feat(phase-16): anonymous play & share telemetry substrate (wave 16.1)

Player-service play-session tracker (floor + 3-bucket classify), SharePopover share tracker with debounce, sendBeacon interop, proxied rate-limited POST api/event/{play,share}, append-only event logs + incremental play_counter with server-side release resolution. Migration authored, not applied. No anonId, no read surface.

DeepDrftAPI/Controllers/EventController.cs

@@ -0,0 +1,82 @@
+using DeepDrftData;
+using DeepDrftModels.DTOs;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.RateLimiting;
+
+namespace DeepDrftAPI.Controllers;
+
+/// <summary>
+/// Anonymous play/share telemetry intake (Phase 16 §2.2 / §4.3). Unauthenticated — same posture as the
+/// public reads — but IP rate-limited (the "events" limiter, registered in Program.cs) and payload-
+/// validated to make casual inflation annoying (§2.5). Both endpoints return <c>202 Accepted</c>: these
+/// are fire-and-forget telemetry, not transactions, and the client (a <c>sendBeacon</c>) never reads the
+/// response. The release dimension on a play is resolved server-side from the track key (§2.3 / D4).
+/// The controller is a thin HTTP boundary; all write logic lives in <see cref="IEventService"/>.
+/// </summary>
+[ApiController]
+[Route("api/event")]
+[EnableRateLimiting("events")]
+public class EventController : ControllerBase
+{
+    // Reject oversized bodies before deserialization — a coarse abuse guard (§2.5). The legitimate
+    // payloads are a track key + an enum, well under 1 KB.
+    private const int MaxBodyBytes = 1024;
+
+    private readonly IEventService _eventService;
+    private readonly ILogger<EventController> _logger;
+
+    public EventController(IEventService eventService, ILogger<EventController> logger)
+    {
+        _eventService = eventService;
+        _logger = logger;
+    }
+
+    // POST api/event/play (unauthenticated, rate-limited)
+    [HttpPost("play")]
+    [RequestSizeLimit(MaxBodyBytes)]
+    public async Task<ActionResult> RecordPlay([FromBody] PlayEventDto payload, CancellationToken ct = default)
+    {
+        // Reject a missing track key and an out-of-range bucket (§2.5). [ApiController] model binding
+        // already 400s a malformed/oversized body and an undefined enum value, but the explicit guards
+        // keep the contract obvious and cover the empty-string key the model binder lets through.
+        if (string.IsNullOrWhiteSpace(payload.TrackEntryKey))
+            return BadRequest("trackEntryKey is required");
+        if (!Enum.IsDefined(payload.Bucket))
+            return BadRequest("bucket is invalid");
+
+        // Wave 16.1 writes no anonId — defend the substrate by dropping any the client sends early.
+        var result = await _eventService.RecordPlay(payload.TrackEntryKey, payload.Bucket, anonId: null, ct);
+        if (!result.Success)
+        {
+            // A telemetry failure must never surface to the listener as an error they can act on, but
+            // we still log it and answer 5xx so a monitor can see the substrate is unhealthy. The
+            // beacon ignores the status either way.
+            _logger.LogWarning("RecordPlay failed: {Error}", result.Messages.FirstOrDefault()?.Message);
+            return StatusCode(500);
+        }
+
+        return Accepted();
+    }
+
+    // POST api/event/share (unauthenticated, rate-limited)
+    [HttpPost("share")]
+    [RequestSizeLimit(MaxBodyBytes)]
+    public async Task<ActionResult> RecordShare([FromBody] ShareEventDto payload, CancellationToken ct = default)
+    {
+        if (string.IsNullOrWhiteSpace(payload.TargetKey))
+            return BadRequest("targetKey is required");
+        if (!Enum.IsDefined(payload.TargetType))
+            return BadRequest("targetType is invalid");
+        if (!Enum.IsDefined(payload.Channel))
+            return BadRequest("channel is invalid");
+
+        var result = await _eventService.RecordShare(payload.TargetType, payload.TargetKey, payload.Channel, anonId: null, ct);
+        if (!result.Success)
+        {
+            _logger.LogWarning("RecordShare failed: {Error}", result.Messages.FirstOrDefault()?.Message);
+            return StatusCode(500);
+        }
+
+        return Accepted();
+    }
+}

DeepDrftAPI/Program.cs

@@ -8,8 +8,10 @@ using DeepDrftData;
 using DeepDrftData.Data;
 using DeepDrftData.Repositories;
 using Microsoft.AspNetCore.HttpOverrides;
+using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.EntityFrameworkCore;
 using NetBlocks.Utilities.Environment;
+using System.Threading.RateLimiting;
 
 // Required credential files — must exist before the app will start.
 // Production secrets stay gitignored; the *.example.json templates at the project root show the shape.
@@ -64,6 +66,14 @@ builder.Services
     .AddScoped<ITrackService>(sp => sp.GetRequiredService<TrackManager>());
 builder.Services.AddScoped<UnifiedTrackService>();
 
+// Phase 16 anonymous telemetry — append-only event logs + incremental play-counter rollup (all SQL).
+// EventManager is the IEventService boundary; EventRepository owns the EF writes and the
+// release-resolution + counter-bump transaction.
+builder.Services
+    .AddScoped<EventRepository>()
+    .AddScoped<EventManager>()
+    .AddScoped<IEventService>(sp => sp.GetRequiredService<EventManager>());
+
 // Release domain — medium-aware read projection + satellite metadata writes. ReleaseManager is the
 // IReleaseService implementation; UnifiedReleaseService orchestrates the vault + SQL satellite writes.
 builder.Services
@@ -118,6 +128,25 @@ builder.Services.Configure<ForwardedHeadersOptions>(options =>
     options.KnownProxies.Clear();
 });
 
+// Per-IP rate limiting for the anonymous telemetry intake (Phase 16 §2.5). Coarse and stateless —
+// a fixed window keyed by the (forwarded) remote IP. The substrate sits behind nginx, so the real
+// client IP is the X-Forwarded-For value UseForwardedHeaders resolves into Connection.RemoteIpAddress.
+// On limit, reject with 429 (the beacon ignores it; this only blunts casual inflation). The 30-window
+// budget is generous for a real listening session and only bites on scripted spam.
+builder.Services.AddRateLimiter(options =>
+{
+    options.RejectionStatusCode = StatusCodes.Status429TooManyRequests;
+    options.AddPolicy("events", httpContext =>
+        RateLimitPartition.GetFixedWindowLimiter(
+            partitionKey: httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown",
+            factory: _ => new FixedWindowRateLimiterOptions
+            {
+                PermitLimit = 30,
+                Window = TimeSpan.FromMinutes(1),
+                QueueLimit = 0,
+            }));
+});
+
 var app = builder.Build();
 
 // Apply AuthBlocks EF migrations, seed system roles, seed admin user on first boot.
@@ -136,6 +165,11 @@ if (app.Environment.IsDevelopment())
 
 app.UseCors("ContentApiPolicy");
 
+// Rate limiter must sit in the pipeline for the [EnableRateLimiting("events")] attribute on
+// EventController to take effect. Only the telemetry endpoints carry the policy; everything else is
+// unaffected (no global limiter is set).
+app.UseRateLimiter();
+
 // ApiKey middleware only enforces on endpoints tagged [ApiKeyAuthorize] (the track surface); it
 // passes all other endpoints through. JWT auth/authorization gate the AuthBlocks endpoints, which
 // carry no [ApiKeyAuthorize] metadata — the two schemes are orthogonal and do not interfere.

DeepDrftData/Data/Configurations/PlayCounterConfiguration.cs

@@ -0,0 +1,47 @@
+using DeepDrftModels.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace DeepDrftData.Data.Configurations;
+
+/// <summary>
+/// EF configuration for the <c>play_counter</c> rollup (Phase 16 §4.1 / D6). One row per track, unique
+/// on track_id so the incremental-on-write bump is an upsert against a single row. <c>TotalPlays</c> is
+/// a computed C# property (sum of the three bucket columns) and is not mapped — it is derived on read.
+/// </summary>
+public class PlayCounterConfiguration : IEntityTypeConfiguration<PlayCounter>
+{
+    public void Configure(EntityTypeBuilder<PlayCounter> builder)
+    {
+        builder.ToTable("play_counter");
+
+        builder.HasKey(e => e.Id);
+        builder.Property(e => e.Id).HasColumnName("id");
+
+        builder.Property(e => e.TrackId)
+            .IsRequired()
+            .HasColumnName("track_id");
+
+        builder.Property(e => e.PartialCount)
+            .IsRequired()
+            .HasDefaultValue(0L)
+            .HasColumnName("partial_count");
+
+        builder.Property(e => e.SampledCount)
+            .IsRequired()
+            .HasDefaultValue(0L)
+            .HasColumnName("sampled_count");
+
+        builder.Property(e => e.CompleteCount)
+            .IsRequired()
+            .HasDefaultValue(0L)
+            .HasColumnName("complete_count");
+
+        // Derived headline figure — never a column.
+        builder.Ignore(e => e.TotalPlays);
+
+        builder.HasIndex(e => e.TrackId)
+            .IsUnique()
+            .HasDatabaseName("IX_play_counter_track_id");
+    }
+}

DeepDrftData/Data/Configurations/PlayEventConfiguration.cs

@@ -0,0 +1,49 @@
+using DeepDrftModels.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace DeepDrftData.Data.Configurations;
+
+/// <summary>
+/// EF configuration for the append-only <c>play_event</c> log (Phase 16 §4.2). Plain entity, not a
+/// <c>BaseEntity</c> — no soft-delete or updated_at, just an immutable fact with a created_at stamp.
+/// Indexed on track key, release id, and anon id (the last reserved for the wave-16.3 distinct-listener
+/// query) so the aggregation paths stay cheap as the log grows.
+/// </summary>
+public class PlayEventConfiguration : IEntityTypeConfiguration<PlayEvent>
+{
+    public void Configure(EntityTypeBuilder<PlayEvent> builder)
+    {
+        builder.ToTable("play_event");
+
+        builder.HasKey(e => e.Id);
+        builder.Property(e => e.Id).HasColumnName("id");
+
+        builder.Property(e => e.TrackEntryKey)
+            .IsRequired()
+            .HasMaxLength(100)
+            .HasColumnName("track_entry_key");
+
+        builder.Property(e => e.ReleaseId)
+            .HasColumnName("release_id");
+
+        builder.Property(e => e.Bucket)
+            .IsRequired()
+            .HasConversion<string>()   // Store the readable bucket name, mirroring ReleaseMedium.
+            .HasMaxLength(20)
+            .HasColumnName("bucket");
+
+        // Reserved nullable token (wave 16.3). Same width as a stringified GUID.
+        builder.Property(e => e.AnonId)
+            .HasMaxLength(64)
+            .HasColumnName("anon_id");
+
+        builder.Property(e => e.CreatedAt)
+            .IsRequired()
+            .HasColumnName("created_at");
+
+        builder.HasIndex(e => e.TrackEntryKey).HasDatabaseName("IX_play_event_track_entry_key");
+        builder.HasIndex(e => e.ReleaseId).HasDatabaseName("IX_play_event_release_id");
+        builder.HasIndex(e => e.AnonId).HasDatabaseName("IX_play_event_anon_id");
+    }
+}

