# Composite Signature Render — Design Spec

**Date:** 2026-06-08
**Status:** Draft — awaiting user spec review
**Authors:** orchestrator + Claude

## Goal

Render a composite's blueprint definition as a **typed signature line** plus a
de-cluttered body, replacing the `[param:<name>]` marker nodes #41 introduced
(which bloat the ASCII graph). The interface moves into the title; the params and
ordered inputs fold into the node labels that already exist.

This is **render-only** — no engine logic changes. The #41 `ParamAlias` data and
`param_space()` are untouched.

For the MACD composite, the definition title becomes:

```
macd(fast:i64, slow:i64, signal:i64) -> (macd, signal, histogram)
```

and the three `[param:*]` marker nodes vanish. Output **names** only (not kinds):
a value-empty `LeafFactory` exposes no output schema pre-build (the `mc_4`/#42
finding), so the typed output arrow (`-> (macd:f64, …)`) is **deferred to #43**.
This cycle references #41 (the surface it refines) and #43 (the deferred typing).

## Architecture

The blueprint-definition view (`render_definition` in `crates/aura-cli/src/graph.rs`)
is the only renderer that changes. Five edits, all in `render_definition` except
one doc-comment fix:

1. **Title = signature, not bare name.** `c.name()` → `name(params) -> (outputs)`.
2. **Leaf labels fold their aliased param names.** `[EMA]` → `[EMA(fast)]`.
3. **Unnamed interior input slots render as positional stubs.** `[Sub]` →
   `[Sub(#A,#B)]`, derived from the interior wiring.
4. **Output markers drop the `out:` prefix.** `[out:macd]` → `[macd]`.
5. **The `[param:<name>]` marker nodes are removed.**

Plus a stale-prose fix in `crates/aura-core/src/node.rs`.

**Why this is renderable now (the ascii-dag history).** `LeafFactory::label`
historically stayed the bare type (`SMA`, not `SMA(length)`) because `ascii-dag`
0.9.1 garbles wide sibling labels inside a **cluster** subgraph. Cycle 0017
removed clusters — both `aura graph` views build **flat** graphs
(`crates/aura-cli/src/graph.rs:13-14`: *"the subgraph layout mis-centres wide
sibling labels, the flat layout does not"*). Wide labels are now safe, which is
what makes `[EMA(fast)]` / `[Sub(#A,#B)]` renderable. The doc-comment at
`node.rs:93-101` still cites the cluster constraint as the reason for bare-type
labels — stale prose this cycle corrects.

### Invariant-neutrality
- **Render-only.** No engine logic change; `ParamAlias`, `param_space()`, the
  compile path, and the run are untouched. Files: `graph.rs` (`render_definition`),
  `main.rs` (render tests/goldens), `node.rs` (doc comment only).
- **C23.** `compiled_view_golden` is byte-identical — only the blueprint-definition
  render changes; the compiled/flat view and the flat graph are unaffected. Boundary
  names still never reach a `Box<dyn Node>`.
- **C8/C7/C4 untouched** — authoring-surface legibility only. `aura run --macd`
  is deterministic and unchanged (render-only).

## Concrete code shapes

### Worked example — `aura graph --macd`, before → after

The MACD definition block today (real output — note the three `[param:*]` markers
and the loose `[in:price]` cluttering the top, and the bare `[EMA]`/`[Sub]`):

```
macd:
  [param:fast]   [in:price]   [param:slow]   [param:signal]
        │             └┐───────┌────┘ ┌─────────────┘
        └──────────────┐       │      │
                       ↓       ↓      │
                     [EMA]   [EMA]    │
                       └───┌───┘      │
                           ↓      ┌───┘
                         [Sub]    │
                       ┌───┘──────│────┐
                       ↓          └────↓
                  [out:macd]      │  [EMA]
                      ┌───────────┌────┘
                      ↓───────────↓
                    [Sub]   [out:signal]
                      └───────┐
                              ↓
                       [out:histogram]
```

After this cycle — title carries the signature, `[param:*]` markers gone, params
folded into the EMAs, ordered Sub inputs shown as stubs, outputs de-prefixed
(exact box-drawing layout is whatever the flat renderer produces; the load-bearing
changes are the labels):

```
macd(fast:i64, slow:i64, signal:i64) -> (macd, signal, histogram):
              [in:price]
               └┐──────┌┘
                ↓      ↓
          [EMA(fast)] [EMA(slow)]
                └──┌────┘
                   ↓
              [Sub(#A,#B)]
              ┌────┘────┐
              ↓         ↓
            [macd]  [EMA(signal)]
                  ┌──────┘
                  ↓
             [Sub(#A,#B)]
              ┌────┘────┐
              ↓         ↓
          [signal]  [histogram]
```

