ADR-070: Visible Decay Model (decay tiers + re-warming nudge)

Status: Implemented Date: 2026-06-07 Sprint: 90 Version: 10.14.0

Context

The trust graph already decays: trust_edges_live.current_weight falls exponentially ([ADR-056], Sprint 68 half-life), and trustEdgeSweepJob deletes an edge once its decayed weight drops below the community's disappearance_threshold. But a member could not see any of this. A bond about to disappear looked identical to a thriving one until it silently vanished. The "relationships that fade when they go quiet" promise was ranking math with no perceptible surface.

Decision

Introduce a qualitative decay tier derived from each edge's decayed weight relative to its disappearance threshold, and render it consistently so bonds perceptibly fade.

The tier model

Let r = current_weight / disappearance_threshold:

Tier	Condition	Meaning
strong	r ≥ 3	Active, well-tended
warm	2 ≤ r < 3	Healthy
fading	1.3 ≤ r < 2	Going quiet; visibly faded
nearly_forgotten	1 ≤ r < 1.3	About to be swept — triggers the re-warming nudge
swept	r < 1	Already deleted by trustEdgeSweepJob; not normally returned

No new decay math — only a classification over values the live view already exposes. The band math lives in one shared pure helper, classifyDecayTier(currentWeight, threshold) in @karmyq/shared, consumed by the social-graph endpoints and their tests so backend and UI never drift.

Where it surfaces

1. Graph + relationship faces fade. The /trust/graph/:communityId(/full) routes attach currentWeight, disappearanceThreshold, and decayTier per edge. The shared TrustPathBadge (the relationship-face element) and the HEB graph edges fade via an opacity/desaturation ramp keyed on the tier (.kq-decay-* tokens), with the tier label on hover.
2. Re-warming nudge. GET /trust/relationships/fading returns nearly_forgotten bonds. The ReWarmingNudge component gently invites the member to reconnect ("You and {name} used to help each other often — reconnect before it fades"). It renders nothing when there are none.
3. Profile memory section. GET /trust/me/memory returns activeCount + fading[] + nearlyForgotten[]. The profile MemorySection shows what's held and what's fading, suppressing rows with no data (no empty placeholder tiles).

Consequences

• Positive: members can feel bonds fading and act before they vanish; the decay promise becomes perceptible and trustworthy; one shared helper guarantees backend/UI agreement.
• Negative / trade-offs: tier bands are a fixed heuristic (not yet community-tunable beyond the threshold); the nudge is gentle and easily ignored (intentional — not a growth-hack).
• Follow-ups: per-community tunable bands; mobile parity (Sprint 91).

Related

• ADR-069: Data Retention and Forgetting — the content half.
• [ADR-056], Sprint 68 interaction half-life; manifesto §7.