feat(agent): new stores use the int8 vector index by default

`MemoryConfig::quantized_index` now defaults to `true`. It holds a quarter of the index memory and, with the exact re-score, is faster at equal recall on every configuration measured: 1.63x the queries per second on x86-64 (AVX2) and 1.18x on a Raspberry Pi 5 (NEON SDOT), with builds 1.8x and 2.3x faster. The one argument for keeping it off — that int8 search was slower on ARM — did not survive being measured. Existing stores do not change. A store written with v2.6.0 or later keeps its persisted setting. One written before the setting existed has no stored value, and it loads as `false` rather than as the new default, so reopening it never changes how its index is held. That case is guarded by a real store written with the v2.5.0 CLI, committed as `tests/fixtures/store_v2_5_0.h5` (6.8 KB): the test asserts it reopens with an f32 index and still searches, and it fails if the load default is changed to `true`. The CLI needed more than a new default. `create --quantized-index` assigned its value straight into the config, so under the new default every CLI-created store would have been forced back to f32 unless the caller knew to ask for int8. It is replaced by `--f32-index`, which only ever switches the default off; `--quantized-index` is still accepted, hidden, as a no-op, and the two conflict. The whole agent suite passes under the new default, including the brute-force recall oracle, now running on int8 plus re-score without being asked to. Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
2026-09-21 18:27:59 -07:00
parent 6598a7d02f
commit 8b85d9364b
9 changed files with 124 additions and 16 deletions
@@ -497,6 +497,9 @@ pub fn validate_and_load(
        wal_max_entries: optional_i64_attr(&attrs, "wal_max_entries")
            .and_then(|v| usize::try_from(v).ok())
            .unwrap_or(500),
+        // `false`, not the new-store default: a store written before this
+        // setting existed was built with an f32 index, and reopening it must
+        // not silently change that.
        quantized_index: optional_bool_attr(&attrs, "quantized_index", false),
        hnsw_m: optional_i64_attr(&attrs, "hnsw_m")
            .and_then(|v| usize::try_from(v).ok())