# aura graph render redesign — pin-graph via model + WASM-Graphviz — Design Spec

**Date:** 2026-06-10
**Status:** Draft — awaiting user spec review
**Authors:** orchestrator + Claude

## Goal

Replace the `aura graph` view. The current renderer (`crates/aura-cli/src/graph.rs`)
is built on `ascii-dag 0.9.1`, whose node model is a single point: it cannot draw
the one structure aura's data actually has — a node with **n input pins and m output
pins**, where an `Edge { from, from_field, to, slot }` wires an *output pin* to an
*input pin*. To compensate, today's renderer invents notation (`#Sf`, `histogram →`,
`:= `) and omits most of the declared interface (input-pin kinds, the firing policy,
leaf output names/kinds) even though `PrimitiveBuilder::schema()` has exposed all of
it pre-build since #43 (cycle 0024).

The redesign renders **homogeneously**: every node is its body (type + param
signature) plus its declared input pins and output pins, drawn from the data,
inventing nothing and omitting nothing. Edges dock pin-to-pin. The graph is laid out
and drawn by **Graphviz compiled to WebAssembly**, run in a browser — so aura ships
no layout engine and stays a *serializer* (C9: graph-as-data, read-only, never
`eval`). The interactive surface (drill-down into composites, inline-expand, per-pin
tooltips) is the near-term graph viewer; the eventual egui playground (C22) is a
separate, later track and is **not** in scope here.

This design was ratified interactively against a working prototype at
`docs/design/prototypes/graph-render/` (run via its `fetch-deps.sh` + a static
server). **The prototype is the visual source of truth**; this spec lifts its worked
shapes.

## Architecture

aura emits a **model**, not pixels and not even DOT. The pipeline is three stages,
and aura owns only the first:

```
 aura (Rust)            viewer (JS, shipped asset)        Graphviz-WASM (browser)
 ───────────            ──────────────────────────        ───────────────────────
 Blueprint  ──to_json──▶  model (JSON)  ──genDot──▶  DOT  ──render──▶  interactive SVG
 (C9 read-only)           drill/expand/tooltips
```

- **Stage 1 — model serializer (Rust, this engine).** A new read-only serializer
  walks the root `Composite` (since 0024 the harness root is an ordinary `Composite`)
  and every distinct composite type it contains, and emits a **deterministic,
  hand-rolled JSON model** — following the existing house pattern `RunReport::to_json`
  (`crates/aura-engine/src/report.rs:80`), which is hand-rolled, serde-free, and
  determinism-tested. No `serde` dependency is added.
- **Stage 2 — viewer (JS asset).** `genDot` (model → DOT) plus the chrome (drill,
  inline-expand, styled tooltips, breadcrumb), ported verbatim from the prototype's
  `index.html`. It is a **render asset**, not authoring logic — it carries no node /
  strategy / experiment logic, so C10 ("all logic is Rust", no DSL) is untouched.
- **Stage 3 — Graphviz-WASM.** `@viz-js/viz` (Graphviz compiled to WASM) does layout,
  SVG, and edge routing entirely in the browser. No native `dot` binary anywhere.
  Validated on a thin client (Chromebook) over LAN.

`aura graph` emits **one self-contained `.html`** to stdout: the JSON model inlined,
the viewer JS inlined, and the WASM-Graphviz asset inlined. The user redirects it to a
file and opens it in any browser; nothing else is fetched at view time.

The deterministic, golden-tested **contract aura owns is the JSON model** (Stage 1
output) — one step before DOT, exactly as `RunReport::to_json` is the tested contract
for a run. DOT and SVG are downstream of Graphviz's version and are never asserted.

### Why this shape (acceptance rationale, applied to the worked code below)

The intended audience — a trader authoring/debugging a strategy in aura via Claude
Code — reaches for `aura graph` to *see* the graph they wrote: which producer feeds
which consumer slot, what type rides each wire, where a composite boundary sits. The
redesign measurably improves on ascii-dag (it surfaces the full declared interface
that #43 exposed and the old view dropped) and reintroduces no failure class the core
constraints forbid: it is read-only (C9), its emitted contract is deterministic
(golden-tested like `RunReport`), and it adds no `eval`-path code.

