Set the fork secondary model in Grok Build

fork_secondary_model under [ui] picks which model the secondary agent uses when you fork. When unset, it follows the main session default. Official: Settings reference, Sessions.

Config

User config (~/.grok/config.toml or $GROK_HOME/config.toml):

[ui]
fork_secondary_model = "grok-build"

Replace the string with any model id available in your catalog (same space as /model and grok models).

How it fits with /fork

1. /fork branches the current session into a peer — Fork a Grok Build session.
2. The secondary peer uses fork_secondary_model when set; otherwise the same default as new sessions ([models] default / GROK_DEFAULT_MODEL).
3. Worktree forks (--worktree / -w) still isolate the checkout; this key only routes the model for that secondary agent.

Related model picks

List ids: List available models with grok models. Switch the active session model: Switch active model in Grok Build.

Pitfalls

• Putting [ui] in project .grok/config.toml — user config only.
• Setting an id that is hidden or disabled in [models] — hidden ids may still work via -m; disabled ids are removed from the catalog.