Traces the ~400x read-path gap (alktty wire_vs_bast bench) to
SequentialReader::read_field_at re-parsing BastDoc::new on every field
read, with the self-referential lifetime constraint as the root cause.
Findings:
- H1: per-field BastDoc::new re-parse in sequential_reader.rs:262
- M1: same re-parse in four one-shot paths (LayoutBuilder::build,
validate_bytes, engine read_field/write_field)
- L1: dead _field_schema param + Value clones in SequentialReader
- L2: ADR-007 Cost section + engine doc comment understate the re-parse
- N1: carry-forward of review #003 N2 (no new action)
Lays out fix options: Option A (owned typed tree, recommended, closes
H1+M1, breaking), Option B (read-plan precompute, fallback, H1 only,
non-breaking), Option C (borrow-from-engine, rejected, contradicts
ADR-007).
Verification: docs-only review; alktype source unchanged.
cab4932
glm-5.2
51cb552715