DeepDrftData/Data/Configurations/ShareEventConfiguration.cs

@@ -0,0 +1,48 @@
+using DeepDrftModels.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace DeepDrftData.Data.Configurations;
+
+/// <summary>
+/// EF configuration for the append-only <c>share_event</c> log (Phase 16 §4.2). Plain immutable-fact
+/// entity. Indexed on the target key so per-target share tallies stay cheap.
+/// </summary>
+public class ShareEventConfiguration : IEntityTypeConfiguration<ShareEvent>
+{
+    public void Configure(EntityTypeBuilder<ShareEvent> builder)
+    {
+        builder.ToTable("share_event");
+
+        builder.HasKey(e => e.Id);
+        builder.Property(e => e.Id).HasColumnName("id");
+
+        builder.Property(e => e.TargetType)
+            .IsRequired()
+            .HasConversion<string>()
+            .HasMaxLength(20)
+            .HasColumnName("target_type");
+
+        builder.Property(e => e.TargetKey)
+            .IsRequired()
+            .HasMaxLength(100)
+            .HasColumnName("target_key");
+
+        builder.Property(e => e.Channel)
+            .IsRequired()
+            .HasConversion<string>()
+            .HasMaxLength(20)
+            .HasColumnName("channel");
+
+        builder.Property(e => e.AnonId)
+            .HasMaxLength(64)
+            .HasColumnName("anon_id");
+
+        builder.Property(e => e.CreatedAt)
+            .IsRequired()
+            .HasColumnName("created_at");
+
+        builder.HasIndex(e => e.TargetKey).HasDatabaseName("IX_share_event_target_key");
+        builder.HasIndex(e => e.AnonId).HasDatabaseName("IX_share_event_anon_id");
+    }
+}

DeepDrftData/Data/DeepDrftContext.cs

@@ -15,6 +15,12 @@ public class DeepDrftContext : DbContext
     public DbSet<SessionMetadata> SessionMetadata { get; set; }
     public DbSet<MixMetadata> MixMetadata { get; set; }
 
+    // Phase 16 anonymous telemetry: append-only event logs + incremental play rollup. All SQL — the
+    // FileDatabase vault is not involved.
+    public DbSet<PlayEvent> PlayEvents { get; set; }
+    public DbSet<ShareEvent> ShareEvents { get; set; }
+    public DbSet<PlayCounter> PlayCounters { get; set; }
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         base.OnModelCreating(modelBuilder);
@@ -23,5 +29,8 @@ public class DeepDrftContext : DbContext
         modelBuilder.ApplyConfiguration(new ReleaseConfiguration());
         modelBuilder.ApplyConfiguration(new SessionMetadataConfiguration());
         modelBuilder.ApplyConfiguration(new MixMetadataConfiguration());
+        modelBuilder.ApplyConfiguration(new PlayEventConfiguration());
+        modelBuilder.ApplyConfiguration(new ShareEventConfiguration());
+        modelBuilder.ApplyConfiguration(new PlayCounterConfiguration());
     }
 }

DeepDrftData/EventManager.cs

@@ -0,0 +1,56 @@
+using DeepDrftData.Repositories;
+using DeepDrftModels.Enums;
+using Microsoft.Extensions.Logging;
+using NetBlocks.Models;
+
+namespace DeepDrftData;
+
+/// <summary>
+/// <see cref="IEventService"/> implementation over <see cref="EventRepository"/>. The layer boundary
+/// matches the rest of DeepDrftData: the repository owns the EF constructs and the write transaction;
+/// this service catches at the boundary and returns a NetBlocks <see cref="Result"/>. Telemetry is
+/// best-effort by design (§2.2) — a failed write is logged and surfaced as a fail result, never thrown
+/// at the caller, so a telemetry hiccup can never reach a listener.
+/// </summary>
+public class EventManager : IEventService
+{
+    private readonly EventRepository _repository;
+    private readonly ILogger<EventManager> _logger;
+
+    public EventManager(EventRepository repository, ILogger<EventManager> logger)
+    {
+        _repository = repository;
+        _logger = logger;
+    }
+
+    public async Task<Result> RecordPlay(
+        string trackEntryKey, PlayBucket bucket, string? anonId = null, CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            await _repository.RecordPlayAsync(trackEntryKey, bucket, anonId, cancellationToken);
+            return Result.CreatePassResult();
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to record play event for track {TrackEntryKey}", trackEntryKey);
+            return Result.CreateFailResult(e.Message);
+        }
+    }
+
+    public async Task<Result> RecordShare(
+        ShareTargetType targetType, string targetKey, ShareChannel channel, string? anonId = null,
+        CancellationToken cancellationToken = default)
+    {
+        try
+        {
+            await _repository.RecordShareAsync(targetType, targetKey, channel, anonId, cancellationToken);
+            return Result.CreatePassResult();
+        }
+        catch (Exception e)
+        {
+            _logger.LogError(e, "Failed to record share event for {TargetType} {TargetKey}", targetType, targetKey);
+            return Result.CreateFailResult(e.Message);
+        }
+    }
+}

DeepDrftData/IEventService.cs

@@ -0,0 +1,23 @@
+using DeepDrftModels.Enums;
+using NetBlocks.Models;
+
+namespace DeepDrftData;
+
+/// <summary>
+/// SQL-side anonymous telemetry service (Phase 16). Records play and share events to the append-only
+/// logs and maintains the incremental play-counter rollup. The release dimension on a play is resolved
+/// server-side from the track key (§2.3 / D4) — callers pass only what the client cheaply knows.
+/// Returns NetBlocks <see cref="Result"/> at the boundary; the controller maps that to 202/4xx/5xx.
+/// </summary>
+public interface IEventService
+{
+    /// <summary>
+    /// Record one play: append a <c>play_event</c> row (release resolved from the track key) and bump
+    /// the track's <c>play_counter</c> in the same transaction. A play of an unknown/removed track key
+    /// still logs (with a null release and no counter bump) rather than failing.
+    /// </summary>
+    Task<Result> RecordPlay(string trackEntryKey, PlayBucket bucket, string? anonId = null, CancellationToken cancellationToken = default);
+
+    /// <summary>Record one share: append a <c>share_event</c> row. Target and channel come straight from the client.</summary>
+    Task<Result> RecordShare(ShareTargetType targetType, string targetKey, ShareChannel channel, string? anonId = null, CancellationToken cancellationToken = default);
+}

DeepDrftData/Migrations/20260619155610_AddPlayShareTelemetry.Designer.cs

@@ -0,0 +1,457 @@
+// <auto-generated />
+using System;
+using DeepDrftData.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace DeepDrftData.Migrations
+{
+    [DbContext(typeof(DeepDrftContext))]
+    [Migration("20260619155610_AddPlayShareTelemetry")]
+    partial class AddPlayShareTelemetry
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.7")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("DeepDrftModels.Entities.MixMetadata", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<bool>("IsDeleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false)
+                        .HasColumnName("is_deleted");
+
+                    b.Property<long>("ReleaseId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("release_id");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated_at");
+
+                    b.Property<string>("WaveformEntryKey")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("character varying(500)")
+                        .HasColumnName("waveform_entry_key");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("IsDeleted")
+                        .HasDatabaseName("IX_mix_metadata_is_deleted");
+
+                    b.HasIndex("ReleaseId")
+                        .IsUnique()
+                        .HasDatabaseName("IX_mix_metadata_release_id");
+
+                    b.ToTable("mix_metadata", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.PlayCounter", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<long>("CompleteCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("complete_count");
+
+                    b.Property<long>("PartialCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("partial_count");
+
+                    b.Property<long>("SampledCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("sampled_count");
+
+                    b.Property<long>("TrackId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("track_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TrackId")
+                        .IsUnique()
+                        .HasDatabaseName("IX_play_counter_track_id");
+
+                    b.ToTable("play_counter", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.PlayEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("AnonId")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)")
+                        .HasColumnName("anon_id");
+
+                    b.Property<string>("Bucket")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("bucket");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<long?>("ReleaseId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("release_id");
+
+                    b.Property<string>("TrackEntryKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("track_entry_key");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AnonId")
+                        .HasDatabaseName("IX_play_event_anon_id");
+
+                    b.HasIndex("ReleaseId")
+                        .HasDatabaseName("IX_play_event_release_id");
+
+                    b.HasIndex("TrackEntryKey")
+                        .HasDatabaseName("IX_play_event_track_entry_key");
+
+                    b.ToTable("play_event", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.ReleaseEntity", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("Artist")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)")
+                        .HasColumnName("artist");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<long?>("CreatedByUserId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("created_by_user_id");
+
+                    b.Property<string>("Description")
+                        .HasMaxLength(4000)
+                        .HasColumnType("character varying(4000)")
+                        .HasColumnName("description");
+
+                    b.Property<string>("EntryKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("entry_key");
+
+                    b.Property<string>("Genre")
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("genre");
+
+                    b.Property<string>("ImagePath")
+                        .HasMaxLength(500)
+                        .HasColumnType("character varying(500)")
+                        .HasColumnName("image_path");
+
+                    b.Property<bool>("IsDeleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false)
+                        .HasColumnName("is_deleted");
+
+                    b.Property<string>("Medium")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Cut")
+                        .HasColumnName("medium");
+
+                    b.Property<DateOnly?>("ReleaseDate")
+                        .HasColumnType("date")
+                        .HasColumnName("release_date");
+
+                    b.Property<string>("ReleaseType")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Single")
+                        .HasColumnName("release_type");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)")
+                        .HasColumnName("title");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("EntryKey")
+                        .IsUnique()
+                        .HasDatabaseName("IX_release_entry_key");
+
+                    b.HasIndex("IsDeleted")
+                        .HasDatabaseName("IX_release_is_deleted");
+
+                    b.HasIndex("Title", "Artist")
+                        .IsUnique()
+                        .HasDatabaseName("IX_release_title_artist")
+                        .HasFilter("\"is_deleted\" = false");
+
+                    b.ToTable("release", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.SessionMetadata", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("HeroImageEntryKey")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("character varying(500)")
+                        .HasColumnName("hero_image_entry_key");
+
+                    b.Property<bool>("IsDeleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false)
+                        .HasColumnName("is_deleted");
+
+                    b.Property<long>("ReleaseId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("release_id");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("IsDeleted")
+                        .HasDatabaseName("IX_session_metadata_is_deleted");
+
+                    b.HasIndex("ReleaseId")
+                        .IsUnique()
+                        .HasDatabaseName("IX_session_metadata_release_id");
+
+                    b.ToTable("session_metadata", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.ShareEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("AnonId")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)")
+                        .HasColumnName("anon_id");
+
+                    b.Property<string>("Channel")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("channel");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("TargetKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("target_key");
+
+                    b.Property<string>("TargetType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("target_type");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AnonId")
+                        .HasDatabaseName("IX_share_event_anon_id");
+
+                    b.HasIndex("TargetKey")
+                        .HasDatabaseName("IX_share_event_target_key");
+
+                    b.ToTable("share_event", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.TrackEntity", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<double?>("DurationSeconds")
+                        .HasColumnType("double precision")
+                        .HasColumnName("duration_seconds");
+
+                    b.Property<string>("EntryKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("entry_key");
+
+                    b.Property<bool>("IsDeleted")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false)
+                        .HasColumnName("is_deleted");
+
+                    b.Property<string>("OriginalFileName")
+                        .HasMaxLength(500)
+                        .HasColumnType("character varying(500)")
+                        .HasColumnName("original_file_name");
+
+                    b.Property<long?>("ReleaseId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("release_id");
+
+                    b.Property<string>("TrackName")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)")
+                        .HasColumnName("track_name");
+
+                    b.Property<int>("TrackNumber")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer")
+                        .HasDefaultValue(1)
+                        .HasColumnName("track_number");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("IsDeleted")
+                        .HasDatabaseName("IX_track_is_deleted");
+
+                    b.HasIndex("ReleaseId");
+
+                    b.ToTable("track", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.MixMetadata", b =>
+                {
+                    b.HasOne("DeepDrftModels.Entities.ReleaseEntity", "Release")
+                        .WithOne("MixMetadata")
+                        .HasForeignKey("DeepDrftModels.Entities.MixMetadata", "ReleaseId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Release");
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.SessionMetadata", b =>
+                {
+                    b.HasOne("DeepDrftModels.Entities.ReleaseEntity", "Release")
+                        .WithOne("SessionMetadata")
+                        .HasForeignKey("DeepDrftModels.Entities.SessionMetadata", "ReleaseId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Release");
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.TrackEntity", b =>
+                {
+                    b.HasOne("DeepDrftModels.Entities.ReleaseEntity", "Release")
+                        .WithMany("Tracks")
+                        .HasForeignKey("ReleaseId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("Release");
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.ReleaseEntity", b =>
+                {
+                    b.Navigation("MixMetadata");
+
+                    b.Navigation("SessionMetadata");
+
+                    b.Navigation("Tracks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

