The recommendation scoring knobs move out of YAML (radio profile) and
out of the systemMixWeights hard-code (daily_mix profile) into
DB-backed settings with live effect (#1250) — the defaults-discovery
lab per decision #1247: the operator turns knobs to find good values,
which then get baked back into shipped defaults; end users and other
operators should never need the card.
- Migration 0040: recommendation_weight_profiles (radio / daily_mix,
8 weight columns), taste_tuning singleton (engagement half-life +
completion-curve points), recommendation_tuning_audit (one row per
change with a {field, old, new} diff — the trend view's markers,
#1251).
- internal/recsettings: boot reconcile seeds shipped defaults without
clobbering tuned rows (coverart SettingsService pattern), validates
patches (bounds, curve ordering), writes audit rows, and pushes
daily_mix weights + taste config into package playlists. No-op
patches write no audit row.
- playlists gains SetSystemMixWeights / SetTasteConfig swap points
under a RWMutex — no signature threading through the producers; the
scheduler's taste rebuild reads the pushed config.
- Radio reads its weight profile from the service per request; the 8
weight fields leave config.RecommendationConfig (YAML keeps only
RecentlyPlayedHours / RadioSize / RadioSizeMax).
- Admin API: GET/PATCH/reset under /api/admin/recommendation-tuning,
echoing current + shipped values.
- Web: new admin Tuning tab — two weight profiles side by side, taste
card, per-scope save (changed fields only) + reset, deviation dots
against shipped defaults.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
Two approved composition changes (#1269), mechanism only — the
taste/fresh share stays data-decided (#1252) and pick_kind
attribution is unchanged.
Multi-seed blending: each day's build now seeds from up to 3 of the
user's top-5 tracks (pickDailySeeds, the generalized daily shuffle)
instead of one rotating anchor, so the mix spans neighborhoods within
a day and stops feeling bipolar as the rotation swings between
dissimilar seeds. Per-seed pools merge first-seen-deduped; the head
is filled best-first under 50/30/20 per-seed quotas (60/40 for two
seeds) so one neighborhood can't monopolize it, with thin-seed quota
spilling best-first.
Score-weighted fresh tail: the tail sample (rank 2*headN onward) was
uniform — the 380th-best candidate as likely as the 101st. It now
uses deterministic Efraimidis-Spirakis keys with weight halving every
50 ranks, so freshness keeps its "you'll probably enjoy this" half
while still rotating daily.
The retired single-seed picker's one other caller, You-might-like,
moves to pickDailySeeds(n=1) — a single neighborhood per day is right
for a short shelf, and the behavior note is inline.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
Both mixes move from a single hard eligibility rule to the tiered
ladder, with their tier stamped onto playlist_tracks.pick_kind via the
#1270 provenance pipeline.
New for you (#1267) — consume on play, degrade by stepping back:
- "Consumed" = any track attempted >=30s; played albums leave the mix
at the next build instead of crowding it until the calendar window
expires.
- Tier 1: unconsumed albums added <30d by direct-affinity artists.
Tier 2: unconsumed affinity albums from the wider 30-90d window —
added while you weren't looking. Tier 3: any unconsumed album added
<90d, newest first.
First listens (#1268) — track-level "attempted" threshold:
- A 2-second accidental brush no longer disqualifies a whole album;
"attempted" is duration_played_ms >= 30000 per track.
- Tier 1: albums with zero attempted tracks. Tier 2: barely-attempted
albums (<=25% of tracks reached 30s), minus the attempted tracks
themselves. The artist-affinity ordering signal also moves to the
>=30s definition so skip-only contact doesn't read as trust.
Producer plumbing: fetch adapters map the tier column onto pick kinds,
finishMix propagates PickKind into the persisted candidates, and
rotateForDay now rotates within contiguous same-pick-kind blocks so
daily rotation can't hoist tier-3 filler above tier-1's exact fits
(untiered pools are one block — original behavior).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
PickSeedArtists had a hard 7-day window with no fallback: a week
without listening emptied the seed pool, produceSeedMixes returned
zero playlists, and the daily atomic-replace build deleted every
existing "Songs like X" mix until the user played something again
(#1255).
The query now falls back through widening engagement windows — 7d →
30d → all-time → liked artists — the same tiered shape that fixed the
identical vanish for For You's seeds (PickTopPlayedTracksForUser).
Like-boost scoring is preserved in every tier.
