# Bound params in the graph model + viewer signature — Implementation Plan

> **Parent spec:** `docs/specs/0037-bound-param-in-graph-model.md`
>
> **For agentic workers:** REQUIRED SUB-SKILL: use the `implement` skill to run
> this plan. Steps use `- [ ]` checkboxes for tracking.

**Goal:** Surface a `bind`-bound param in the graph model and the `aura graph`
viewer signature — all slots shown, the bound one as `name=value`, dimmed — while
leaving the tunable surface (`param_space` / sweep axes) untouched.

**Architecture:** A conditional field threaded `engine → model → viewer`, the
twin of cycle 0035's instance-name thread. `PrimitiveBuilder::bind` records a
`BoundParam` (original slot position + name + kind + value); `prim_record` emits a
conditional `"bound"` field via a new `scalar_str` helper; `graph-viewer.js`
merges free + bound params into slot order by position and renders the bound slot
dimmed. Render/debug surface only — dropped at lowering (C23), model stays
deterministic (C14). Purely additive: a new struct, a `Vec::new()`-default field,
a new accessor, a conditional model field defaulting to empty, a viewer field
defaulting to `[]`. No call site of `bind`/`prim_record`/`adaptNodes`/`genDot`/
`cellLabel` changes arity.

**Tech Stack:** `crates/aura-core/src/node.rs` (Rust), `crates/aura-engine/src/
graph_model.rs` (Rust), `crates/aura-cli/assets/graph-viewer.js` (JS),
`crates/aura-cli/tests/` (Rust + headless `node` guards), the
`crates/aura-cli/tests/fixtures/sample-model.json` golden.

---

**Files this plan creates or modifies:**

- Modify: `crates/aura-core/src/node.rs` — `BoundParam` struct (after `ParamSpec`,
  ~:67), `PrimitiveBuilder.bound` field (struct :77-85), init in `new` (:96),
  record in `bind` (between the kind-assert :172 and `remove(pos)` :173),
  `bound_params()` accessor (after `instance_name()` :120-122), unit test (tests
  mod :229+, beside `bind_removes_slot_and_reconstructs_positionally` :386).
- Modify: `crates/aura-engine/src/graph_model.rs` — `scalar_str` helper (beside
  `kind_str` :14-21), conditional `"bound"` field in `prim_record` (:72-89; field
  block after the `name` conditional :80-83, `{bound}` in the format string :85),
  unit test (tests mod, beside `prim_record_emits_name_for_explicit_only` :383).
- Modify: `crates/aura-cli/assets/graph-viewer.js` — `adaptNodes` (:32), `genDot`
  leaf-emit cellLabel call (:111), `cellLabel` `sp`/`sig` (:72-73).
- Modify: `crates/aura-cli/tests/fixtures/sample-model.json` — re-capture; the
  `signals` composite's node `"2"` (`blend`) gains `"bound":[[2,"weights[2]","f64","0.5"]]`.
- Create: `crates/aura-cli/tests/viewer_bound_param.mjs` — headless render guard
  (trailing + middle bind).
- Create: `crates/aura-cli/tests/viewer_bound_param.rs` — Rust shell that runs the
  `.mjs` via `node`. Mirror of `viewer_name_prefix.rs`.

**Note on verification commands (project memory):** use ONE positional
`cargo test` filter per invocation (a multi-filter `cargo test X Y` silently
prints nothing here); for "everything still green" use an unfiltered per-crate run
and read the summary count. The viewer guards REQUIRE `node` on PATH
(`/usr/bin/node`, v26 confirmed) — a skipped guard is not a guard.

**Parse-the-bytes gate:** the project declares no `spec_validation` parser (see
CLAUDE.md project facts), so the inline-body parse gate is a documented no-op; the
Rust bodies are caught by the `implement` compile gate and the JS by the `node`
guard run.

