tmux 3.6b: "open terminal failed: not a terminal" on Linux — caused by brew ncurses 6.6

## `brew config` AND `brew doctor` output ``` HOMEBREW_VERSION: 5.1.13 ORIGIN: https://github.com/Homebrew/brew HEAD: d8deaca5574faf79a27f110caedc9e153709e628 Last commit: 3 days ago Branch: stable Core tap JSON: 24 May 13:08 UTC HOMEBREW_PREFIX: /home/linuxbrew/.linuxbrew HOMEBREW_MAKE_JOBS: 4 Homebrew Ruby: 4.0.5 CPU: quad-core 64-bit Git: 2.54.0 Curl: 8.5.0 Kernel: Linux 6.8.0-107-generic x86_64 GNU/Linux OS: Ubuntu 24.04.4 LTS (noble) Host glibc: 2.39 brew doctor: Your system is ready to brew. ``` ## What were you trying to do (and why)? Attach to an existing tmux session via `tmux attach -t <name>` — the most basic tmux operation. ## What happened (include all command output)? After `brew install tmux` (installs 3.6b), **every `tmux attach` fails** in multiple common environments: - Interactive SSH shell (`ssh user@host`, then `tmux a`) - VS Code Remote integrated terminal - `script`-created PTY ``` $ tmux new -d -s test $ tmux a -t test open terminal failed: not a terminal ``` The **only** environment where attach works is `ssh -t host "tmux a -t test"` (forced PTY with terminal size forwarding). ### Root cause: brew's ncurses 6.6 The brew tmux binary links against brew's `ncurses 6.6` (`/home/linuxbrew/.linuxbrew/opt/ncurses/lib/libncursesw.so.6`). The tmux server receives the client's PTY fd via `SCM_RIGHTS`, then calls `tty_init()` → ncurses `setupterm()`. Brew's ncurses 6.6 rejects certain valid PTY devices that the system ncurses (6.4) accepts. **Proof — same binary, different libraries:** ```sh # Fails: brew tmux + brew ncurses script -qc 'tmux new -d -s x && tmux a -t x' /dev/null # → open terminal failed: not a terminal # Works: brew tmux + system ncurses script -qc 'LD_LIBRARY_PATH=/lib/x86_64-linux-gnu tmux new -d -s y && tmux a -t y' /dev/null # → attaches successfully # Works: system tmux 3.4 + system ncurses script -qc '/usr/bin/tmux -S /tmp/t34 new -d -s z && /usr/bin/tmux -S /tmp/t34 a -t z' /dev/null # → attaches successfully ``` `strace` confirms the tmux server's `tty_init()` path fails, causing `CLIENT_TERMINAL` flag to not be set — the tmux source code for this check is identical between 3.4 and 3.6b, so the behavioral difference is entirely from the linked ncurses library. ## What did you expect to happen? `tmux attach` should work in an interactive SSH session and VS Code terminals, same as the system-packaged `tmux 3.4` and same as `brew tmux` with system libraries. ## Step-by-step reproduction instructions ```sh # 1. Install tmux via brew on Linux (Ubuntu 24.04) brew install tmux # 2. Verify brew tmux is first in PATH which tmux # → /home/linuxbrew/.linuxbrew/bin/tmux # 3. Reproduce (script simulates a PTY environment like SSH/VSCode) script -qc 'tmux new -d -s repro && tmux a -t repro; echo "exit=$?"' /dev/null # → open terminal failed: not a terminal # → exit=1 # 4. Confirm it's the linked ncurses — same binary, system libs → works script -qc 'LD_LIBRARY_PATH=/lib/x86_64-linux-gnu tmux new -d -s repro2 && tmux a -t repro2 -d; echo "exit=$?"' /dev/null # → exit=0 (success) # 5. Cleanup tmux kill-server 2>/dev/null LD_LIBRARY_PATH=/lib/x86_64-linux-gnu tmux kill-server 2>/dev/null ``` ## Environment | Component | Version | |-----------|---------| | OS | Ubuntu 24.04.4 LTS | | Kernel | 6.8.0-107-generic | | Homebrew | 5.1.13 | | brew tmux | 3.6b | | brew ncurses | 6.6 | | system tmux | 3.4-1ubuntu0.1 | | system ncurses | 6.4+20240113 | ## Suggested fix The tmux formula could either: - Link against the system ncurses (`uses_from_macos "ncurses"` already exists for macOS — add equivalent Linux handling), or - Pin ncurses to a version that doesn't exhibit this regression