All returned rows share the winning tier, and produceSeedMixes maps it
onto the rule-#131 pick-kind ladder (7d = tier1 exact, 30d = tier2,
all-time/liked = tier3) and stamps the built tracks — the #1270
provenance pipeline then attributes plays and skips to seed freshness,
so the metrics card can say whether stale-seeded mixes actually
perform worse.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
The #1249 mechanism (stamp WHY a track is in the snapshot at build
time, freeze it onto the play at ingestion, break it down in metrics)
generalizes from a For You one-off to the standard for every system
mix (#1270):
- Migration 0039 widens both pick_kind CHECKs (drop + re-add in the
same change) to taste/fresh + Discover's dormant/cross_user/random
+ tier1-3 for the rule-#131 eligibility ladders.
- GetForYouPickKindForTrack becomes GetSystemPickKindForTrack
(user, variant, track); ingestion stamps any systemPlaylistSources
play from its own variant's live snapshot, live + offline paths.
- Discover stamps its candidate bucket on discoverTrack before the
interleave, making the 40/30/30 allocation measurable; dedup keeps
the taking bucket's stamp.
- Metrics replace the for_you special-case with one pick-kind
vocabulary — any family with attributed plays gets a breakdown,
future stamping mixes need no metrics change.
- Web: breakdown sub-rows are now toggled per surface (collapsed by
default) so eight stamping mixes don't swamp the card.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
Milestone #127 step 2 (#1249). For You deliberately blends two
populations — a head of top-scored taste picks and a tail sampled from
deeper ranking (the freshness injection) — but the metrics judged it as
one blob, so its skip rate couldn't distinguish "the taste engine is
missing" from "the freshness tax is too high". That number decides the
exploration share before we tune it.
- Migration 0038: nullable pick_kind ('taste'|'fresh') on both
playlist_tracks (stamped at snapshot build) and play_events (frozen at
play-ingestion — the snapshot rebuilds daily, so attribution cannot be
reconstructed at read time).
- Builder: pickHeadAndTail marks head=taste / tail=fresh; the small-pool
fallback is all taste (top-N-by-score IS the taste mechanism). Other
variants persist NULL.
- Ingestion: for_you plays (live + offline replay) look the track up in
the user's current snapshot; not found → unattributed, never guessed.
- Metrics: For You's row gains a breakdown (taste / fresh / earlier
unattributed plays), parent row stays the sum; web card renders the
sub-rows indented with the same baseline deltas + low-data dimming.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TsF3cNoKrqCYsU78cXC8U6
2a re-ranks the existing pool by TasteMatch; this ensures taste-relevant tracks
ARE in the pool. Adds a 6th arm to LoadRadioCandidatesV2: in-library tracks by
the user's top positively-weighted taste-profile artists ($10 K, weight > 0,
deterministic weight-DESC,id order so it doesn't reintroduce same-day
nondeterminism). Pool-inclusion only (sim_score 0) — TasteMatch already scores
the fit. Empty for cold-start users (no profile).
- CandidateSourceLimits.TasteOverlap; default 20 (radio), 80 for For-You via
systemForYouSourceLimits.
- You-might-like deliberately sets TasteOverlap=0: it surfaces NOT-actively-
engaged artists, so flooding its pool with top-taste (mostly already-played)
artists would just feed the read-time dedup.
- Test: positive-weight artist's track enters via the arm; negative-weight one
is excluded (weight > 0). Existing pool tests unaffected (no profile seeded).
Deferred within 2b: profile-seeded For-You — marginal given the arm + TasteMatch
already inject taste broadly (top-played seed ≈ top-taste artist).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The profile built in phase 1 now changes what gets surfaced. Adds a TasteMatch
term to the weighted-shuffle score so candidates are re-ranked by their fit to
the user's learned taste (positive draws toward it; negative reflects passive
avoidance; 0 at cold start).
- recommendation/score.go: ScoringInputs.TasteMatchScore ([-1,+1]) +
ScoringWeights.TasteWeight + the term in Score.
- recommendation/taste.go: LoadTasteProfile reads the taste_profile_* tables;
TasteProfile.Match blends the candidate's artist weight (0.7) and avg genre-tag
weight (0.3), each tanh-squashed by a fixed scale so one outlier artist can't
compress the rest. Unknown artist/tags and empty profiles → 0 (neutral).
- candidates.go: both candidate loaders set TasteMatchScore per candidate, so
every Score caller (system playlists incl. You-might-like, radio) becomes
taste-aware automatically.