DeepDrftData/Migrations/20260619155610_AddPlayShareTelemetry.cs

@@ -0,0 +1,110 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace DeepDrftData.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddPlayShareTelemetry : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "play_counter",
+                columns: table => new
+                {
+                    id = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    track_id = table.Column<long>(type: "bigint", nullable: false),
+                    partial_count = table.Column<long>(type: "bigint", nullable: false, defaultValue: 0L),
+                    sampled_count = table.Column<long>(type: "bigint", nullable: false, defaultValue: 0L),
+                    complete_count = table.Column<long>(type: "bigint", nullable: false, defaultValue: 0L)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_play_counter", x => x.id);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "play_event",
+                columns: table => new
+                {
+                    id = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    track_entry_key = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: false),
+                    release_id = table.Column<long>(type: "bigint", nullable: true),
+                    bucket = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    anon_id = table.Column<string>(type: "character varying(64)", maxLength: 64, nullable: true),
+                    created_at = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_play_event", x => x.id);
+                });
+
+            migrationBuilder.CreateTable(
+                name: "share_event",
+                columns: table => new
+                {
+                    id = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    target_type = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    target_key = table.Column<string>(type: "character varying(100)", maxLength: 100, nullable: false),
+                    channel = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false),
+                    anon_id = table.Column<string>(type: "character varying(64)", maxLength: 64, nullable: true),
+                    created_at = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_share_event", x => x.id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_play_counter_track_id",
+                table: "play_counter",
+                column: "track_id",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_play_event_anon_id",
+                table: "play_event",
+                column: "anon_id");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_play_event_release_id",
+                table: "play_event",
+                column: "release_id");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_play_event_track_entry_key",
+                table: "play_event",
+                column: "track_entry_key");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_share_event_anon_id",
+                table: "share_event",
+                column: "anon_id");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_share_event_target_key",
+                table: "share_event",
+                column: "target_key");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "play_counter");
+
+            migrationBuilder.DropTable(
+                name: "play_event");
+
+            migrationBuilder.DropTable(
+                name: "share_event");
+        }
+    }
+}

DeepDrftData/Migrations/DeepDrftContextModelSnapshot.cs

@@ -67,6 +67,94 @@ namespace DeepDrftData.Migrations
                     b.ToTable("mix_metadata", (string)null);
                 });
 
+            modelBuilder.Entity("DeepDrftModels.Entities.PlayCounter", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<long>("CompleteCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("complete_count");
+
+                    b.Property<long>("PartialCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("partial_count");
+
+                    b.Property<long>("SampledCount")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasDefaultValue(0L)
+                        .HasColumnName("sampled_count");
+
+                    b.Property<long>("TrackId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("track_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TrackId")
+                        .IsUnique()
+                        .HasDatabaseName("IX_play_counter_track_id");
+
+                    b.ToTable("play_counter", (string)null);
+                });
+
+            modelBuilder.Entity("DeepDrftModels.Entities.PlayEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("AnonId")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)")
+                        .HasColumnName("anon_id");
+
+                    b.Property<string>("Bucket")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("bucket");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<long?>("ReleaseId")
+                        .HasColumnType("bigint")
+                        .HasColumnName("release_id");
+
+                    b.Property<string>("TrackEntryKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("track_entry_key");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AnonId")
+                        .HasDatabaseName("IX_play_event_anon_id");
+
+                    b.HasIndex("ReleaseId")
+                        .HasDatabaseName("IX_play_event_release_id");
+
+                    b.HasIndex("TrackEntryKey")
+                        .HasDatabaseName("IX_play_event_track_entry_key");
+
+                    b.ToTable("play_event", (string)null);
+                });
+
             modelBuilder.Entity("DeepDrftModels.Entities.ReleaseEntity", b =>
                 {
                     b.Property<long>("Id")
@@ -209,6 +297,53 @@ namespace DeepDrftData.Migrations
                     b.ToTable("session_metadata", (string)null);
                 });
 
+            modelBuilder.Entity("DeepDrftModels.Entities.ShareEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint")
+                        .HasColumnName("id");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<string>("AnonId")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)")
+                        .HasColumnName("anon_id");
+
+                    b.Property<string>("Channel")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("channel");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("TargetKey")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("target_key");
+
+                    b.Property<string>("TargetType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasColumnName("target_type");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AnonId")
+                        .HasDatabaseName("IX_share_event_anon_id");
+
+                    b.HasIndex("TargetKey")
+                        .HasDatabaseName("IX_share_event_target_key");
+
+                    b.ToTable("share_event", (string)null);
+                });
+
             modelBuilder.Entity("DeepDrftModels.Entities.TrackEntity", b =>
                 {
                     b.Property<long>("Id")

DeepDrftData/Repositories/EventRepository.cs

@@ -0,0 +1,121 @@
+using DeepDrftData.Data;
+using DeepDrftModels.Entities;
+using DeepDrftModels.Enums;
+using Microsoft.EntityFrameworkCore;
+
+namespace DeepDrftData.Repositories;
+
+/// <summary>
+/// Data access for the Phase 16 anonymous telemetry tables (all SQL — the FileDatabase vault is not
+/// involved). Owns the append-only writes to <c>play_event</c> / <c>share_event</c> and the
+/// incremental-on-write bump of the <c>play_counter</c> rollup (D6). Server-side release resolution
+/// (§2.3 / D4) lives here: a play event carries only the track key, and this repository joins
+/// track→release at write time and stamps the release id on the row.
+///
+/// <para>
+/// Unlike <see cref="TrackRepository"/> these entities are not <c>BaseEntity</c>/<c>IEntity</c> (no
+/// soft-delete lifecycle), so this is a plain context-backed repository rather than an extension of the
+/// BlazorBlocks <c>Repository&lt;&gt;</c> base. It holds the same scoped <see cref="DeepDrftContext"/>
+/// the rest of the SQL layer uses, never a service locator.
+/// </para>
+/// </summary>
+public class EventRepository
+{
+    private readonly DeepDrftContext _context;
+
+    public EventRepository(DeepDrftContext context)
+    {
+        _context = context;
+    }
+
+    /// <summary>
+    /// Append one play event and bump the track's counter in a single transaction (D6). The release id
+    /// is resolved here from the track key (§2.3 / D4): a live track contributes its release id (null
+    /// for a loose track); an unknown key records the event with a null release and no counter bump
+    /// (there is no track to roll up against). Returns true when the event was written.
+    /// </summary>
+    public async Task<bool> RecordPlayAsync(
+        string trackEntryKey, PlayBucket bucket, string? anonId, CancellationToken ct = default)
+    {
+        // Resolve the track→release link server-side. Soft-deleted tracks resolve to null so a play of
+        // a since-removed track still logs (with no counter bump) rather than throwing.
+        var track = await _context.Tracks
+            .Where(t => t.EntryKey == trackEntryKey && !t.IsDeleted)
+            .Select(t => new { t.Id, t.ReleaseId })
+            .FirstOrDefaultAsync(ct);
+
+        // The append and the counter bump must commit together — wrap them in one transaction so a
+        // counter that drifts from the log is impossible. Reuse an ambient transaction if the caller
+        // already opened one.
+        var ownsTransaction = _context.Database.CurrentTransaction is null;
+        var transaction = ownsTransaction
+            ? await _context.Database.BeginTransactionAsync(ct)
+            : null;
+        try
+        {
+            _context.PlayEvents.Add(new PlayEvent
+            {
+                TrackEntryKey = trackEntryKey,
+                ReleaseId = track?.ReleaseId,
+                Bucket = bucket,
+                AnonId = anonId,
+                CreatedAt = DateTime.UtcNow,
+            });
+
+            if (track is not null)
+                await BumpCounterAsync(track.Id, bucket, ct);
+
+            await _context.SaveChangesAsync(ct);
+            if (transaction is not null)
+                await transaction.CommitAsync(ct);
+            return true;
+        }
+        catch
+        {
+            if (transaction is not null)
+                await transaction.RollbackAsync(ct);
+            throw;
+        }
+        finally
+        {
+            if (transaction is not null)
+                await transaction.DisposeAsync();
+        }
+    }
+
+    /// <summary>Append one share event. No rollup table for shares in wave 16.1 — a plain insert.</summary>
+    public async Task RecordShareAsync(
+        ShareTargetType targetType, string targetKey, ShareChannel channel, string? anonId,
+        CancellationToken ct = default)
+    {
+        _context.ShareEvents.Add(new ShareEvent
+        {
+            TargetType = targetType,
+            TargetKey = targetKey,
+            Channel = channel,
+            AnonId = anonId,
+            CreatedAt = DateTime.UtcNow,
+        });
+        await _context.SaveChangesAsync(ct);
+    }
+
+    // Bump the matching bucket column on the track's counter row, creating the row on first play. The
+    // row is added to the change tracker but not saved here — the caller's SaveChanges/commit persists
+    // it inside the same transaction as the event append.
+    private async Task BumpCounterAsync(long trackId, PlayBucket bucket, CancellationToken ct)
+    {
+        var counter = await _context.PlayCounters.FirstOrDefaultAsync(c => c.TrackId == trackId, ct);
+        if (counter is null)
+        {
+            counter = new PlayCounter { TrackId = trackId };
+            _context.PlayCounters.Add(counter);
+        }
+
+        switch (bucket)
+        {
+            case PlayBucket.Partial: counter.PartialCount++; break;
+            case PlayBucket.Sampled: counter.SampledCount++; break;
+            case PlayBucket.Complete: counter.CompleteCount++; break;
+        }
+    }
+}

