[BUG] Ctrl+Z (SIGTSTP) no longer suspends to the shell. It drops to an in-Claude session dashboard requiring a second action to reach the actual command line

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?

Previously, Ctrl+Z performed a normal terminal suspend (SIGTSTP) — it backgrounded the Claude Code process and dropped you straight back to your actual shell prompt, standard Unix job-control behavior (fg to resume).

That has changed. Ctrl+Z now instead opens an in-app "process organizer" / session dashboard screen within Claude Code itself — not your real shell. On 2.1.278 this screen looked like:

▎ Claude Code v2.1.278
▎ Sonnet 5 · [project directory]
▎ 1 awaiting input · 0 working · 0 completed
▎
▎ Your conversation moved to the background — enter opens it · esc returns to it · ctrl+c twice quits
▎
▎ Needs input — Sessions that have a question or need your decision land here
▎ Working — Sessions Claude is actively working on — they keep running even if you close the terminal
▎ Completed — Finished sessions wait here for you to review

This is a Claude Code UI screen (agent view), not a real shell. To actually get back to a usable terminal command line, you have to leave this screen with a second action (another Ctrl+Z, or quitting).

In the update from 2.1.278 to 2.1.283, it now takes two steps to reach the shell where one press of Ctrl+Z used to get you there directly.

What Should Happen?

Ctrl+Z performs a standard terminal suspend straight to the shell prompt, same as normal Unix job control and as it behaved on 2.1.278

Error Messages/Logs

Steps to Reproduce

1. Run Claude Code v2.1.283.
2. Start a session
3. Press Ctrl-Z

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.278

Claude Code Version

2.1.283

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

Checking the 2.1.279–2.1.283 changelog range (CHANGELOG.md on main) directly, there is no entry in that range which mentions Ctrl+Z, SIGTSTP, or suspend behavior, so this looks undocumented.

This is especially disruptive for developers who run Claude Code alongside Vim in a split pane/tmux workflow, where Ctrl+Z is the standard, muscle-memory way to jump out to the shell mid-edit and fg straight back into the editor. With Ctrl+Z now landing in Claude's own dashboard instead of the shell, that entire flow is broken — every jump-out now detours through an unrelated UI screen before reaching a real prompt, which defeats the point of using Ctrl+Z for quick context switches at all.

Related to https://github.com/anthropics/claude-code/issues/16727 and https://github.com/anthropics/claude-code/issues/16520