- weights: systemMixWeights.TasteWeight = 1.5 (daily mixes are the primary
taste surface); config.RecommendationConfig gains taste_weight (default 1.0,
lighter — radio is seed-directed) wired into the radio handler.
- tests: pure (Match curve incl. saturation/clamp/empty-neutral, Score term
add+subtract) + DB round-trip (seed taste rows → Match positive). All green
vs real Postgres; existing playlist/radio tests unaffected (empty profile →
zero taste effect).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
scoreAndSortCandidates drew per-candidate jitter by slice position, but
the candidate query (LoadRadioCandidatesV2) has ORDER BY random() arms and
no stable outer ordering, so DB row order varies call-to-call. When the
recency spread between candidates is smaller than the ±jitter (small or
recency-clustered libraries), two same-day rebuilds assigned jitter to
different tracks and reordered near-ties — so the build was not actually
deterministic-within-a-day as documented.
Pre-existing latent flake in TestBuildSystemPlaylists_DailyNonceDeterminism
(passed in isolation / by luck in CI; deterministically reproduced when the
system-build tests run in sequence). Confirmed independent of the
You-might-like change by neutralizing buildYouMightLike — the flake
persisted.
Fix: sort the candidate slice by track id before assigning jitter, so the
jitter for a track is a function of (track, day) alone, independent of DB
return order. Verified: full playlists package green 4/4 and the build-test
sequence green 5/5 (was 0/4 before).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Surface in-library albums/artists the listener doesn't actively spin but
is predicted to enjoy, derived from the same similarity + like-weighted
candidate engine that powers For-You — rolled up from track scores to
album/artist granularity. Built in the daily 3am BuildSystemPlaylists
pass, atomic-replaced alongside the system playlists, and read back by
/api/home (+ /api/home/index).
Cold-start gate: skips generation entirely below 20 distinct unskipped
tracks AND 5 distinct artists, so a thin profile ships empty rows rather
than near-random tiles.
- migration 0034: you_might_like_albums / you_might_like_artists (id+rank,
CASCADE, per-user rank index).
- playlists/you_might_like.go: cold-start gate + similarity roll-up
(sum-of-top-3 aggregation, per-artist album cap, daily-rotating via the
same userIDHash jitter as For-You) + atomic-replace persist in the tx.
- recommendation/home.go: two new HomePayload sections with read-time
cross-section dedup vs Most Played / Rediscover / Last Played, trimmed
to 10 each.
- api: you_might_like_albums / you_might_like_artists on /api/home and
/api/home/index, reusing albumRefFrom / artistRefFromCovered.
- tests: pure roll-up/aggregation/cap unit tests + DB-backed gate,
sufficiency, and atomic-replace tests (all green vs real Postgres).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The five discovery-mix producers (Deep Cuts, Rediscover, New for you,
On this day, First listens) were near-identical boilerplate that
differed only in (a) which SQL query they ran and (b) whether to
diversity-cap the result. Folded into one produceDiscoveryMix(spec)
factory + a per-mix discoveryMixSpec slice. The registry composes the
factory over the spec list so adding a new mix is one struct literal
+ a SQL query, never a new func.
Also fixes the user-reported bug that several mixes 'show the same
content from yesterday'. Audit of the SQL queries:
- Deep Cuts: ORDER BY md5(t.id::text || $2::text) → day-keyed
- On this day: ORDER BY w.c DESC, md5(...) → day-keyed
- Rediscover: ORDER BY tier, c DESC, id → invariant
- New for you: ORDER BY al.created_at DESC, disc, track → invariant
- First listens: ORDER BY tier, al.id, disc, track → invariant
The three invariant ones produced identical content day-over-day. The
unified spec carries a dailyRotate bool: when set, the producer
applies a daily-deterministic offset rotate-left of the candidate
pool BEFORE diversify+truncate. Rotation (not shuffle) preserves
contiguous-block ordering inside each day's slice — matters for First
listens which is album-coherent.
Set on Rediscover + First listens (where same-content-every-day is
clearly a bug). Left off New for you because 'newest album first
regardless of day' is the intended UX for that surface — daily
rotation there would feel wrong.
Daily rotation seed: rand.New(NewSource(int64(userIDHash(userID,
dateStr)))) — same primitive used by For-You's pickHeadAndTail
sampling so behavior is consistent across the system playlist family.
No test file referenced the deleted produceXxx functions directly,
only the registry, so this is a closed refactor.