---

### Task 1: aura-core — `BoundParam`, `bind` records original position, `bound_params()`

**Files:**
- Modify: `crates/aura-core/src/node.rs`
- Test: `crates/aura-core/src/node.rs` (tests mod)

- [ ] **Step 1: Write the failing test**

In `crates/aura-core/src/node.rs`, inside `#[cfg(test)] mod tests` (after
`bind_removes_slot_and_reconstructs_positionally`, ~:408), add:

```rust
    #[test]
    fn bind_records_bound_param_at_original_position() {
        // middle-of-three: binding `b` records its ORIGINAL slot position (1).
        let mid = probe3().bind("b", Scalar::I64(8));
        assert_eq!(
            mid.bound_params(),
            [BoundParam { pos: 1, name: "b".into(), kind: ScalarKind::I64, value: Scalar::I64(8) }]
                .as_slice(),
        );

        // chained reverse-order bind (b then a): each entry carries its ORIGINAL
        // position regardless of the shrinking array — positions {1, 0} in call order.
        let pair = probe3().bind("b", Scalar::I64(8)).bind("a", Scalar::I64(7));
        assert_eq!(
            pair.bound_params(),
            [
                BoundParam { pos: 1, name: "b".into(), kind: ScalarKind::I64, value: Scalar::I64(8) },
                BoundParam { pos: 0, name: "a".into(), kind: ScalarKind::I64, value: Scalar::I64(7) },
            ]
            .as_slice(),
        );

        // an unbound builder records nothing.
        assert!(probe3().bound_params().is_empty());
    }
```

- [ ] **Step 2: Run test to verify it fails**

Run: `cargo test -p aura-core bind_records_bound_param_at_original_position`
Expected: FAIL — does not compile: `cannot find type BoundParam in this scope` /
`no method named bound_params found for struct PrimitiveBuilder`.

- [ ] **Step 3: Write the implementation**

(3a) Add the `BoundParam` struct immediately after `ParamSpec` (after its closing
`}` at ~:67, before the `PrimitiveBuilder` doc-comment at :69). `Scalar` /
`ScalarKind` are already imported at `node.rs:13` — no new import:

```rust
/// One param bound to a structural constant by [`PrimitiveBuilder::bind`] — a
/// render/debug surface only (C23), dropped at lowering. `pos` is the slot's
/// position in the node's ORIGINAL (pre-bind) param list, so the model serializer
/// and viewer can place it back into slot order regardless of bind sequence.
#[derive(Clone, Debug, PartialEq)]
pub struct BoundParam {
    pub pos: usize,
    pub name: String,
    pub kind: ScalarKind,
    pub value: Scalar,
}
```

(3b) Add the `bound` field to `PrimitiveBuilder` (struct at :77-85). Replace:

```rust
pub struct PrimitiveBuilder {
    name: &'static str,
    instance_name: Option<String>,
    schema: NodeSchema,
    // The build closure's type is exactly the recipe contract (a param slice in, a
    // boxed node out); a type alias would not clarify it.
    #[allow(clippy::type_complexity)]
    build: Box<dyn Fn(&[Scalar]) -> Box<dyn Node>>,
}
```

with:

```rust
pub struct PrimitiveBuilder {
    name: &'static str,
    instance_name: Option<String>,
    schema: NodeSchema,
    bound: Vec<BoundParam>,
    // The build closure's type is exactly the recipe contract (a param slice in, a
    // boxed node out); a type alias would not clarify it.
    #[allow(clippy::type_complexity)]
    build: Box<dyn Fn(&[Scalar]) -> Box<dyn Node>>,
}
```

(3c) Initialize `bound` in `new` (:96). Replace:

```rust
        Self { name, instance_name: None, schema, build: Box::new(build) }
```

with:

```rust
        Self { name, instance_name: None, schema, bound: Vec::new(), build: Box::new(build) }
```

