Capture the positioning fox articulated: arborist's per-document ingest
is ~10-100x cheaper than building a vector-DB representation — same
SQLite substrate, different retrieval philosophy — which is the
difference between "ingest + search runs on a phone" and "the NPU is
now a hand-warmer."
New docs/lexical-first-rationale.md (positioning/architecture
reference, not a ticket): the cost asymmetry with the measured numbers
(FTS5 + SHA-256 leaf + Merkle commit + sqlite + zstd pipeline << 1 ms/
chunk vs bge-small ONNX inference ~5-30 ms/chunk, worse contended; the
query side too — a vec query embeds the query string first, an FTS5
query is B-tree lookups); the same-SQLite-different-philosophy table
(inverted index vs dense vectors + ANN; build cost; query cost;
matching; proof-bearing); the deep version of the point — arborist IS
the Merkle Providence model and that model is cheap by construction,
embeddings are a soft signal (CLAUDE.md "soft hash vs hard hash") that
never enter a proof and are the expensive bolt-on; the edge/mobile
consequence; the honest caveat (lexical-first trades the semantic
allusion gap — which is why vec is opt-in/additive, never the default,
and the embed pass is lazy/out-of-band so the heavy transformer work
runs off-device/off-peak; int8 keeps the storage tax at +6%).
Wired in: TICKETS.md "Distinction from other docs" reference list gains
the doc; #000039 §14.6 gains a "Strategic framing" pointer to it.
(A possible follow-up: fold the mobile-viability argument into the
Merkle Providence Reverse RAG whitepaper proper — noted in the doc's
references; not done here, that's a deliberate cross-repo paper edit.)
Doc-only.
russell@unturf.com
1d4d7c549c