Multiline selection highlight no longer fills the editor width

Problem

In IntelliJ IDEA 2026.1, the highlight for a multiline selection no longer extends as a full rectangular block to the right edge of the editor. Instead, the highlight ends at the last character of each line.

This makes it harder to tell whether the trailing newline at the end of a multiline selection is included. When growing a selection with repeated Extend Selection actions (Ctrl+W) — for example, to select a method together with its annotations and doc comment — it is difficult to see when the selection has reached the intended boundary, leading to overshooting the target block.

Cause

IntelliJ IDEA 2026.1 changed the default rendering of the multiline selection highlight so that it extends only to the end of the text on each line rather than filling the full editor width.

Solution

The previous full-width selection highlight can be restored through a registry key:

1. Press Shift twice to open Search Everywhere, type Registry, and open the Registry... action.
2. Locate the key editor.old.full.horizontal.selection.
3. Enable the key.

The full-line selection highlight is restored after this change.