# Tidy 0014 — scalar re-export + Recorder-fixture dedup — Implementation Plan

> **Parent spec:** none — this is a post-cycle **tidy iteration** dispatched per
> the `audit` skill's "fix path: planner + implement for a tidy iteration". The
> source of truth is two Gitea tidy issues (#29, #14) plus the orchestrator's
> scope constraints. (#27 was the third candidate but is **out of this plan**:
> its only remaining content after the bit-identical-test protection and the
> `aura run` out-of-scope rule is a cross-crate dedup of a concrete `sma_cross`
> composite, which has no C9-clean home — orchestrator decided to narrow/close
> #27 with that rationale rather than bend C9 in a tidy.)
>
> **For agentic workers:** REQUIRED SUB-SKILL: use the `implement` skill to run
> this plan. Steps use `- [ ]` checkboxes for tracking.

**Goal:** Close #29 (aura-engine re-exports the core scalar vocabulary) and #14
(remove the two near-identical `#[cfg(test)]` Recorder fixtures in aura-engine,
using the shipped `aura-std::Recorder`).

**Architecture:** Two independent, behaviour-preserving tidies. (1) Add one
`pub use aura_core::{...}` line to `aura-engine`'s crate root so a Blueprint
builder needs one import surface, not two. (2) Delete the private f64/all-kind
`#[cfg(test)]` Recorder structs in `report.rs` and `harness.rs` and import the
shipped `aura_std::Recorder` instead — its constructor signature, schema, and
`try_iter()` drain are call-for-call identical to both fixtures, so **no call
site changes**; only the struct/impl deletion and one import line per file.

**Tech Stack:** `crates/aura-engine/src/{lib,report,harness}.rs`; the shipped
`aura-std::Recorder` (already a `[dev-dependencies]` of aura-engine).

---

## Files this plan creates or modifies

- Modify: `crates/aura-engine/src/lib.rs:38-40` — add `pub use aura_core::{Firing, Scalar, ScalarKind, Timestamp};` after the existing re-exports.
- Test: `crates/aura-engine/src/lib.rs` (new `#[cfg(test)]` module) — assert the four scalar symbols resolve at the aura-engine crate root.
- Modify: `crates/aura-engine/src/report.rs:203` — add `Recorder` to the existing `use aura_std::{...}`.
- Modify: `crates/aura-engine/src/report.rs:217-255` — delete the private `#[cfg(test)] struct Recorder` + its `impl Recorder::new` + `impl Node`.
- Modify: `crates/aura-engine/src/harness.rs:340` — add `Recorder` to the existing `use aura_std::{...}`.
- Modify: `crates/aura-engine/src/harness.rs:496-559` — delete the private `#[cfg(test)] struct Recorder` + its `impl Recorder::new` + `impl Node` (leave the separate `TapForward` fixture at L564-585 untouched).

---

## Task 1: #29 — aura-engine re-exports the core scalar vocabulary

**Files:**
- Modify: `crates/aura-engine/src/lib.rs:38-40`
- Test: `crates/aura-engine/src/lib.rs` (new `#[cfg(test)]` module at end of file)

- [ ] **Step 1: Add the re-export line**

In `crates/aura-engine/src/lib.rs`, the current re-exports are:

```rust
pub use blueprint::{Blueprint, BlueprintNode, CompileError, Composite, OutPort};
pub use harness::{BootstrapError, Edge, Harness, SourceSpec, Target};
pub use report::{f64_field, summarize, RunManifest, RunMetrics, RunReport};
```

Add one line immediately after `pub use report::{...};`:

```rust
// #29: re-export the core scalar vocabulary a Blueprint builder needs
// (SourceSpec.kind is a ScalarKind; sources/Recorder columns are Scalar /
// Firing / Timestamp) so a graph builder has one import surface, not two.
pub use aura_core::{Firing, Scalar, ScalarKind, Timestamp};
```

- [ ] **Step 2: Add a test that the four symbols resolve at the crate root**

Append to `crates/aura-engine/src/lib.rs` (if the file already ends with a
`#[cfg(test)]` module, add this as a sibling module — do not merge):

```rust
#[cfg(test)]
mod reexport_tests {
    // #29: the core scalar vocabulary a Blueprint builder needs is reachable
    // from aura-engine alone (crate::X == external aura_engine::X), so a
    // downstream author does not add a second aura-core import for ScalarKind.
    #[test]
    fn core_scalar_vocabulary_is_reexported_from_crate_root() {
        use crate::{Firing, Scalar, ScalarKind, Timestamp};
        let _k: ScalarKind = ScalarKind::F64;
        let _f: Firing = Firing::Any;
        let _s: Scalar = Scalar::F64(0.0);
        let _t: Timestamp = Timestamp(0);
    }
}
```

- [ ] **Step 3: Build + test + lint**

Run: `cargo build -p aura-engine && cargo test -p aura-engine reexport_tests && cargo clippy -p aura-engine --all-targets -- -D warnings`
Expected: build OK; `core_scalar_vocabulary_is_reexported_from_crate_root` PASS (1 test run, not 0); clippy clean (no `unused_imports`, no `ambiguous_glob_reexports`).

