# supertensor

A shape-aware toolkit for drawing tensor formulas: a LaTeX/TikZ macro package, a build
pipeline that fails on silent corruption, worked examples, and an agent skill that ties
them together.

It exists because figures of this kind fail in a specific way — they compile, they look
clean, and they tell the reader something false. A face captioned `Kᵀ` that was never
transposed; shards that do not tile their parent; an index tensor drawn with a lightness
ramp. The package's job is to make the correct thing the easy thing.

```
SKILL.md              the skill entry point (lean; loads references on demand)
references/           geometry, semantics, layout, style, api, checklist, antipatterns
assets/supertensor.sty  the macro package
scripts/preflight.sh  is the TikZ + CJK path available?
scripts/build.sh      compile, audit the log, export pdf/svg/png/thumb
examples/             three golden examples + an anti-pattern gallery
```

## Quick start

```bash
./scripts/preflight.sh                       # 0 = full path, 1 = degraded, 2 = no LaTeX
./scripts/build.sh examples/mha-causal.tex   # -> examples/build/mha-causal.{pdf,svg,png}
```

A minimal figure:

```tex
\documentclass[border=10pt]{standalone}
\usepackage[cjk]{supertensor}

\stsetrole{act}{stTeal}      % one hue per tensor role, held across every stage
\stsetrole{w}{stOrange}
\stdim{T}{6}                 % one symbolic axis -> one physical edge length
\stdim{d}{4}

\begin{document}\begin{tikzpicture}
  \stface[role=act, bracket=true]{X}{(0,0)}{T}{d}
  \node[st op, right=6mm of X] (m) {$\times$};
  \stface[role=w]{W}{($(m)+(1.4,0)$)}{d}{d}
  \node[inner sep=0pt, fit=(X)(W)] (row) {};
  \stlane{row}
  \stcaption{X}{$\mathbf X$}{$T\times d$}
  \stcaption{W}{$\mathbf W$}{$d\times d$}
  \stnolane
\end{tikzpicture}\end{document}
```

Because `T` and `d` come from the ledger, the contracted axis is automatically one edge
length in both operands, `d×d` is automatically square, and any other face of shape `T×d`
in the figure is automatically identical to `X`.

See `references/api.md` for the full macro list.

## Examples

| file | shows |
|---|---|
| `tp-ffn-allreduce.tex` | column-then-row sharding, exact tiling, one hue per TP rank, a collective as a real node |
| `mha-causal.tex` | leading axes as stack depth, a physically swapped `Kᵀ`, a mask in a different grammar from the scores it gates |
| `moe-topk-gather.tex` | scores → indices → Boolean support → gather, with all three cell grammars side by side |
| `antipatterns.tex` | four figures that compile cleanly and still teach something false |

## Using it as an agent skill

`SKILL.md` is the entry point; the `references/` files are loaded on demand. Point your
agent runtime at this directory (for Claude Code, symlink or copy it under
`~/.claude/skills/`). The skill assumes `scripts/` and `assets/` sit beside it.

## Why the build script fails on warnings

Two LaTeX warnings produce a figure that is quietly wrong rather than visibly broken:
`Missing character` (a CJK glyph silently dropped — the label just is not there) and
`Overfull \hbox` (text escaping its reserved lane and landing on a tensor). `build.sh`
greps for both and exits non-zero. A `Package supertensor Warning` — an undeclared role
falling back to gray — is treated the same way.

A clean build still proves nothing about collisions, hue budget or whether the math is
right. That is what `references/checklist.md` is for.

## Provenance

Extracted from the `tensor-formula-viz` skill in `wdkns-skills`, which remains in place
unchanged. The prose rules that could be enforced mechanically became macros; the rest
became `references/`.