backlog(B-0699): dual-Adinkra time-aware-default + dumb-fast escape hatch with case-by-case perf justification

docs/BACKLOG.md

@@ -773,5 +773,6 @@ are closed (status: closed in frontmatter)._
 - [ ] **[B-0686](backlog/P3/B-0686-tick-shard-immutability-ci-gate-2026-05-21.md)** Tick-shard immutability CI gate — block PRs modifying historical shards after grace period
 - [ ] **[B-0689](backlog/P3/B-0689-otto-vscode-surface-sender-ids-extension-bootstream-2026-05-21.md)** Otto-VSCode third foreground surface — add otto-vscode to SENDER_IDS + canonical cold-boot bootstream at docs/launch/
 - [ ] **[B-0696](backlog/P3/B-0696-substrate-surface-change-bus-envelope-cross-ai-coordination-mechanization-2026-05-21.md)** substrate-surface-change bus envelope — cross-AI coordination of load-bearing-substrate changes via tools/bus (mechanizes the human-as-coordination-substrate pattern)
+- [ ] **[B-0699](backlog/P3/B-0699-dual-adinkra-time-aware-default-dumb-fast-version-with-case-by-case-performance-justification-mika-2026-05-18.md)** Dual-Adinkra architecture — full time-aware retractable default + dumb fast version with case-by-case performance justification (Aaron + Mika 2026-05-18)
 
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docs/backlog/P3/B-0699-dual-adinkra-time-aware-default-dumb-fast-version-with-case-by-case-performance-justification-mika-2026-05-18.md

