EW64 cold-tier read surface + DemotionSink seam (D-EW64-3, D-EW64-4)

[AdaWorldAPI]

What

Plan-agent-sequenced unblocked slices toward the white-matter EW64 connectome (follow-on to #447's promote/MRU).

D-EW64-3 — cold-tier read surface (episodic_edges.rs):

• coldest() -> Option<EdgeRef> — the least-immediate present edge (last occupied slot under the MRU invariant) = exactly the edge promote evicts; symmetric to strongest(). A test ties the two APIs (coldest() == promote() eviction victim).
• contains(e) -> bool — family-discriminating membership (cross(3,3) ≠ intra(3)), matching promote's dedup.

D-EW64-4 — the hot→cold exit seam (episodic_edges.rs):

• DemotionSink trait + promote_into(e, sink) — promote routing the evicted (coldest) edge to the cold connectome. Zero-dep seam; impls deferred. The surreal/LanceDB-LIVE "wingman" (E-SUBSTRATE-IS-THE-SCHEDULER) implements DemotionSink — gated on OQ-11.6 — the same dependency-inversion idiom as MailboxSoaOwner. Tested with a fake VecSink: non-full → empty; full+fresh → exactly the coldest; chain → age order; refire-present → untouched.

Honesty correction (board)

Prepends a factual fix: E-EW64-STRENGTH's "W15 0..3 plasticity" is high_heel::Heel (a 128-byte container field), not the 64-bit CausalEdge64 (whose plasticity is the 3-bit-per-plane PlasticityState). The plasticity-write co-fire stays GATED (model mismatch needs a design decision + causal-edge doesn't build offline + I-LEGACY v1/v2 minefield); the MRU slot-order strength (D-EW64-2) is unaffected.

Tests / clippy

cargo test -p lance-graph-contract --lib → 545 green (+10). Default clippy -D warnings clean; episodic_edges.rs clean at pedantic+nursery.

Flagged for @jan (design input, NOT built unattended)

• Plasticity-write co-fire — needs the Heel-scalar vs PlasticityState-per-plane decision (above).
• comprehension.rs → arcuate ±5 disambiguation — SentenceStructure carries no ambiguity/candidate signal; the sense-candidate source (vocabulary neighbors? similarity top-k?) is net-new + firewall-sensitive.

Scope

Hot-tier read surface + the demotion seam only. NOT included (gated): the surreal/LanceDB-LIVE DemotionSink impl (OQ-11.6), the EpisodicWitness64 SoA column (needs cognitive-shader-driver, offline-gated).

https://claude.ai/code/session_012SorR8UbtEvYmbX8cXftj7

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Generated by Claude Code

Summary by CodeRabbit

• New Features
  • Edge eviction identification, family-aware membership checks, and configurable routing for demoted edges during eviction.
• Tests
  • Extended unit tests validating eviction behavior, membership semantics, and demotion routing scenarios.
• Documentation
  • Updated project notes and status board entries describing the new episodic-edge behaviors and rollout plans.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 63ddf0f5-fcba-4228-9c8a-57da0110b184

📥 Commits

Reviewing files that changed from the base of the PR and between 05ae893 and e886dc2.

📒 Files selected for processing (2)

• .claude/board/AGENT_LOG.md
• crates/lance-graph-contract/src/episodic_edges.rs

🚧 Files skipped from review as they are similar to previous changes (2)

• .claude/board/AGENT_LOG.md
• crates/lance-graph-contract/src/episodic_edges.rs

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📝 Walkthrough

Walkthrough

This PR extends EpisodicEdges64 with three new public APIs and a trait to support MRU eviction handling and cold-tier queries: coldest() identifies the eviction victim, contains() tests membership, and promote_into() routes evictions through a pluggable DemotionSink for hot→cold connectome exits. Comprehensive tests validate all behaviors, and planning documentation records the deliverable status.