---

## Task 2: #14 (part 1) — report.rs uses the shipped Recorder

**Files:**
- Modify: `crates/aura-engine/src/report.rs:203` (import) and `:217-255` (delete fixture)

The private fixture's constructor is `Recorder::new(&[ScalarKind], Firing, mpsc::Sender<(Timestamp, Vec<Scalar>)>)`, identical to `aura_std::Recorder::new`; both schemas are one `InputSpec` per kind with empty output; both drain via `rx.try_iter()`. The two call sites (`report.rs:275-276`, read back at `:308-309`) construct `Recorder::new(&[ScalarKind::F64], Firing::Any, tx_*)` and stay **byte-identical** — they resolve to `aura_std::Recorder` once the private struct is gone and the import is added.

- [ ] **Step 1: Add `Recorder` to the aura-std import**

In `crates/aura-engine/src/report.rs`, the test-module import is:

```rust
use aura_std::{Exposure, SimBroker, Sma, Sub};
```

Replace it with (alphabetical, `Recorder` inserted):

```rust
use aura_std::{Exposure, Recorder, SimBroker, Sma, Sub};
```

- [ ] **Step 2: Delete the private Recorder fixture**

In `crates/aura-engine/src/report.rs`, delete the entire private fixture block
spanning the `#[cfg(test)] struct Recorder { ... }` declaration, its
`impl Recorder { fn new(...) -> Self { ... } }`, and its `impl Node for Recorder { ... }` (the contiguous region at lines ~217-255, ending just before the next test-support item). Delete nothing else — leave every `Recorder::new(...)` call site and every other helper intact.

- [ ] **Step 3: Build + test + lint**

Run: `cargo test -p aura-engine --lib report && cargo clippy -p aura-engine --all-targets -- -D warnings`
Expected: `report_is_deterministic_end_to_end` (report.rs:329) PASS (≥1 test run, not 0); no `unused_imports` for `Recorder`; no "cannot find type `Recorder`" error; clippy clean.

---

## Task 3: #14 (part 2) — harness.rs uses the shipped Recorder

**Files:**
- Modify: `crates/aura-engine/src/harness.rs:340` (import) and `:496-559` (delete fixture)

The private fixture here is the all-four-kinds variant (matches on `I64/F64/Bool/Timestamp`), behaviourally identical to `aura_std::Recorder`. Its ~30 call sites (enumerated in recon: L594…L1768, all `Recorder::new(&[<kinds>], <Firing>, <tx>)`, all drained via `rx.try_iter()`) stay **byte-identical**. The separate `TapForward` fixture (L564-585) is NOT a Recorder and is left untouched.

- [ ] **Step 1: Add `Recorder` to the aura-std import**

In `crates/aura-engine/src/harness.rs`, the test-module import is:

```rust
use aura_std::{Exposure, Sma, SimBroker, Sub};
```

Replace it with (`Recorder` inserted):

```rust
use aura_std::{Exposure, Recorder, Sma, SimBroker, Sub};
```

- [ ] **Step 2: Delete the private Recorder fixture**

In `crates/aura-engine/src/harness.rs`, delete the entire private fixture block
spanning the `#[cfg(test)] struct Recorder { ... }` declaration, its
`impl Recorder { fn new(...) -> Self { ... } }`, and its `impl Node for Recorder { ... }` (the contiguous region at lines ~496-559). Do NOT touch the `TapForward` struct/impl that follows at ~564-585, and delete no call site.

- [ ] **Step 3: Build + full workspace test + lint**

Run: `cargo build --workspace && cargo test --workspace && cargo clippy --workspace --all-targets -- -D warnings`
Expected: build OK; all tests PASS — in particular `composite_sma_cross_runs_bit_identical_to_hand_wired`, `run_sample_is_deterministic_and_non_trivial`, `swapped_sma_inputs_render_differently`, the aura-cli golden snapshots, the aura-std SMA disambiguation test, and every harness.rs recording test (e.g. `recorder_records_mixed_scalar_kinds`, `milestone_end_to_end_mixed_dag_records_every_stream_deterministically`, `signal_quality_loop_is_deterministic`) stay green; no `unused_imports`; clippy clean.