DeepDrftModels/DTOs/PlayEventDto.cs

@@ -0,0 +1,18 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftModels.DTOs;
+
+/// <summary>
+/// Wire payload for <c>POST api/event/play</c> (Phase 16 §2.2 / §4.3). The client sends only what it
+/// cheaply knows — the track key and the client-computed completion bucket; the server resolves the
+/// release. No duration or raw position is transmitted (a privacy plus — only a coarse bucket leaves
+/// the browser). <see cref="AnonId"/> is reserved for wave 16.3 and stays null in wave 16.1.
+/// </summary>
+public class PlayEventDto
+{
+    public string? TrackEntryKey { get; set; }
+
+    public PlayBucket Bucket { get; set; }
+
+    public string? AnonId { get; set; }
+}

DeepDrftModels/DTOs/ShareEventDto.cs

@@ -0,0 +1,19 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftModels.DTOs;
+
+/// <summary>
+/// Wire payload for <c>POST api/event/share</c> (Phase 16 §2.2 / §4.3). The popover knows the target
+/// and channel at the point of the action, so the payload is self-describing — no server-side resolution.
+/// <see cref="AnonId"/> is reserved for wave 16.3 and stays null in wave 16.1.
+/// </summary>
+public class ShareEventDto
+{
+    public ShareTargetType TargetType { get; set; }
+
+    public string? TargetKey { get; set; }
+
+    public ShareChannel Channel { get; set; }
+
+    public string? AnonId { get; set; }
+}

DeepDrftModels/Entities/PlayCounter.cs

@@ -0,0 +1,28 @@
+namespace DeepDrftModels.Entities;
+
+/// <summary>
+/// Incremental rollup of play counts per track (Phase 16 §4.1 / D6). One row per track, bumped inside
+/// the same transaction that appends the <see cref="PlayEvent"/> — no background aggregation job. The
+/// home card and per-target reads sum these instead of <c>COUNT(*)</c>-ing the event log on every
+/// landing. Release totals are <em>derived</em> (D4) by summing the counters of the release's tracks,
+/// so there is no separate release-counter row — this keeps the rollup normalized at one row per track.
+/// </summary>
+public class PlayCounter
+{
+    public long Id { get; set; }
+
+    /// <summary>The track these counts belong to (SQL id). Unique — one counter row per track.</summary>
+    public long TrackId { get; set; }
+
+    /// <summary>Count of plays that ended in the <c>Partial</c> bucket (&lt; 30%).</summary>
+    public long PartialCount { get; set; }
+
+    /// <summary>Count of plays that ended in the <c>Sampled</c> bucket (30%–80%).</summary>
+    public long SampledCount { get; set; }
+
+    /// <summary>Count of plays that ended in the <c>Complete</c> bucket (&gt; 80%).</summary>
+    public long CompleteCount { get; set; }
+
+    /// <summary>Total plays for the track — the sum of the three bucket counts (headline figure).</summary>
+    public long TotalPlays => PartialCount + SampledCount + CompleteCount;
+}

DeepDrftModels/Entities/PlayEvent.cs

@@ -0,0 +1,36 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftModels.Entities;
+
+/// <summary>
+/// Append-only log row for one recorded play (Phase 16 §4.2). Written once at session close, after the
+/// engagement floor is crossed; never updated or deleted. Deliberately NOT a <c>BaseEntity</c>: events
+/// have no soft-delete lifecycle, no <c>UpdatedAt</c> — they are immutable facts. The release link is
+/// resolved server-side from the track key at write time (§2.3 / D4) and stored here so release-total
+/// plays are a cheap sum over this column.
+/// </summary>
+public class PlayEvent
+{
+    public long Id { get; set; }
+
+    /// <summary>The played track's vault entry key (the only target the client sends).</summary>
+    public required string TrackEntryKey { get; set; }
+
+    /// <summary>
+    /// The owning release's SQL id, resolved from <see cref="TrackEntryKey"/> at write time. Null when
+    /// the track is loose (no release) or the key did not resolve to a live track at write time.
+    /// </summary>
+    public long? ReleaseId { get; set; }
+
+    /// <summary>The completion bucket computed client-side from the high-water fraction (§1a / D1).</summary>
+    public PlayBucket Bucket { get; set; }
+
+    /// <summary>
+    /// Anonymous listener token (Phase 16 §3, wave 16.3). Reserved nullable; nothing writes it in wave
+    /// 16.1 — the client sends none and the column stays NULL. Wave 16.3 lights it up for the
+    /// distinct-listener count.
+    /// </summary>
+    public string? AnonId { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+}

DeepDrftModels/Entities/ShareEvent.cs

@@ -0,0 +1,34 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftModels.Entities;
+
+/// <summary>
+/// Append-only log row for one recorded share (Phase 16 §4.2). Written once per share action that
+/// survives the per-(target,channel) client debounce; never updated or deleted. Like <see cref="PlayEvent"/>
+/// it is deliberately NOT a <c>BaseEntity</c> — an immutable fact with no soft-delete lifecycle. Shares
+/// carry their target directly (the popover knows track vs. release), so no server-side resolution step.
+/// </summary>
+public class ShareEvent
+{
+    public long Id { get; set; }
+
+    /// <summary>Whether the share targets a track or a release.</summary>
+    public ShareTargetType TargetType { get; set; }
+
+    /// <summary>
+    /// The shared target's key: a track's vault <c>EntryKey</c> or a release's public <c>EntryKey</c>,
+    /// selected by <see cref="TargetType"/>. Stored as the opaque key, not resolved to a SQL id — the
+    /// share metric is a simple per-target tally and needs no join in wave 16.1.
+    /// </summary>
+    public required string TargetKey { get; set; }
+
+    /// <summary>The channel the share was performed through (link vs. embed).</summary>
+    public ShareChannel Channel { get; set; }
+
+    /// <summary>
+    /// Anonymous listener token (Phase 16 §3, wave 16.3). Reserved nullable; unused in wave 16.1.
+    /// </summary>
+    public string? AnonId { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+}

DeepDrftModels/Enums/PlayBucket.cs

@@ -0,0 +1,26 @@
+using System.Text.Json.Serialization;
+
+namespace DeepDrftModels.Enums;
+
+/// <summary>
+/// Completion bucket for a recorded play (Phase 16 §1a / D1). The three buckets are exhaustive and
+/// non-overlapping, classified by the high-water playback fraction reached before the session closed:
+/// <c>Partial</c> [0, 30%), <c>Sampled</c> [30%, 80%], <c>Complete</c> (80%, 100%]. The headline
+/// "Plays" figure is the sum of all three — every started listen that crosses the engagement floor
+/// is a play; the buckets are the texture beneath it.
+///
+/// Serialized as its string name on the wire — the converter on the type makes the
+/// client to proxy to API JSON contract string-based regardless of host serializer config.
+/// </summary>
+[JsonConverter(typeof(JsonStringEnumConverter<PlayBucket>))]
+public enum PlayBucket
+{
+    /// <summary>Reached &lt; 30% of duration — a skip or a brief partial listen (still past the floor).</summary>
+    Partial,
+
+    /// <summary>Reached 30%–80% of duration — a real listen that was neither a skip nor a finish.</summary>
+    Sampled,
+
+    /// <summary>Reached &gt; 80% of duration — effectively a finished listen.</summary>
+    Complete
+}

DeepDrftModels/Enums/ShareChannel.cs

@@ -0,0 +1,33 @@
+using System.Text.Json.Serialization;
+
+namespace DeepDrftModels.Enums;
+
+/// <summary>
+/// The channel a share was performed through (Phase 16 §1b). Today both originate from
+/// <c>SharePopover</c>'s clipboard actions; a future native/Web-Share button would add a channel
+/// without reshaping the metric. Serialized as its string name on the wire.
+/// </summary>
+[JsonConverter(typeof(JsonStringEnumConverter<ShareChannel>))]
+public enum ShareChannel
+{
+    /// <summary>Copy-link — the canonical track or release URL placed on the clipboard.</summary>
+    Link,
+
+    /// <summary>Copy-embed — the <c>&lt;iframe&gt;</c> snippet for the single-track FramePlayer.</summary>
+    Embed
+}
+
+/// <summary>
+/// What a share targets (Phase 16 §1b). Tracks and releases are both shareable; the popover knows
+/// which it is at the point of the action, so no server-side resolution is needed for shares.
+/// Serialized as its string name on the wire.
+/// </summary>
+[JsonConverter(typeof(JsonStringEnumConverter<ShareTargetType>))]
+public enum ShareTargetType
+{
+    /// <summary>The share targets a single track, addressed by its vault <c>EntryKey</c>.</summary>
+    Track,
+
+    /// <summary>The share targets a release, addressed by its public <c>EntryKey</c>.</summary>
+    Release
+}

