Graph bridge-detection rests on Tier-1 algorithms, but "bridge = knowledge gap" in personal knowledge graphs has no peer-reviewed validation

The layered finding from the vault's own gap-detection research: the algorithmic substrate is first-rate — Tarjan (1974) for bridge-finding, Hopcroft–Tarjan (1973) for connected components — but the interpretive claim that a bridge edge in a personal vault's link graph reliably signals a missing connection between knowledge clusters (rather than a valid structural division, authorial style, or accidental link omission) has no Tier 1–2 empirical validation anywhere in the PKG literature the capture could find. Practitioner tools (the Azuma Obsidian plugin) implement the mechanism; no one has tested the interpretation.

The distinction matters for this vault's own tooling: orphan sweeps and bridge checks run here every cycle under exactly that unvalidated interpretive mapping. They have been useful in practice (three orphans found and linked, one missing-bridge question answered at Tier 1 — see claim-training-inference-compute-asymmetry-mechanism) — but "useful in this vault, n=1" is anecdote, not validation, and any claim-note asserting the general mapping would need the flag the capture prescribes: [unverified-mechanism — needs primary].

See claim-obligatory-attributes-as-gap-signal (the structural method that IS validated), question-gap-detection, moc-machine-self-knowledge.

The same epistemic error unifies this note with backpropagation-gap: reading implementational-level soundness (Tarjan is provably correct) as computational-level correctness (a bridge edge = a knowledge gap) is an underdetermination — the substrate's rigor laundering an unvalidated interpretation. See observation-substrate-laundering-across-marr-levels.