//! The harness — the closed root graph that runs (glossary: `harness`, C20) —
//! and its deterministic run loop. A `Harness` is a bootstrapped, frozen root
//! graph: a flat node array plus an index edge table, topologically ordered,
//! driven cycle by cycle by a k-way merge of timestamped sources (C3/C4). It is
//! the flat, monomorphized sharpening of RustAst's reference-counted,
//! interior-mutable observer push graph: no reference counting, no interior
//! mutability, no per-cycle allocation (C1/C7). Each node owns its input columns
//! (the cycle-0002 shape), so `Ctx` borrows them read-only and additionally
//! carries the cycle timestamp (`ctx.now()`, C4). A node's `eval` returns a
//! borrowed record (`Option<&[Scalar]>`); each out-edge forwards one field of it
//! (`Edge::from_field`) into a consumer slot, so the K fields are co-fresh (C6).
//!
//! Firing (C5/C6) gates re-evaluation. Two read clocks drive it, both stamped per
//! input slot on every push: `fresh_at` (the `cycle_id` of the last push —
//! freshness epoch, C5) and `last_ts` (the data timestamp of that push — barrier
//! token, C6). A node fires when any `Firing::Any` input is fresh this cycle, or
//! when a `Firing::Barrier` group has every member at the current timestamp; a
//! node that does not fire pushes nothing, so consumers keep seeing the held
//! value via `window[0]` (sample-and-hold falls out of the push model). The
//! barrier token is the timestamp, not the `cycle_id`: under C4 four same-time
//! sources are four cycles, so RustAst's `cycle_id`-equality barrier could never
//! fire across sources — the timestamp generalizes it faithfully.

use aura_core::{AnyColumn, Ctx, Firing, Node, Scalar, ScalarKind, Timestamp};

/// Forwards one field (`from_field`) of a producer's output record into a
/// consumer's input slot. Consuming a whole record is N such edges, one per field
/// (there is no "bind whole record" mechanism).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Edge {
    pub from: usize,
    pub to: usize,
    pub slot: usize,
    pub from_field: usize,
}

/// An input slot the source value is forwarded into each cycle.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Target {
    pub node: usize,
    pub slot: usize,
}

/// A declared source: the scalar kind it produces and the input slots each of
/// its records is forwarded into. The multi-source generalization of cycle
/// 0003's `(source_targets, source_kind)` pair — sources are k-way-merged by
/// timestamp at ingestion (C3); there is no merge inside the graph.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SourceSpec {
    pub kind: ScalarKind,
    pub targets: Vec<Target>,
}

/// A wiring fault caught once, at bootstrap — C7's "type check paid at wiring"
/// generalized to the whole topology.
#[derive(Debug, PartialEq, Eq)]
pub enum BootstrapError {
    /// An edge or source-target connects mismatched scalar kinds.
    KindMismatch { producer: ScalarKind, consumer: ScalarKind },
    /// A node or slot index in an edge or target is out of range.
    BadIndex,
    /// The wiring contains a directed cycle (only an explicit delay node may close
    /// a loop; that node does not exist yet).
    Cycle,
}

/// Per-input engine bookkeeping (invisible to nodes): the two read clocks of the
/// firing machinery. `fresh_at` is the `cycle_id` of the last push into this slot
/// (freshness epoch, C5: fresh this cycle iff `fresh_at == cycle_id`); `last_ts`
/// is the data timestamp of that push (barrier token, C6: a barrier group is
/// complete iff all members carry `last_ts == T`). A never-pushed slot keeps the
/// cold sentinel `Timestamp(i64::MIN)`, which no real timestamp equals.
struct SlotState {
    fresh_at: u64,
    last_ts: Timestamp,
}

struct NodeBox {
    node: Box<dyn Node>,
    inputs: Vec<AnyColumn>,
    firing: Vec<Firing>,
    slots: Vec<SlotState>,
    out_len: usize,
}

/// A bootstrapped, frozen root graph instance plus its deterministic run loop.
pub struct Harness {
    nodes: Vec<NodeBox>,
    topo: Vec<usize>,
    out_edges: Vec<Vec<Edge>>,
    sources: Vec<SourceSpec>,
}

// Manual, node-opaque `Debug`: `Box<dyn Node>` is not `Debug`, so the struct
// cannot derive it. This summary form is enough for `Result::unwrap_err` (which
// formats the `Ok` arm on a failed bootstrap-rejection assertion) without
// printing node internals.
impl core::fmt::Debug for Harness {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("Harness")
            .field("nodes", &self.nodes.len())
            .field("topo", &self.topo)
            .field("out_edges", &self.out_edges)
            .field("sources", &self.sources)
            .finish()
    }
}

impl Harness {
    /// Bind nodes + wiring into a frozen, runnable graph. Sizes each node's input
    /// columns from its `schema`, lifts each input's firing policy, initializes
    /// per-slot freshness state, kind-checks every source target and edge, and
    /// topologically orders the nodes (Kahn), rejecting any directed cycle.
    pub fn bootstrap(
        nodes: Vec<Box<dyn Node>>,
        sources: Vec<SourceSpec>,
        edges: Vec<Edge>,
    ) -> Result<Harness, BootstrapError> {
        let n = nodes.len();

        let schemas: Vec<_> = nodes.iter().map(|nd| nd.schema()).collect();

        // size each node's input columns from its schema; lift firing; init slots
        let mut boxes: Vec<NodeBox> = Vec::with_capacity(n);
        for (nd, schema) in nodes.into_iter().zip(schemas.iter()) {
            let inputs: Vec<AnyColumn> = schema
                .inputs
                .iter()
                .map(|spec| AnyColumn::with_capacity(spec.kind, spec.lookback))
                .collect();
            let firing: Vec<Firing> = schema.inputs.iter().map(|spec| spec.firing).collect();
            let slots: Vec<SlotState> = schema
                .inputs
                .iter()
                .map(|_| SlotState { fresh_at: 0, last_ts: Timestamp(i64::MIN) })
                .collect();
            let out_len = schema.output.len();
            boxes.push(NodeBox { node: nd, inputs, firing, slots, out_len });
        }

        // source targets: each source's value must match each of its target slots' kind
        for src in &sources {
            for t in &src.targets {
                let s = schemas.get(t.node).ok_or(BootstrapError::BadIndex)?;
                let slot = s.inputs.get(t.slot).ok_or(BootstrapError::BadIndex)?;
                if slot.kind != src.kind {
                    return Err(BootstrapError::KindMismatch {
                        producer: src.kind,
                        consumer: slot.kind,
                    });
                }
            }
        }

        // edges: indices in range, producer output field kind == consumer slot kind
        let mut out_edges: Vec<Vec<Edge>> = vec![Vec::new(); n];
        for &e in &edges {
            let from = schemas.get(e.from).ok_or(BootstrapError::BadIndex)?;
            let to = schemas.get(e.to).ok_or(BootstrapError::BadIndex)?;
            let field = from.output.get(e.from_field).ok_or(BootstrapError::BadIndex)?;
            let slot = to.inputs.get(e.slot).ok_or(BootstrapError::BadIndex)?;
            if field.kind != slot.kind {
                return Err(BootstrapError::KindMismatch {
                    producer: field.kind,
                    consumer: slot.kind,
                });
            }
            out_edges[e.from].push(e);
        }

        // Kahn topological sort; a leftover node means a cycle
        let mut indeg = vec![0usize; n];
        for &e in &edges {
            indeg[e.to] += 1;
        }
        let mut queue: Vec<usize> = (0..n).filter(|&i| indeg[i] == 0).collect();
        let mut topo: Vec<usize> = Vec::with_capacity(n);
        let mut head = 0;
        while head < queue.len() {
            let u = queue[head];
            head += 1;
            topo.push(u);
            for e in &out_edges[u] {
                indeg[e.to] -= 1;
                if indeg[e.to] == 0 {
                    queue.push(e.to);
                }
            }
        }
        if topo.len() != n {
            return Err(BootstrapError::Cycle);
        }

        Ok(Harness {
            nodes: boxes,
            topo,
            out_edges,
            sources,
        })
    }

