[BUG] Shell escape (! prefix) commands show no output since recent update

Description

Since a recent update, shell escape commands (! <command>) no longer display any output in the Claude Code terminal UI. The command executes (confirmed by side effects) but the output area is completely empty.

Before: ! ls -al would display the directory listing inline in the conversation.
After: ! ls -al shows nothing — just the next prompt appears.

Steps to reproduce

1. Open Claude Code CLI (macOS)
2. Type ! ls -al in the prompt
3. Press Enter

Expected: Directory listing appears in the conversation
Actual: No output displayed. The prompt returns with (Bash completed with no output).

Screenshot

The ! ls -al .. command runs but output is blank:

!image

Note: screenshot available but cannot be attached via CLI. The output section after ! ls -al is completely empty.

Environment

• Platform: macOS (Darwin 25.4.0, Apple Silicon)
• Claude Code model: Opus 4.6 (1M context)
• Shell: zsh
• Issue started: after latest update (noticed 2026-04-09)
• Affects: all ! prefix commands, not just ls

Workaround

Asking Claude to run the command via the Bash tool works fine and displays output normally. Only the ! shell escape is affected.