Plan: Edge Semantics (provenance + typed rel- edges) - IMPLEMENTED (branch edge-semantics, 2026-07-13)

Fills the "Edge semantics: give edges more information" roadmap gap from the 2026-07-13 knowledge-layer analysis. Implemented in one changeset on branch edge-semantics; awaiting commit + PR.

What shipped

Two halves, zero server/protocol/store changes:

Edge provenance: every crawled edge carries the link's label text, the source section anchor it appears under, and an occurrence count. Duplicate links between the same pair aggregate into one counted edge; first non-empty label wins.
Typed relations: publisher-metadata convention rel-<predicate> (hyphen, never colon; metadata keys allow only [a-z0-9-]), CSV values resolved against the doc URL, ingested by both crawlers as typed edges. Malformed refs, self-refs, and empty predicates are skipped silently.

Design decisions

Edge identity is {From, To, Rel}; plain body links have Rel "". A plain link and a typed relation between the same pair are two distinct edges.
Store Merge is last-crawl-wins for Label/Anchor/Count (mirrors node upserts): idempotent, counts never inflate.
graph.json schema stays v1 (new StoredEdge fields are omitempty; legacy files load with Count normalized to 1).
/graph.md Edges table widened to | From | To | Rel | Label | Anchor | Count |; ParseExport accepts both this and the legacy 2-column row.
One shared annotation renderer graph.EdgeAnnotation ( [supersedes], ("Getting started", #intro, x3)) used by client MCP, broker MCP, and both backlink lists; pinned-literal tests on both sides guard drift.
Fetch callback widened to a struct returning (graph.FetchResult, error) with a Metadata field; this also paid the /debt.md "Crawl fetcher callback returns four positional values" item and deleted the caller-less graph.ClientFetcher adapter.
Shared enriched extraction lives in client/mdoutline.AnchoredLinks (mdoutline already imports links, so links could not host it without a cycle).

Touched surfaces

client/mdoutline (new AnchoredLinks), client/graph (Edge fields, AddEdgeInfo aggregation, EdgeAnnotation, RelEdges parser, crawl enrichment), client/graphstore (StoredEdge, Merge, BacklinkEntry enrichment, dual-format export/parse), client/internal/fedcrawl (recordEdges via AnchoredLinks + RelEdges with existing loopback/normalize filters), demarkus-mcp (formatGraph, backlinks, explore, tool descriptions), broker (same surfaces + MCP-API.md), docs (ADR 0004, DESIGN.md, agent-cookbook).

Verification done

Full test suites green in client and tools modules; bash pre-commit.sh clean.
Live e2e: dev server on :6399, published adr.md with -meta rel-supersedes=/old.md and a twice-linked doc under a ## Context heading; crawl produced | adr.md | design.md | | design doc | context | 2 | and | adr.md | old.md | supersedes | | | 1 |.
Legacy compat live: the real pre-change ~/.mark/graph.json (133 nodes / 190 edges) loads and exports through the new binary with Count normalized to 1.

Follow-ups

Surface labels/rels in the TUI graph view (deliberately deferred this round).
When publish-time edge extraction lands in the store backends, capture the same fields; conformance suite first per the backend-parity principle.
Consider a curated rel- predicate vocabulary in the plugins (supersedes, implements, depends-on, derived-from).

See repo docs/adr/0004-edge-semantics-rel-convention.md for the full decision record.

PR 251 review round (CodeRabbit, 2026-07-13)

Four of five findings addressed, one declined:

Fixed: RelEdges now rejects any internal whitespace via unicode.IsSpace (newlines from a hostile or broken remote server no longer pass).
Fixed (the sharp one): Merge now replaces the stored outgoing edge set for every source the crawl actually fetched, so deleted links and dropped rel- predicates no longer linger in backlink queries. External/error sources keep their stored edges. This stale-edge behavior predated the PR but the enrichment made it worth fixing here. ADR 0004 updated.
Fixed: empty-label links keep section provenance; LinkInfo gains BlockStart (enclosing block start, valid even when brackets are unknown; headings cannot split a block, so it is section-accurate). Bracket positions stay -1 so the TUI marker-injection contract is untouched.
Fixed: AnchoredLinks heading attribution is now a binary search per link instead of a rescan.
Declined: bumping graph.json schemaVersion to 2 for the enriched edges. The file is a rebuildable crawl cache, not a source of truth; an old binary reading a new file degrades gracefully (drops enrichment, output identical to pre-feature) and any loss is repaired by the next crawl, while a version bump would make every old binary hard-reject the file. The version exists for breaking shape changes, and this one is additive.

PR 251 review round 2 (CodeRabbit, 2026-07-13)

Fixed (critical, real): the BlockStart ancestor walk called p.Lines() on inline parents, and goldmark's BaseInline.Lines() panics by contract, so any link wrapped in emphasis (**[text](url)**) crashed extraction. Guard with p.Type() == ast.TypeBlock. Reproduced the panic against the committed code with a new test before fixing (test fails pre-fix, passes post-fix). Regression coverage added at all three levels: links (link inside bold), mdoutline (bold and italic wrapped links), crawl (bold link records label and anchor).
Declined: debug-level log for skipped malformed rel- refs. RelEdges is a pure function with no logging dependency; the skip rules are deterministic and documented in code and ADR 0004; CodeRabbit itself rated it low value.
Duplicate schema-bump comment: prior decline stands (rebuildable cache, additive omitempty fields, hard version bump is the worse failure mode).

Lesson: when a helper walks AST ancestors, test links nested inside inline formatting; the first review's tests only covered formatting inside links, not links inside formatting.

PR 251 review round 3 (CodeRabbit, 2026-07-13)

One nitpick, accepted: the links-level extraction tests never asserted the new LinkInfo.BlockStart field. Added a case with a link in a second paragraph (non-zero BlockStart 18) plus an empty-label link in the same block (bracket positions -1, BlockStart still 18), and wired BlockStart into the per-field compare loop so every existing case now pins it too.

Merged

PR #251, merged to main 2026-07-14 as commit 8798d0a. Roadmap entry flipped to DONE; the resolved fetch-callback item removed from /debt.md. This plan is complete; follow-ups live in the roadmap (TUI display, publish-time edge extraction) and the next increment is /plans/graph-hub-seed.md.