bvandeusenandClaude Opus 5
14aa22198f
The Discover request surface was the one recommendation surface still on its M5c implementation from early May. #796's taste profile, #1488's taste_unheard bucket and #1490's folksonomy enrichment all modernized in-library surfaces; this one was never in scope for any of them, so it still projected raw likes + plays through artist_similarity_unmatched. Two defects fall out of that signal, `5*liked + Σexp(-age/halflife)` summed over every play of the artist. It is unbounded, and contribution is signal × similarity — so a handful of heavily-played artists monopolize all twelve slots, and their share GROWS the more the user listens. The surface entrenched harder the better it knew you, which is exactly backwards and matches the reported "goes stale once it has a strong signal of your taste". It also counted every play_event with no was_skipped filter, so skipping an artist repeatedly INCREASED its signal and pushed more of its neighbours at the user. ListMostPlayedTracksForUser and the taste engine both filter skips; this query was the odd one out. Seeds now come from taste_profile_artists.weight, which the taste engine has already engagement-graded, time-decayed and signed — an artist the user drifted away from stops contributing instead of accumulating forever, and can even contribute negatively. Tiered per rule #131 rather than hard-switched: tier 1 is the profile, tier 2 is likes + completed plays for a user who has no profile rows yet (new account, or before the first daily recompute), so the surface never empties. The old unfiltered-play signal is gone, not kept behind a toggle. The signal is also log-damped, so one artist cannot take every slot even when its weight dwarfs the rest. $2 stays wired to the tier-2 decay: it is genuinely still used there, and dropping the parameter would have changed the generated signature. sqlc's image is not on this workstation and the change preserves the query signature exactly — same three params, same seven columns — so only the embedded SQL const moves. Both copies are edited and verified byte-identical rather than pulling a container onto the operator's machine; a malformed query fails the integration lane loudly, which is the real check either way. Four integration tests cover what changed: a taste weight alone seeds with no like or play; tier 2 does not run alongside tier 1; a non-positive weight never seeds (guarded by a second positive row, so an empty tier 1 can't make it pass for the wrong reason); and skip-only history seeds nothing. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>