The Explore walk got stuck in dense signatures — neighbours all too similar, so
forward-arrow couldn't escape and Random was the only exit. Root cause: MMR only
diversifies WITHIN the nearest ~400 pool; in a dense cluster that whole pool is
near-identical, so there's no escape route in it.
- gallery_service.similar(reach=0.0, exclude_ids=None): reach>0 widens the pool
(cap 400→1000) and _reach_sample strides across an outward-growing distance span
so the set handed to MMR spans near→mid-far (guaranteed escape routes), not just
the tight cluster. exclude_ids drops already-walked images. Gallery 'more like
this' (reach=0) is unchanged.
- api/gallery similar: parse reach + exclude_ids.
- explore store: default reach 0.4 (auto-diversifies without touching the dial),
pass the breadcrumb as exclude_ids, setReach action.
- ExploreView: a Near↔Far reach slider in the trail.
- tests: _reach_sample math (deeper ranks with higher reach, near kept); similar
exclude_ids drops walked + reach path runs clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
bvandeusen
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