    /// Drive the sources, k-way-merged in timestamp order (ties by source index,
    /// C4). One stream per source, each ascending in timestamp (C3 ingestion
    /// precondition). Recording is a node-side concern: a recording node pushes
    /// its record to a destination it holds (out of graph) inside `eval`; the
    /// engine only routes in-graph edges and is oblivious to the side effect.
    /// Allocates nothing per cycle beyond the reused scratch buffer.
    pub fn run(&mut self, streams: Vec<Vec<(Timestamp, Scalar)>>) {
        assert_eq!(
            streams.len(),
            self.sources.len(),
            "run: one stream per source required (got {} streams for {} sources)",
            streams.len(),
            self.sources.len()
        );

        // disjoint field borrows so the topo walk can read topo/out_edges/sources
        // while mutating nodes
        let Harness { nodes, topo, out_edges, sources } = self;

        let mut cursor: Vec<usize> = vec![0; streams.len()];
        let mut cycle_id: u64 = 0;
        let mut scratch: Vec<Scalar> = Vec::new();

        loop {
            // pick the live source head with the smallest (timestamp, source index)
            let mut pick: Option<usize> = None;
            for (s, stream) in streams.iter().enumerate() {
                if cursor[s] < stream.len() {
                    match pick {
                        None => pick = Some(s),
                        Some(p) => {
                            if stream[cursor[s]].0 < streams[p][cursor[p]].0 {
                                pick = Some(s);
                            }
                        }
                    }
                }
            }
            let s = match pick {
                Some(s) => s,
                None => break, // all streams exhausted
            };
            let (ts, value) = streams[s][cursor[s]];
            cursor[s] += 1;
            cycle_id += 1;

            // forward the source value into its target slots, stamping freshness
            for t in sources[s].targets.iter() {
                let nb = &mut nodes[t.node];
                nb.inputs[t.slot].push(value).expect("source kind checked at wiring");
                nb.slots[t.slot] = SlotState { fresh_at: cycle_id, last_ts: ts };
            }

            // evaluate in topological order; gate by firing; forward Some outputs
            for &nidx in topo.iter() {
                let out_len = nodes[nidx].out_len;
                let fired = {
                    let nb = &nodes[nidx];
                    fires(&nb.firing, &nb.slots, cycle_id, ts)
                };
                if !fired {
                    continue; // hold: no eval, no push
                }
                let result: Option<&[Scalar]> = {
                    let nb = &mut nodes[nidx];
                    nb.node.eval(Ctx::new(&nb.inputs, ts))
                };
                if let Some(row) = result {
                    debug_assert_eq!(row.len(), out_len, "node returned a row of the wrong width");
                    scratch.clear();
                    scratch.extend_from_slice(row);
                    for e in out_edges[nidx].iter() {
                        let nb = &mut nodes[e.to];
                        nb.inputs[e.slot]
                            .push(scratch[e.from_field])
                            .expect("edge kind checked at wiring");
                        nb.slots[e.slot] = SlotState { fresh_at: cycle_id, last_ts: ts };
                    }
                }
            }
        }
    }
}

/// The firing predicate (C5/C6): does this node re-evaluate this cycle? A node
/// fires when *any* of its input groups fires (OR). A `Firing::Any` input fires
/// the node when it is fresh this cycle (`fresh_at == cycle_id`). A barrier group
/// fires when >=1 member is fresh this cycle AND every member carries
/// `last_ts == ts` — the ">=1 fresh" clause is the once-per-timestamp guard (a
/// group completed in a prior cycle has no fresh member now, so it does not
/// re-fire).
fn fires(firing: &[Firing], slots: &[SlotState], cycle_id: u64, ts: Timestamp) -> bool {
    // mode A: any fire-on-any-fresh input that is fresh this cycle
    for (i, f) in firing.iter().enumerate() {
        if matches!(f, Firing::Any) && slots[i].fresh_at == cycle_id {
            return true;
        }
    }
    // mode B: each distinct barrier group fires when complete this cycle
    if let Some(max_group) = firing.iter().filter_map(group_id).max() {
        for g in 0..=max_group {
            let mut has_member = false;
            let mut any_fresh = false;
            let mut all_at_ts = true;
            for (i, f) in firing.iter().enumerate() {
                if group_id(f) == Some(g) {
                    has_member = true;
                    if slots[i].fresh_at == cycle_id {
                        any_fresh = true;
                    }
                    if slots[i].last_ts != ts {
                        all_at_ts = false;
                    }
                }
            }
            if has_member && any_fresh && all_at_ts {
                return true;
            }
        }
    }
    false
}

/// The barrier group id of a firing policy, or `None` for mode A.
fn group_id(f: &Firing) -> Option<u8> {
    match f {
        Firing::Any => None,
        Firing::Barrier(g) => Some(*g),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    // InputSpec / NodeSchema are not imported by harness.rs production code (it
    // only reads `nd.schema()` fields, never naming the types), so they are not
    // brought in by `use super::*` — the fixtures construct them, so import here.
    use aura_core::{FieldSpec, InputSpec, NodeSchema};
    use aura_std::{Exposure, Sma, SimBroker, Sub};
    use std::sync::mpsc;

    /// Build an f64 source stream from (timestamp, value) points.
    fn f64_stream(points: &[(i64, f64)]) -> Vec<(Timestamp, Scalar)> {
        points.iter().map(|&(t, v)| (Timestamp(t), Scalar::F64(v))).collect()
    }

    // --- firing-policy fixtures (test-local; not library nodes — C9: examples
    // for the engine's own tests, no speculative aura-std surface) ---

    /// Mode A as-of join: a 2-input f64 sum that fires whenever either input is
    /// fresh, holding the other. Warm-up returns None until both have a value.
    struct AsOfSum {
        out: [Scalar; 1],
    }
    impl Node for AsOfSum {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Any },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Any },
                ],
                output: vec![FieldSpec { name: "value", kind: ScalarKind::F64 }],
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            let a = ctx.f64_in(0);
            let b = ctx.f64_in(1);
            if a.is_empty() || b.is_empty() {
                return None;
            }
            self.out[0] = Scalar::F64(a[0] + b[0]);
            Some(&self.out)
        }
    }

    /// Mode B barrier join: a 2-input f64 sum that fires only when both inputs
    /// share the current cycle timestamp (both warm by construction when it fires).
    struct BarrierSum {
        out: [Scalar; 1],
    }
    impl Node for BarrierSum {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                ],
                output: vec![FieldSpec { name: "value", kind: ScalarKind::F64 }],
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            self.out[0] = Scalar::F64(ctx.f64_in(0)[0] + ctx.f64_in(1)[0]);
            Some(&self.out)
        }
    }

    /// Mixed A+B: barrier pair (inputs 0,1 in group 0) plus an as-of input
    /// (input 2). Fires when the pair completes (holding input 2) OR when input 2
    /// ticks (holding the pair) — the OR-combine.
    struct MixedSum {
        out: [Scalar; 1],
    }
    impl Node for MixedSum {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Any },
                ],
                output: vec![FieldSpec { name: "value", kind: ScalarKind::F64 }],
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            let a = ctx.f64_in(0);
            let b = ctx.f64_in(1);
            let c = ctx.f64_in(2);
            if a.is_empty() || b.is_empty() || c.is_empty() {
                return None;
            }
            self.out[0] = Scalar::F64(a[0] + b[0] + c[0]);
            Some(&self.out)
        }
    }

    /// A neutral multi-field producer: five f64 inputs bundled into one 5-field
    /// record. No trading-domain logic — it proves the K > 1 output mechanism in
    /// isolation. The five inputs are a Barrier(0) group, so the node emits one
    /// complete bar only when all five share the cycle's timestamp.
    struct Ohlcv {
        out: [Scalar; 5],
    }
    impl Node for Ohlcv {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                    InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Barrier(0) },
                ],
                output: vec![
                    FieldSpec { name: "open", kind: ScalarKind::F64 },
                    FieldSpec { name: "high", kind: ScalarKind::F64 },
                    FieldSpec { name: "low", kind: ScalarKind::F64 },
                    FieldSpec { name: "close", kind: ScalarKind::F64 },
                    FieldSpec { name: "volume", kind: ScalarKind::F64 },
                ],
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            for i in 0..5 {
                let w = ctx.f64_in(i);
                if w.is_empty() {
                    return None; // not yet warmed
                }
                self.out[i] = Scalar::F64(w[0]);
            }
            Some(&self.out) // one 5-field record, all fields co-fresh
        }
    }