DeepDrftPublic.Client/Controls/AudioPlayerProvider.razor.cs

@@ -10,6 +10,8 @@ public partial class AudioPlayerProvider : ComponentBase, IAsyncDisposable
     [Inject] public required AudioInteropService AudioInterop { get; set; }
     [Inject] public required TrackMediaClient TrackMediaClient { get; set; }
     [Inject] public required ILogger<StreamingAudioPlayerService> Logger { get; set; }
+    [Inject] public required BeaconInterop Beacon { get; set; }
+    [Inject] public required IPlayEventSink PlayEventSink { get; set; }
 
     private IStreamingPlayerService? _audioPlayerService;
     private QueueService? _queueService;
@@ -23,7 +25,16 @@ public partial class AudioPlayerProvider : ComponentBase, IAsyncDisposable
         // EnsureInitializedAsync — that path is correct because audio contexts
         // require a user gesture anyway. Initializing eagerly here causes 4+
         // SignalR round-trips before any content is stable.
-        _audioPlayerService = new StreamingAudioPlayerService(AudioInterop, TrackMediaClient, Logger);
+        var player = new StreamingAudioPlayerService(AudioInterop, TrackMediaClient, Logger);
+
+        // Phase 16: bind the play-session tracker to the player after construction, the same way the
+        // queue binds — the player is built with `new`, not DI, so threading telemetry through its
+        // constructor would force the provider to over-resolve. The tracker owns the floor/bucket logic
+        // and emits via the injected sink (the beacon in production); the beacon also drives the
+        // page-unload close so a mid-play tab-close still records the listen. Attached on the concrete
+        // type before it is exposed through the IStreamingPlayerService field.
+        player.AttachTracker(new PlayTracker(PlayEventSink), Beacon);
+        _audioPlayerService = player;
 
         // Provider is the SOLE owner of OnStateChanged. When the service fires,
         // the provider re-renders, which cascades to its children automatically.

DeepDrftPublic.Client/Controls/SharePopover.razor.cs

@@ -1,5 +1,6 @@
 using DeepDrftModels.Enums;
 using DeepDrftPublic.Client.Common;
+using DeepDrftPublic.Client.Services;
 using Microsoft.AspNetCore.Components;
 using Microsoft.JSInterop;
 
@@ -27,6 +28,7 @@ public partial class SharePopover : ComponentBase, IDisposable
 
     [Inject] public required NavigationManager Navigation { get; set; }
     [Inject] public required IJSRuntime JS { get; set; }
+    [Inject] public required ShareTracker ShareTracker { get; set; }
 
     private bool IsReleaseMode => ReleaseEntryKey is not null;
 
@@ -67,6 +69,14 @@ public partial class SharePopover : ComponentBase, IDisposable
     {
         if (await CopyToClipboard(LinkUrl))
         {
+            // Record a share only after the clipboard write succeeds (§1b). Release mode targets the
+            // release EntryKey; track mode targets the track EntryKey. The tracker debounces repeat
+            // copies of the same (target, channel) into one event.
+            if (IsReleaseMode)
+                ShareTracker.RecordShare(ShareTargetType.Release, ReleaseEntryKey!, ShareChannel.Link);
+            else if (!string.IsNullOrWhiteSpace(EntryKey))
+                ShareTracker.RecordShare(ShareTargetType.Track, EntryKey, ShareChannel.Link);
+
             _linkCopied = true;
             await ResetAfterDelay(() => _linkCopied = false);
         }
@@ -76,6 +86,11 @@ public partial class SharePopover : ComponentBase, IDisposable
     {
         if (await CopyToClipboard(EmbedSnippet))
         {
+            // Embed is a single-track affordance only (release mode hides it), so this always targets a
+            // track with channel = embed.
+            if (!string.IsNullOrWhiteSpace(EntryKey))
+                ShareTracker.RecordShare(ShareTargetType.Track, EntryKey, ShareChannel.Embed);
+
             _embedCopied = true;
             await ResetAfterDelay(() => _embedCopied = false);
         }

DeepDrftPublic.Client/Services/AudioPlayerService.cs

@@ -260,6 +260,9 @@ public abstract class AudioPlayerService : IPlayerService, IAsyncDisposable
     private async Task OnProgressCallback(double currentTime)
     {
         CurrentTime = currentTime;
+        // Telemetry hook (Phase 16 §2.1): a subclass advances the play-session high-water mark here, on
+        // the same throttled tick the UI already consumes. Base implementation is a no-op.
+        OnProgressTick(currentTime);
         await NotifyStateChanged();
     }
 
@@ -270,6 +273,10 @@ public abstract class AudioPlayerService : IPlayerService, IAsyncDisposable
         IsLoaded = false;
         CurrentTime = 0;
         Duration = null;
+        // Telemetry hook: organic end closes the play session (the bucket reflects how far they got)
+        // BEFORE the state notification and TrackEnded fan-out, so the session that just ended is the
+        // one recorded — not whatever a queue auto-advance opens next. Base implementation is a no-op.
+        OnPlaybackEnded();
         await NotifyStateChanged();
 
         // Fire AFTER the state notification so any queue orchestrator that advances on this
@@ -279,6 +286,18 @@ public abstract class AudioPlayerService : IPlayerService, IAsyncDisposable
         TrackEnded?.Invoke();
     }
 
+    /// <summary>
+    /// Telemetry seam (Phase 16): called on each progress tick with the current playback position. The
+    /// streaming subclass overrides this to advance the play-session high-water mark. No-op in the base.
+    /// </summary>
+    protected virtual void OnProgressTick(double currentTime) { }
+
+    /// <summary>
+    /// Telemetry seam (Phase 16): called on organic end-of-stream, before <see cref="TrackEnded"/> fires.
+    /// The streaming subclass overrides this to close the play session. No-op in the base.
+    /// </summary>
+    protected virtual void OnPlaybackEnded() { }
+
 
     protected async Task EnsureInitializedAsync()
     {

DeepDrftPublic.Client/Services/BeaconInterop.cs

@@ -0,0 +1,60 @@
+using Microsoft.JSInterop;
+
+namespace DeepDrftPublic.Client.Services;
+
+/// <summary>
+/// Thin C# wrapper over the <c>window.DeepDrftBeacon</c> TS interop (Phase 16 §2.2). Wraps the
+/// <c>navigator.sendBeacon</c> POST and the page-unload registration so the rest of the client never
+/// touches <see cref="IJSRuntime"/> string identifiers directly. All calls are best-effort: a JS
+/// failure (module not yet loaded, interop unavailable during prerender) is swallowed — telemetry must
+/// never throw into the UI or the playback path.
+/// </summary>
+public sealed class BeaconInterop
+{
+    private readonly IJSRuntime _js;
+
+    public BeaconInterop(IJSRuntime js)
+    {
+        _js = js;
+    }
+
+    /// <summary>Queue a fire-and-forget POST of a JSON body to the given absolute URL.</summary>
+    public async Task SendAsync(string url, string json)
+    {
+        try
+        {
+            await _js.InvokeAsync<bool>("DeepDrftBeacon.send", url, json);
+        }
+        catch
+        {
+            // Module not loaded / not interactive yet — drop the event silently.
+        }
+    }
+
+    /// <summary>Register a .NET unload callback (fires on pagehide / visibility→hidden) under a key.</summary>
+    public async Task RegisterUnloadAsync<T>(string key, DotNetObjectReference<T> dotNetRef, string methodName)
+        where T : class
+    {
+        try
+        {
+            await _js.InvokeVoidAsync("DeepDrftBeacon.registerUnload", key, dotNetRef, methodName);
+        }
+        catch
+        {
+            // Best-effort — without the unload handler, mid-play tab-close simply isn't recorded.
+        }
+    }
+
+    /// <summary>Detach a previously-registered unload callback.</summary>
+    public async Task UnregisterUnloadAsync(string key)
+    {
+        try
+        {
+            await _js.InvokeVoidAsync("DeepDrftBeacon.unregisterUnload", key);
+        }
+        catch
+        {
+            // Disposal best-effort.
+        }
+    }
+}

DeepDrftPublic.Client/Services/BeaconPlayEventSink.cs

@@ -0,0 +1,40 @@
+using System.Text.Json;
+using DeepDrftModels.DTOs;
+using DeepDrftModels.Enums;
+using Microsoft.AspNetCore.Components;
+
+namespace DeepDrftPublic.Client.Services;
+
+/// <summary>
+/// Production <see cref="IPlayEventSink"/> (Phase 16 §2.2): serializes the play classification and fires
+/// it via <c>navigator.sendBeacon</c> to the proxied <c>api/event/play</c> route. Fire-and-forget by
+/// design — <see cref="IPlayEventSink.EmitPlay"/> is synchronous (it is called from the player's close
+/// path and the unload handler, neither of which can await), so the beacon is dispatched without
+/// awaiting and its failure is irrelevant. No <c>anonId</c> is sent in wave 16.1.
+/// </summary>
+public sealed class BeaconPlayEventSink : IPlayEventSink
+{
+    private readonly BeaconInterop _beacon;
+    private readonly string _playUrl;
+
+    public BeaconPlayEventSink(BeaconInterop beacon, NavigationManager navigation)
+    {
+        _beacon = beacon;
+        // The WASM client posts to its own host, which proxies to DeepDrftAPI. BaseUri carries a
+        // trailing slash; the route does not lead with one.
+        _playUrl = $"{navigation.BaseUri}api/event/play";
+    }
+
+    public void EmitPlay(string trackEntryKey, PlayBucket bucket)
+    {
+        var json = JsonSerializer.Serialize(new PlayEventDto
+        {
+            TrackEntryKey = trackEntryKey,
+            Bucket = bucket,
+        });
+
+        // Fire-and-forget: do not await. The beacon survives unload; the C# task may not, and we do not
+        // act on the result either way.
+        _ = _beacon.SendAsync(_playUrl, json);
+    }
+}

DeepDrftPublic.Client/Services/IPlayEventSink.cs

@@ -0,0 +1,16 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftPublic.Client.Services;
+
+/// <summary>
+/// The emit seam for the <see cref="PlayTracker"/> (Phase 16 §2.1). The tracker owns the session
+/// lifecycle, the engagement floor, and the bucket classification but knows nothing about transport —
+/// it hands a finished classification to a sink. The production sink fires a <c>sendBeacon</c> POST to
+/// <c>api/event/play</c>; tests substitute a fake sink to assert floor and bucket behaviour with no
+/// JS interop. This keeps the tracker's logic testable behind one seam, as the spec calls for.
+/// </summary>
+public interface IPlayEventSink
+{
+    /// <summary>Emit one recorded play. Called at most once per session, only when the floor is crossed.</summary>
+    void EmitPlay(string trackEntryKey, PlayBucket bucket);
+}

