# Java 26.1 Snapshot 1
-# https://www.minecraft.net/article/minecraft-26-1-snapshot-1
## Changes
- What trades are unlocked by villager professions are now determined using deterministic random sequences
- The algorithm that maps block and sky light levels to how bright things appear on screen has been fully rewritten
### Lightmap Algorithm Changes
- The new algorithm is supposed to mostly provide the same overall results as before, but:
- It is simpler and more straightforward, and fixes multiple issues of the previous one
- The Darkness effect and world darkening effect of the Wither fight now works the same way in all dimensions
- The Night Vision effect now simply adds ambient light instead of scaling the resulting colors
### Lightmap Debug Renderer
- A new debug renderer for the lightmap was added, which can be enabled using the `F3 + 4` keybind
- It shows the lightmap texture in real-time in the bottom right corner of the screen
- The vertical axis of the texture represent sky light levels (0-15 from bottom to top)
- The horizontal axis of the texture represent block light levels (0-15 from left to right)
- The color of each pixel represents the resulting color that will be applied to blocks and entities lit with the corresponding block and sky light levels
## Technical Changes
- The Data Pack version is now 95
- Trades offered by Villagers and Wandering Traders are now data-driven and can be customized by datapack developers. For more details, refer to the blog post
- If a server's disk space is low, a toast will now be shown to server operators
- The game now requires Java 25
- The included Java distribution is now the Microsoft build of OpenJDK 25
- Added `swing` command that enables swinging of entities arms
...And many more changes and fixes!
Join the official feedback discord server and discuss these changes here: https://discord.com/channels/1138536747932864532/1450507863037444127