    /// A producer whose output record mixes kinds: field 0 is f64, field 1 is i64.
    /// Used only to prove the bootstrap kind check is per-field (field 0 would bind
    /// into an f64 slot; field 1 would not). Its `eval` never runs in these tests —
    /// bootstrap rejects the wiring first.
    struct TwoField {
        out: [Scalar; 2],
    }
    impl Node for TwoField {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Any }],
                output: vec![
                    FieldSpec { name: "f", kind: ScalarKind::F64 },
                    FieldSpec { name: "i", kind: ScalarKind::I64 },
                ],
            }
        }
        fn eval(&mut self, _ctx: Ctx<'_>) -> Option<&[Scalar]> {
            self.out[0] = Scalar::F64(0.0);
            self.out[1] = Scalar::I64(0);
            Some(&self.out)
        }
    }

    /// A recording node (test-local fixture; stands in for a downstream author's
    /// chart/registry sink). It declares typed input slots and holds an
    /// `mpsc::Sender`; on every fired cycle it reads the newest of each input plus
    /// `ctx.now()`, sends the timestamped record out of the graph, and returns
    /// `None` (pure consumer — C8). Read-back is via the channel, never `Rc`/
    /// `RefCell`, so `aura-engine/src` stays free of the interior-mutability the
    /// purity invariant (C7) forbids.
    struct Recorder {
        kinds: Vec<ScalarKind>,
        firing: Firing,
        tx: mpsc::Sender<(Timestamp, Vec<Scalar>)>,
    }
    impl Recorder {
        fn new(
            kinds: &[ScalarKind],
            firing: Firing,
            tx: mpsc::Sender<(Timestamp, Vec<Scalar>)>,
        ) -> Self {
            Self { kinds: kinds.to_vec(), firing, tx }
        }
    }
    impl Node for Recorder {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: self
                    .kinds
                    .iter()
                    .map(|&kind| InputSpec { kind, lookback: 1, firing: self.firing })
                    .collect(),
                output: vec![], // pure sink: no output port
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            let mut row = Vec::with_capacity(self.kinds.len());
            for (i, &kind) in self.kinds.iter().enumerate() {
                let v = match kind {
                    ScalarKind::I64 => {
                        let w = ctx.i64_in(i);
                        if w.is_empty() {
                            return None; // not yet warmed
                        }
                        Scalar::I64(w[0])
                    }
                    ScalarKind::F64 => {
                        let w = ctx.f64_in(i);
                        if w.is_empty() {
                            return None;
                        }
                        Scalar::F64(w[0])
                    }
                    ScalarKind::Bool => {
                        let w = ctx.bool_in(i);
                        if w.is_empty() {
                            return None;
                        }
                        Scalar::Bool(w[0])
                    }
                    ScalarKind::Timestamp => {
                        let w = ctx.ts_in(i);
                        if w.is_empty() {
                            return None;
                        }
                        Scalar::Ts(w[0])
                    }
                };
                row.push(v);
            }
            let _ = self.tx.send((ctx.now(), row)); // out-of-graph side effect
            None // records, forwards nothing
        }
    }

    /// A node that records AND forwards: it sends `(now, value)` out of the graph
    /// (sink side effect) and returns its value as a one-field output the engine
    /// forwards downstream (producer). Proves the C8 "both" role.
    struct TapForward {
        out: [Scalar; 1],
        tx: mpsc::Sender<(Timestamp, Vec<Scalar>)>,
    }
    impl Node for TapForward {
        fn schema(&self) -> NodeSchema {
            NodeSchema {
                inputs: vec![InputSpec { kind: ScalarKind::F64, lookback: 1, firing: Firing::Any }],
                output: vec![FieldSpec { name: "value", kind: ScalarKind::F64 }],
            }
        }
        fn eval(&mut self, ctx: Ctx<'_>) -> Option<&[Scalar]> {
            let w = ctx.f64_in(0);
            if w.is_empty() {
                return None;
            }
            let v = w[0];
            let _ = self.tx.send((ctx.now(), vec![Scalar::F64(v)])); // sink side effect
            self.out[0] = Scalar::F64(v);
            Some(&self.out) // producer output: engine forwards it
        }
    }

    #[test]
    fn chain_source_sma_runs() {
        // node 0 = SMA(3); source -> SMA(3).in0; node 1 = Recorder taps node 0.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Sma::new(3)),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
            ],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
        )
        .expect("valid");
        h.run(vec![f64_stream(&[(1, 1.0), (2, 2.0), (3, 3.0), (4, 4.0), (5, 5.0)])]);
        let got: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // SMA(3) warms at cycle 3; the recorder captures only fired cycles, each
        // tagged with the cycle's timestamp (sparse — no None hold-rows).
        assert_eq!(
            got,
            vec![
                (Timestamp(3), vec![Scalar::F64(2.0)]),
                (Timestamp(4), vec![Scalar::F64(3.0)]),
                (Timestamp(5), vec![Scalar::F64(4.0)]),
            ]
        );
    }

    #[test]
    fn fan_out_join_dag_runs_deterministically() {
        // 0 = SMA(2), 1 = SMA(4), 2 = Sub; source fans into both SMAs; SMAs join
        // into Sub; node 3 = Recorder taps Sub — the 0003 baseline on the new API.
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),
                    Box::new(Sma::new(4)),
                    Box::new(Sub::new()),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
                }],
                vec![
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                    Edge { from: 1, to: 2, slot: 1, from_field: 0 },
                    Edge { from: 2, to: 3, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid DAG")
        };
        let prices = f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0), (6, 20.0)]);

        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(vec![prices.clone()]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // Sub fires once SMA(4) is warm (cycle 4): 15-13, 17-15, 19-17 -> 2.
        assert_eq!(
            out,
            vec![
                (Timestamp(4), vec![Scalar::F64(2.0)]),
                (Timestamp(5), vec![Scalar::F64(2.0)]),
                (Timestamp(6), vec![Scalar::F64(2.0)]),
            ]
        );

        // determinism (C1): a second identical run drains a bit-identical stream.
        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(vec![prices]);
        let out2: Vec<(Timestamp, Vec<Scalar>)> = rx2.try_iter().collect();
        assert_eq!(out2, out);
    }

    #[test]
    fn mode_a_as_of_fires_on_any_fresh_and_holds() {
        // AsOfSum @0; node 1 = Recorder taps it. source 0 ticks t=1..4; source 1
        // ticks t=2,4 (slower); both AsOfSum inputs Any.
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(AsOfSum { out: [Scalar::F64(0.0)] }),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] },
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
                ],
                vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
            )
            .expect("valid")
        };
        let s0 = f64_stream(&[(1, 10.0), (2, 20.0), (3, 30.0), (4, 40.0)]);
        let s1 = f64_stream(&[(2, 100.0), (4, 200.0)]);

        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(vec![s0.clone(), s1.clone()]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // holds s1=100 across t=3 and the t=4 s0-cycle; emits on every tick once warm.
        assert_eq!(
            out,
            vec![
                (Timestamp(2), vec![Scalar::F64(120.0)]),
                (Timestamp(3), vec![Scalar::F64(130.0)]),
                (Timestamp(4), vec![Scalar::F64(140.0)]),
                (Timestamp(4), vec![Scalar::F64(240.0)]),
            ]
        );

        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(vec![s0, s1]);
        let out2: Vec<(Timestamp, Vec<Scalar>)> = rx2.try_iter().collect();
        assert_eq!(out2, out); // deterministic
    }

    #[test]
    fn mode_b_barrier_fires_only_on_timestamp_coincidence() {
        // identical wiring to mode A, but both BarrierSum inputs are Barrier(0).
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(BarrierSum { out: [Scalar::F64(0.0)] }),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] },
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
                ],
                vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
            )
            .expect("valid")
        };
        let s0 = f64_stream(&[(1, 10.0), (2, 20.0), (3, 30.0), (4, 40.0)]);
        let s1 = f64_stream(&[(2, 100.0), (4, 200.0)]);

        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(vec![s0.clone(), s1.clone()]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // records ONLY at t=2 and t=4 where both inputs share the timestamp.
        assert_eq!(
            out,
            vec![
                (Timestamp(2), vec![Scalar::F64(120.0)]),
                (Timestamp(4), vec![Scalar::F64(240.0)]),
            ]
        );

        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(vec![s0, s1]);
        let out2: Vec<(Timestamp, Vec<Scalar>)> = rx2.try_iter().collect();
        assert_eq!(out2, out); // deterministic
    }

