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Builder Journey

The fastest way to build well in Cessy is to move from business language to runtime verification in a tight loop. Do not begin with REST endpoints or page layouts. Begin with the decisions the business needs to make and the facts the business needs to remember.

Journey map

StepBuilder questionCessy artifact
1. UnderstandWhat business decision is being made?Decision model, command names, event names
2. ModelWhat state is required to decide safely?Decider scope, command schema, event schema
3. ReadWhat questions must users and systems answer?Projections and projection views
4. AutomateWhat should happen after an event?Policies, webhooks, subscriptions
5. ProtectWho may do what?Roles, attributes, permissions, principals
6. OperateHow do builders and users inspect behavior?Data Explorer, Activity, channels, errors
7. ExtendWhat needs a custom experience?Custom pages, adapters, runtime APIs

Use Design MCP from the start

Design MCP is part of onboarding, not an advanced integration. A connected builder agent can inspect the real app, fetch Cessy-specific reference material, validate changes, and use workspace changesets instead of guessing from stale screenshots.

Use the read-only Design MCP endpoint for discovery, review, product shaping, and PRD work. Use the full Design MCP endpoint only for trusted agents that are allowed to mutate the model.

Definition of done

A builder change is ready to publish when:

  • the current model has been inspected, not assumed
  • the change is isolated in a workspace or clearly scoped manual edit
  • validation passes without ignored errors
  • generated runtime contracts still express the intended external behavior
  • permissions are verified for the expected actors
  • at least one command and one projection path have been smoke-tested after publish

Common trap

Avoid treating Cessy as a CRUD generator. Commands are business decisions, events are durable facts, and projections are read models. If a proposed endpoint does not map to that language, model the business flow first and only then expose the runtime contract.