/excalidraw-generator

name: excalidraw-generator
description: "Generate diagrams as valid Excalidraw JSON — flowcharts, architecture, ER diagrams, mind maps, sequence diagrams, wireframes, C4 models, and more. Don't use for draw.io/Mermaid output, slide decks, or pixel-perfect brand graphics."
license: MIT
effort: high
metadata:
  version: 1.5.0
  author: "Luong NGUYEN <luongnv89@gmail.com>"

Excalidraw Diagram Generator

Generate professional diagrams as valid Excalidraw JSON. Every request flows through four phases — **Understand**, **Propose**, **Generate**, **Validate** — before the file is written. The body stays lean to respect the agent's context budget; depth lives in `references/`.

> Part of the **diagram-generator** suite. For precise, editable-in-draw.io output, use `drawio-generator` instead; the `diagram-generator` umbrella routes between the two.

When to Use

The frontmatter `description` sets triggers and exclusions. Output: a `.excalidraw` file, plus a companion `.md` only on request.

Environment Check

If the Agent tool is available, use subagents per *Subagent Architecture* for large diagrams; fresh-context validation avoids single-pass context overflow. Without it (e.g., Claude.ai), run every phase inline and self-review against the 10 checks.

Repo Sync Before Edits (mandatory)

Run this once: before reading an existing `.excalidraw` file (*Iteration*), otherwise before the Phase 4 write. The sync target is the output file's directory.

1. Run `repo="$(git -C "<output dir>" rev-parse --show-toplevel)"`. If it fails, skip the sync and record `sync: skipped (not a git repo)`. 2. Run `git -C "$repo" remote get-url origin`. If it fails, skip steps 3–7 and record `sync: skipped (no origin)`. 3. Run `branch="$(git -C "$repo" rev-parse --abbrev-ref HEAD)"`. If it prints `HEAD`, skip steps 4–7 and record `sync: skipped (detached HEAD)`. 4. Run `git -C "$repo" status --porcelain`. If the output is empty, run `git -C "$repo" fetch origin && git -C "$repo" pull --rebase origin "$branch"`. 5. If the output is not empty, run `git -C "$repo" stash push -u -m "excalidraw-generator pre-sync"`, then the same fetch and pull, then `git -C "$repo" stash pop`. 6. If `fetch` or `pull` fails before a rebase starts (network, authentication, or a missing remote branch), do not retry. Run `git -C "$repo" stash pop` when step 5 stashed, record `sync: failed (<first error line>)`, and continue. The Final Report repeats it on the `Uncertainty:` line. 7. If the rebase conflicts, run `git -C "$repo" rebase --abort`, then `git -C "$repo" stash pop` when step 5 stashed. If the stash pop conflicts, leave the stash in place. In both cases do not write the file; stop and ask the user how to continue. With no answer, the status is `BLOCKED`.

This skill commits nothing.

Core Workflow

Phase 1: Understand

Confirm what to draw before generating anything.

• **Clear request** — restate it in one sentence and propose a visualization type.
• **Ambiguous input** — ask about entities, relationships, flow direction, style.
• **Code, data, schemas, or files** — extract structure (SQL → ER, steps → flowchart; full mapping in `references/diagram-types.md`).

Phase 2: Propose

Present the numbered plan below.

• If the request names the diagram type and every element, or the user says "just do it", state the defaults you chose in one line and proceed to Phase 3. Defaults: hand-drawn, `roughness: 1`, Virgil font (`fontFamily: 1`), best-fit layout.
• Otherwise, wait for the user to confirm or change the plan. Do not generate JSON before the user answers.

1. **Diagram type** — catalogue in `references/diagram-types.md`; offer numbered alternatives if several fit. 2. **Key elements** — list the nodes and shapes. 3. **Layout** — e.g. `(A) Top-to-bottom`, `(B) Left-to-right`, `(C) Radial`. 4. **Style** — rendering style (hand-drawn, sketchy, clean) and a color scheme that fits the purpose; variants in `references/style-and-iteration.md`. No fixed palette. 5. **Estimated complexity** — small (<10 elements), medium (10–30), large (>30).

Phase 3: Generate

Compose the `.excalidraw` document in memory (raw JSON, no wrapper). Phase 4 writes the file.

Output path: use the path the user gave. Otherwise use a descriptive kebab-case name ending in `.excalidraw` (`auth-flow.excalidraw`) in the current working directory. If that file exists and the user did not ask to update it, confirm with the user before you overwrite it; to update it, follow *Iteration*.

Start from the envelope in `references/excalidraw-format.md` → *Top-Level Structure* (`type`, `version`, `source`, `elements`, `appState`, `files`); set `theme` and `viewBackgroundColor` to suit the diagram. That file holds the full element schema and field defaults.

Critical rules every element must follow:

• Include every required field from `references/validation-checks.md` → *Check 2*.
• Use descriptive kebab-case IDs (`node-api-gateway`).
• Size each container to fit its bound text (*Check 10*); grow the shape, never shrink the text below `fontSize: 16`.
• Bind text and arrows in both directions (`containerId` ↔ `boundElements`, `startBinding`/`endBinding` ↔ `boundElements`).

**Embedding in Markdown:** only when asked, write the `.excalidraw` file first, then a companion `.md` holding the same JSON in a fenced block tagged `excalidraw`.

Phase 4: Validate

Run all 10 checks on the in-memory JSON before writing the file. See `references/validation-checks.md` for checks, the Check 10 formula, and fixes.

1. Run the 10 checks. If all pass, run *Repo Sync*, write the file, and give the *Final Report* with status `COMPLETE`. 2. If a check fails, fix it and re-run all 10 checks. A failure of check 1 or 8 needs a Phase 3 regeneration, not a patch. Stop after 3 fix cycles. 3. If checks 1–6 pass but a check from 7–10 still fails after cycle 3, run *Repo Sync*, write the file, and report `PARTIAL` with the failed check numbers. 4. If a check from 1–6 still