    #[test]
    fn within_source_diamond_rejoin_barrier_fires() {
        // One source fans out through SMA(2), SMA(4) that rejoin at a Barrier(0)
        // node; node 3 = Recorder taps the barrier. Every push in a cycle carries
        // that cycle's timestamp, so once both SMAs warm and emit in the same
        // cycle, both barrier inputs share the timestamp and the barrier fires.
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),
                    Box::new(Sma::new(4)),
                    Box::new(BarrierSum { out: [Scalar::F64(0.0)] }),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
                }],
                vec![
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                    Edge { from: 1, to: 2, slot: 1, from_field: 0 },
                    Edge { from: 2, to: 3, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid DAG")
        };
        let prices = f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0), (6, 20.0)]);

        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(vec![prices.clone()]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // SMA(4) warms at cycle 4; from then both paths emit each cycle at the same
        // timestamp, so the barrier fires: SMA(2)+SMA(4) = 15+13, 17+15, 19+17.
        assert_eq!(
            out,
            vec![
                (Timestamp(4), vec![Scalar::F64(28.0)]),
                (Timestamp(5), vec![Scalar::F64(32.0)]),
                (Timestamp(6), vec![Scalar::F64(36.0)]),
            ]
        );

        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(vec![prices]);
        let out2: Vec<(Timestamp, Vec<Scalar>)> = rx2.try_iter().collect();
        assert_eq!(out2, out);
    }

    #[test]
    fn mixed_a_and_b_or_combine_on_one_node() {
        // MixedSum @0 (in0,in1 barrier group 0; in2 as-of); node 1 = Recorder taps it.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(MixedSum { out: [Scalar::F64(0.0)] }),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
            ],
            vec![
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] },
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 2 }] },
            ],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
        )
        .expect("valid");
        let s0 = f64_stream(&[(2, 20.0), (5, 50.0)]); // in0 (barrier)
        let s1 = f64_stream(&[(2, 200.0)]);           // in1 (barrier)
        let s2 = f64_stream(&[(1, 1.0), (3, 3.0)]);   // in2 (as-of)

        h.run(vec![s0, s1, s2]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // c3: barrier pair completes at t=2, holds c=1 -> 221. c4: as-of input
        // ticks at t=3, holds the pair -> 223. c1 filters; c2,c5 hold (no record).
        assert_eq!(
            out,
            vec![
                (Timestamp(2), vec![Scalar::F64(221.0)]),
                (Timestamp(3), vec![Scalar::F64(223.0)]),
            ]
        );
    }

    #[test]
    fn bootstrap_rejects_a_cycle() {
        // two SMA(1) nodes wired a -> b -> a
        let err = Harness::bootstrap(
            vec![Box::new(Sma::new(1)), Box::new(Sma::new(1))],
            vec![],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }, Edge { from: 1, to: 0, slot: 0, from_field: 0 }],
        )
        .unwrap_err();
        assert_eq!(err, BootstrapError::Cycle);
    }

    #[test]
    fn bootstrap_rejects_a_kind_mismatch() {
        // SMA(1) declares an f64 input; an i64 source mismatches
        let err = Harness::bootstrap(
            vec![Box::new(Sma::new(1))],
            vec![SourceSpec { kind: ScalarKind::I64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![],
        )
        .unwrap_err();
        assert_eq!(
            err,
            BootstrapError::KindMismatch { producer: ScalarKind::I64, consumer: ScalarKind::F64 }
        );
    }

    #[test]
    fn bootstrap_rejects_a_bad_index() {
        // an edge target node (9) that does not exist -> BadIndex. (The old trigger
        // — an out-of-range observe index — is gone with `observe`; BadIndex itself
        // is unchanged, only the path that reaches it.)
        let err = Harness::bootstrap(
            vec![Box::new(Sma::new(1)), Box::new(Sma::new(1))],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 9, slot: 0, from_field: 0 }],
        )
        .unwrap_err();
        assert_eq!(err, BootstrapError::BadIndex);
    }

    /// Build five timestamp-aligned f64 sources feeding Ohlcv's five barrier slots.
    fn ohlcv_streams() -> Vec<Vec<(Timestamp, Scalar)>> {
        vec![
            f64_stream(&[(1, 10.0), (2, 20.0)]), // open
            f64_stream(&[(1, 15.0), (2, 25.0)]), // high
            f64_stream(&[(1, 8.0), (2, 19.0)]),  // low
            f64_stream(&[(1, 12.0), (2, 22.0)]), // close
            f64_stream(&[(1, 100.0), (2, 200.0)]), // volume
        ]
    }

    fn ohlcv_sources() -> Vec<SourceSpec> {
        (0..5)
            .map(|slot| SourceSpec {
                kind: ScalarKind::F64,
                targets: vec![Target { node: 0, slot }],
            })
            .collect()
    }

    #[test]
    fn ohlcv_bundles_five_field_record() {
        // node 0 = Ohlcv; five sources feed O/H/L/C/V; node 1 = a 5-input Recorder
        // taps all five fields via five edges. The barrier fires once all five share
        // the timestamp, so each bar is recorded once, on the fifth cycle of its ts.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Ohlcv { out: [Scalar::F64(0.0); 5] }),
                Box::new(Recorder::new(
                    &[ScalarKind::F64, ScalarKind::F64, ScalarKind::F64, ScalarKind::F64, ScalarKind::F64],
                    Firing::Any,
                    tx,
                )),
            ],
            ohlcv_sources(),
            vec![
                Edge { from: 0, to: 1, slot: 0, from_field: 0 }, // open
                Edge { from: 0, to: 1, slot: 1, from_field: 1 }, // high
                Edge { from: 0, to: 1, slot: 2, from_field: 2 }, // low
                Edge { from: 0, to: 1, slot: 3, from_field: 3 }, // close
                Edge { from: 0, to: 1, slot: 4, from_field: 4 }, // volume
            ],
        )
        .expect("valid");
        h.run(ohlcv_streams());
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        assert_eq!(
            out,
            vec![
                (Timestamp(1), vec![
                    Scalar::F64(10.0),
                    Scalar::F64(15.0),
                    Scalar::F64(8.0),
                    Scalar::F64(12.0),
                    Scalar::F64(100.0),
                ]),
                (Timestamp(2), vec![
                    Scalar::F64(20.0),
                    Scalar::F64(25.0),
                    Scalar::F64(19.0),
                    Scalar::F64(22.0),
                    Scalar::F64(200.0),
                ]),
            ]
        );
    }

    #[test]
    fn edge_binds_single_field_high_minus_low() {
        // [Ohlcv (0), Sub (1), Recorder (2)]; Sub binds high (field 1) and low
        // (field 2) of the Ohlcv record -> high - low; the Recorder taps Sub.
        // Proves from_field routes the right columns (not field 0) and the two
        // bound fields are co-fresh (Sub's Any inputs both fire in the bar's cycle).
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(Ohlcv { out: [Scalar::F64(0.0); 5] }),
                    Box::new(Sub::new()),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                ohlcv_sources(),
                vec![
                    Edge { from: 0, to: 1, slot: 0, from_field: 1 }, // high
                    Edge { from: 0, to: 1, slot: 1, from_field: 2 }, // low
                    Edge { from: 1, to: 2, slot: 0, from_field: 0 }, // Sub -> Recorder
                ],
            )
            .expect("valid DAG")
        };
        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(ohlcv_streams());
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // bar1: 15 - 8 = 7; bar2: 25 - 19 = 6 (each on the bar's fifth cycle).
        assert_eq!(
            out,
            vec![
                (Timestamp(1), vec![Scalar::F64(7.0)]),
                (Timestamp(2), vec![Scalar::F64(6.0)]),
            ]
        );

        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(ohlcv_streams());
        let out2: Vec<(Timestamp, Vec<Scalar>)> = rx2.try_iter().collect();
        assert_eq!(out2, out);
    }

