Getting started

Draw the system. Get the spec.

specsketch is an Excalidraw canvas that turns architecture diagrams into OpenSpec change proposals — written straight into your openspec/ change directory, next to the diagram that produced them. Local-only: the server binds to 127.0.0.1 and generation runs with your own Anthropic credentials.

Run it

npx @coopcli/specsketch ./openspec/changes/new-feature-change
# or: npm install -g @coopcli/specsketch
#     specsketch ./openspec/changes/new-feature-change

Open the printed URL, draw labeled boxes and arrows (loose text becomes design notes), and press Generate Spec. The change directory is the workspace:

openspec/changes/new-feature-change/
├── diagram.excalidraw      ← the drawing, autosaved, agent-readable
├── specsketch.json         ← title/summary/timestamps + generation manifest
├── proposal.md
├── design.md
├── tasks.md
└── specs/<capability>/spec.md

Stop and rerun with the same directory to resume. Existing artifacts are the baseline: generation makes the smallest revision that fulfills the drawing.

Requirements & auth

• Node ≥ 22 (the CLI checks at startup).
• Anthropic credentials — only needed for Generate Spec; drawing works without them. Either export ANTHROPIC_API_KEY=sk-ant-... or the Anthropic CLI's login profile.

CLI reference

specsketch <path-to-openspec-change-dir> [--port <n>] [--share]

• The directory is created if missing; its basename becomes the change name.
• --port sets the preferred port (default 8787); if taken, the server moves to the next free port.
• --share hosts the canvas as a live multiplayer session — see Sharing a canvas.