contract: edges is byte-backed — bytes are stored, integers are projected

[AdaWorldAPI]

Bytes are stored. Integers are projected. Byte-agnosticism is the storage superpower; little-endian is the compute superpower. This lands the one site in the tree that mixed them.

The violation

NodeRow is #[repr(C, align(64))] and as_le_bytes() reinterprets &[NodeRow] → &[u8] for Lance — so the row's in-memory image is its stored image. edges was a FacetCascade, whose facet_classid is a native-endian u32. That is a stored projection, which is the only shape this failure ever takes. #1246 held the seam shut with a target_endian assert; this replaces the stopgap with structure.

The change

EdgeFacet([u8; 16]), #[repr(C, align(16))] — the exact mirror of NodeGuid — with as_bytes / as_bytes_mut / from_bytes / to_bytes / facet() and From/Into against FacetCascade. pub type EdgeBlock = EdgeFacet keeps every call site compiling.

Consequence: all three NodeRow fields are byte arrays ([u8;16] | [u8;16] | [u8;480]), so the 512 bytes contain no native-endian integer at all, and as_le_bytes is byte-identical across targets by construction rather than by assertion.

It ratifies what the code already did

Two of three facet sites already obeyed the doctrine before it was written down:

site	form	verdict
NodeGuid([u8; 16])	stores bytes, projects via .facet()	obeys — the exemplar
AttentionFocusFacet	holds the typed facet, not repr(C), no SoaEnvelope, reaches bytes only via the explicit to_bytes() encode	obeys — compute, contained
NodeRow::edges	stored a FacetCascade inside the reinterpreted row	violated

Census, read rather than grepped: every EdgeBlock site is default() / as_bytes() / as_bytes_mut() / from_bytes() / equality / Copy, and every struct-literal and every .facet_classid / .tiers read is on a projected facet — not one is a field access on NodeRow::edges, because #1246 had already moved them all to bytes. The two real consumers (symbiont::key_render, soa_graph) read eb.as_bytes()[..12] / [12..] and are untouched.

Correction to #1246

Its arc entry and PR body both said this would "retire the target_endian guard entirely." Wrong, and the code said so. FacetCascade::as_bytes is still a reinterpret by design — that reinterpret is the 1.72 ns byte-chain LCP hot path from #1245's probe — so the reinterpret == encode identity is still assumed and the guard stays. What changed is its blast radius: it now protects a value in flight, never a row at rest. Its comment is rewritten to say that, not deleted.

Both canonical_node.rs SAFETY comments are corrected in place. One ended by asserting EdgeBlock was "the one field that is not" a byte array — true when written, false now, struck rather than silently reworded.

Verification

• Falsifier asserts both superpowers in one test — stored bytes verbatim (endian-free) and facet().facet_classid decoding 0xDEAD_BEEF little-endian. Both hold on any target, which is the point.
• Disable-run red-then-green: byte-swapping the first four bytes in from_bytes fails it on "stored bytes are verbatim"; restore passes. Files were backed up to the scratchpad rather than trusting git checkout, since the work was uncommitted — the ruff commit-before-you-disable trap.
• 1356 contract tests green · weather-poc 40 green · planner builds · clippy clean under -D warnings · fmt clean.
• cargo check --workspace --all-targets green locally (exit 0, 2m 26s) on 5ba50f62, including the lance-dependent crates. ⊘ Struck: the earlier claim that this was "blocked in this container by a missing protoc … CI covers it." The block was real but self-inflicted — protobuf-compiler was simply not installed and I routed around it instead of installing it. With libprotoc 3.21.12 present the full workspace builds here. The one warning is pre-existing and unrelated to this diff (unused import: MailboxSoaView, crates/surreal_container/tests/scheduler_seam.rs:15).

Board

EPIPHANIES E-BYTES-ARE-STORED-INTEGERS-ARE-PROJECTED-1 (doctrine, census, the reusable pattern byte-backed newtype + .facet() projection, and the correction above) and a LATEST_STATE contract-inventory delta, both in the same commit as the type. Supersession index regenerated after the board writes — byte-identical.

Residue unchanged: readers that still split those 16 bytes at 12 remain named in ISS-EDGE-BLOCK-WAS-A-SECOND-TYPE-FOR-THE-SAME-FACET. Byte-backing neither fixes nor worsens that — it is a reading, and the ClassView should decide it.

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Summary by CodeRabbit

• New Features

  • Edge data is now stored as portable, target-independent bytes for consistent cross-platform handling.
  • Edge data can be explicitly converted to and from its computed facet representation.
  • Existing edge-block compatibility is preserved.

• Bug Fixes

  • Corrected byte-order handling to prevent platform-dependent interpretation of stored edge data.
  • Added validation for byte preservation and little-endian projection during computation.

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📝 Walkthrough

Walkthrough

The change adds byte-backed EdgeFacet storage for NodeRow::edges. It preserves EdgeBlock compatibility, adds explicit FacetCascade projection, updates serialization and safety contracts, and tests byte-preserving behavior.

Changes

Byte-backed edge storage

Layer / File(s)	Summary
EdgeFacet contract and storage crates/lance-graph-contract/src/canonical_node.rs	EdgeFacet stores 16 bytes verbatim, exposes byte accessors, and converts explicitly to and from FacetCascade. Serialization and safety documentation now describe byte-backed NodeRow fields.
Projection validation and contract records crates/lance-graph-contract/src/canonical_node.rs, crates/lance-graph-contract/src/facet.rs, .claude/board/*	Tests verify byte preservation and little-endian projection. The endian guard and architectural records describe the retained compute-time reinterpretation path.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant NodeRow
  participant EdgeFacet
  participant FacetCascade
  NodeRow->>EdgeFacet: store edge bytes
  EdgeFacet->>FacetCascade: facet() projects bytes
  FacetCascade-->>NodeRow: provide typed compute value

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Suggested reviewers: claude

Merge Risk: ⚪ Minimal · up to adba7

The storage migration documents its intentional API break and includes coverage for byte preservation and little-endian projection. No unresolved merge-blocking issue remains.

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✅ 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 concisely describes the main change: edges now stores bytes and projects integers when needed.
Docstring Coverage	✅ Passed	Docstring coverage is 84.62% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 13 functions across 2 files.
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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Inline comments:
In `@crates/lance-graph-contract/src/canonical_node.rs`:
- Line 758: Document the breaking API change for the public EdgeBlock alias,
including the loss of FacetCascade’s facet_classid, tiers, and inherent methods,
and describe the migration to EdgeFacet or an available compatibility surface.
Update the contract crate’s release/version metadata to the next SemVer-breaking
version, or add a deprecation/compatibility path before applying the
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• .claude/board/LATEST_STATE.md
• crates/lance-graph-contract/src/canonical_node.rs
• crates/lance-graph-contract/src/facet.rs

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