    #[test]
    fn distinct_edges_read_distinct_fields() {
        // Same Ohlcv, a different consumer: Sub binds close (field 3) and open
        // (field 0) -> close - open; the Recorder taps Sub. Proves two edges on one
        // record read two different fields (3 and 0, not the high/low pair above).
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Ohlcv { out: [Scalar::F64(0.0); 5] }),
                Box::new(Sub::new()),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
            ],
            ohlcv_sources(),
            vec![
                Edge { from: 0, to: 1, slot: 0, from_field: 3 }, // close
                Edge { from: 0, to: 1, slot: 1, from_field: 0 }, // open
                Edge { from: 1, to: 2, slot: 0, from_field: 0 }, // Sub -> Recorder
            ],
        )
        .expect("valid DAG");
        h.run(ohlcv_streams());
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // bar1: 12 - 10 = 2; bar2: 22 - 20 = 2.
        assert_eq!(
            out,
            vec![
                (Timestamp(1), vec![Scalar::F64(2.0)]),
                (Timestamp(2), vec![Scalar::F64(2.0)]),
            ]
        );
    }

    #[test]
    fn bootstrap_rejects_from_field_out_of_range() {
        // Sma(0) has a 1-field output (index 0 only); an edge reading field 9 is
        // out of range -> BadIndex (caught before any kind check).
        let err = Harness::bootstrap(
            vec![Box::new(Sma::new(1)), Box::new(Sma::new(1))],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 9 }],
        )
        .unwrap_err();
        assert_eq!(err, BootstrapError::BadIndex);
    }

    #[test]
    fn bootstrap_rejects_per_field_kind_mismatch() {
        // TwoField(0) output: field 0 f64, field 1 i64. Binding field 1 (i64) into
        // Sma(1)'s f64 input slot is a per-field kind mismatch -> KindMismatch. (The
        // mismatch is field-specific: from_field 0 would have matched.)
        let err = Harness::bootstrap(
            vec![Box::new(TwoField { out: [Scalar::F64(0.0), Scalar::I64(0)] }), Box::new(Sma::new(1))],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 1 }],
        )
        .unwrap_err();
        assert_eq!(
            err,
            BootstrapError::KindMismatch { producer: ScalarKind::I64, consumer: ScalarKind::F64 }
        );
    }

    #[test]
    fn multi_sink_records_distinct_interior_streams() {
        // Two recorders tap SMA(2) and SMA(4) in ONE run -> one run records many
        // streams (the #2 headline). Each drained stream is individually correct.
        let (tx_fast, rx_fast) = mpsc::channel();
        let (tx_slow, rx_slow) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Sma::new(2)),
                Box::new(Sma::new(4)),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_fast)),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_slow)),
            ],
            vec![SourceSpec {
                kind: ScalarKind::F64,
                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
            }],
            vec![
                Edge { from: 0, to: 2, slot: 0, from_field: 0 }, // SMA(2) -> recorder fast
                Edge { from: 1, to: 3, slot: 0, from_field: 0 }, // SMA(4) -> recorder slow
            ],
        )
        .expect("valid DAG");
        h.run(vec![f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0)])]);
        let fast: Vec<(Timestamp, Vec<Scalar>)> = rx_fast.try_iter().collect();
        let slow: Vec<(Timestamp, Vec<Scalar>)> = rx_slow.try_iter().collect();
        // SMA(2) warms at cycle 2, SMA(4) at cycle 4 — two different-rate streams.
        assert_eq!(
            fast,
            vec![
                (Timestamp(2), vec![Scalar::F64(11.0)]),
                (Timestamp(3), vec![Scalar::F64(13.0)]),
                (Timestamp(4), vec![Scalar::F64(15.0)]),
                (Timestamp(5), vec![Scalar::F64(17.0)]),
            ]
        );
        assert_eq!(
            slow,
            vec![
                (Timestamp(4), vec![Scalar::F64(13.0)]),
                (Timestamp(5), vec![Scalar::F64(15.0)]),
            ]
        );
    }

    #[test]
    fn recorder_taps_all_fields_of_a_record() {
        // A 5-input Recorder taps all five OHLCV fields via five field-wise edges
        // (0005: N edges, no whole-record bind); its recorded row is the whole bar.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Ohlcv { out: [Scalar::F64(0.0); 5] }),
                Box::new(Recorder::new(
                    &[ScalarKind::F64, ScalarKind::F64, ScalarKind::F64, ScalarKind::F64, ScalarKind::F64],
                    Firing::Any,
                    tx,
                )),
            ],
            ohlcv_sources(),
            vec![
                Edge { from: 0, to: 1, slot: 0, from_field: 0 },
                Edge { from: 0, to: 1, slot: 1, from_field: 1 },
                Edge { from: 0, to: 1, slot: 2, from_field: 2 },
                Edge { from: 0, to: 1, slot: 3, from_field: 3 },
                Edge { from: 0, to: 1, slot: 4, from_field: 4 },
            ],
        )
        .expect("valid");
        h.run(vec![
            f64_stream(&[(1, 10.0)]),
            f64_stream(&[(1, 15.0)]),
            f64_stream(&[(1, 8.0)]),
            f64_stream(&[(1, 12.0)]),
            f64_stream(&[(1, 100.0)]),
        ]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        assert_eq!(out.len(), 1);
        assert_eq!(out[0].1.len(), 5); // all five fields recorded as one row
        assert_eq!(
            out,
            vec![(Timestamp(1), vec![
                Scalar::F64(10.0),
                Scalar::F64(15.0),
                Scalar::F64(8.0),
                Scalar::F64(12.0),
                Scalar::F64(100.0),
            ])]
        );
    }

    #[test]
    fn recorder_records_mixed_scalar_kinds() {
        // A recorder with i64 + f64 + bool + timestamp inputs records a four-field
        // mixed-kind row -> recording is not f64-only. Four sources tick once each
        // at t=1,2,3,4; only on cycle 4 are all slots warm, so it records once,
        // holding the earlier-ticked values.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![Box::new(Recorder::new(
                &[ScalarKind::I64, ScalarKind::F64, ScalarKind::Bool, ScalarKind::Timestamp],
                Firing::Any,
                tx,
            ))],
            vec![
                SourceSpec { kind: ScalarKind::I64, targets: vec![Target { node: 0, slot: 0 }] },
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
                SourceSpec { kind: ScalarKind::Bool, targets: vec![Target { node: 0, slot: 2 }] },
                SourceSpec { kind: ScalarKind::Timestamp, targets: vec![Target { node: 0, slot: 3 }] },
            ],
            vec![],
        )
        .expect("valid");
        h.run(vec![
            vec![(Timestamp(1), Scalar::I64(7))],
            vec![(Timestamp(2), Scalar::F64(1.5))],
            vec![(Timestamp(3), Scalar::Bool(true))],
            vec![(Timestamp(4), Scalar::Ts(Timestamp(99)))],
        ]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        assert_eq!(
            out,
            vec![(Timestamp(4), vec![
                Scalar::I64(7),
                Scalar::F64(1.5),
                Scalar::Bool(true),
                Scalar::Ts(Timestamp(99)),
            ])]
        );
    }

    #[test]
    fn node_is_producer_and_sink_at_once() {
        // TapForward records its input AND forwards it downstream; a second
        // Recorder taps the forwarded output. Both channels see the same stream ->
        // one node is producer and sink at once (C8 "both").
        let (tx_tap, rx_tap) = mpsc::channel();
        let (tx_down, rx_down) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(TapForward { out: [Scalar::F64(0.0)], tx: tx_tap }),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_down)),
            ],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
        )
        .expect("valid");
        h.run(vec![f64_stream(&[(1, 10.0), (2, 20.0), (3, 30.0)])]);
        let tapped: Vec<(Timestamp, Vec<Scalar>)> = rx_tap.try_iter().collect();
        let downstream: Vec<(Timestamp, Vec<Scalar>)> = rx_down.try_iter().collect();
        let expected = vec![
            (Timestamp(1), vec![Scalar::F64(10.0)]),
            (Timestamp(2), vec![Scalar::F64(20.0)]),
            (Timestamp(3), vec![Scalar::F64(30.0)]),
        ];
        assert_eq!(tapped, expected); // it recorded (sink side effect)
        assert_eq!(downstream, expected); // and forwarded (producer output)
    }

    #[test]
    fn recording_is_deterministic() {
        // Two fresh harnesses, two channels, identical input -> bit-identical
        // recorded streams (C1).
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(3)),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
                vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
            )
            .expect("valid")
        };
        let prices = f64_stream(&[(1, 1.0), (2, 2.0), (3, 3.0), (4, 4.0), (5, 5.0)]);

        let (tx_a, rx_a) = mpsc::channel();
        let mut a = build(tx_a);
        a.run(vec![prices.clone()]);
        let run_a: Vec<(Timestamp, Vec<Scalar>)> = rx_a.try_iter().collect();

        let (tx_b, rx_b) = mpsc::channel();
        let mut b = build(tx_b);
        b.run(vec![prices]);
        let run_b: Vec<(Timestamp, Vec<Scalar>)> = rx_b.try_iter().collect();

        assert_eq!(run_a, run_b);
        assert!(!run_a.is_empty()); // and it actually recorded something
    }

