Scenarios

These are recipes: “I need to do X — how?” Each one is short and assumes you’ve built a slice or two (the tutorial is the long way round). For the why and the full set of options, follow the links into the reference.

Recipe	When you reach for it
Validate a command	Reject malformed or duplicate input before it writes state
Return a result or an error	A command needs to hand back more than “it worked” — a value, or a typed failure
Query data across slices	A screen needs data that spans more than one feature
Run a command from React	Wire a form or button to a command through the generated proxy
Test a command	Prove a slice works through the real pipeline — no HTTP, no database
Authorize a command or query	Restrict who may run a command or read a query

Event-sourced Arc slices have their own Chronicle-specific recipes, starting with React to an event.

Missing a recipe you expected? The Backend and Frontend guides cover the long tail, and Troubleshooting catches the common snags.