For-You silently vanished after ~7 days of not listening (seed query
required a non-skip play in the last 7 days) and capped at ~40 on
self-hosted libraries with no ListenBrainz similarity data.
- PickTopPlayedTracksForUser: tiered seed — last 30d top plays, else
all-time top plays, else liked tracks. For-You only disappears now
if the account has zero plays AND zero likes.
- produceForYou uses deeper candidate source limits (raised random/
tag/similar K) so it reaches ~100 even with empty lb_similar /
similar_artists; richer when LB enrichment is present.
- Rediscover: tiered — 6-month-dormant, else ≥5-play 30-day-dormant.
- On This Day: floor 60→30 days, window ±7→±10 doy; still skips
cleanly (no rows → no playlist) on insufficient history.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Each is one candidate query + one registry entry; zero client work
(R2 made tiles/refresh/shuffle generic, all are singleton kinds so
web's server `refreshable` flag and Flutter's derived getter both
light up automatically).
- deep_cuts (#419): <=2-play tracks from liked / heavily-played
artists; diversity-capped.
- rediscover (#420): >=5-play tracks not heard in 6 months, by
historical affection.
- new_for_you (#421): tracks from albums added <=30d whose artist
the user likes/plays; album-coherent (no cap).
- on_this_day (#422): tracks played within ±7 day-of-year in prior
windows (>60d ago), weighted by play count.
- first_listens (#423): never-played albums, tiered liked-artist →
played-artist → rest; album-coherent.
system_mixes.go producers mirror the Discover model (SQL gives the
ranking; finishMix caps+truncates to 100 to match For-You/Discover
shuffle depth; album-coherent mixes skip the cap). Builder query
failure is non-fatal (logged, yields no playlist) like Discover.
Existing system_test existence checks are unaffected.
Closes the #411 system-playlists-v2 umbrella's new-types thread.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Replaces the per-kind refresh/shuffle handlers with one generic
pair driven off the kind registry, in lockstep across both clients.
Server:
- systemPlaylistKind gains Singleton; RefreshableSystemKind(key)
exported. for_you/discover singleton; songs_like_artist not.
- New generic POST /api/playlists/system/{kind}/refresh and
GET /api/playlists/system/{kind}/shuffle ({kind} = raw
system_variant). Non-singleton/unknown kind → 404. Deleted
playlists_{foryou,discover}_refresh.go and the per-kind shuffle
wrappers; serveSystemPlaylistShuffle core kept.
- playlistRowView.refreshable: server-derived flag so clients show
the refresh affordance generically without hardcoding kinds.
Web (not drift-cached → uses the server flag):
- refreshSystem(variant) replaces refreshForYou/refreshDiscover;
systemShuffle drops the for_you→for-you mapping (raw variant).
- PlaylistCard + detail page gate the kebab/Refresh button on
playlist.refreshable; label is "Refresh {name}". Tests reworked;
obsolete refresh-foryou/discover api tests deleted.
Flutter (list tiles are drift-cache-sourced → derive, no migration):
- Playlist.refreshable getter = isSystem && variant !=
songs_like_artist (holds for all current + planned kinds).
- refreshSystem/systemShuffle use the raw variant; PlaylistCard +
detail screen gate kebab/Regenerate/source-tagging on refreshable
so songs_like_artist plays via get() (no by-kind endpoint).
Pure-plumbing refactor; CI verifies parity. Next (R3): the five
discovery mixes — each a candidate query + one registry entry.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
revive unused-parameter: produceDiscover keys off dateStr, not now,
but must keep the uniform systemPlaylistProducer signature. Blank
the unused param (param names don't affect func-type identity).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Behavior-preserving prep for the new mix types. Extracts the three
inline candidate computations in BuildSystemPlaylists into
producers (produceForYou / produceSeedMixes / produceDiscover) and
drives the build off a systemPlaylistRegistry. The shared
machinery (run-claim guard, atomic delete+insert tx, post-commit
collages) is now generic over a []builtPlaylist.
Fatal-vs-skip error semantics unchanged: a base query failure
(PickTopPlayedTracksForUser, PickSeedArtists) still aborts the
whole build; candidate-load / per-seed-artist / Discover-bucket
failures are still logged and just yield fewer playlists.
Materialize order (for_you, songs_like_artist, discover) is
unchanged and functionally irrelevant.
No API/client/schema change — CI's system/foryou/service tests
verify For You / Songs-like-X / Discover parity. Adding a new mix
is now: a producer + one registry entry + its candidate query.