(3d) Add the `bound_params()` accessor immediately after `instance_name()`
(after its closing `}` at :122):

```rust
    /// The params bound to structural constants by [`bind`](Self::bind), in
    /// bind-call order, each carrying its ORIGINAL slot position. The render-
    /// surface twin of [`instance_name`](Self::instance_name): the model
    /// serializer reads it to show a bound slot's fixed value (the value captured
    /// in the build closure is otherwise unreachable to it). Empty when no binds.
    pub fn bound_params(&self) -> &[BoundParam] {
        &self.bound
    }
```

(3e) In `bind`, record the `BoundParam` at its original position. Insert between
the kind-assert (ends :172) and `self.schema.params.remove(pos);` (:173):

```rust
        // [render side] record the bound slot for the model/viewer at its ORIGINAL
        // pre-bind position. `pos` indexes the already-shrunk array (earlier binds
        // removed), so map it back to the full-arity index by adding one for each
        // earlier-bound slot at an original position <= it. Render/debug only (C23);
        // the closure capture below is what bootstrap actually reads.
        let name = self.schema.params[pos].name.clone();
        let kind = self.schema.params[pos].kind;
        let mut orig = pos;
        let mut prior: Vec<usize> = self.bound.iter().map(|b| b.pos).collect();
        prior.sort_unstable();
        for p in prior {
            if p <= orig {
                orig += 1;
            }
        }
        self.bound.push(BoundParam { pos: orig, name, kind, value });
```

- [ ] **Step 4: Run test to verify it passes**

Run: `cargo test -p aura-core bind_records_bound_param_at_original_position`
Expected: PASS (`test ... ok`, 1 passed).

- [ ] **Step 5: Verify aura-core suite stays green**

Run: `cargo test -p aura-core`
Expected: PASS — all tests ok, 0 failed (existing `bind_*` tests included).

---

### Task 2: aura-engine — `scalar_str` + conditional `"bound"` in `prim_record`

**Files:**
- Modify: `crates/aura-engine/src/graph_model.rs`
- Test: `crates/aura-engine/src/graph_model.rs` (tests mod)

- [ ] **Step 1: Write the failing test**

In `crates/aura-engine/src/graph_model.rs`, inside `#[cfg(test)] mod tests` (after
`prim_record_emits_name_for_explicit_only`, ~:394), add. The tests mod already
imports `Scalar`, `PrimitiveBuilder` (:244-245) and `aura_std::{Exposure, …, Sma}`
(:247):

```rust
    #[test]
    fn prim_record_emits_bound_only_when_bound() {
        // a bound i64 param → a "bound" field carrying [pos,"name","kind","value"]
        let bound = prim_record(&Sma::builder().bind("length", Scalar::I64(5)));
        assert!(bound.contains(r#""bound":[[0,"length","i64","5"]]"#), "{bound}");
        // the bound slot also leaves the tunable "params" surface (bind's tuning side)
        assert!(bound.contains(r#""params":[]"#), "{bound}");

        // a bound f64 value renders canonically (shortest round-trip), e.g. 0.5
        let f = prim_record(&Exposure::builder().bind("scale", Scalar::F64(0.5)));
        assert!(f.contains(r#""bound":[[0,"scale","f64","0.5"]]"#), "{f}");

        // an unbound builder → no "bound" field at all
        let unbound = prim_record(&Sma::builder());
        assert!(!unbound.contains(r#""bound""#), "{unbound}");
    }
```

- [ ] **Step 2: Run test to verify it fails**

Run: `cargo test -p aura-engine prim_record_emits_bound_only_when_bound`
Expected: FAIL — does not compile: `no method named bound_params` (until Task 1
lands) OR, with Task 1 present, assertion failure (`"bound"` substring absent).

