+ssh terminfo installation overrides an existing ControlPath and prompts for authentication

[rtgibbons]

Issue Description

On Ghostty commit  8112f7676 , automatic terminfo installation opens a new authenticated SSH connection instead of reusing my existing OpenSSH control socket.
In my scenerio the master connection is maintained by CoreTunnel. After removing an unrelated stale socket and reconnecting,  /usr/bin/ssh -S -O check   succeeds, and connecting directly through that socket works without another password prompt. Connecting through Ghostty’s  +ssh  wrapper prompts for authentication during terminfo setup.

Expected Behavior

Terminfo installation respects the caller’s existing control connection and does not require separate authentication.

Actual Behavior

The terminfo installation phase prompts for authentication even though the supplied control socket is working.

Reproduction Steps

1. Establish an authenticated SSH master with a working control socket.
2. Verify that  /usr/bin/ssh -S -O check   succeeds.
3. Verify that a direct connection reuses it:
   /usr/bin/ssh -o ControlMaster=no -S <socket> <destination>
4. With terminfo installation not cached for the destination, connect through:

ghostty +ssh --verbose -- \
  -o ControlMaster=no \
  -S <socket> \
  <destination>

Ghostty Logs

No response

Ghostty Version

Ghostty 1.3.2-main+8112f7676

Version
  - version: 1.3.2-main+8112f7676
  - channel: tip
Build Config
  - Zig version   : 0.17.0
  - build mode    : .fast
  - app runtime   : .none
  - font engine   : .coretext
  - renderer      : renderer.generic.Renderer(renderer.Metal)
  - libxev        : kqueue

OS Version Information

macOS Golden Gate 27.2

(Linux only) Display Server

None

(Linux only) Desktop Environment/Window Manager

No response

Minimal Ghostty Configuration

shell-integration = detect
shell-integration-features = ssh-terminfo

Additional Relevant Configuration

No response

I acknowledge that:

• I have reviewed the FAQ and confirm that my issue is NOT among them.
• I have searched the Ghostty documentation and confirm there doesn't exist a configuration option that solves my issue.
• I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
• I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (```) on separate lines.

[rtgibbons]

Source findings

In  src/cli/ssh.zig ,  installRemoteTerminfo()  creates a random temporary control path and prepends these options before  opts._ssh_args.items :

&.{
    "-o", "ControlMaster=yes",
    "-o", "ControlPersist=no",
    "-o", control_path_opt,
},
opts._ssh_args.items,

For user-supplied  -o ControlMaster=...  and  -o ControlPath=... , the injected options take precedence. The installer therefore creates its own connection instead of honoring the caller’s multiplexing settings.

The subsequent main SSH invocation does not prepend those control options.

Proposed direction

Have the terminfo installer respect the caller’s effective SSH multiplexing configuration instead of unconditionally prepending ControlMaster=yes, ControlPersist=no, and a temporary ControlPath.

If configuration inspection is needed, extend Ghostty’s existing ssh -G resolution step to capture controlpath and controlmaster alongside the destination. This avoids an additional subprocess and covers configuration supplied through -S, -o, and SSH configuration files; Ghostty already invokes ssh -G before installation.

When a control path is configured, omit all three injected multiplexing options and let SSH use the caller’s settings. Do not retain ControlMaster=yes while merely substituting the caller’s path: yes creates a master rather than attempting to reuse one, whereas no and auto permit reuse.

Let SSH handle socket validation and its configured fallback behavior rather than checking for a socket file or requiring a separate -O check. Preserve explicit settings such as ControlMaster=no and ControlPath=none; do not silently enable a persistent master when the caller has not requested.

Keep this change scoped to respecting existing connection-sharing configuration. Eliminating repeated authentication when no master exists would require a separate design for sharing a connection across installation and the interactive session.

This approach remains unimplemented and untested. Validation should cover command-line and SSH-config settings, a working master, missing or stale sockets, disabled multiplexing, and ordinary ad hoc connections.

AI assistance disclosure

(Human rewritten) Perplexity Chat and Computer (on 'High' w/ Astra) assisted with troubleshooting, inspecting the source at  8112f7676 , and drafting this report. I reviewed and edited the report.

[nicholas-greenwood]

for your coretunnel connection, i'd bypass just the terminfo installer:

ghostty +ssh --ssh=/usr/bin/ssh --terminfo=false --verbose -- \
  -o ControlMaster=no \
  -S <socket> \
  <destination>

keep --terminfo=false before --
on 8112f7676, it skips the installer. the main connection gets your multiplexing options unchanged, so this bypasses the problem you traced without fixing it

ghostty asks ssh for TERM=xterm-256color, so the remote needs that entry. apps using terminfo lose some capabilities, including coloured and styled underlines

[rtgibbons]

Thanks, that's exactly what I ended up doing.

I've got a fix https://github.com/rtgibbons/ghostty/tree/fix/ssh-terminfo-control-socket - i'm having to update Xcode after upgrading to 27.2 last night. So I haven't tested yet. Just tested this on the my local mac and it works.

Also while digging in; it appears the old terminfo installer would setup the ControlMaster and re-use it when connecting after the terminfo install. But with the new zig +ssh implementation - it appears it's a regression in that it doesn't use it. The above branch doesn't continue that fix as I wasn't sure if that was on purpose or not.