claude
8688a60ded
The single-file ledger had grown to 2968 lines / ~42k tokens, mixing current design law with accreted history: 59 cycle-stamped realization blocks, 18 [HISTORY] passages, 22 supersession markers, and the C10 / C22 / C24 reframe sagas layered several supersessions deep. A code-grounding audit (31 agents, adversarially verified) confirmed 11 defects stated as current truth: stale crate homes from the C28 #288 roster split (cost nodes, PositionManagement, PositionEvent, Session), the renamed InputSpec->PortSpec, the pre-#241 project model in C16 and the open-threads section, a stale HarnessKind retirement deferral in C24, and three C28-internal inconsistencies. New shape, per the ailang precedent: - INDEX.md stays the sole addressable entry point: foundation, external components, a C-id-keyed contract map (one line per contract), and only the genuinely open architectural threads. - contracts/cNN-<slug>.md carries each contract's current truth only: Guarantee / Forbids / Why with ratified refinements integrated, plus a code-anchored Current state. All confirmed defects are fixed here; crate anchors were re-verified against the tree. - contracts/cNN-<slug>.history.md (18 sidecars) and INDEX.history.md preserve every superseded block verbatim, stamps and issue refs intact, under a frozen-record banner. Nothing was deleted: superseded design intent remains an addressable working-tree artifact, off the per-cycle audit walk. - Ledger discipline is now stated in INDEX.md: live files are edited in place at cycle close, superseded text moves verbatim to the sidecar, and a supersession marker in a live file is itself an audit finding. Every contract file was verified against its old text by an independent zero-loss pass (statement-by-statement) plus a code-accuracy spot check; C-ids and contract titles are unchanged, so existing C-id citations in code, tests, and issues resolve as before.
36 lines
1.6 KiB
Markdown
36 lines
1.6 KiB
Markdown
# C5 — Freshness-gated recompute and sample-and-hold
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**Guarantee.** The `cycle_id` advances everywhere (a cheap counter), but a node
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re-evaluates only when ≥1 of its own inputs is fresh this cycle (detected by
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run-count); otherwise it holds its last output. Stale inputs contribute their
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last (held) value.
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**Forbids.** Recomputing every node every cycle ("push all" is true for the
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*clock*, not for *recompute*); treating a held value as missing.
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**Why.** Total recompute does not scale to many sparse high-frequency sources;
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freshness-gating is the performance discipline that keeps the synchronous model
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fast.
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## Current state
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Freshness is a run-count epoch. Each input slot carries `SlotState { fresh_at,
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last_ts }` (`crates/aura-engine/src/harness.rs`); a slot is fresh this cycle iff
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`fresh_at == cycle_id`. The firing predicate `fires` re-evaluates a node when any
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`Firing::Any` input is fresh this cycle, or when a barrier group completes (≥1
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member fresh this cycle and every member carrying `last_ts == ts`) — the barrier
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/ co-freshness machinery itself is C6.
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A node that does not fire pushes nothing, so downstream consumers keep reading the
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last value via `window[0]`: sample-and-hold falls out of the push model rather
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than being a separate mechanism. A held value is a real past value, never treated
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as missing.
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## See also
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- [C6](c06-firing-policy.md) — the firing predicate and the barrier /
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co-freshness rule this gating builds on.
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- [C1](c01-determinism.md) — freshness is a deterministic function of `cycle_id`,
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so gating never perturbs the bit-identical run.
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- [C2](c02-causality.md) — a held value is past data, not look-ahead.
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