DeepDrftPublic.Client/Services/PlayTracker.cs

@@ -0,0 +1,129 @@
+using DeepDrftModels.Enums;
+
+namespace DeepDrftPublic.Client.Services;
+
+/// <summary>
+/// Per-session play tracker (Phase 16 §2.1). Observes the player-service playback lifecycle — open on
+/// playback start, advance the high-water mark on each progress tick, close on organic end / track-switch
+/// / stop / page-unload — and emits at most one play event per session, classified into a completion
+/// bucket, but only once the engagement floor is crossed (§1d / D2).
+///
+/// <para>
+/// Deliberately free of any player, HTTP, or JS dependency: it takes an <see cref="IPlayEventSink"/> and
+/// owns only session state and the floor/classification arithmetic, so its behaviour is unit-testable
+/// against a fake sink with no interop (the spec's "testable behind one seam"). The production sink fires
+/// the beacon. Instrumented at the player-service level ONLY — never the HTTP/media client — so a
+/// seek-beyond-buffer re-fetch is the same play, not a new one (§1d).
+/// </para>
+///
+/// <para>Not thread-safe: the WASM dispatcher is single-threaded, and every call originates there.</para>
+/// </summary>
+public sealed class PlayTracker
+{
+    // Engagement floor (§1d / D2): a listen counts only once playback reaches at least 3 seconds OR
+    // 5% of duration, whichever is SMALLER — so a sub-60s clip floors on the percentage and anything
+    // longer floors on the 3-second wall. Single tunable constant pair; one place to retune.
+    private const double FloorSeconds = 3.0;
+    private const double FloorFraction = 0.05;
+
+    // Bucket thresholds (§1a / D1): partial [0, 30%), sampled [30%, 80%], complete (80%, 100%].
+    private const double SampledThreshold = 0.30;
+    private const double CompleteThreshold = 0.80;
+
+    private readonly IPlayEventSink _sink;
+
+    private string? _trackEntryKey;
+    private double? _duration;
+    private double _highWater;
+    private bool _closed;
+
+    public PlayTracker(IPlayEventSink sink)
+    {
+        _sink = sink;
+    }
+
+    /// <summary>True while a session is open (playback started, not yet closed). Drives the unload beacon.</summary>
+    public bool HasOpenSession => _trackEntryKey is not null && !_closed;
+
+    /// <summary>
+    /// Open a session for the track whose playback just started. Supersedes any still-open session by
+    /// closing it first — a track-switch that did not route through <see cref="Close"/> still records the
+    /// prior listen. Duration is unknown at open and arrives later via <see cref="SetDuration"/>.
+    /// </summary>
+    public void OnPlaybackStarted(string trackEntryKey)
+    {
+        if (HasOpenSession)
+            Close();
+
+        _trackEntryKey = trackEntryKey;
+        _duration = null;
+        _highWater = 0;
+        _closed = false;
+    }
+
+    /// <summary>
+    /// Record the duration once the WAV header has set it. Idempotent — only the first non-positive-guarded
+    /// value is taken, matching the player which sets <c>Duration</c> exactly once.
+    /// </summary>
+    public void SetDuration(double durationSeconds)
+    {
+        if (!HasOpenSession) return;
+        if (_duration is null && durationSeconds > 0)
+            _duration = durationSeconds;
+    }
+
+    /// <summary>
+    /// Advance the high-water mark from a progress tick. Monotonic — seeking backward never lowers it,
+    /// so a seek-to-end-then-back still classifies by the furthest point reached (§1d).
+    /// </summary>
+    public void OnProgress(double currentTime)
+    {
+        if (!HasOpenSession) return;
+        if (currentTime > _highWater)
+            _highWater = currentTime;
+    }
+
+    /// <summary>
+    /// Close the open session and emit a play event if the engagement floor was crossed; below the floor
+    /// nothing is sent (it was a preview/skip, §1d). Idempotent and safe to call when no session is open —
+    /// organic end, track-switch, stop, dispose, and the unload beacon may all race to close, and only the
+    /// first call emits.
+    /// </summary>
+    public void Close()
+    {
+        if (!HasOpenSession)
+        {
+            // Mark closed even if never opened so a stray late callback cannot reopen-then-emit.
+            _closed = true;
+            return;
+        }
+
+        var key = _trackEntryKey!;
+        _closed = true;
+
+        // Without a known duration there is no fraction to classify and no floor to test — drop the
+        // session. In practice the WAV header sets duration well before any meaningful listen, so this
+        // only drops listens that ended before the header parsed (i.e. effectively no listen).
+        if (_duration is not { } duration || duration <= 0)
+            return;
+
+        var fraction = Math.Clamp(_highWater / duration, 0.0, 1.0);
+
+        if (!CrossesFloor(_highWater, duration))
+            return;
+
+        _sink.EmitPlay(key, Classify(fraction));
+    }
+
+    // The floor is the SMALLER of the absolute-seconds wall and the percentage of duration (§1d / D2).
+    private static bool CrossesFloor(double highWater, double duration)
+    {
+        var floor = Math.Min(FloorSeconds, FloorFraction * duration);
+        return highWater >= floor;
+    }
+
+    private static PlayBucket Classify(double fraction)
+        => fraction < SampledThreshold ? PlayBucket.Partial
+            : fraction <= CompleteThreshold ? PlayBucket.Sampled
+            : PlayBucket.Complete;
+}

DeepDrftPublic.Client/Services/ShareTracker.cs

@@ -0,0 +1,70 @@
+using System.Text.Json;
+using DeepDrftModels.DTOs;
+using DeepDrftModels.Enums;
+using Microsoft.AspNetCore.Components;
+
+namespace DeepDrftPublic.Client.Services;
+
+/// <summary>
+/// Records share events from <c>SharePopover</c> (Phase 16 §1b / §2.1). After a successful clipboard
+/// write the popover calls <see cref="RecordShare"/>; this tracker applies the per-(target,channel)
+/// debounce — at most one event per target+channel per <see cref="DebounceWindow"/> per session — and
+/// fires the event via <c>navigator.sendBeacon</c> to the proxied <c>api/event/share</c> route.
+///
+/// <para>
+/// Scoped (per-session) so the debounce memory lives for the session and resets on a fresh load, matching
+/// the "feels like one act" intent: copying the same link three times in a row is one share, not three.
+/// The beacon send is fire-and-forget; no <c>anonId</c> is sent in wave 16.1.
+/// </para>
+/// </summary>
+public sealed class ShareTracker
+{
+    // One event per (target, channel) per this window per session (§1b). 60s matches the spec's
+    // recommendation — long enough to fold a flurry of repeat copies into one intent.
+    private static readonly TimeSpan DebounceWindow = TimeSpan.FromSeconds(60);
+
+    private readonly BeaconInterop _beacon;
+    private readonly string _shareUrl;
+    private readonly Dictionary<string, DateTimeOffset> _lastSent = new();
+
+    public ShareTracker(BeaconInterop beacon, NavigationManager navigation)
+    {
+        _beacon = beacon;
+        _shareUrl = $"{navigation.BaseUri}api/event/share";
+    }
+
+    /// <summary>
+    /// Record a share unless an identical (target, channel) was recorded within the debounce window.
+    /// Returns true when an event was fired, false when debounced — primarily so tests can assert the
+    /// debounce without reaching into the beacon.
+    /// </summary>
+    public bool RecordShare(ShareTargetType targetType, string targetKey, ShareChannel channel)
+        => RecordShare(targetType, targetKey, channel, DateTimeOffset.UtcNow);
+
+    /// <summary>
+    /// Debounce-aware record with an injectable <paramref name="now"/> so the 60s window is testable
+    /// without wall-clock waits. The parameterless overload above passes <see cref="DateTimeOffset.UtcNow"/>.
+    /// </summary>
+    public bool RecordShare(ShareTargetType targetType, string targetKey, ShareChannel channel, DateTimeOffset now)
+    {
+        if (string.IsNullOrWhiteSpace(targetKey))
+            return false;
+
+        var dedupeKey = $"{targetType}:{targetKey}:{channel}";
+        if (_lastSent.TryGetValue(dedupeKey, out var last) && now - last < DebounceWindow)
+            return false;
+
+        _lastSent[dedupeKey] = now;
+
+        var json = JsonSerializer.Serialize(new ShareEventDto
+        {
+            TargetType = targetType,
+            TargetKey = targetKey,
+            Channel = channel,
+        });
+
+        // Fire-and-forget — a dropped share telemetry event is acceptable.
+        _ = _beacon.SendAsync(_shareUrl, json);
+        return true;
+    }
+}

DeepDrftPublic.Client/Services/StreamingAudioPlayerService.cs

@@ -2,6 +2,7 @@ using DeepDrftModels.DTOs;
 using DeepDrftPublic.Client.Clients;
 using System.Buffers;
 using Microsoft.Extensions.Logging;
+using Microsoft.JSInterop;
 
 namespace DeepDrftPublic.Client.Services;
 
@@ -32,6 +33,22 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
     private readonly ILogger<StreamingAudioPlayerService> _logger;
     private string? _currentTrackId;
 
+    // Phase 16 play-session telemetry (§2.1). The tracker observes the playback lifecycle and emits at
+    // most one bucketed play event per session, behind the engagement floor. Attached after construction
+    // by AudioPlayerProvider (the player is not DI-registered), mirroring how QueueService binds — no
+    // constructor growth propagated through DI, no construction cycle. Null when telemetry is not wired
+    // (e.g. unit tests that construct the player without it), so every call is null-guarded.
+    private PlayTracker? _playTracker;
+    private BeaconInterop? _beacon;
+    private DotNetObjectReference<StreamingAudioPlayerService>? _unloadRef;
+    private string? _unloadKey;
+
+    // One-shot guard so the play session opens exactly once per LoadTrackStreaming — never on the
+    // SeekBeyondBuffer re-stream, which reuses _currentTrackId and re-runs the playback-start transition
+    // with _streamingPlaybackStarted reset. A seek-beyond-buffer is the SAME play (§1d), so it must not
+    // open a new session. Set true when the session opens; reset only by LoadTrackStreaming.
+    private bool _sessionOpened;
+
     public StreamingAudioPlayerService(
         AudioInteropService audioInterop, 
         TrackMediaClient trackMediaClient,
@@ -41,6 +58,41 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
         _logger = logger;
     }
 
