Shift+Enter newline stopped working in JetBrains plugin

Description

Shift+Enter for newline input stopped working in the JetBrains IDE plugin after a recent update. Option+Enter works as an alternative, but Shift+Enter was the previous default and matches the behavior of the Claude Desktop app.

Environment

• Claude Code version: v2.1.39
• IDE: JetBrains (plugin)
• OS: macOS (Darwin 25.2.0)

Expected behavior

Shift+Enter should insert a newline in the chat input, as it did previously.

Actual behavior

Shift+Enter no longer inserts a newline. Only Option+Enter works.

Additional context

• This is a regression — Shift+Enter was working just hours before the update
• The Claude Desktop app still uses Shift+Enter for newline, so the inconsistency is confusing
• Shift+Enter is distinguishable from Enter in JetBrains' terminal emulator, so the terminal limitation argument doesn't apply here