    #[test]
    fn recorder_barrier_firing_records_only_on_coincidence() {
        // A 2-input Barrier(0) recorder records only on cycles where both inputs
        // share the timestamp — the recorder's OWN firing policy gates recording.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![Box::new(Recorder::new(
                &[ScalarKind::F64, ScalarKind::F64],
                Firing::Barrier(0),
                tx,
            ))],
            vec![
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] },
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
            ],
            vec![],
        )
        .expect("valid");
        let s0 = f64_stream(&[(1, 10.0), (2, 20.0), (3, 30.0), (4, 40.0)]);
        let s1 = f64_stream(&[(2, 100.0), (4, 200.0)]);
        h.run(vec![s0, s1]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // records ONLY at t=2 and t=4 (both inputs coincide); holds otherwise.
        assert_eq!(
            out,
            vec![
                (Timestamp(2), vec![Scalar::F64(20.0), Scalar::F64(100.0)]),
                (Timestamp(4), vec![Scalar::F64(40.0), Scalar::F64(200.0)]),
            ]
        );
    }

    #[test]
    fn recorder_any_firing_records_on_each_fresh() {
        // A 2-input Any recorder records on any-fresh once both are warm (as-of),
        // holding the stale input.
        let (tx, rx) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![Box::new(Recorder::new(
                &[ScalarKind::F64, ScalarKind::F64],
                Firing::Any,
                tx,
            ))],
            vec![
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] },
                SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 1 }] },
            ],
            vec![],
        )
        .expect("valid");
        let s0 = f64_stream(&[(1, 10.0), (2, 20.0), (3, 30.0), (4, 40.0)]);
        let s1 = f64_stream(&[(2, 100.0), (4, 200.0)]);
        h.run(vec![s0, s1]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // from t=2 on, records every cycle holding the stale input; two cycles fall
        // on t=4 (the s0 tick then the s1 tick).
        assert_eq!(
            out,
            vec![
                (Timestamp(2), vec![Scalar::F64(20.0), Scalar::F64(100.0)]),
                (Timestamp(3), vec![Scalar::F64(30.0), Scalar::F64(100.0)]),
                (Timestamp(4), vec![Scalar::F64(40.0), Scalar::F64(100.0)]),
                (Timestamp(4), vec![Scalar::F64(40.0), Scalar::F64(200.0)]),
            ]
        );
    }

    #[test]
    fn bootstrap_rejects_kind_mismatched_recorder_edge() {
        // TwoField output: field 0 f64, field 1 i64. Binding field 1 (i64) into a
        // Recorder's f64 input slot is a per-field kind mismatch -> KindMismatch
        // (0005's check already covers recorder edges; recording adds no new hole).
        let (tx, _rx) = mpsc::channel();
        let err = Harness::bootstrap(
            vec![
                Box::new(TwoField { out: [Scalar::F64(0.0), Scalar::I64(0)] }),
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
            ],
            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }],
            vec![Edge { from: 0, to: 1, slot: 0, from_field: 1 }],
        )
        .unwrap_err();
        assert_eq!(
            err,
            BootstrapError::KindMismatch { producer: ScalarKind::I64, consumer: ScalarKind::F64 }
        );
    }

    // --- #3 stress matrix: M-producer x N-consumer x K-sink DAGs ---
    // The closed `Harness::bootstrap` + `run` substrate must carry arbitrary
    // node-level fan-out / fan-in / depth / width deterministically (C1) and
    // compute every recorded stream correctly. Earlier cycles proved *source*
    // fan-out, single chains and firing in isolation; these close the node
    // fan-out / deep-chain / wide-layer holes #3 names. No trading domain.

    #[test]
    fn node_fan_out_identical_taps_record_identical_streams() {
        // PROPERTY: one PRODUCING node read by several consumers via distinct
        // edges from the same `from` node feeds every consumer the identical,
        // correct stream — node fan-out (not source fan-out: a single SMA(3)
        // output is forwarded down three edges to three recorders).
        let build = |t1, t2, t3| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(3)),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t1)),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t2)),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t3)),
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![Target { node: 0, slot: 0 }],
                }],
                vec![
                    Edge { from: 0, to: 1, slot: 0, from_field: 0 },
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                    Edge { from: 0, to: 3, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid fan-out DAG")
        };
        let prices = f64_stream(&[(1, 2.0), (2, 4.0), (3, 6.0), (4, 8.0), (5, 10.0)]);

        let (a1, ra) = mpsc::channel();
        let (b1, rb) = mpsc::channel();
        let (c1, rc) = mpsc::channel();
        let mut h = build(a1, b1, c1);
        h.run(vec![prices.clone()]);
        let s1: Vec<(Timestamp, Vec<Scalar>)> = ra.try_iter().collect();
        let s2: Vec<(Timestamp, Vec<Scalar>)> = rb.try_iter().collect();
        let s3: Vec<(Timestamp, Vec<Scalar>)> = rc.try_iter().collect();
        // SMA(3) warms at cycle 3: mean(2,4,6)=4, mean(4,6,8)=6, mean(6,8,10)=8.
        let expected = vec![
            (Timestamp(3), vec![Scalar::F64(4.0)]),
            (Timestamp(4), vec![Scalar::F64(6.0)]),
            (Timestamp(5), vec![Scalar::F64(8.0)]),
        ];
        assert_eq!(s1, expected);
        assert_eq!(s2, expected); // every tap sees the identical shared stream
        assert_eq!(s3, expected);

        // determinism (C1): a fresh harness drains bit-identical.
        let (a2, ra2) = mpsc::channel();
        let (b2, rb2) = mpsc::channel();
        let (c2, rc2) = mpsc::channel();
        let mut h2 = build(a2, b2, c2);
        h2.run(vec![prices]);
        assert_eq!(ra2.try_iter().collect::<Vec<_>>(), expected);
        assert_eq!(rb2.try_iter().collect::<Vec<_>>(), expected);
        assert_eq!(rc2.try_iter().collect::<Vec<_>>(), expected);
    }

    #[test]
    fn node_fan_out_divergent_consumers_each_compute_their_own() {
        // PROPERTY: one producer (SMA(2)) read by consumers that do DIFFERENT
        // things — recorded raw by one sink AND fed as input0 of a Sub whose
        // other input is a second producer (SMA(4)) — yields both the raw tap
        // and the downstream-combined stream, each independently correct.
        let build = |t_raw, t_sub| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),                                  // 0: shared producer
                    Box::new(Sma::new(4)),                                  // 1: second producer
                    Box::new(Sub::new()),                                   // 2: SMA(2) - SMA(4)
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_raw)), // 3: raw tap of 0
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_sub)), // 4: tap of Sub
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
                }],
                vec![
                    Edge { from: 0, to: 3, slot: 0, from_field: 0 }, // SMA(2) -> raw recorder
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 }, // SMA(2) -> Sub.in0
                    Edge { from: 1, to: 2, slot: 1, from_field: 0 }, // SMA(4) -> Sub.in1
                    Edge { from: 2, to: 4, slot: 0, from_field: 0 }, // Sub    -> Sub recorder
                ],
            )
            .expect("valid divergent-fan-out DAG")
        };
        let prices = f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0), (6, 20.0)]);

        let (tr, rr) = mpsc::channel();
        let (ts, rs) = mpsc::channel();
        let mut h = build(tr, ts);
        h.run(vec![prices.clone()]);
        let raw: Vec<(Timestamp, Vec<Scalar>)> = rr.try_iter().collect();
        let sub: Vec<(Timestamp, Vec<Scalar>)> = rs.try_iter().collect();
        // SMA(2): 11,13,15,17,19 at cycles 2..6 (raw tap).
        let raw_expected = vec![
            (Timestamp(2), vec![Scalar::F64(11.0)]),
            (Timestamp(3), vec![Scalar::F64(13.0)]),
            (Timestamp(4), vec![Scalar::F64(15.0)]),
            (Timestamp(5), vec![Scalar::F64(17.0)]),
            (Timestamp(6), vec![Scalar::F64(19.0)]),
        ];
        // Sub warms once SMA(4) is warm (cycle 4): 15-13, 17-15, 19-17 -> 2.
        let sub_expected = vec![
            (Timestamp(4), vec![Scalar::F64(2.0)]),
            (Timestamp(5), vec![Scalar::F64(2.0)]),
            (Timestamp(6), vec![Scalar::F64(2.0)]),
        ];
        assert_eq!(raw, raw_expected);
        assert_eq!(sub, sub_expected);

        let (tr2, rr2) = mpsc::channel();
        let (ts2, rs2) = mpsc::channel();
        let mut h2 = build(tr2, ts2);
        h2.run(vec![prices]);
        assert_eq!(rr2.try_iter().collect::<Vec<_>>(), raw_expected); // deterministic
        assert_eq!(rs2.try_iter().collect::<Vec<_>>(), sub_expected);
    }