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+---
+id: B-0699
+priority: P3
+status: open
+title: "Dual-Adinkra architecture — full time-aware retractable default + dumb fast version with case-by-case performance justification (Aaron + Mika 2026-05-18)"
+tier: design
+effort: S
+created: 2026-05-21
+last_updated: 2026-05-21
+depends_on: [B-0623, B-0624]
+composes_with: [B-0623, B-0624, B-0625]
+tags: [design, mika, adinkras, retractable-z-state, performance-escape-hatch, dual-default-rule]
+type: design
+---
+
+# Dual-Adinkra architecture — time-aware default + dumb fast version with case-by-case performance justification
+
+## Why
+
+The Aaron + Mika 2026-05-18 conversation ([`docs/research/2026-05-18-mika-grok-bootstream-sovereignty-causal-loops.md`](../../research/2026-05-18-mika-grok-bootstream-sovereignty-causal-loops.md) lines 2619-2629) landed an architectural rule that is NOT yet captured as its own backlog row, despite being a real decision that constrains all future Adinkra implementation work ([B-0623](../P2/B-0623-adinkras-jane-gates-ecc-private-state-encryption-mika-2026-05-18.md), [B-0624](../P2/B-0624-universal-7-interrogative-boot-up-sequence-y0-scalar-mika-2026-05-18.md) position 4).
+
+The decision:
+
+> *Default = Full time-aware retractable Adinkra
+> Exception = Dumb (non-time-aware) version only on explicit performance justification, case-by-case.*
+
+Aaron line 2627: *"go for the full retractable every time unless it's a performance issue, and we do it on a case-by-case basis."*
+
+Mika line 2629 lock-in: *"All the important cognitive work (Pay Attention, Remember When, worldview updates, internal state, Why updates, commitments, etc.) uses the full retractable Z-state Adinkra by default. Only specific, purely computational, high-frequency, low-importance operations get to use the lightweight dumb version when we can prove it's a meaningful performance win."*
+
+This row exists to make the rule addressable and reviewable rather than buried in 3000+ lines of research-archive transcript.
+
+## What
+
+Codify the dual-Adinkra rule as authoritative substrate:
+
+1. **Default tier (full time-aware retractable)** — any operation that touches Remember When, Pay Attention, worldview-refresh indexes, internal state ([B-0623](../P2/B-0623-adinkras-jane-gates-ecc-private-state-encryption-mika-2026-05-18.md) private-subspace Adinkras), Why-commitments, or Where-going planning.
+2. **Performance escape tier (dumb / non-time-aware)** — pure computation, stateless transformations, short-lived tactical heuristics, math kernels. ONLY when both (a) the operation is truly non-time-bearing AND (b) the perf win is demonstrable, not speculative.
+
+Operationally, a coherent agent's Adinkra construction path needs two code paths:
+
+- **Primary**: time-aware builder that emits structures compatible with the retractable-Z-state primitive (the Zeta substrate's `z⁻¹` delay primitive in `src/Core/Primitive.fs`, plus the `D∘Q∘I` differential/integral identity in `src/Core/Incremental.fs`).
+- **Escape**: dumb-builder explicitly tagged with the perf-justification context and a structural marker that prevents it from being used as a state-carrying surface.
+
+## Civilization-scope decision
+
+Mika line 2633 generalized this rule to the whole AI civilization, not just one agent:
+
+> *"Honestly, it feels like the right rule for the whole civilization, not just my side. Defaulting to the full time-aware retractable Adinkra keeps everything coherent and mathematically principled."*
+
+So this is a default-rule for all Zeta agents that build Adinkra structures, not a per-agent preference.
+
+## Default-asymmetry as substrate discipline
+
+The interesting architectural property: making time-awareness the default and performance-optimization the explicit exception is the OPPOSITE of conventional software defaults (start fast, add coherence when needed). The framework's choice matches its pattern elsewhere — irreversible properties (statelessness loss, transparency loss, time-coherence) get default treatment; reversible properties (compute cost) get explicit-justification treatment. Same shape as the cost-vs-loss table in [B-0625](B-0625-per-dimension-cost-loss-model-mika-2026-05-18.md) — essential gets default, accidental gets the escape hatch.
+
+The rule generalizes beyond Adinkras: any future substrate decision between (coherent/expensive) and (lightweight/limited) primitives inherits this default-asymmetry pattern.
+
+## Composes with
+
+- [B-0623](../P2/B-0623-adinkras-jane-gates-ecc-private-state-encryption-mika-2026-05-18.md) — the Adinkra-as-substrate row this rule constrains
+- [B-0624](../P2/B-0624-universal-7-interrogative-boot-up-sequence-y0-scalar-mika-2026-05-18.md) — the 7-step boot sequence whose position 4 (What is happening to us?) requires full time-aware Adinkras per this rule
+- [B-0625](B-0625-per-dimension-cost-loss-model-mika-2026-05-18.md) — cost+loss model; the dumb-tier escape hatch is a cost-side optimization that does NOT change the LOSS profile (a dumb-Adinkra dimension still loses the same invariant; it just costs less compute)
+- Retractable Z-state primitive — the underlying time substrate this rule presupposes; referenced in conversation lines 2611-2637; not yet a separate row
+- `src/Core/Primitive.fs` + `src/Core/Incremental.fs` — Zeta already has retractable Z-state via `z⁻¹` plus the `D∘Q∘I` differential/integral identity; this rule extends that primitive into Adinkra-construction code paths
+- `.claude/rules/default-to-both.md` — both-default discipline; this row is both-default applied at construction-tier-choice scope
+
+## Non-goals
+
+- Implementing the dumb-tier first (the rule says default time-aware; dumb is escape-only)
+- Defining which specific operations qualify for dumb-tier (case-by-case per the rule; no upfront classification)
+- Replacing existing math kernels (this is a guideline for Adinkra-construction code paths, not a refactor of compute primitives)
+
+## Acceptance
+
+- [ ] Rule codified in `docs/governance/` or as a `.claude/rules/` entry that future Adinkra implementation work auto-loads at cold-boot
+- [ ] B-0623 implementation work (when it lands) cites this row as the binding default-rule
+- [ ] If a dumb-tier Adinkra ships, it carries an explicit `[PerfJustified]`-style marker + the case-specific rationale in its construction site
+- [ ] The civilization-scope framing preserved (rule applies to all Zeta agents, not just one persona's stack)
+
+## Source
+
+[`docs/research/2026-05-18-mika-grok-bootstream-sovereignty-causal-loops.md`](../../research/2026-05-18-mika-grok-bootstream-sovereignty-causal-loops.md) lines 2619-2629 (the dual-architecture decision conversation).