Cycle 0005 (BLOCKER, milestone walking-skeleton): generalize a node's output
from a single scalar to a record of base-scalar columns (K >= 1), with a scalar
being the degenerate K = 1 case. A node keeps exactly one output port; that
port's payload becomes an ordered list of named, typed base columns (a composite
stream, C7). This unblocks every multi-column producer the engine needs next --
OHLCV bars and, later, the C10 position-event table -- none of which can exist
while a node emits at most one column. This revises C8 and sharpens C7.
The load-bearing design call, made with the user: the eval output representation
under C7's "no per-event heap allocation". eval becomes
`-> Option<&[Scalar]>` -- the node fills a buffer it owns (sized once at
construction) and returns a borrowed K-field row; the engine copies it into one
reused scratch row (resolving the borrow, zero per-cycle alloc once warm) and
scatters each field to its out-edges. `None` still means filter/not-warmed.
Rejected alternatives, on substance: returning `Option<Vec<Scalar>>` allocates
per fire (violates C7's forbids); an inline fixed `[Scalar; N]` record bakes a
magic width cap; engine-owned output columns invert the eval model (write-into-out
+ a fired flag) and split "fired" from "produced" for an output-lookback benefit
we do not need (history is bound as an input, not read from a node's own past).
The borrowed row is the minimal faithful generalization of today's
`Some(Scalar)` push route, K-wide.
Binding stays field-wise only: `Edge` gains `from_field`; consuming a whole
record is N edges; no "bind whole record" mechanism. The K fields of one record
are co-fresh by construction (one eval, one timestamp), so C6 is untouched. The
record is structural bundling over the four base types (C7 intact) -- no fifth
scalar type, no dyn Any, no heterogeneous buffer.
Scope is the substrate only: the contract change, the Sma/Sub degenerate
migration, the engine from_field wiring, and a neutral OHLCV proof (a 5-field
bundler fed by five timestamp-aligned barrier sources + a downstream Sub binding
high - low field-wise, plus must-fail cases: from_field out of range -> BadIndex,
per-field kind mismatch -> KindMismatch). The C10 position table and broker nodes
are out of scope -- later cycles that consume this capability.
Self-review clean; grounding-check PASS (14 load-bearing "before"-state
assumptions ratified by named green tests; C6/C7/C8 match the ledger as written;
parse-every-block a documented no-op -- profile declares no spec_validation).
refs #1
refs walking-skeleton
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Brummel
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