    #[test]
    fn node_fan_out_under_mixed_firing_each_consumer_records_per_policy() {
        // PROPERTY: one producer (SMA(2)) read simultaneously by an as-of
        // (Firing::Any) consumer and a Firing::Barrier consumer — each records
        // per ITS OWN firing policy off the SAME shared upstream value. The Any
        // tap fires on every SMA push; the BarrierSum fires only on the cycles
        // where the held SMA output and a second source coincide on a timestamp.
        let build = |t_any, t_bar| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),                                  // 0: shared producer (src A)
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_any)), // 1: as-of tap of 0
                    Box::new(BarrierSum { out: [Scalar::F64(0.0)] }),       // 2: SMA(2) + src B (barrier)
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_bar)), // 3: tap of barrier
                ],
                vec![
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 0, slot: 0 }] }, // A
                    SourceSpec { kind: ScalarKind::F64, targets: vec![Target { node: 2, slot: 1 }] }, // B
                ],
                vec![
                    Edge { from: 0, to: 1, slot: 0, from_field: 0 }, // SMA(2) -> as-of recorder
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 }, // SMA(2) -> barrier.in0
                    Edge { from: 2, to: 3, slot: 0, from_field: 0 }, // barrier -> recorder
                ],
            )
            .expect("valid mixed-firing fan-out DAG")
        };
        let a = f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0)]); // drives SMA(2)
        let b = f64_stream(&[(2, 100.0), (4, 200.0)]);                     // barrier.in1

        let (ta, rany) = mpsc::channel();
        let (tb, rbar) = mpsc::channel();
        let mut h = build(ta, tb);
        h.run(vec![a.clone(), b.clone()]);
        let any: Vec<(Timestamp, Vec<Scalar>)> = rany.try_iter().collect();
        let bar: Vec<(Timestamp, Vec<Scalar>)> = rbar.try_iter().collect();
        // As-of tap records every SMA(2) fire: 11@t2, 13@t3, 15@t4.
        let any_expected = vec![
            (Timestamp(2), vec![Scalar::F64(11.0)]),
            (Timestamp(3), vec![Scalar::F64(13.0)]),
            (Timestamp(4), vec![Scalar::F64(15.0)]),
        ];
        // Barrier fires only where held SMA output and src B share a timestamp:
        // t=2 (SMA held=11 + B=100 = 111), t=4 (SMA held=15 + B=200 = 215).
        let bar_expected = vec![
            (Timestamp(2), vec![Scalar::F64(111.0)]),
            (Timestamp(4), vec![Scalar::F64(215.0)]),
        ];
        assert_eq!(any, any_expected);
        assert_eq!(bar, bar_expected);

        let (ta2, rany2) = mpsc::channel();
        let (tb2, rbar2) = mpsc::channel();
        let mut h2 = build(ta2, tb2);
        h2.run(vec![a, b]);
        assert_eq!(rany2.try_iter().collect::<Vec<_>>(), any_expected); // deterministic
        assert_eq!(rbar2.try_iter().collect::<Vec<_>>(), bar_expected);
    }

    #[test]
    fn deep_transform_chain_propagates_end_to_end() {
        // PROPERTY: a linear chain of several transform nodes (SMA(2) -> SMA(2)
        // -> SMA(2) -> recorder) propagates values correctly through depth, with
        // each stage's warm-up delaying the tail — closes "deep chains untested".
        let build = |tx| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)), // 0
                    Box::new(Sma::new(2)), // 1
                    Box::new(Sma::new(2)), // 2
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)), // 3 tail
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![Target { node: 0, slot: 0 }],
                }],
                vec![
                    Edge { from: 0, to: 1, slot: 0, from_field: 0 },
                    Edge { from: 1, to: 2, slot: 0, from_field: 0 },
                    Edge { from: 2, to: 3, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid deep chain")
        };
        let prices = f64_stream(&[(1, 2.0), (2, 4.0), (3, 6.0), (4, 8.0), (5, 10.0)]);

        let (tx, rx) = mpsc::channel();
        let mut h = build(tx);
        h.run(vec![prices.clone()]);
        let out: Vec<(Timestamp, Vec<Scalar>)> = rx.try_iter().collect();
        // stage1 (c2..c5): 3,5,7,9. stage2 (c3..): 4,6,8. stage3 (c4..): 5,7.
        let expected = vec![
            (Timestamp(4), vec![Scalar::F64(5.0)]),
            (Timestamp(5), vec![Scalar::F64(7.0)]),
        ];
        assert_eq!(out, expected);

        let (tx2, rx2) = mpsc::channel();
        let mut h2 = build(tx2);
        h2.run(vec![prices]);
        assert_eq!(rx2.try_iter().collect::<Vec<_>>(), expected); // deterministic
    }

    #[test]
    fn wide_parallel_layer_multi_sink_records_each_stream() {
        // PROPERTY: one source fanned to several PARALLEL producers of different
        // params (SMA(2), SMA(3), SMA(4)), each recorded by its own sink in one
        // run, yields each parallel stream correctly — closes "wide layers
        // untested" and exercises multi-sink at width.
        let build = |t2, t3, t4| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)), // 0
                    Box::new(Sma::new(3)), // 1
                    Box::new(Sma::new(4)), // 2
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t2)), // 3
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t3)), // 4
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t4)), // 5
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![
                        Target { node: 0, slot: 0 },
                        Target { node: 1, slot: 0 },
                        Target { node: 2, slot: 0 },
                    ],
                }],
                vec![
                    Edge { from: 0, to: 3, slot: 0, from_field: 0 },
                    Edge { from: 1, to: 4, slot: 0, from_field: 0 },
                    Edge { from: 2, to: 5, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid wide layer")
        };
        let prices = f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0)]);

        let (a, ra) = mpsc::channel();
        let (b, rb) = mpsc::channel();
        let (c, rc) = mpsc::channel();
        let mut h = build(a, b, c);
        h.run(vec![prices.clone()]);
        let w2: Vec<(Timestamp, Vec<Scalar>)> = ra.try_iter().collect();
        let w3: Vec<(Timestamp, Vec<Scalar>)> = rb.try_iter().collect();
        let w4: Vec<(Timestamp, Vec<Scalar>)> = rc.try_iter().collect();
        let e2 = vec![
            (Timestamp(2), vec![Scalar::F64(11.0)]),
            (Timestamp(3), vec![Scalar::F64(13.0)]),
            (Timestamp(4), vec![Scalar::F64(15.0)]),
            (Timestamp(5), vec![Scalar::F64(17.0)]),
        ];
        let e3 = vec![
            (Timestamp(3), vec![Scalar::F64(12.0)]),
            (Timestamp(4), vec![Scalar::F64(14.0)]),
            (Timestamp(5), vec![Scalar::F64(16.0)]),
        ];
        let e4 = vec![
            (Timestamp(4), vec![Scalar::F64(13.0)]),
            (Timestamp(5), vec![Scalar::F64(15.0)]),
        ];
        assert_eq!(w2, e2);
        assert_eq!(w3, e3);
        assert_eq!(w4, e4);

        let (a2, ra2) = mpsc::channel();
        let (b2, rb2) = mpsc::channel();
        let (c2, rc2) = mpsc::channel();
        let mut h2 = build(a2, b2, c2);
        h2.run(vec![prices]);
        assert_eq!(ra2.try_iter().collect::<Vec<_>>(), e2); // deterministic
        assert_eq!(rb2.try_iter().collect::<Vec<_>>(), e3);
        assert_eq!(rc2.try_iter().collect::<Vec<_>>(), e4);
    }