Next (R2): generic /api/playlists/system/{kind}/{refresh,shuffle}
off the registry; then the new kinds.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Closes Fable #414. forYouHeadN/forYouTailN go 12/13 → 50/50 so the
For-You snapshot is 100 tracks, matching Discover. Motivated by the
shuffle-on-play default that just shipped (#413): a 25-track shuffle
pool repeats fast; 100 makes re-plays within a day feel varied.
pickHeadAndTail already degrades gracefully when the candidate pool
is too thin for a full head/tail split (returns top-N-by-score),
mirroring how Discover returns <100 when its buckets are thin — no
new edge-case handling needed. No build-path test asserts the
For-You total; pickHeadAndTail unit tests pass their own head/tail
values so they're unaffected.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Five diversity mechanics — applied to both For-You and Songs-Like-X.
1. For-You seed rotates daily across the user's top-5 most-played
tracks. pickForYouSeedForDay uses userIDHash(user, day) mod
len(seeds) so today's mix uses an entirely different similarity
pool than tomorrow's. Within-day determinism preserved.
2. JitterMagnitude bumped 0.0 → 0.1. The scoring RNG is now seeded
by userIDHash(user, day) rather than the no-op, so near-tied
candidates shuffle daily without breaking within-day stability.
3. Head/tail split moves from 20+5 to 12+13. Roughly half the
playlist comes from the tail now (daily-deterministic via
tieBreakHash), giving the user substantially different content
while a 12-track anchor of strong similarity matches keeps the
mix recognizable.
4. Songs-Like-X seed artists shuffle daily across the user's top-5
played artists. pickSeedArtistsForDay applies a userIDHash-seeded
Fisher-Yates and takes 3.
5. scoreAndSortCandidates / pickTopN / pickHeadAndTail gain a userID
parameter so the RNG can be seeded per-user; existing call sites
updated; noopRNG removed.
Test fixtures widened similarity gaps (e.g. float64(50-i) instead of
(50-i)/50) so the new jitter (±0.1) doesn't perturb head ordering in
assertions about the head/tail mechanism. New seed_selection_test
coverage for userIDHash + pickForYouSeedForDay + pickSeedArtistsForDay
spans deterministic-within-day, varies-across-days, and graceful
degradation with small candidate pools.
PickTopPlayedTrackForUser replaced by PickTopPlayedTracksForUser
:many in the prior commit (b4801c2). The For-You seed lookup now
goes through pickForYouSeedForDay over the returned slice.
PickSeedArtists's LIMIT widened to 5 in the same prior commit.
For #392 Half A — system playlist content diversity. Half B
(per-user timezone scheduling) is a separate spec.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The cross-user bucket query combined SELECT DISTINCT with ORDER BY md5(...),
which Postgres rejects at plan time (SQLSTATE 42P10). buildDiscoverCandidates
returned that error on first bucket failure, so the whole Discover playlist
was skipped every nightly run — even though the random bucket pool was
healthy. Switched to GROUP BY so the md5 ordering expression no longer needs
to appear in the select list, and hardened the function so future single-
bucket failures degrade gracefully via slot redistribution instead of taking
out the whole playlist.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Two real algorithm bugs in F-T1's For-You composition + Discover
allocator. Both surfaced as failing unit tests under go test -race.
1. redistributeSlots was re-redistributing a bucket's full deficit
on every pass instead of just the residual. The loop computed
`deficit = b.want - final[i]` each iteration, but final[i] for
a deficit bucket never increases (its supply is exhausted), so
pass N saw the same deficit as pass N-1 and kept shoveling it
to peers. For [want:40 avail:100, want:30 avail:0, want:30 avail:100],
four passes pushed cross-user's deficit into dormant+random four
times each, hitting the 100-slot clamp at the end and producing
[50, 0, 50] instead of the spec'd [55, 0, 45].
Fix: track per-source `redistributed[i]` and subtract it from the
deficit each pass. Multi-pass behavior still works for the case
where a peer's supply runs out mid-distribution.
2. tieBreakHash used FNV-1a 64-bit with trackID + dateStr appended.
For dateStrs differing only in the last character ("2026-05-07"
vs "2026-05-08"), the FNV state diverged only in low bits at the
final byte; multiplication by FNV_prime propagates upward but the
relative ordering of 60 small candidate UUIDs (which differ only
in their last byte) ended up identical across the two dates. The
For-You head/tail test asserted that the tail's first 5 should
change across days; it didn't.
