Visual Thinking

One job: when a discussion outgrows chat text, materialize it. A single self-contained HTML canvas — Mermaid diagrams, export buttons, no build step — that the user opens in the browser while the conversation continues.

The canvas is a thinking surface, not a deliverable. It holds the current shape of an idea: what is settled, what is open, what competes with what.

Rules

1. Render when the discussion has >=3 moving parts (options, unknowns, flows, decisions). A single small question stays in chat.
2. One diagram, one point. If a diagram needs a paragraph, redraw the diagram.
3. 2–5 blocks per canvas, picked to fit the discussion. Never one of each type.
4. Use the user's terms and the domain language of AGENTS.md. Never rename entities on the canvas.
5. Nothing lands in the repo. OS temp dir, open it, report the absolute path.
6. The canvas is a snapshot, not the record. Regenerate as decisions land; ADRs and AGENTS.md stay the source of truth.

Process

1. Extract

Compress the discussion into its skeleton: topic, what is settled, what is open, options in play, decisions and their dependencies, flows. If the canvas restates everything already said in chat, it failed.

2. Compose

Pick blocks from references/diagrams.md:

• Idea map — the overview: parts and how they relate.
• Before / After — current state vs proposed state, side by side. Add an explicit Delta list when the change needs it (Added / Removed / Changed).
• Delta — the explicit diff under Before / After (or standalone when no diagrams fit).
• Options — alternatives in competition, trade-offs, one recommendation.
• Decision tree — what is settled, what is open, what unlocks what.
• Sequence — who calls whom, in what order, how many round-trips.
• Code sketch — the shape of the change in a few lines of code.

3. Render

Fill assets/canvas-template.html following the contract in references/diagrams.md. Write to <tmpdir>/visual-thinking-<timestamp>.html (%TEMP% on Windows, $TMPDIR or /tmp elsewhere), open it (start / open / xdg-open), tell the user the absolute path.

4. Feed back

Ask which branch to work next. When a decision lands, offer to re-render with a fresh timestamp — never edit diagrams in place. If the plan is worth stress-testing, offer the grilling skill. If a rejected option carries a load-bearing reason, offer an ADR.