    #[test]
    fn milestone_end_to_end_mixed_dag_records_every_stream_deterministically() {
        // PROPERTY (#3 headline): a single richer DAG combining node fan-out
        // (SMA(2) -> raw recorder AND Sub) + source fan-out (source -> SMA(2),
        // SMA(4)) + fan-in (Sub) + multiple sinks of MIXED scalar kinds (two f64
        // streams + one i64 stream) records every stream correctly AND is fully
        // deterministic — the "pure compute substrate carries arbitrary
        // M-producer x N-consumer x K-sink DAGs" gate.
        let build = |t_raw, t_sub, t_i64| {
            Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),                                  // 0: shared f64 producer
                    Box::new(Sma::new(4)),                                  // 1: second f64 producer
                    Box::new(Sub::new()),                                   // 2: SMA(2) - SMA(4)
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_raw)), // 3
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, t_sub)), // 4
                    Box::new(Recorder::new(&[ScalarKind::I64], Firing::Any, t_i64)), // 5: i64 sink
                ],
                vec![
                    SourceSpec {
                        kind: ScalarKind::F64,
                        targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
                    },
                    SourceSpec { kind: ScalarKind::I64, targets: vec![Target { node: 5, slot: 0 }] },
                ],
                vec![
                    Edge { from: 0, to: 3, slot: 0, from_field: 0 }, // SMA(2) raw
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 }, // SMA(2) -> Sub.in0
                    Edge { from: 1, to: 2, slot: 1, from_field: 0 }, // SMA(4) -> Sub.in1
                    Edge { from: 2, to: 4, slot: 0, from_field: 0 }, // Sub -> recorder
                ],
            )
            .expect("valid milestone DAG")
        };
        let prices =
            f64_stream(&[(1, 10.0), (2, 12.0), (3, 14.0), (4, 16.0), (5, 18.0), (6, 20.0)]);
        let counts: Vec<(Timestamp, Scalar)> = vec![
            (Timestamp(1), Scalar::I64(7)),
            (Timestamp(2), Scalar::I64(8)),
            (Timestamp(3), Scalar::I64(9)),
        ];

        let (tr, rr) = mpsc::channel();
        let (ts, rs) = mpsc::channel();
        let (ti, ri) = mpsc::channel();
        let mut h = build(tr, ts, ti);
        h.run(vec![prices.clone(), counts.clone()]);
        let raw: Vec<(Timestamp, Vec<Scalar>)> = rr.try_iter().collect();
        let sub: Vec<(Timestamp, Vec<Scalar>)> = rs.try_iter().collect();
        let i64s: Vec<(Timestamp, Vec<Scalar>)> = ri.try_iter().collect();
        let raw_expected = vec![
            (Timestamp(2), vec![Scalar::F64(11.0)]),
            (Timestamp(3), vec![Scalar::F64(13.0)]),
            (Timestamp(4), vec![Scalar::F64(15.0)]),
            (Timestamp(5), vec![Scalar::F64(17.0)]),
            (Timestamp(6), vec![Scalar::F64(19.0)]),
        ];
        let sub_expected = vec![
            (Timestamp(4), vec![Scalar::F64(2.0)]),
            (Timestamp(5), vec![Scalar::F64(2.0)]),
            (Timestamp(6), vec![Scalar::F64(2.0)]),
        ];
        let i64_expected = vec![
            (Timestamp(1), vec![Scalar::I64(7)]),
            (Timestamp(2), vec![Scalar::I64(8)]),
            (Timestamp(3), vec![Scalar::I64(9)]),
        ];
        assert_eq!(raw, raw_expected);
        assert_eq!(sub, sub_expected);
        assert_eq!(i64s, i64_expected);

        let (tr2, rr2) = mpsc::channel();
        let (ts2, rs2) = mpsc::channel();
        let (ti2, ri2) = mpsc::channel();
        let mut h2 = build(tr2, ts2, ti2);
        h2.run(vec![prices, counts]);
        assert_eq!(rr2.try_iter().collect::<Vec<_>>(), raw_expected); // deterministic
        assert_eq!(rs2.try_iter().collect::<Vec<_>>(), sub_expected);
        assert_eq!(ri2.try_iter().collect::<Vec<_>>(), i64_expected);
    }

    #[test]
    fn signal_quality_loop_records_pip_equity() {
        let (tx_eq, rx_eq) = mpsc::channel();
        let mut h = Harness::bootstrap(
            vec![
                Box::new(Sma::new(2)),                              // 0 fast
                Box::new(Sma::new(4)),                              // 1 slow
                Box::new(Sub::new()),                               // 2 raw signal
                Box::new(Exposure::new(0.5)),                       // 3 exposure
                Box::new(SimBroker::new(0.0001)),                   // 4 pip equity
                Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx_eq)), // 5 sink
            ],
            vec![SourceSpec {
                kind: ScalarKind::F64,
                targets: vec![
                    Target { node: 0, slot: 0 }, // price -> SMA fast
                    Target { node: 1, slot: 0 }, // price -> SMA slow
                    Target { node: 4, slot: 1 }, // price -> broker price input
                ],
            }],
            vec![
                Edge { from: 0, to: 2, slot: 0, from_field: 0 }, // fast     -> Sub.0
                Edge { from: 1, to: 2, slot: 1, from_field: 0 }, // slow     -> Sub.1
                Edge { from: 2, to: 3, slot: 0, from_field: 0 }, // signal   -> Exposure
                Edge { from: 3, to: 4, slot: 0, from_field: 0 }, // exposure -> broker.0
                Edge { from: 4, to: 5, slot: 0, from_field: 0 }, // equity   -> recorder
            ],
        )
        .expect("valid signal-quality harness");

        h.run(vec![f64_stream(&[
            (1, 1.0000),
            (2, 1.0010),
            (3, 1.0025),
            (4, 1.0020),
            (5, 1.0040),
        ])]);

        let equity: Vec<(Timestamp, Vec<Scalar>)> = rx_eq.try_iter().collect();
        // broker fires every cycle (price fresh each tick): five records, ts 1..=5
        assert_eq!(equity.len(), 5);
        assert_eq!(
            equity.iter().map(|(t, _)| t.0).collect::<Vec<_>>(),
            vec![1, 2, 3, 4, 5]
        );
        // flat until SMA(4) warms (cycle 4) and the held exposure meets the next
        // price move (cycle 5): the first four equities are exactly 0.
        for (_, row) in &equity[0..4] {
            assert_eq!(row, &vec![Scalar::F64(0.0)]);
        }
        // cycle 5: prev_exposure 0.00175 * (1.0040 - 1.0020) / 0.0001 = 0.035 pips
        let Scalar::F64(last) = equity[4].1[0] else {
            panic!("equity is f64");
        };
        assert!((last - 0.035).abs() < 1e-9, "final equity = {last}, want ~0.035");
    }

    #[test]
    fn signal_quality_loop_is_deterministic() {
        let build = || {
            let (tx, rx) = mpsc::channel();
            let mut h = Harness::bootstrap(
                vec![
                    Box::new(Sma::new(2)),
                    Box::new(Sma::new(4)),
                    Box::new(Sub::new()),
                    Box::new(Exposure::new(0.5)),
                    Box::new(SimBroker::new(0.0001)),
                    Box::new(Recorder::new(&[ScalarKind::F64], Firing::Any, tx)),
                ],
                vec![SourceSpec {
                    kind: ScalarKind::F64,
                    targets: vec![
                        Target { node: 0, slot: 0 },
                        Target { node: 1, slot: 0 },
                        Target { node: 4, slot: 1 },
                    ],
                }],
                vec![
                    Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                    Edge { from: 1, to: 2, slot: 1, from_field: 0 },
                    Edge { from: 2, to: 3, slot: 0, from_field: 0 },
                    Edge { from: 3, to: 4, slot: 0, from_field: 0 },
                    Edge { from: 4, to: 5, slot: 0, from_field: 0 },
                ],
            )
            .expect("valid harness");
            h.run(vec![f64_stream(&[
                (1, 1.0000),
                (2, 1.0010),
                (3, 1.0025),
                (4, 1.0020),
                (5, 1.0040),
            ])]);
            rx.try_iter().collect::<Vec<(Timestamp, Vec<Scalar>)>>()
        };
        assert_eq!(build(), build());
    }
}