Most of Frontier is configured per workspace, but a couple of things are set once and inherited everywhere: a fallback working directory, used when a run happens somewhere that has no worktree of its own yet, and which CLI coding tool actually runs on your behalf.
The coding tool is the consequential one. Frontier drives an existing CLI rather than talking to a model itself, so whichever Connector you pick here is what every run in every workspace spawns — unless a particular workspace overrides it (see Choosing a connector per workspace).
Note that the fallback directory is not where your workspaces live — an activated workspace always gets its own checkout in Frontier's own data directory (see Workspaces & Threads), and that location is not something you set here.
Everything here is a default rather than a rule. A workspace that needs something different can say so, and nothing you set here retroactively changes work that has already happened.
Credentials is where the keys your agents need live: a Stripe key, a Linear key, whatever a setup you installed asks for. Save one under the name the setup gives you, and thread runs and agent replies in that context get it from then on. A key is never shown again once saved, and it stays on this computer, out of your backups.
How Frontier looks is set here too, under Appearance: light, dark or following your system, one of a few color palettes, the moving particle fabric behind the page or a still gradient or nothing, and whether to turn motion down. Appearance belongs to the context you're in rather than to a workspace, so a work context and a personal one can look different at a glance, and the phone app matches whichever context it has open.