Create a process and lanes

An F4 flow shows how work moves through your system: steps, decisions, and hand-offs organized into lanes. This guide gets you from nothing to a lane structure ready for activities. The concept behind it: The F4 flow model.

Step 1 — Create a process

The F4 editor's process tree

Open the Flow (F4) editor from the menu. In the left sidebar, add a process — the piece of business behavior you're describing ("Handle a claim", "Onboard a customer"). Each process holds one or more flow diagrams; a new process starts with one.

Step 2 — Add lanes

A lane's details form, with its C4 binding selector

Add lanes — one per actor or system part that does work in this process: "Claims Handler", "Claims API", "Payment Provider". Where a lane is one of your C4 elements, bind it: pick the element in the lane's form. Bound lanes stay in sync with your structure and enable zoom-level reading.

Step 3 — Nesting happens by itself

Lanes nested under their parent system's lane

Lanes bound to C4 elements nest automatically following the structure: lanes for containers tuck inside the lane of their parent system. You read the ownership directly off the canvas.

Reorder lanes

Within a section (or among top-level lanes), you control the left-to-right order. Open a lane's form and find the Order row. Up/down arrow buttons move the lane among its siblings; the counter shows "Position X of N" so you know where you are. Dragging the lane header on the canvas also reorders it (when in edit mode).

Add activities and child lanes from the form

When you select a swimlane, its details form shows two action buttons at the bottom:

  • Add activity — quickly insert a new activity into this lane. The new activity opens in rename mode so you can type its name immediately.
  • Add {type} lane — if the lane is bound to a C4 element, this button appears with the type of container it can hold (e.g., "Add Container lane" if this lane represents a System). Click it to create a child lane with the correct C4 binding.

These shortcuts let you build the lane structure without switching back to the canvas.

Organize with sections

By default, a diagram has one section — a horizontal band where all top-level lanes live. For larger flows, split them into sections so readers can focus on one part at a time.

Open the Diagram form (select the diagram from the left tree) and scroll to Sections. Each section shows:

  • A name field — optional, defaults to "Section N". Name it for the phase or responsibility it covers ("Request phase", "Approval lane", "Payment processing").
  • An add button — quick way to insert a new lane at the bottom of this section.
  • A delete button — remove the section and its lanes. (You can't delete if only one section remains.)

Click Add section to create a new one. Sections stack top to bottom in the order they were created; move a lane between sections by editing its Section field (for a top-level lane).

Seed lanes from C4 containers

If you've already modeled your C4 structure with containers, you can jump-start lane creation. When you add a new diagram or open an existing one for the first time, if containers exist in your C4 model, CRAYON-C4 offers a lane-seed picker modal: "Seed lanes from C4 containers?"

In the picker:

  • Search for containers by name.
  • Check the boxes of containers you want to pre-populate as swimlanes.
  • Click Add N lane(s).

Each seeded lane is automatically bound to its C4 container and inherits the right nesting. You can skip the picker and add lanes manually afterward — seeding is optional, just a shortcut to avoid creating them one by one.

Choosing good lanes

  • Roles and systems, never people. "Billing", not "Alice".
  • Stay under ~7 lanes. Beyond that, readability collapses — split the process into linked flows.
  • Decide what each lane stands for before you start. An actor-lane and a container-lane in one flow is fine; a lane that means different things in different places is not.

Where next