## Concrete code shapes

### The user-facing program (north star — the acceptance evidence)

```sh
# emit the self-contained interactive graph viewer
aura graph > graph.html
# open graph.html in any browser (locally, or served to a thin client):
#   python3 -m http.server 8000 --bind 0.0.0.0   # then open http://<host>:8000/graph.html
```

What the user gets, for the sample MACD harness: every node a box with its input pins
(top), body `macd(fast, slow, signal)`, and output pins (bottom); wires docking
pin-to-pin and coloured by scalar type; `price`/`volume` sources green at the top rank,
`Recorder` sinks maroon; clicking `[+]` on `macd` expands it inline as a framed
cluster, clicking its body drills into its interior with a breadcrumb; hovering any
pin/body/edge shows a styled tooltip. This is the prototype, rendered from aura's
emitted model.

### The deterministic contract aura emits (the golden-tested artefact)

The JSON model for the sample MACD harness (shape, abridged — keys in a fixed,
canonical order, exactly as `RunReport::to_json` fixes its order):

```json
{
  "root": {
    "nodes": {
      "price":  { "prim": { "type": "price", "role": "source",
                            "params": [], "ins": [], "outs": [["price","f64"]] } },
      "macd":   { "comp": "macd" },
      "expo":   { "prim": { "type": "Exposure", "role": "node",
                            "params": [["scale","f64"]],
                            "ins": [["signal","f64"]], "outs": [["exposure","f64"]] } },
      "broker": { "prim": { "type": "SimBroker", "role": "node",
                            "params": [["spread","f64"]],
                            "ins": [["exposure","f64"],
                                    ["price","f64",{"firing":"barrier 0"}]],
                            "outs": [["equity","f64"]] } },
      "rec_e":  { "prim": { "type": "Recorder", "role": "sink",
                            "params": [], "ins": [["exposure","f64"]], "outs": [] } }
    },
    "edges": [["price.o0","macd.i0"], ["macd.o2","expo.i0"],
              ["price.o0","broker.i1"], ["expo.o0","broker.i0"],
              ["expo.o0","rec_e.i0"], ["broker.o0","rec_q.i0"]]
  },
  "composites": {
    "macd": {
      "inputs": [["price","f64"]],
      "outputs": [["macd","f64"],["signal","f64"],["histogram","f64"]],
      "nodes": { "ema_f": { "prim": { "type":"EMA","role":"node",
                                      "params":[["fast","i64"]],
                                      "ins":[["price","f64"]],"outs":[["ema","f64"]] } },
                 "sub_h": { "prim": { "type":"Sub","role":"node","params":[],
                                      "ins":[["a","f64"],["b","f64"]],
                                      "outs":[["diff","f64"]] } } },
      "edges": [["@price","ema_f.i0"], ["sub_h.o0","#2"]]
    }
  }
}
```

Endpoint encoding in `edges` re-expresses the engine's wiring: `"key.oN"` = node `key`
output field `N`; `"key.iN"` = node `key` input slot `N`; `"@role"` = a composite
input role (from `input_roles().targets`); `"#N"` = a composite output binding (from
`output()[N]`). This is the exact endpoint vocabulary the prototype's `genDot`
consumes.

### The viewer's DOT (what `genDot` produces in the browser — reference, not aura's output)

For one view, `genDot` turns the model into DOT (lifted from the prototype). The node
template is a Graphviz HTML-like-label table with per-cell ids; edges dock by port:

```dot
digraph g {
  bgcolor="#16161a"; rankdir=TB; nodesep=0.5; ranksep=0.65;
  node [shape=plaintext, fontname="Courier", fontsize=12];   // core font: box sizing matches text
  edge [penwidth=1.7, arrowsize=0.8];

  macd [label=<<table border="0" cellborder="1" cellspacing="0" cellpadding="6">
    <tr><td port="i0" id="P_macd_i0" href="#" bgcolor="#222b33"><font color="#89b4fa">price</font></td></tr>
    <tr><td colspan="3" bgcolor="#5b4b8a"><table border="0" cellborder="0" cellspacing="3"><tr>
      <td id="plus_macd" href="#" align="center" valign="middle" fixedsize="true" width="24" height="24"
          border="1" color="#a594c8" bgcolor="#7c6ba8"><font color="#f5f5f5"><b>+</b></font></td>
      <td id="B_macd" href="#"><font color="#f5f5f5"><b>macd</b></font><font color="#bac2de">(fast, slow, signal)</font></td>
    </tr></table></td></tr>
    <tr><td port="o0" id="P_macd_o0" href="#" bgcolor="#332b22"><font color="#89b4fa">macd</font></td>
        <td port="o1" id="P_macd_o1" href="#" bgcolor="#332b22"><font color="#89b4fa">signal</font></td>
        <td port="o2" id="P_macd_o2" href="#" bgcolor="#332b22"><font color="#89b4fa">histogram</font></td></tr>
  </table>>];

  price:o0:s -> macd:i0:n [color="#89b4fa"];      // pin-to-pin, wire coloured by scalar kind
  {rank=min; price; volume; price -> volume [style=invis];}   // sources/inputs: top rank, signature order
  {rank=max; bout_0;}                                          // outputs: bottom rank, free order; sinks unpinned
}
```