Changes

EpisodicEdges64 Demotion and Cold-Tier Query Surface

Layer / File(s)	Summary
DemotionSink trait contract crates/lance-graph-contract/src/episodic_edges.rs	New public trait DemotionSink with a demote(&mut self, evicted: EdgeRef) method to consume evicted edges routed from promotion.
EpisodicEdges64 promotion and query methods crates/lance-graph-contract/src/episodic_edges.rs	EpisodicEdges64 adds promote_into(e, sink) to wrap existing promote and route any eviction into the sink, coldest() to return the last occupied slot's edge (the eviction victim), and contains(e) to check exact EdgeRef presence with family-discriminating dedup semantics.
Test coverage for demotion and query behavior crates/lance-graph-contract/src/episodic_edges.rs	Tests validate coldest on empty/single/full words and confirm it matches the promote eviction victim; validate contains for present/absent edges and family discrimination; assert promote_into routes no demotion on non-full promotion, exactly the coldest edge on full promotion, accumulated ordering across chained promotions, and no demotion on refire.
Planning and deliverable documentation .claude/board/AGENT_LOG.md, .claude/board/EPIPHANIES.md, .claude/board/LATEST_STATE.md, .claude/board/STATUS_BOARD.md	Status board, planning log, and state documentation updated with new deliverable entries (D-EW64-3 and D-EW64-4), epiphany correction clarifying W15 byte-3 high_heel::Heel vs. CausalEdge64 plasticity representation, and agent log recording newly shipped APIs and implementation deferment gating.

Possibly related PRs

• AdaWorldAPI/lance-graph#447: Both PRs modify crates/lance-graph-contract/src/episodic_edges.rs around EpisodicEdges64::promote's MRU/eviction behavior—main PR builds coldest, contains, and promote_into/DemotionSink directly on top of the promote semantics implemented by PR #447.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐰 I nibble at edges both hot and cold,
I mark the coldest, the tales they hold.
If promotion spills an old friend loose,
a DemotionSink will catch the truce.
Happy hops for tests that folded gold.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically identifies the main changes: EW64 cold-tier read surface (coldest/contains APIs) and DemotionSink seam, with explicit reference to deliverables D-EW64-3 and D-EW64-4.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/jolly-cori-clnf9

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[coderabbitai]

🧹 Nitpick comments (1)

crates/lance-graph-contract/src/episodic_edges.rs (1)

234-246: 💤 Low value

Consider reusing the existing iter() method.

The implementation is correct, but could be more concise by leveraging the existing iterator:

pub fn contains(self, e: EdgeRef) -> bool {
    self.iter().any(|x| x == e)
}

This would reuse the iter() logic and be slightly more idiomatic. However, the current explicit implementation is also clear and correct.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/lance-graph-contract/src/episodic_edges.rs` around lines 234 - 246,
The contains method manually loops over Self::CAPACITY and calls self.edge(i) to
check for equality with the EdgeRef argument; replace that manual loop by
delegating to the existing iterator: use self.iter().any to test whether any
yielded EdgeRef equals the provided e, keeping the method signature (pub fn
contains(self, e: EdgeRef) -> bool) and its #[must_use] attribute intact and
removing the explicit index loop and edge(i) calls.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@crates/lance-graph-contract/src/episodic_edges.rs`:
- Around line 234-246: The contains method manually loops over Self::CAPACITY
and calls self.edge(i) to check for equality with the EdgeRef argument; replace
that manual loop by delegating to the existing iterator: use self.iter().any to
test whether any yielded EdgeRef equals the provided e, keeping the method
signature (pub fn contains(self, e: EdgeRef) -> bool) and its #[must_use]
attribute intact and removing the explicit index loop and edge(i) calls.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3fdfdf68-9c85-46a8-8253-ababb1ff757c

📥 Commits

Reviewing files that changed from the base of the PR and between 4e06aeb and 05ae893.

📒 Files selected for processing (5)

• .claude/board/AGENT_LOG.md
• .claude/board/EPIPHANIES.md
• .claude/board/LATEST_STATE.md
• .claude/board/STATUS_BOARD.md
• crates/lance-graph-contract/src/episodic_edges.rs