The `sma_cross` sample (named role, **no** aliases) confirms the empty-param case
renders cleanly — no params in the signature, leaves stay bare:

```
sma_cross() -> (cross):
        [in:price]
         └┐──────┌┘
          ↓      ↓
        [SMA]  [SMA]
          └──┌───┘
             ↓
        [Sub(#A,#B)]
             │
             ↓
          [cross]
```

### The label-annotation rule (pinned)

A leaf item's label in `render_definition` is `factory.label()` plus an optional
parenthesised annotation built in this order:

1. **Aliased param names** for this leaf — every `a.name` in `c.params()` with
   `a.node == this_index`, in `c.params()` order.
2. **Input-slot stubs** — only if the leaf has **>1** distinct wired input slot:
   one positional stub per slot in slot order (`#A`, `#B`, `#C`, …). A single-input
   leaf gets no stub (no ordering ambiguity).

If both are present, the annotation is `factory.label()` + `(` + params + `; ` +
stubs + `)` (params and stubs separated by `; `). If only one is present, no
separator. If neither, the bare label (today's behaviour). In the worked MACD/SMA
graphs every leaf hits exactly one branch — EMAs have one aliased param and one
input (→ `[EMA(fast)]`); Subs have no params and two inputs (→ `[Sub(#A,#B)]`) —
the combined `; ` form is defined for completeness, not exercised here.

A node's wired input slots are the distinct `.slot` values targeting it, collected
from **both** `c.edges()` (entries with `to == index`) **and** `c.input_roles()`
(each role's `targets` with `node == index`). Nested-composite interior items keep
rendering as their opaque `name()` (unchanged; their own definition renders
separately).

### Before → after — `render_definition` (`crates/aura-cli/src/graph.rs`)

Today (the relevant parts): leaves labelled bare; an `[in:k]`, `[param:name]`, and
`[out:name]` marker per role/alias/output; title is `c.name()`.

```rust
fn render_definition(c: &Composite) -> String {
    let mut labels: Vec<String> = Vec::with_capacity(c.nodes().len());
    for inner in c.nodes() {
        labels.push(match inner {
            BlueprintNode::Leaf(factory) => factory.label(),
            BlueprintNode::Composite(inner_c) => inner_c.name().to_string(),
        });
    }
    let mut edges: Vec<(usize, usize)> = Vec::new();
    for e in c.edges() {
        edges.push((e.from, e.to));
    }
    for role in c.input_roles() {
        let in_id = labels.len();
        labels.push(format!("in:{}", role.name));
        for t in &role.targets {
            edges.push((in_id, t.node));
        }
    }
    for a in c.params() {
        let p_id = labels.len();
        labels.push(format!("param:{}", a.name));
        edges.push((p_id, a.node));
    }
    for of in c.output() {
        let out_id = labels.len();
        labels.push(format!("out:{}", of.name));
        edges.push((of.node, out_id));
    }
    format!("{}:\n{}", c.name(), render_flat(&labels, &edges))
}
```

After: leaf labels annotated (params folded + input stubs), the `[param:*]` loop
removed, outputs de-prefixed, the title built from a new `signature(c)` helper.

```rust
fn render_definition(c: &Composite) -> String {
    let mut labels: Vec<String> = Vec::with_capacity(c.nodes().len());
    for (i, inner) in c.nodes().iter().enumerate() {
        labels.push(match inner {
            BlueprintNode::Leaf(factory) => leaf_label(c, i, factory),
            BlueprintNode::Composite(inner_c) => inner_c.name().to_string(),
        });
    }
    let mut edges: Vec<(usize, usize)> = Vec::new();
    for e in c.edges() {
        edges.push((e.from, e.to));
    }
    for role in c.input_roles() {
        let in_id = labels.len();
        labels.push(format!("in:{}", role.name));
        for t in &role.targets {
            edges.push((in_id, t.node));
        }
    }
    // params are no longer marker nodes — they fold into leaf labels (leaf_label)
    // and the signature title (signature). The [param:*] loop is removed.
    for of in c.output() {
        let out_id = labels.len();
        labels.push(of.name.clone()); // [out:macd] -> [macd]
        edges.push((of.node, out_id));
    }
    format!("{}:\n{}", signature(c), render_flat(&labels, &edges))
}
```

with two new render-side helpers (shapes; exact bodies are the planner's):

```rust
// "macd(fast:i64, slow:i64, signal:i64) -> (macd, signal, histogram)"
// param kinds from the interior leaf's factory().params()[slot].kind;
// output names only (kinds deferred to #43).
fn signature(c: &Composite) -> String { /* ... */ }

// "EMA(fast)" / "Sub(#A,#B)" / bare "SMA" per the label-annotation rule above.
fn leaf_label(c: &Composite, index: usize, factory: &LeafFactory) -> String { /* ... */ }
```