- [ ] **Step 3: Write the implementation**

(3a) Add the `scalar_str` helper immediately after `kind_str` (after its closing
`}` at :21):

```rust
/// A scalar VALUE as a canonical, deterministic string for the model (C14). `f64`
/// uses the shortest round-trippable debug form, which keeps a decimal point on
/// whole values (`1.0`, not `1`) so a bound f64 is never mistaken for an i64 in
/// the render. The value side of `kind_str`.
fn scalar_str(s: aura_core::Scalar) -> String {
    use aura_core::Scalar;
    match s {
        Scalar::I64(n) => n.to_string(),
        Scalar::F64(f) => format!("{f:?}"),
        Scalar::Bool(b) => b.to_string(),
        Scalar::Ts(t) => t.0.to_string(),
    }
}
```

(3b) In `prim_record` (:72-89), add the `bound` field block after the `name`
conditional (after its closing line :83, before the `format!` at :84):

```rust
    // bound params: present only when the node has binds (mirrors the conditional
    // "name" field). each entry: [pos,"name","kind","value"].
    let bound = if b.bound_params().is_empty() {
        String::new()
    } else {
        let items = join(b.bound_params().iter().map(|bp| {
            format!(
                "[{},{},{},{}]",
                bp.pos,
                json_str(&bp.name),
                json_str(kind_str(bp.kind)),
                json_str(&scalar_str(bp.value)),
            )
        }));
        format!(r#","bound":[{items}]"#)
    };
```

(3c) Insert `{bound}` into the `format!` template (:85), after `"params":[{params}]`
and before `,"ins"`. Replace:

```rust
        r#"{{"prim":{{{name}"type":{},"role":{},"params":[{params}],"ins":[{ins}],"outs":[{outs}]}}}}"#,
```

with:

```rust
        r#"{{"prim":{{{name}"type":{},"role":{},"params":[{params}]{bound},"ins":[{ins}],"outs":[{outs}]}}}}"#,
```

- [ ] **Step 4: Run test to verify it passes**

Run: `cargo test -p aura-engine prim_record_emits_bound_only_when_bound`
Expected: PASS (1 passed).

- [ ] **Step 5: Verify the no-bind golden stays byte-stable**

Run: `cargo test -p aura-engine model_golden`
Expected: PASS — the inline `model_golden` (`sample_root`, no binds) is unchanged:
the conditional field is inert for unbound nodes.

- [ ] **Step 6: Verify aura-engine suite stays green**

Run: `cargo test -p aura-engine`
Expected: PASS — all tests ok, 0 failed (`model_is_deterministic` included).

---

### Task 3: graph-viewer.js — carry `bound`, render the merged signature

**Files:**
- Modify: `crates/aura-cli/assets/graph-viewer.js`

- [ ] **Step 1: `adaptNodes` carries `bound`**

In `crates/aura-cli/assets/graph-viewer.js` (:32), replace:

```js
      out[key] = { prim: { name: p.name, type: p.type, role: p.role, params: p.params, ins: adaptIns(p.ins), outs: p.outs } };
```

with:

```js
      out[key] = { prim: { name: p.name, type: p.type, role: p.role, params: p.params, bound: p.bound || [], ins: adaptIns(p.ins), outs: p.outs } };
```

- [ ] **Step 2: `genDot` leaf-emit forwards `bound`**

In `genDot` (:111), replace:

```js
        block += `${cid} [label=${cellLabel(cid, { name: s.name, type: s.type, params: s.params, ins: s.ins, outs: s.outs, bodyBg: bodyBgFor(s.role), composite: false }, showTypes)}];\n`;
```

with:

```js
        block += `${cid} [label=${cellLabel(cid, { name: s.name, type: s.type, params: s.params, bound: s.bound, ins: s.ins, outs: s.outs, bodyBg: bodyBgFor(s.role), composite: false }, showTypes)}];\n`;
```

