ADR-0004 — Evidence, provenance and confidence are first-class edge fields

Status: Accepted · 2026-08-18 · Enforces RULES 004–006

Context

The interface-defining question is "show me exactly why you think these two things are connected." Competitors assert relationships; Cartograph's moat is producing evidence for them. Retrofitting evidence onto a bare A→B graph later is expensive and, for already-analysed repositories, impossible.

Decision

Every edge carries kind, confidence, provenance, evidence, source location, commit and created_at from the first commit of the domain model. Edge has no Default, no public fields, no partial builder — the only constructor requires all of them, so an unevidenced edge does not compile. Provenance (the method) decides derived-vs-inferred rendering, not a threshold on the confidence number.

Alternatives

• Optional metadata fields — rejected: optional means absent under deadline pressure.
• Confidence threshold for "derived" — rejected: whether a claim was computed or estimated is a property of the method, not the number.

Consequences

Constructing edges is verbose (testkit absorbs this in tests). Storage costs more per edge. The benchmark (M08), the DIFF surface (M13) and the edge-record UI (M11) all build on fields that already exist.