+    /// <summary>
+    /// Wire the play-session tracker and beacon transport into the player after construction (Phase 16
+    /// §2.1). Called once by <c>AudioPlayerProvider</c>. Kept off the constructor deliberately: the player
+    /// is built with <c>new</c> by the provider (not DI), so threading the tracker through the constructor
+    /// would force the provider to resolve it too — instead the provider injects the tracker's collaborators
+    /// and hands a built tracker here, the same post-construction binding QueueService uses. Also registers
+    /// the page-unload handler so a mid-play tab-close still records the play via sendBeacon.
+    /// </summary>
+    public void AttachTracker(PlayTracker tracker, BeaconInterop beacon)
+    {
+        _playTracker = tracker;
+        _beacon = beacon;
+
+        _unloadRef = DotNetObjectReference.Create(this);
+        _unloadKey = PlayerId;
+        // Fire-and-forget: registration only needs to have happened before the listener leaves; it
+        // never gates playback. A failure simply means tab-close mid-play isn't recorded.
+        _ = _beacon.RegisterUnloadAsync(_unloadKey, _unloadRef, nameof(OnPageUnload));
+    }
+
+    /// <summary>
+    /// Close the open play session as the page unloads (pagehide / visibility→hidden). Invoked
+    /// synchronously from the beacon's unload handler so the session's beacon is queued before the page
+    /// freezes. <see cref="PlayTracker.Close"/> is idempotent, so a later organic close is a no-op.
+    /// </summary>
+    [JSInvokable]
+    public void OnPageUnload() => _playTracker?.Close();
+
+    // Advance the play-session high-water mark on each progress tick (§2.1). Seeking backward never
+    // lowers it — the tracker takes the max.
+    protected override void OnProgressTick(double currentTime) => _playTracker?.OnProgress(currentTime);
+
+    // Organic end-of-stream closes the session; the bucket reflects the high-water fraction reached.
+    protected override void OnPlaybackEnded() => _playTracker?.Close();
+
     public override async Task SelectTrack(TrackDto track)
     {
         await SelectTrackStreaming(track);
@@ -88,6 +140,10 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
 
         // Save track ID for seek operations
         _currentTrackId = track.EntryKey;
+        // A fresh load is a fresh play candidate (§1d: replays = multiple plays). Arm the
+        // one-shot session-open guard; the session actually opens at the playback-start transition
+        // below (a track that fails to load never reaches it, so it does not count).
+        _sessionOpened = false;
         // Expose to UI immediately — Now-Playing surfaces should reflect the selected
         // track while it's still loading, not only after playback starts.
         CurrentTrack = track;
@@ -303,6 +359,10 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
                     {
                         Duration = chunkResult.Duration.Value;
                         _logger.LogInformation("Duration set from WAV header: {Duration:F2} seconds", Duration);
+                        // Feed the same once-only duration to the play session so it can compute the
+                        // completion fraction at close. Safe before/after session open — SetDuration
+                        // is a no-op when no session is open and idempotent otherwise.
+                        _playTracker?.SetDuration(chunkResult.Duration.Value);
                     }
 
                     // Start playback as soon as we can
@@ -316,6 +376,20 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
                             IsPaused = false;
                             IsLoaded = true; // Track is loaded and ready to play (even if still downloading)
                             ErrorMessage = null;
+
+                            // Open the play session exactly once per load, at the moment playback truly
+                            // begins (§2.1). The _sessionOpened guard keeps the SeekBeyondBuffer re-stream
+                            // — which re-enters this transition with _streamingPlaybackStarted reset —
+                            // from opening a second session for the same play. Duration may already be
+                            // known from a prior chunk, so re-feed it after opening.
+                            if (!_sessionOpened && _currentTrackId is { } trackKey)
+                            {
+                                _sessionOpened = true;
+                                _playTracker?.OnPlaybackStarted(trackKey);
+                                if (Duration is { } d)
+                                    _playTracker?.SetDuration(d);
+                            }
+
                             await NotifyStateChanged(); // Immediate notification for critical state change
                         }
                         else
@@ -533,6 +607,13 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
     /// </summary>
     private async Task ResetToIdle()
     {
+        // 0. Close any open play session BEFORE tearing down (§2.1). ResetToIdle is the single funnel
+        //    for stop / unload / dispose / track-switch (a new LoadTrackStreaming calls it first), so a
+        //    superseded listen is recorded here with its high-water bucket. Close is idempotent — if the
+        //    session already closed organically or via the unload beacon, this is a no-op.
+        _playTracker?.Close();
+        _sessionOpened = false;
+
         // 1. Cancel any ongoing streaming operation and wait for it to exit
         //    before tearing down JS state. Otherwise the loop's pending
         //    ProcessStreamingChunk call can land after StopAsync/UnloadAsync.
@@ -630,12 +711,24 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
     {
         try
         {
+            // ResetToIdle closes any open play session, so a dispose mid-play still records the listen.
             await ResetToIdle();
         }
         catch
         {
             // Disposal must not throw; any failure here is best-effort cleanup.
         }
+
+        // Detach the page-unload handler so the torn-down circuit is never invoked, then release the
+        // self-reference. Best-effort — the JS side tolerates an absent key.
+        if (_unloadKey is not null && _beacon is not null)
+        {
+            try { await _beacon.UnregisterUnloadAsync(_unloadKey); }
+            catch { /* best-effort */ }
+        }
+        _unloadRef?.Dispose();
+        _unloadRef = null;
+
         await base.DisposeAsync();
     }
 

DeepDrftPublic.Client/Startup.cs

@@ -33,6 +33,14 @@ public static class Startup
         // Waveform visualizer controls — scoped so the eight slider positions persist across navigation
         // within a session and reset on a fresh page load (see WaveformVisualizerControlState).
         services.AddScoped<WaveformVisualizerControlState>();
+
+        // Phase 16 anonymous telemetry (client side). BeaconInterop wraps sendBeacon; the play sink and
+        // share tracker fire events through it. The play tracker itself is NOT registered — the player
+        // is not DI-registered, so AudioPlayerProvider constructs the tracker and attaches it. ShareTracker
+        // is scoped so its per-(target,channel) debounce memory lives for the session.
+        services.AddScoped<BeaconInterop>();
+        services.AddScoped<IPlayEventSink, BeaconPlayEventSink>();
+        services.AddScoped<ShareTracker>();
     }
 
     public static void ConfigureApiHttpClient(IServiceCollection services, string baseAddress)

DeepDrftPublic/Components/App.razor

@@ -25,6 +25,7 @@
 <script src=@Assets["_content/MudBlazor/MudBlazor.min.js"]></script>
 <script type="module">
         import('./js/audio/index.js');
+        import('./js/telemetry/beacon.js');
     </script>
 </body>
 </html>

DeepDrftPublic/Controllers/EventProxyController.cs

@@ -0,0 +1,70 @@
+using System.Text;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DeepDrftPublic.Controllers;
+
+/// <summary>
+/// Proxies the anonymous telemetry write endpoints (<c>POST api/event/play</c> / <c>api/event/share</c>)
+/// to DeepDrftAPI so the WASM client never makes a cross-origin request (Phase 16 §2.2). Mirrors
+/// <see cref="TrackProxyController"/>'s idiom — the named <c>"DeepDrft.API"</c> client forwards the
+/// request upstream — but for a POST write: the small JSON body is buffered and relayed verbatim, and
+/// the upstream status (202 on success, 4xx on a rejected payload, 429 on rate limit) passes back so the
+/// beacon's fire-and-forget contract is preserved end to end. SSR never posts these — they originate
+/// from the browser player/share surfaces only.
+/// </summary>
+// A sendBeacon POST cannot attach a Blazor antiforgery token, so the telemetry write routes opt out
+// explicitly. They are anonymous, idempotent-enough fire-and-forget logging — there is no
+// state-changing user action to protect with CSRF tokens, and the upstream rate-limits by IP.
+[ApiController]
+[Route("api/event")]
+[IgnoreAntiforgeryToken]
+public class EventProxyController : ControllerBase
+{
+    private readonly HttpClient _upstream;
+    private readonly ILogger<EventProxyController> _logger;
+
+    public EventProxyController(IHttpClientFactory httpClientFactory, ILogger<EventProxyController> logger)
+    {
+        _upstream = httpClientFactory.CreateClient("DeepDrft.API");
+        _logger = logger;
+    }
+
+    /// <summary>Proxies a play event upstream. Body is opaque JSON — validated by DeepDrftAPI, not here.</summary>
+    [HttpPost("play")]
+    public Task<ActionResult> ForwardPlay(CancellationToken ct = default) => Forward("api/event/play", ct);
+
+    /// <summary>Proxies a share event upstream.</summary>
+    [HttpPost("share")]
+    public Task<ActionResult> ForwardShare(CancellationToken ct = default) => Forward("api/event/share", ct);
+
+    private async Task<ActionResult> Forward(string upstreamPath, CancellationToken ct)
+    {
+        // Buffer the small JSON body and relay it verbatim. Reading the raw body keeps the proxy
+        // transparent — it does not deserialize or re-shape the payload, just forwards it.
+        string body;
+        using (var reader = new StreamReader(Request.Body, Encoding.UTF8))
+        {
+            body = await reader.ReadToEndAsync(ct);
+        }
+
+        using var content = new StringContent(body, Encoding.UTF8, "application/json");
+
+        HttpResponseMessage upstream;
+        try
+        {
+            upstream = await _upstream.PostAsync(upstreamPath, content, ct);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Upstream call to DeepDrftAPI {Path} failed", upstreamPath);
+            return StatusCode(502, "Upstream unavailable");
+        }
+
+        // Relay the upstream status as-is. Telemetry is fire-and-forget; the beacon never reads the
+        // body, so there is nothing to relay beyond the code (202 / 400 / 429 / 5xx).
+        using (upstream)
+        {
+            return StatusCode((int)upstream.StatusCode);
+        }
+    }
+}