- [ ] **Step 3: `cellLabel` merges free + bound params into slot order**

In `cellLabel` (:72-73), replace:

```js
  const sp = o.params.map(([n, k]) => `<font color="${col(k)}">${showTypes && k ? `${n}:${k}` : n}</font>`);
  const sig = o.params.length ? `<font color="#9399b2">[</font>${sp.join('<font color="#9399b2">, </font>')}<font color="#9399b2">]</font>` : "";
```

with:

```js
  // merge free params and bound params back into slot order by original position;
  // a bound slot renders as a dimmed name=value (reuses the 0035 separator grey).
  const bnd = o.bound || [];
  const total = o.params.length + bnd.length;
  const byPos = new Map(bnd.map(([pos, n, k, v]) => [pos, [n, k, v]]));
  const slots = [];
  let fi = 0;
  for (let pos = 0; pos < total; pos++) {
    if (byPos.has(pos)) {
      const [n, , v] = byPos.get(pos);
      slots.push(`<font color="#9399b2">${n}=${v}</font>`);
    } else {
      const [n, k] = o.params[fi++];
      slots.push(`<font color="${col(k)}">${showTypes && k ? `${n}:${k}` : n}</font>`);
    }
  }
  const sig = total ? `<font color="#9399b2">[</font>${slots.join('<font color="#9399b2">, </font>')}<font color="#9399b2">]</font>` : "";
```

(`o.bound || []` keeps the composite / boundary `cellLabel` calls — which pass no
`bound` — rendering exactly as before: `total` collapses to `params.length`.)

- [ ] **Step 4: Verify the existing viewer guards stay green**

The existing guards exercise `genDot`/`cellLabel` over models with no `bound`
field; the merge must render them identically. They read the OLD fixture (Task 4
re-captures it) — both states are backward-compatible.

Run: `cargo test -p aura-cli --test viewer_name_prefix`
Expected: PASS.

Run: `cargo test -p aura-cli --test viewer_dot`
Expected: PASS.

Run: `cargo test -p aura-cli --test viewer_nested_depth`
Expected: PASS.

---

### Task 4: Re-capture the `sample-model.json` fixture

**Files:**
- Modify: `crates/aura-cli/tests/fixtures/sample-model.json`
- Modify (temporary): `crates/aura-cli/src/main.rs` (a throwaway capture test, removed in Step 4)

- [ ] **Step 1: Add a temporary capture test**

In `crates/aura-cli/src/main.rs`, inside `#[cfg(test)] mod tests` (:560,
`use super::*` already present), add:

```rust
    #[test]
    fn capture_sample_model_tmp() {
        println!("AURA_MODEL_CAPTURE:{}", aura_engine::model_to_json(&sample_blueprint()));
    }
```

- [ ] **Step 2: Capture the model into the fixture**

Run (one positional filter, per project note):

```bash
cargo test -p aura-cli capture_sample_model_tmp -- --nocapture 2>/dev/null \
  | grep '^AURA_MODEL_CAPTURE:' | sed 's/^AURA_MODEL_CAPTURE://' \
  > crates/aura-cli/tests/fixtures/sample-model.json
```

Expected: the fixture is rewritten as a single JSON line. Verify the `blend`
node gained the bound field:

```bash
grep -c '"bound":\[\[2,"weights\[2\]","f64","0.5"\]\]' crates/aura-cli/tests/fixtures/sample-model.json
```

Expected: `1`.

- [ ] **Step 3: Validate the fixture is well-formed JSON**

Run:

```bash
node -e "JSON.parse(require('fs').readFileSync('crates/aura-cli/tests/fixtures/sample-model.json','utf8')); console.log('OK valid JSON')"
```

Expected: `OK valid JSON`.

- [ ] **Step 4: Remove the temporary capture test**

Delete the `capture_sample_model_tmp` test added in Step 1 from
`crates/aura-cli/src/main.rs`.

- [ ] **Step 5: Verify the fixture consumers stay green**

The two consumers assert DOT-id grammar / nesting depth, not params, and read the
re-captured fixture (now carrying `bound`, handled by Task 3's `p.bound || []`).

