Recipes: Forms and User Tasks

Recipes for the human side of a Camunda 8 process: the form on a start event and the assignment of a user task.

How do I set a start event form?

Pass formId to startEvent. It writes a zeebe:formDefinition with that id; the form itself is a Camunda Form deployed to the cluster.

import { Bpmn } from "@bpmnkit/core"

const defs = Bpmn.createProcess("request")
	.executable(true)
	.startEvent("start", { name: "Request received", formId: "request-form" })
	.endEvent("end")
	.build()

console.log(Bpmn.export(defs))

How do I set the assignee of a user task?

While building, pass assignee, candidateGroups, candidateUsers, dueDate, followUpDate and priority to userTask. They write zeebe:assignmentDefinition, zeebe:taskSchedule and zeebe:priorityDefinition. A FEEL expression must start with =; priority should be 0 to 100 (not validated).

import { Bpmn } from "@bpmnkit/core"

const defs = Bpmn.createProcess("review")
	.executable(true)
	.startEvent("start")
	.userTask("review", {
		name: "Review request",
		assignee: "alice",
		candidateGroups: "reviewers,managers",
		dueDate: "P2D",
		priority: 80,
	})
	.endEvent("end")
	.build()

console.log(Bpmn.export(defs))

How do I change the assignee, due date or priority of an existing user task?

Use an update operation with applyBpmnOperations. The patch takes the same field names, and an empty string clears the field. A field the element cannot carry (an assignee on a service task) is an error, and in strict mode (the default) nothing is applied.

import { Bpmn, applyBpmnOperations } from "@bpmnkit/core"

const parsed = Bpmn.createProcess("review")
	.executable(true)
	.startEvent("start")
	.userTask("review", { assignee: "alice", dueDate: "P2D" })
	.endEvent("end")
	.build()

const { definitions, applied } = applyBpmnOperations(parsed, [
	{
		op: "update",
		id: "review",
		patch: { assignee: "bob", candidateGroups: "reviewers", dueDate: "", priority: 90 },
	},
])
console.log(applied, Bpmn.export(definitions))

Through the MCP server, call update_element with processId, elementId and changes, for example {"assignee": "bob", "dueDate": ""}. The same fields and the same empty-string clearing apply.