[BUG] Submitted prompt is not processed when switching away from session and returning

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When a user types a prompt in a Claude Code session, presses Enter to submit it, and then switches to a different terminal tab/session before Claude begins processing, the prompt is silently dropped. When the user returns to the original session, the submitted message has not been processed at all — Claude is idle as if no input was ever sent.

The user expects that once Enter is pressed, the prompt is queued and will be processed regardless of whether the terminal tab is in the foreground. Instead, the message appears to be lost entirely.

Expected Behavior

After pressing Enter to submit a prompt:

1. The message should be queued and processed by Claude
2. When the user returns to the session, the response (or in-progress processing) should be visible
3. Switching terminal tabs/sessions should not affect message processing

Actual Behavior

1. User types a prompt and presses Enter
2. User switches to another terminal tab/session
3. User returns to the original session
4. The prompt was never processed — Claude is idle, no response was generated, no task was started
5. The submitted text may or may not still be visible, but no action was taken on it

Environment

• Claude Code version: 2.1.42
• OS: macOS 26.3 (Build 25D125)
• Shell: zsh
• Interface: Terminal CLI (not VSCode extension)

Steps to Reproduce

1. Open Claude Code in a terminal session
2. Type a prompt and press Enter
3. Immediately switch to a different terminal tab or application
4. Wait 30+ seconds
5. Switch back to the Claude Code session
6. Observe that the prompt was not processed

Additional Context

• This happens frequently and is reliably reproducible
• It suggests that prompt submission may depend on the terminal session being in the foreground, or that there is a race condition between input submission and the processing loop
• This is particularly disruptive for users who multi-task across multiple terminal sessions