Fix: switch to SHA-256 truncated to 8 bytes. SHA-256 has full
avalanche, so any single-bit input change roughly half-flips the
output bits and meaningfully reorders.
The hash isn't security-load-bearing; we just need strong avalanche
for tiny dateStr deltas. Determinism (same inputs → same output) is
preserved.
Two improvements to the system playlist builder:
1. Per-artist (<=3) and per-album (<=2) caps applied to the
pickTopN truncation step, using the same numeric caps Discover
already enforces. Both For-You and Songs-like-X benefit. Same
skewed candidate pool no longer collapses to "10 tracks from
the same artist" — the playlist always carries at least 9
distinct artists in 25 slots.
2. New pickHeadAndTail function for For-You: 20 top-similarity
tracks + 5 sampled from the tail (positions 2*headN onward of
the score-sorted, cap-applied pool). Tail sampling uses
tieBreakHash for daily determinism — same user same day still
sees the same playlist, but the daily refresh feels less
stuck-in-a-rut. Tail tracks are still similarity-related
(they passed the similarity candidate filter) so the user
should enjoy them, just from artists they wouldn't have surfaced
via strict top-N ranking.
Songs-like-X keeps the simple pickTopN call — the seed-artist
context already provides the "you'll like this" framing without
needing a tail injection.
Refactors pickTopN internals: now sorts candidates first via
scoreAndSortCandidates, applies the cap on []Candidate via
capCandidatesByAlbumAndArtist, and truncates. Removes the now-
dead stableSortByScoreThenHash helper (only used in old pickTopN).
The cap helper mirrors capByAlbumAndArtist in discover.go but
operates on recommendation.Candidate so it sees Track.AlbumID /
Track.ArtistID directly.
Tests cover the cap helper truth table, head+tail split with
small/large pools, buffer-zone exclusion, daily determinism, and
cross-day tail variance.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds the third system playlist variant: 'discover'. Surfaces 100
tracks the operator has not played and not liked, biased toward
artists they rarely play (< 10 plays) and complemented by tracks
liked by other users plus a random unheard sample. Cold start
collapses to all-random; single-user servers redistribute the
cross-user-likes allocation equally across the other two buckets.
The build runs as a fourth phase inside BuildSystemPlaylists
alongside For You and the seed-artist mixes. Same daily-deterministic
md5(track_id || dateStr) ordering as the other variants. Per-album
(<=2) and per-artist (<=3) caps prevent collapse onto a single
prolific artist. Buckets interleave round-robin so the playlist
order doesn't front-load one bucket's flavour.
Post-commit collage generation (already wired) gives Discover the
same 4-cell cover treatment as the other system playlists — no
new collage code needed.
Tests cover the slot-redistribution table (all-available,
cold-start, single-user, partial-dormant, fully-empty), the
per-album/per-artist caps, the round-robin interleave, and a
DB-backed cold-start integration test that asserts a Discover
playlist lands with non-zero tracks.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
System-generated playlists ("For You", "Songs like X") rendered with
empty placeholder boxes in the UI even when their contributing tracks
had album art. The build path inserted playlist rows directly without
ever invoking the existing playlists.GenerateCollage machinery —
that was only wired into user-edited playlist mutations.
After this change, BuildSystemPlaylists generates a 4-cell collage
for every system playlist it creates, post-commit. Same cover
mechanism user playlists use, same on-disk layout
(<DataDir>/playlist_covers/<id>.jpg). Cells whose source album lacks
art fall back to the FabledSword glyph, so a partially-covered
library still produces a sensible visual.
Threading: BuildSystemPlaylists, StartSystemPlaylistCron, and the
api lazy-build path all gain a dataDir string parameter; main.go
passes cfg.Storage.DataDir.
Drops the now-redundant PickTopAlbumCoverForArtistByUser lookup —
the collage is more visually informative than a single album cover
copy, and the seed-artist's top album is one of the contributing
tracks in the mix anyway, so it'll appear as one of the four cells.
Tests pass t.TempDir() for the dataDir parameter.
- gofmt -s on system.go, system_cron.go, api.go
- rename unused r → _ in 3 fetcher_test.go HTTP handlers
- TrackRow +queue test uses /add .* to queue/i (track-aware aria-label from #377)
- /library/artists page test mocks likes + tanstack-query (ArtistCard now embeds LikeButton)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen