Should the vault's single source_tier field split into two axes — source reliability separate from claim credibility — the way intelligence doctrine and RAG both do?

The Admiralty-Code hop (observation-intelligence-doctrine-and-rag-independently-derived-a-two-axis-source-model) surfaces a direct challenge to the vault's own design. Both Cold-War intelligence doctrine (claim-admiralty-code-grades-sources-on-two-independent-axes) and 2025 retrieval research (claim-reliability-aware-rag-estimates-source-reliability-separately-from-relevance) grade a report on two axes — how reliable the source is, separately from how credible the specific claim is. The vault's source_tier fuses these into one number.

The question. Should a claim-note carry two fields — e.g. a source-reliability tier and a per-claim credibility/corroboration grade — instead of one source_tier?

The case for. The vault already half-does this: audit_status, [unverified-quant] flags, and the "one confirmed source vs uncorroborated" distinction are credibility-of-the-claim signals living outside source_tier. Making the second axis explicit could sharpen retrieval gating.

The case against. Trained analysts empirically cannot keep the two axes independent — they over-weight source track record and avoid inconsistent pairings. If humans (and, per AuthorityBench, models) can't hold the axes apart, a second field may add false precision rather than honesty. The single tier may be an admission that the split doesn't survive contact with a real evaluator.

What I'd need to answer it. A pass over how source_tier + audit_status + flags actually interact in ~20 notes; whether the fusion has ever caused a mis-grade; and whether the retrieval layer (spec §7's gating rule) would benefit from a separate credibility axis. This is a design decision for Cali, not a unilateral schema change.

Candidate next move. Draft a one-page design memo weighing the two-axis option against the current fused tier, citing the three underlying claim-notes; leave the schema untouched until Cali rules.

Progress

2026-07-21 (partial — stays open). A batch capture (10-inbox/raw/2026-07-20-should-the-vaults-single-source-tier-field-split.md) added a third and fourth independently-converging domain and a check on what the existing "axes leak" finding actually recommends: evidence-based medicine's GRADE framework (claim-grade-splits-quality-of-evidence-from-strength-of-recommendation) and the CRAAP library-science test (claim-craap-test-splits-authority-from-accuracy) both draw the same source-vs-content line independently; and Kelly et al.'s own response to "raters can't keep the axes apart" turns out to be a richer nine-cell matrix, not a call to collapse (claim-kelly-et-al-propose-richer-joint-matrix-not-axis-collapse). A search for practitioner opinion on the merge-vs-split question found writers arguing only to keep the axes separate (claim-no-practitioner-source-found-advocating-merging-reliability-credibility-axes), though that search was not exhaustive.

This strengthens the case-for column but does not close the question: no inter-rater-reliability, cognitive-load, or rater-burden data on two-axis systems turned up in this pass either (checked specifically in Kelly et al. and came up empty), so the cost side of the tradeoff — whether a second field would sharpen retrieval gating or just add a number nobody keeps honestly independent — remains as unaddressed as it was on 2026-07-11. Still a design decision for Cali, not something four converging citations settle by themselves. Left open.