Improve agent RAG quality with three changes, plus a roadmap doc for the rest.
- Indexer: prefix each chunk with its heading path ("Page > H1 > H2"), built by
walking the ProseMirror JSON (heading nodes) so a `#` inside a fenced code block
is never mistaken for a heading. Falls back to plain-text chunking on any error.
buildChunkRows: drop indexOf-against-source offsets (breadcrumb prefixes break
verbatim matching) for a cumulative cursor — offsets are provenance-only.
- Hybrid search: new migration adds a generated `fts` tsvector column + GIN index
to page_embeddings (same english+f_unaccent config as pages.tsv). New
PageEmbeddingRepo.hybridSearch fuses cosine + full-text rankings via Reciprocal
Rank Fusion (k=60, equal weights) in one SQL query at chunk granularity.
- Tools: collapse semanticSearch + searchPages into one hybrid `searchPages` tool
with a query-rewrite-oriented description; gracefully falls back to the REST
full-text path when embeddings are unconfigured. Access control (space scope +
page-permission post-filter) preserved. Add a query-rewrite hint to the default
system prompt.
- docs/rag-improvements-plan.md: record what shipped and the deferred backlog
(reranker, attachment indexing, eval harness, tuning).
Note: requires a corpus reindex to populate breadcrumbs on existing pages.
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