The scalar-type palette is exactly the four base types (C4): `i64 #f9e2af`,
`f64 #89b4fa`, `bool #a6e3a1`, `timestamp #cba6f7`. Body colours encode role:
leaf `#45475a`, composite `#5b4b8a`, source `#2e5a3a`, sink `#5a2e3e`.

### Implementation shape — before → after (secondary)

`crates/aura-cli/src/graph.rs` (the ascii-dag adapter, ~505 lines) is **retired**. Its
public entry points (`render_blueprint`, `render_flat_graph`) and the `ascii-dag`
dependency in `crates/aura-cli/Cargo.toml` are removed.

```rust
// BEFORE — ascii-dag adapter (graph.rs), point-nodes + invented label notation:
pub fn render_blueprint(bp: &Composite, color: Color) -> String { /* ascii_dag::Graph … */ }
pub fn render_flat_graph(nodes: &[Box<dyn Node>], …) -> String  { /* ascii_dag::Graph … */ }

// AFTER — a read-only model serializer (new module, e.g. graph_model.rs),
// hand-rolled deterministic JSON in the RunReport::to_json house style (no serde):
/// Serialize the harness root composite + every distinct composite type into the
/// canonical graph model the viewer consumes. Read-only (C9); never calls eval.
pub fn model_to_json(root: &Composite) -> String { /* walk nodes()/edges()/input_roles()/
                                                       output()/schema(); stable key order */ }
```

```rust
// crates/aura-cli/src/main.rs — the `graph` command emits the self-contained viewer:
["graph"] => print!("{}", graph::render_html(&sample_blueprint())),
//                         render_html = model_to_json + inlined viewer JS + inlined WASM-Graphviz
```

The current golden tests `blueprint_view_golden` and `compiled_view_golden`
(`crates/aura-cli/src/main.rs`) and the `aura graph --compiled` / `--macd` flag
plumbing are replaced; the new golden test asserts `model_to_json` (see Testing).

## Components

1. **`graph_model` (new, `aura-cli` or `aura-engine`).** The Rust serializer:
   `model_to_json(&Composite) -> String`. Walks the blueprint via existing read-only
   accessors (`nodes`, `edges`, `input_roles`, `output`, `params`, `schema`, `name`);
   maps each `BlueprintNode::Primitive` to a `prim` record (type, role, params, ins,
   outs from `NodeSchema`), each `BlueprintNode::Composite` to a `{comp: name}`
   reference; re-encodes edges/roles/outputs into the `@role` / `key.oN` / `key.iN` /
   `#N` endpoint vocabulary; collects each distinct composite type once (like today's
   `collect_distinct_composites`). Deterministic key order, hand-rolled like
   `RunReport::to_json`. **Role derivation:** `source` = a root node with no inputs and
   a bound source role; `sink` = `output: vec![]` (C8 pure consumer); else `node`.
2. **Viewer asset (new, vendored JS).** `genDot` + chrome, ported from the prototype
   `index.html`. Lives as a static asset under the cli crate (e.g.
   `crates/aura-cli/assets/graph-viewer.js`). Plus the vendored WASM-Graphviz
   (`@viz-js/viz@3.7.0`) and `svg-pan-zoom@3.6.1`, restored by the prototype's
   `fetch-deps.sh` pattern (git-ignored blob, build-time fetch or checked-in per the
   planner's call).
3. **`render_html` (new, `aura-cli`).** Assembles the self-contained page: a template
   shell with the model JSON, the viewer JS, and the WASM asset inlined. Emitted by
   `aura graph`.