Run: `cargo test -p aura-cli --test viewer_dot`
Expected: PASS.

Run: `cargo test -p aura-cli --test viewer_nested_depth`
Expected: PASS.

---

### Task 5: New headless render guard — bound slot in true slot order

**Files:**
- Create: `crates/aura-cli/tests/viewer_bound_param.mjs`
- Create: `crates/aura-cli/tests/viewer_bound_param.rs`

- [ ] **Step 1: Write the headless guard script**

Create `crates/aura-cli/tests/viewer_bound_param.mjs`:

```js
// Headless render guard for the `aura graph` viewer (graph-viewer.js).
//
// Property protected: a bind-bound param slot renders in the node signature as a
// DIMMED `name=value`, in TRUE slot order (by original position), with the free
// slots in their type colour — never dropped. Covers a trailing bind (the
// cycle-0036 showcase shape) AND a non-trailing (middle) bind, which an
// append-after-free design would render in the wrong order.
//
// It loads the real viewer module and drives the exported pure `genDot`. `node`
// is REQUIRED: a skipped guard is not a guard.

import { createRequire } from "node:module";
import { fileURLToPath } from "node:url";
import { dirname, join } from "node:path";

const require = createRequire(import.meta.url);
const here = dirname(fileURLToPath(import.meta.url));

// Load the viewer once with an empty model; normalizeModel/genDot are pure and
// take the model/def explicitly, so each case is rendered by passing its own.
global.window = { AURA_MODEL: { root: { nodes: {}, edges: [] }, composites: {} } };
const { normalizeModel, genDot } = require(join(here, "..", "assets", "graph-viewer.js"));
const dotFor = (model) => genDot(normalizeModel(model).root, "root", new Set(), false).dot;

const fail = (msg, dot) => {
  console.error(msg + "\n--- dot ---\n" + dot);
  process.exit(1);
};

// --- Model A: trailing bind (the cycle-0036 showcase shape) ---
const trailing = {
  root: { nodes: { "0": { prim: {
    name: "blend", type: "LinComb", role: "node",
    params: [["weights[0]", "f64"], ["weights[1]", "f64"]],
    bound: [[2, "weights[2]", "f64", "0.5"]],
    ins: [["f64", "any", "term[0]"], ["f64", "any", "term[1]"], ["f64", "any", "term[2]"]],
    outs: [["value", "f64"]],
  } } }, edges: [] },
  composites: {},
};
const dotA = dotFor(trailing);

const BOUND = '<font color="#9399b2">weights[2]=0.5</font>';
const FREE0 = '<font color="#89b4fa">weights[0]</font>';
const FREE1 = '<font color="#89b4fa">weights[1]</font>';
if (!dotA.includes(BOUND)) fail("trailing: bound slot weights[2]=0.5 not rendered dimmed", dotA);
if (!dotA.includes(FREE0) || !dotA.includes(FREE1)) fail("trailing: a free weight slot is missing or not type-coloured", dotA);
const a0 = dotA.indexOf(FREE0), a1 = dotA.indexOf(FREE1), ab = dotA.indexOf(BOUND);
if (!(a0 < a1 && a1 < ab)) fail("trailing: slot order is not weights[0] < weights[1] < weights[2]=0.5", dotA);

// --- Model B: NON-TRAILING (middle) bind — pins slot-order faithfulness ---
const middle = {
  root: { nodes: { "0": { prim: {
    name: "mid", type: "Probe", role: "node",
    params: [["a", "f64"], ["c", "f64"]],
    bound: [[1, "b", "f64", "9.0"]],
    ins: [["f64", "any", "t0"], ["f64", "any", "t1"], ["f64", "any", "t2"]],
    outs: [["value", "f64"]],
  } } }, edges: [] },
  composites: {},
};
const dotB = dotFor(middle);

const MA = '<font color="#89b4fa">a</font>';
const MB = '<font color="#9399b2">b=9.0</font>';
const MC = '<font color="#89b4fa">c</font>';
if (!dotB.includes(MA) || !dotB.includes(MB) || !dotB.includes(MC)) fail("middle: a free or bound slot is missing", dotB);
const ba = dotB.indexOf(MA), bb = dotB.indexOf(MB), bc = dotB.indexOf(MC);
if (!(ba < bb && bb < bc)) fail("middle: bound slot b=9.0 not placed between free a and c (append-only bug)", dotB);

console.log("OK — bound slot renders dimmed name=value in true slot order (trailing + middle bind).");
process.exit(0);
```

