**Description** This PR is a small follow-up to @matthewmcneely's `matthewmcneely/fix-similarity-based-hnsw-indexing` that tightens the construction-time pruning path in `tok/hnsw/helper.go:addNeighbors`. - Makes construction pruning explicitly maintain the best-to-worst top‑k neighbour list capped at `efConstruction` (rather than relying on heap/slice side-effects) - Avoids duplicate/self edges during construction updates - Aligns the pruning unit test with the same helper used by production to reduce test/production drift This is intended to be easy to cherrypick into the [PR branch](#9559) ### Why The directionality fix is the key part (and @matthewmcneely's [PR](#9559) nails that), but the existing pruning loop still had a couple of structure-level issues (heap initialisation/slice truncation semantics) that could make construction behaviour hard to reason about -- especially under similarity metrics ### Testing - `go test ./tok/hnsw -count=1` - Synthetic recall harness (25k vectors) shows massively improved recall vs. `main` (per my [comment](#9559 (comment))) and stable miss-rate and expected build/query behaviour vs. #9559 **Checklist** - [x] The PR title follows the [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/#summary) syntax, leading with `fix:`, `feat:`, `chore:`, `ci:`, etc. - [x] Code compiles correctly and linting (via trunk) passes locally - [x] Tests added for new functionality, or regression tests for bug fixes added as applicable

Commits

Commits on Jan 8, 2026

Add functionality to correctly evaluate scores

Rename min init function for clarity

Commits on Jan 12, 2026

fix(vector): Make construction pruning deterministic and align tests (#9563)

Rename type to better-represent functionality