## Data flow

`aura graph` → `sample_blueprint()` (existing fixture) → `model_to_json(&root)` →
JSON string → `render_html` inlines {model, viewer JS, WASM} into one HTML → stdout.
In the browser: viewer parses the model → `genDot(model, view, expanded)` → DOT →
Graphviz-WASM → SVG → DOM; user interaction (drill/expand/tooltip) re-runs `genDot`
for the new view/expansion and re-renders. No engine round-trip; the whole model
ships once.

## Error handling

- The serializer is **total** over a well-formed blueprint (the engine already
  validates wiring at build, #41): every accessor returns concrete data. A malformed
  alias / missing field falls back to a `?`-style placeholder rather than panicking,
  matching today's `signature()` discipline (graph.rs).
- The serializer never calls `eval`, never constructs a sized instance — read-only
  (C9). It cannot fail a backtest invariant because it touches none.
- Viewer-side: a model that references an unknown composite or an out-of-range field
  degrades to showing the opaque node / the field index (the prototype's
  `multi_output_field_name` fallback), never throws.

## Testing strategy

- **Golden test on the model (the contract).** `model_to_json(&sample_blueprint())`
  asserted byte-for-byte against a checked-in expected string — the same form as the
  existing render goldens, but now over the deterministic JSON. Re-capturable on
  intended drift. This replaces `blueprint_view_golden` / `compiled_view_golden`.
- **Determinism test.** `model_to_json(&bp) == model_to_json(&bp)` and a swapped-param
  / mis-wired blueprint produces a *different* model (the property the old
  `swapped_param_vector_changes_the_compiled_render` and the
  `mc_2_miswire_render` fieldtest protected — carried forward to the model).
- **Read-only assertion.** The serializer signature takes `&Composite` and returns
  `String`; a test confirms no `eval`/build path is on the call (mirrors the C9
  audit note for the old renderer).
- **Structural assertions** (not pixels): the model for a multi-input composite has
  `inputs.len() == 2`; a sink has `outs == []`; a nested composite appears once in
  `composites`. The viewer/DOT/SVG are **not** golden-tested (Graphviz-version
  dependent); the prototype is the visual reference, exercised by hand.
- No `spec_validation` parser is configured in the profile, so the fenced blocks above
  carry no automated parse gate (no-op); the `dot`/`json`/`rust` blocks are
  illustrative shapes lifted from the validated prototype, not asserted bytes.

## Acceptance criteria

1. `aura graph` emits a single self-contained `.html` that, opened in a browser with
   no native dependency, renders the sample harness as a homogeneous pin-graph (body +
   input pins + output pins per node), edges docked pin-to-pin and coloured by scalar
   type, sources/sinks distinguished, composites navigable by drill-down and inline
   expand, with per-element styled tooltips — i.e. the ratified prototype, driven by
   aura's emitted model.
2. The model is produced by a **read-only** serializer (C9 — no `eval`, no build) and
   is **deterministic** (golden-tested byte-for-byte, like `RunReport::to_json`), with
   no `serde` dependency added.
3. The model **omits nothing and invents nothing**: every node carries its declared
   `NodeSchema` (input ports with kind + firing, output fields with name + kind,
   params with name + kind); the invented `#Sf` / `histogram →` / `:=` notation is
   gone.
4. `ascii-dag` is removed from `aura-cli`'s dependencies; `graph.rs`'s ascii-dag
   entry points and the stale `#43` comment are retired.
5. The four-colour type palette is exactly the four scalar base types (C4); no fifth
   colour, no type outside `i64`/`f64`/`bool`/`timestamp`.

## Iteration scope

**Iteration 1 (foundation):** the Rust `graph_model` serializer + its golden +
determinism + read-only tests — the deterministic contract everything downstream
consumes. No viewer wiring yet; `aura graph` may temporarily print the JSON model.
This is the bite-sized, fully-testable core.

**Iteration 2 (viewer):** vendor the viewer JS (ported from the prototype) + WASM
assets; `render_html` self-contained assembly; `aura graph` emits the HTML; retire
`ascii-dag` and the old goldens/flags.

The planner decomposes from here.
