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`cass index` fails with `graph topology attestation failed`

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Source: Troubleshooting reference

build HNSW index failed: hnsw error: graph topology attestation failed:
parallel construction failed (search entry origin 6219 reaches only 92908/97513
points at the base layer); serial rebuild also failed

Transcripts contain thousands of byte-identical tool stubs — [Tool: apply_patch] alone repeats 4,383 times — and identical text embeds to identical vectors. Under DistDot those form zero-distance cliques larger than the layer-0 fanout (max_nb_connection 16 → ~32 links), so a clique fills every member’s neighbour list with its own duplicates and nothing outside ever links in. HNSW reachability is directional, so the whole group is unreachable from the entry point and cass’s attestation rejects the graph.

It is deterministic: retrying fails identically, which is why the serial rebuild also failed and why retryable=true in the error is misleading.

Fix: drop --build-hnsw (the manual memory.sh semantic mode does not use it). HNSW only backs --approximate; exact search over ~100k vectors is fast enough, and the flag has never once succeeded on this archive — every semantic_manifest.json here records "hnsw": null. Restore it if cass starts deduping identical vectors before insert.