Opening the shared document…
Write your own diagram
C4, sequence, flowchart, use case, ER or dictionary — .alab, arch-lab JSON, or Mermaid, auto-detected and rendered live. C4 nodes can be dragged on the canvas, and sequence messages and lifelines added, edited, repointed, reordered, numbered and removed on it; the other kinds lay themselves out from the text. Nothing leaves your browser. Syntax reference
How .alab, JSON and Mermaid relate
.alab is the format to write: it is what the syntax reference documents, what share links carry, and what reads cleanly in a code review. .archlab.json is the same C4 model on disk — the interchange form any other tool can read without implementing a grammar; the two are lossless twins in both directions (proved on every build), so you never have to write the JSON by hand. Mermaid is read and written too, lossily — the format toggle above the pane converts in place and states what each direction drops. Nothing you type is uploaded or stored.
The same model as .archlab.json, the format it saves to. You never have to write it by hand.
Tab indents · Esc then Tab leaves the editor · syntax reference
Inspect the diagram
Click any element to see what it is and what it talks to, or any connector — the line or its label — to trace that relationship.
Click an element or connector for details · double-click or the zoom chip to zoom in · Ctrl + scroll zooms · Esc steps back · drag or Space + drag to pan
Coffee Shop
View mode · read-onlyA tiny two-level example — edit either pane and the other follows.