all work must be done and merged before June 2025 (as Blender 4.5 will enter Beta on 04/06/2025).
Note that Blendfile breakage will likely require two working branches, one to implement forward compatibility changes in 4.5, and the other for the actual breaking changes in 5.0. Having these two branches in parallel will also make it easier to test blendfiles compatibility during development.