Fourth walking-skeleton cycle: the reactive-semantics layer — both firing
policies (C6), the k-way ingestion merge (C3), the monotonic cycle_id clock
(C4), and freshness-gated recompute / sample-and-hold (C5). This is the first
point where the engine departs from RustAst rather than sharpening it.
Both rails ship together (user directive: "must sit right from the start"):
- A = fire-on-any-fresh + hold (as-of join);
- B = all-fresh barrier (synchronizing join), accumulating across cycles.
Per-input-group, mixable on one node. Encoded as Firing::{Any, Barrier(u8)} on
InputSpec (where C8 places firing); default Any keeps Sma/Sub unchanged.
Key design resolution (studied against RustAst src/ast/rtl/streams/): the
barrier token is the data *timestamp*, not cycle_id. RustAst's
last_cycle_per_input.all(== cycle_id) synchronizes one source's fan-out but
cannot synchronize independent sources — under C4 four same-timestamp sources
are four different cycle_ids, so the cycle_id barrier never fires for C6's own
OHLC example. Substituting timestamp is the minimal faithful generalization
(fires both the diamond rejoin and the multi-source bar). Mode A and the k-way
merge are both new (RustAst had neither).
Two read clocks, both load-bearing (resolves the 0003 audit's "0004 owns
cycle_id" with no write-only field): cycle_id is the freshness epoch (C5 reads
it via per-slot fresh_at == cycle_id); timestamp is the barrier token (C6 reads
it via last_ts == T). Sample-and-hold falls out of the existing push model — a
non-firing node pushes nothing, so consumers see the held value via window[0].
Scope (user-chosen): reactive semantics only — in-memory (timestamp, value)
sources; the merge is the permanent ingestion core, the Source trait (C11) +
data-server IO are a later orthogonal cycle. bootstrap/run/InputSpec signatures
change (the 0003 tests re-express on the multi-source API).
Headline test pair (identical sources, firing-only difference): A emits
[None,None,120,130,140,240] (holds); B emits [None,None,120,None,None,240]
(waits for timestamp coincidence). Plus determinism (C1), mixed A+B, the 0003
fan-out/join compat baseline, and the bootstrap rejections.
Grounding-check PASS: 10 load-bearing substrate assumptions ratified by green
tests; the spec's "before" shapes match disk exactly.
refs walking-skeleton
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Third walking-skeleton cycle: aura-engine's first real content — a Sim that
runs a wired DAG of nodes deterministically, cycle by cycle. First point where
authored nodes execute against data, not just under a hand-fed Ctx.
Engine shape (contract-forced): a flat Vec<NodeBox> + an index edge table,
topologically ordered (Kahn), owned &mut by the loop — the flat, monomorphized
sharpening of RustAst's Rc<RefCell<dyn Observer>> push graph (C1/C7). Each node
owns its input columns (cycle-0002 shape), so Ctx is unchanged and the per-cycle
path allocates nothing. Wiring is by forwarding: a producer's eval output is
pushed into its consumers' input columns; a None forwards nothing (the seed of
sample-and-hold).
Bootstrap generalizes C7's "type check paid once at wiring" to the whole
topology: size input columns from each node's schema, kind-check every edge,
reject directed cycles (BootstrapError). A worked 2-input Sub node lands in
aura-std so the loop is proven on a real fan-out+join DAG
(source -> {SMA(2), SMA(4)} -> Sub -> observe), with a determinism assertion (C1).
Deliberately deferred (recorded as decisions): freshness gating / sample-and-hold
(C5 -> cycle 0004, only testable once a second source at a different rate exists);
the Source trait + data-server ingestion + k-way merge (C3/C11); the ergonomic
builder API (C19); the real sink + run registry (C18/C22); cross-sim parallelism.
Grounding-check PASS: all assumptions about the 0001 substrate and 0002 node
contract ratified by green tests; no phantom methods.
refs walking-skeleton
The second walking-skeleton cycle, on top of the 0001 streaming substrate:
the Node contract (C8) and its evaluation context.
Scope (one iteration):
- `Node` trait — `schema() -> NodeSchema` (inputs: kind + lookback; output
kind) + `eval(&mut self, Ctx) -> Option<Scalar>` (None = filter / not warmed).
- `Ctx` — a Copy borrow-wrapper handing eval zero-copy, financial-indexed
Windows per input (`ctx.f64_in(i)[k]`, index 0 = newest).
- Read-side `AnyColumn::as_f64/as_i64/as_bool/as_ts` — mirrors the existing
write-side `as_*_mut` and closes the cycle-0001 audit gap.
- `Sma` in aura-std — the worked producer node (the skeleton's first block),
driven by a hand-written test that mimics the future sim loop.
Deliberate deferrals (recorded as decisions, not gaps): the sim loop (C4),
freshness gating (C5), firing policies (C6, so InputSpec carries no firing
field yet), schema-level tunable params (C12/C19), and sinks / no-output
nodes (C8 consumer side). The hand-driven test stands in for the loop.
Grounding-check PASS: all load-bearing assumptions about the 0001 substrate
(Column/Window/AnyColumn/Scalar, financial indexing) ratified by green tests.
refs walking-skeleton
The first walking-skeleton cycle: the aura-core data substrate everything
streams through — the four scalar base types (Scalar/ScalarKind/Timestamp,
C7), the fixed-capacity financial-indexed SoA Column with its zero-copy
Window (C8), the type-erased AnyColumn edge with an edge-time kind check
(C7), and the per-column run_count freshness primitive (C5). Sharpens the
RustAst reference: no boxed Value, no VecDeque, no RefCell/Rc, no per-event
allocation. Node trait, Ctx, firing policies, and the sim loop are deferred
to subsequent cycles.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Cargo workspace aura-core -> aura-engine -> aura-cli (bin `aura`) plus nodes/ for hot-reloadable cdylib node crates. Crate bodies are intentionally API-free; types arrive from the first spec. Adds the skills profile (.claude/dev-cycle-profile.yml), the project CLAUDE.md with the eight domain invariants, and the design-ledger skeleton.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Brummel