- [ ] **Step 2: Write the Rust shell**

Create `crates/aura-cli/tests/viewer_bound_param.rs`:

```rust
//! Integration guard: the `aura graph` viewer renders a bind-bound param slot as
//! a dimmed `name=value` in true slot order (trailing + non-trailing bind).
//!
//! The property lives in JavaScript (`cellLabel` in assets/graph-viewer.js), so
//! this shells out to `node` running the headless guard
//! `tests/viewer_bound_param.mjs`, which loads the real viewer module and drives
//! the exported `genDot` over two minimal models.
//!
//! `node` is REQUIRED: if it is not on PATH this test FAILS (a skipped guard is
//! not a guard).

use std::path::PathBuf;
use std::process::Command;

#[test]
fn viewer_renders_bound_param_in_slot_order() {
    let script = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .join("tests")
        .join("viewer_bound_param.mjs");
    assert!(script.exists(), "guard script missing at {}", script.display());

    let out = match Command::new("node").arg(&script).output() {
        Ok(out) => out,
        Err(e) => panic!(
            "node is required for the viewer bound-param guard but could not be run \
             ({e}); install Node.js or ensure `node` is on PATH"
        ),
    };

    let stdout = String::from_utf8_lossy(&out.stdout);
    let stderr = String::from_utf8_lossy(&out.stderr);
    assert!(
        out.status.success(),
        "viewer bound-param guard failed (exit {:?}).\n--- node stdout ---\n{stdout}\n--- node stderr ---\n{stderr}",
        out.status.code()
    );
}
```

- [ ] **Step 3: Run the new guard to verify it passes**

Run: `cargo test -p aura-cli --test viewer_bound_param`
Expected: PASS — `viewer_renders_bound_param_in_slot_order ... ok`; the `.mjs`
prints `OK — bound slot renders dimmed name=value in true slot order …`.

---

### Task 6: Full-workspace gate

**Files:** none (verification only)

- [ ] **Step 1: Build**

Run: `cargo build --workspace`
Expected: finishes, 0 errors.

- [ ] **Step 2: Test**

Run: `cargo test --workspace`
Expected: all tests pass, 0 failed (the new aura-core + aura-engine unit tests,
the new `viewer_bound_param` guard, and every existing test — the sweep param
pins at `main.rs:595-598` and `cli_run.rs:214` stay byte-identical, since the
tunable surface is unchanged).

- [ ] **Step 3: Lint**

Run: `cargo clippy --workspace --all-targets -- -D warnings`
Expected: finishes, 0 warnings.

---

## Spec coverage map

| Spec section | Task |
|---|---|
| `BoundParam` + `bind` records original position + `bound_params()` | Task 1 |
| `scalar_str` + conditional `"bound"` in `prim_record` | Task 2 |
| `adaptNodes`/`genDot`/`cellLabel` merge + dimmed render | Task 3 |
| `sample-model.json` re-capture (blend gains `"bound"`) | Task 4 |
| Headless render guard (trailing + middle bind, slot order) | Task 5 |
| Goldens / sweep pins stay green; build/test/clippy clean | Tasks 2, 4, 6 |
| Acceptance criteria #1–#4 | Tasks 1–6 (render: 3+5; model: 2+4; tunable surface untouched: 6; tests: 1,2,5) |
