ssh --proxy-mode prints the update banner to stdout, breaking OpenSSH ProxyCommand

[fredchu]

Posting here per CONTRIBUTING.

Summary

When a newer release is cached, colab ssh --proxy-mode prints the upgrade banner to stdout. In proxy mode stdout is the SSH byte stream, so every OpenSSH ProxyCommand connection breaks during the banner exchange. docs/06_ssh_access.md promises the opposite ("stdout stays the clean ssh byte stream").

The nasty part is timing: a setup that works today breaks silently on the day the next version is published, without any local change.

Reproduction (v0.7.4, macOS; no runtime needed)

Use a throwaway HOME whose cached latest_version is newer than the installed one:

H=$(mktemp -d); mkdir -p "$H/.config/colab-cli"
printf '{"last_check":"%s","enable_update_check":true,"latest_version":"99.0.0"}' \
  "$(date -u +%Y-%m-%dT%H:%M:%S.000000Z)" > "$H/.config/colab-cli/settings.json"
HOME="$H" colab ssh --proxy-mode </dev/null 2>/dev/null

stdout:

[colab] A new version of Colab CLI is available: 99.0.0 (current: 0.7.4)
[colab] Run 'colab update' to update.
[colab] To silence this check, set "enable_update_check": false in ~/.config/colab-cli/settings.json

[colab] Error: No active sessions found. Create one with 'colab new'.

With "enable_update_check": false, the banner lines are gone. (The trailing error is expected here because there is no session; with a live session that line is not printed, but the banner still comes first.)

Cause

• cli.py: the global callback runs auto_update.run_background_check() for every subcommand not in _AUTO_UPDATE_SUPPRESSED. ssh is not in that set.
• auto_update.py: announce_upgrade() / maybe_show_cached_banner() print with typer.echo(...) (stdout).

Suggested fix

Either of these would do it:

1. Skip the update check when --proxy-mode is set (or add ssh to _AUTO_UPDATE_SUPPRESSED).
2. Print the banner with typer.echo(..., err=True). That also keeps it out of colab exec output that people pipe into other tools.

Workaround

Set "enable_update_check": false in ~/.config/colab-cli/settings.json. We now set it automatically before using colab ssh --proxy-mode as a ProxyCommand in an unattended pipeline.

[sethtroisi]

Thanks for finding this. I'll look at auto supressing the update text in proxy mode; the update text is already suprressed in some commands and adding ssh to that list should be easy.

[fredchu]

Thanks for the quick reply! Setting enable_update_check: false works as a workaround for now, so no rush on our side.