### node.rs doc-comment fix (`crates/aura-core/src/node.rs:93-101`)

The `LeafFactory::label` doc currently reads (paraphrased) "the label stays the bare
type because ascii-dag overlaps two wide sibling boxes inside a cluster subgraph".
Replace that rationale: the renderer is flat (no clusters) since cycle 0017, so wide
labels are safe; the factory label stays the bare param-generic type because
**alias / handle names are composite-level concepts resolved at render**
(`render_definition` folds them via `c.params()`), not because of any ascii-dag
constraint. Behaviour-neutral (a comment).

## Components

| Component | File | Change |
|-----------|------|--------|
| `render_definition` | `crates/aura-cli/src/graph.rs` | title = `signature(c)`; leaf labels via `leaf_label`; drop `[param:*]` loop; outputs de-prefixed |
| `signature` (new) | `crates/aura-cli/src/graph.rs` | builds the `name(params) -> (outputs)` line; param kinds from `factory().params()[slot].kind`; output names only |
| `leaf_label` (new) | `crates/aura-cli/src/graph.rs` | folds aliased param names + input-slot stubs per the pinned rule |
| `LeafFactory::label` doc | `crates/aura-core/src/node.rs:93-101` | replace stale cluster rationale (comment only) |
| render tests / goldens | `crates/aura-cli/src/main.rs` | `blueprint_view_golden` re-capture; new assertions; `compiled_view_golden` untouched |

## Data flow

Render is a pure read over the blueprint (C9 graph-as-data): `render_definition`
reads `c.nodes()`, `c.edges()`, `c.input_roles()`, `c.params()`, `c.output()` and
the interior leaves' `factory().label()` / `factory().params()`. No build, no
param vector, no engine call. `signature` resolves param kinds by indexing the
aliased leaf's `factory().params()`; output kinds are intentionally not resolved
(deferred to #43).

## Error handling

Render is total over a well-formed blueprint (the same blueprints the existing
`render_definition` already renders). An alias is validated at compile
(`BadInteriorIndex`, #41); the renderer is reached only for renderable blueprints,
so `signature`/`leaf_label` index `c.params()`/`factory().params()` within the
bounds an already-constructed composite guarantees. No new error paths.

## Testing strategy

- **`blueprint_view_golden`** (`crates/aura-cli/src/main.rs`) re-captured — the
  definition render changed. Run the test, paste the actual rendered output
  wholesale into the golden literal.
- **New render assertions** on the MACD definition: contains the signature
  substring `macd(fast:i64, slow:i64, signal:i64) -> (macd, signal, histogram)`,
  contains `[EMA(fast)]`, `[Sub(#A,#B)]`, `[macd]`, `[in:price]`; and asserts
  `[param:` is **absent** (markers removed) and `[out:` is **absent** (prefix
  dropped).
- **`compiled_view_golden`** byte-identical (C23 guard — must stay green,
  untouched; a drift here is a bug, not a re-capture).
- **`run_macd…deterministic`** green, metrics unchanged (render-only).
- **No-alias case**: a `sma_cross` render assertion confirms `sma_cross() -> (cross)`
  (empty param list) and bare `[SMA]` leaves render cleanly.

## Acceptance criteria

- A trader reading `aura graph --macd` sees the composite's interface as a typed
  signature line (`macd(fast:i64, slow:i64, signal:i64) -> (macd, signal,
  histogram)`) and an uncluttered body — the `[param:*]` marker bloat is gone,
  params read on the EMAs (`[EMA(fast)]`), the ordered Sub inputs are visible
  (`[Sub(#A,#B)]`). The worked before→after is the evidence.
- Render-only: `compiled_view_golden` byte-identical; `aura run --macd`
  deterministic and unchanged; no engine/`ParamAlias`/`param_space()` change.
- Output kinds are honestly omitted (names only), with the typed arrow deferred to
  #43; the spec and commit reference #41 (surface) and #43 (deferred typing), and
  this cycle `closes` no issue.
- `cargo build/test/clippy --workspace` (-D warnings) green.
