zed-industries/zed · error

failed to connect: {}

Error message

failed to connect: {}

What it means

Immediately after the connection race, Zed checks whether the ssh master already terminated (try_status() is Some); if so it drains the process's stderr and reports it verbatim as `failed to connect: <stderr>`. The embedded text is ssh's own error output and pinpoints why the connection dropped.

Source

Thrown at crates/remote/src/transport/ssh.rs:712

                _ = master_process.wait_connected().fuse() => {
                    anyhow::Ok(())
                }
            };

            if let Err(e) = result {
                return Err(e.context("Failed to connect to host"));
            }

            if master_process.as_mut().try_status()?.is_some() {
                let mut output = Vec::new();
                let mut stderr = master_process.as_mut().stderr.take().unwrap();
                stderr.read_to_end(&mut output).await?;

                let error_message = format!(
                    "failed to connect: {}",
                    String::from_utf8_lossy(&output).trim()
                );
                anyhow::bail!(error_message);
            }

            let socket = SshSocket::new(connection_options, socket_path).await?;
            drop(askpass);
            (socket, Some(master_process))
        };

        #[cfg(windows)]
        let (socket, master_process_option) = {
            let askpass_delegate = askpass::AskPassDelegate::new_with_cancellation(cx, {
                let delegate = delegate.clone();
                move |prompt, tx, cancellation, cx| {
                    delegate.ask_password(prompt, tx, cancellation, cx)
                }
            });

            let mut askpass =
                askpass::AskPassSession::new(cx.background_executor().clone(), askpass_delegate)

View on GitHub (pinned to f4178619ac)

Solutions

1. Read the embedded ssh stderr — it names the exact cause (host key, auth, network)
2. Host key changed after rebuild: `ssh-keygen -R <host>` (or edit known_hosts), then reconnect
3. Auth: confirm the key is loaded (`ssh-add -l`) and the username is correct
4. Re-check any additional ssh arguments in the connection options for validity

Example fix

# before: stderr says 'Host key verification failed.'
ssh-keygen -R host.example.com

# after: reconnect from Zed; handshake completes

// Preflight the same options Zed will use:
// ssh -o BatchMode=yes -o ConnectTimeout=5 <user>@<host> true
// non-zero exit + stderr predicts this failure before opening Zed's session

if let Err(e) = connect(&opts, cx).await {
    if let Some(stderr) = e.to_string().strip_prefix("failed to connect: ") {
        // display ssh's own stderr (host key, auth, network) to the user verbatim
    }
    return Err(e);
}

When it happens

Trigger: The Unix master ssh process exits during/right after establishment: host key verification failure, permission denied (publickey/password), connection reset, unsupported KEX/ciphers, or invalid options passed through connection_options additional args.

Common situations: REMOTE HOST IDENTIFICATION HAS CHANGED after a server rebuild; agent missing the right key (Permission denied (publickey)); bastions or middleboxes resetting the session; typos in extra ssh arguments configured for the connection.

Related errors

• ssh process exited before connection established
• connecting to host timed out
• build ids may only contain lowercase letters, numbers, '.',
• unknown judge preset '{name}' (valid: {valid})
• registry dataset requires a name

AI-assisted analysis of zed-industries/zed@f4178619ac (2026-08-20). Data as JSON: /api/errors/8a0eeaf876007622. Report an issue: GitHub.