DeepDrftPublic/Interop/telemetry/beacon.ts

@@ -0,0 +1,88 @@
+/**
+ * Telemetry beacon interop (Phase 16 §2.2). A thin wrapper over navigator.sendBeacon for fire-and-forget
+ * play/share events, plus a page-unload handler that lets the player close an open play session as the
+ * tab goes away. sendBeacon (not fetch) is the load-bearing choice: it survives page unload, where a
+ * fetch would be cancelled — exactly the tab-close edge case the play metric must still record.
+ *
+ * Exposed on window.DeepDrftBeacon; imported once in App.razor alongside the audio engine.
+ */
+
+// .NET interop type — a DotNetObjectReference the unload handler invokes back into.
+interface DotNetObjectReference {
+    invokeMethodAsync(methodName: string, ...args: unknown[]): Promise<unknown>;
+    invokeMethod(methodName: string, ...args: unknown[]): unknown;
+}
+
+// Registered unload listeners. Holding the handler lets us detach on dispose so a torn-down player
+// circuit does not get called into.
+type UnloadEntry = { dotNetRef: DotNetObjectReference; methodName: string };
+const unloadHandlers = new Map<string, UnloadEntry>();
+
+let unloadWired = false;
+
+// Fire every registered unload handler synchronously. invokeMethod (sync) — not invokeMethodAsync — is
+// required here: in pagehide/visibilitychange→hidden the event loop will not pump a microtask before the
+// page is frozen, so an awaited call would never run. The .NET side does only synchronous beacon work.
+function fireUnloadHandlers(): void {
+    for (const { dotNetRef, methodName } of unloadHandlers.values()) {
+        try {
+            dotNetRef.invokeMethod(methodName);
+        } catch {
+            // A torn-down circuit or a transient interop failure must never block unload.
+        }
+    }
+}
+
+function wireUnloadOnce(): void {
+    if (unloadWired) return;
+    unloadWired = true;
+
+    // pagehide is the canonical "page is going away" signal (covers tab close, navigation, and the
+    // bfcache freeze). visibilitychange→hidden additionally covers the mobile case where the tab is
+    // backgrounded and may be discarded without a pagehide. Both funnel to the same close path; the
+    // .NET side is idempotent, so a double-fire closes the session at most once.
+    window.addEventListener('pagehide', fireUnloadHandlers);
+    document.addEventListener('visibilitychange', () => {
+        if (document.visibilityState === 'hidden') fireUnloadHandlers();
+    });
+}
+
+const DeepDrftBeacon = {
+    /**
+     * Queue a fire-and-forget POST of a small JSON body. Returns false if the browser refused to queue
+     * the beacon (e.g. over the per-origin byte budget) — callers ignore it; a dropped telemetry event
+     * is acceptable by design.
+     */
+    send: (url: string, json: string): boolean => {
+        try {
+            const blob = new Blob([json], { type: 'application/json' });
+            return navigator.sendBeacon(url, blob);
+        } catch {
+            return false;
+        }
+    },
+
+    /**
+     * Register a .NET callback to run on page unload (and on visibility→hidden). Keyed so a given player
+     * registers once and can replace/detach cleanly across its lifecycle.
+     */
+    registerUnload: (key: string, dotNetRef: DotNetObjectReference, methodName: string): void => {
+        wireUnloadOnce();
+        unloadHandlers.set(key, { dotNetRef, methodName });
+    },
+
+    /** Detach a previously-registered unload callback (player dispose). */
+    unregisterUnload: (key: string): void => {
+        unloadHandlers.delete(key);
+    },
+};
+
+declare global {
+    interface Window {
+        DeepDrftBeacon: typeof DeepDrftBeacon;
+    }
+}
+
+window.DeepDrftBeacon = DeepDrftBeacon;
+
+export { DeepDrftBeacon };

DeepDrftTests/PlayEventQueryTests.cs

@@ -0,0 +1,174 @@
+using DeepDrftData.Data;
+using DeepDrftData.Repositories;
+using DeepDrftModels.Entities;
+using DeepDrftModels.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+
+namespace DeepDrftTests;
+
+/// <summary>
+/// Storage-layer tests for the Phase 16 telemetry writes (<see cref="EventRepository"/>): server-side
+/// release resolution (§2.3 / D4), the incremental play-counter bump in the same write (D6), the
+/// derived-release-total shape (a release's plays are the sum of its tracks'), and the share append.
+/// Runs on the EF in-memory provider like <see cref="HomeStatsQueryTests"/>. In-memory does not support
+/// real transactions, so the transaction-ignored warning is suppressed — the production Postgres path
+/// wraps the append + bump in one transaction, which the warning would otherwise turn into an error here.
+/// </summary>
+[TestFixture]
+public class PlayEventQueryTests
+{
+    private DeepDrftContext _context = null!;
+
+    [SetUp]
+    public void SetUp()
+    {
+        var options = new DbContextOptionsBuilder<DeepDrftContext>()
+            .UseInMemoryDatabase(databaseName: Guid.NewGuid().ToString())
+            .ConfigureWarnings(w => w.Ignore(InMemoryEventId.TransactionIgnoredWarning))
+            .Options;
+        _context = new DeepDrftContext(options);
+    }
+
+    [TearDown]
+    public void TearDown() => _context.Dispose();
+
+    private EventRepository CreateRepository() => new(_context);
+
+    private async Task<(ReleaseEntity Release, TrackEntity Track)> SeedTrackAsync(string trackKey)
+    {
+        var release = new ReleaseEntity
+        {
+            EntryKey = Guid.NewGuid().ToString("N"),
+            Title = "R",
+            Artist = "A",
+            Medium = ReleaseMedium.Cut,
+        };
+        var track = new TrackEntity { EntryKey = trackKey, TrackName = "T", Release = release };
+        _context.Releases.Add(release);
+        _context.Tracks.Add(track);
+        await _context.SaveChangesAsync();
+        return (release, track);
+    }
+
+    // A play that reaches the repository (the floor is the tracker's job) writes exactly one play_event
+    // row with the release id resolved server-side, and bumps the matching bucket on the track's counter.
+    [Test]
+    public async Task RecordPlayAsync_ResolvesReleaseAndBumpsCounter()
+    {
+        var (release, track) = await SeedTrackAsync("track-1");
+
+        await CreateRepository().RecordPlayAsync("track-1", PlayBucket.Complete, anonId: null);
+
+        var ev = await _context.PlayEvents.SingleAsync();
+        Assert.That(ev.TrackEntryKey, Is.EqualTo("track-1"));
+        Assert.That(ev.ReleaseId, Is.EqualTo(release.Id), "release resolved server-side from the track key");
+        Assert.That(ev.Bucket, Is.EqualTo(PlayBucket.Complete));
+        Assert.That(ev.AnonId, Is.Null, "no anonId is written in wave 16.1");
+
+        var counter = await _context.PlayCounters.SingleAsync(c => c.TrackId == track.Id);
+        Assert.That(counter.CompleteCount, Is.EqualTo(1));
+        Assert.That(counter.TotalPlays, Is.EqualTo(1));
+    }
+
+    // Each bucket bumps its own column; total plays is the sum across buckets.
+    [Test]
+    public async Task RecordPlayAsync_BucketsAccumulateIndependently()
+    {
+        var (_, track) = await SeedTrackAsync("track-1");
+        var repo = CreateRepository();
+
+        await repo.RecordPlayAsync("track-1", PlayBucket.Partial, null);
+        await repo.RecordPlayAsync("track-1", PlayBucket.Sampled, null);
+        await repo.RecordPlayAsync("track-1", PlayBucket.Sampled, null);
+        await repo.RecordPlayAsync("track-1", PlayBucket.Complete, null);
+
+        var counter = await _context.PlayCounters.SingleAsync(c => c.TrackId == track.Id);
+        Assert.That(counter.PartialCount, Is.EqualTo(1));
+        Assert.That(counter.SampledCount, Is.EqualTo(2));
+        Assert.That(counter.CompleteCount, Is.EqualTo(1));
+        Assert.That(counter.TotalPlays, Is.EqualTo(4));
+        Assert.That(await _context.PlayEvents.CountAsync(), Is.EqualTo(4));
+    }
+
+    // Release totals are derived (D4): summing the counters of the release's tracks gives release plays;
+    // there is no separate release-counter row.
+    [Test]
+    public async Task RecordPlayAsync_ReleaseTotalIsSumOfTrackCounters()
+    {
+        var release = new ReleaseEntity
+        {
+            EntryKey = Guid.NewGuid().ToString("N"), Title = "R", Artist = "A", Medium = ReleaseMedium.Cut,
+        };
+        var t1 = new TrackEntity { EntryKey = "t1", TrackName = "T1", Release = release };
+        var t2 = new TrackEntity { EntryKey = "t2", TrackName = "T2", Release = release };
+        _context.Releases.Add(release);
+        _context.Tracks.AddRange(t1, t2);
+        await _context.SaveChangesAsync();
+
+        var repo = CreateRepository();
+        await repo.RecordPlayAsync("t1", PlayBucket.Complete, null);
+        await repo.RecordPlayAsync("t1", PlayBucket.Partial, null);
+        await repo.RecordPlayAsync("t2", PlayBucket.Sampled, null);
+
+        var releaseTotal = await _context.PlayCounters
+            .Where(c => _context.Tracks.Any(t => t.Id == c.TrackId && t.ReleaseId == release.Id))
+            .SumAsync(c => c.PartialCount + c.SampledCount + c.CompleteCount);
+
+        Assert.That(releaseTotal, Is.EqualTo(3));
+    }
+
+    // A loose track (no release) logs the event with a null release id and still bumps its own counter.
+    [Test]
+    public async Task RecordPlayAsync_LooseTrack_NullReleaseStillCounts()
+    {
+        var track = new TrackEntity { EntryKey = "loose", TrackName = "T" };
+        _context.Tracks.Add(track);
+        await _context.SaveChangesAsync();
+
+        await CreateRepository().RecordPlayAsync("loose", PlayBucket.Sampled, null);
+
+        var ev = await _context.PlayEvents.SingleAsync();
+        Assert.That(ev.ReleaseId, Is.Null);
+        Assert.That((await _context.PlayCounters.SingleAsync(c => c.TrackId == track.Id)).SampledCount, Is.EqualTo(1));
+    }
+
+    // A play of an unknown/removed track key still logs (null release, no counter bump) rather than failing.
+    [Test]
+    public async Task RecordPlayAsync_UnknownTrackKey_LogsEventWithoutCounter()
+    {
+        await CreateRepository().RecordPlayAsync("does-not-exist", PlayBucket.Partial, null);
+
+        var ev = await _context.PlayEvents.SingleAsync();
+        Assert.That(ev.ReleaseId, Is.Null);
+        Assert.That(await _context.PlayCounters.AnyAsync(), Is.False, "no track to roll up against");
+    }
+
+    // A soft-deleted track resolves to null (the !IsDeleted guard) — the play still logs, no counter bump.
+    [Test]
+    public async Task RecordPlayAsync_SoftDeletedTrack_DoesNotResolveRelease()
+    {
+        var (_, track) = await SeedTrackAsync("gone");
+        track.IsDeleted = true;
+        await _context.SaveChangesAsync();
+
+        await CreateRepository().RecordPlayAsync("gone", PlayBucket.Complete, null);
+
+        var ev = await _context.PlayEvents.SingleAsync();
+        Assert.That(ev.ReleaseId, Is.Null);
+        Assert.That(await _context.PlayCounters.AnyAsync(c => c.TrackId == track.Id), Is.False);
+    }
+
+    // A share append writes one row with the target, channel, and a null anonId.
+    [Test]
+    public async Task RecordShareAsync_AppendsRow()
+    {
+        await CreateRepository().RecordShareAsync(ShareTargetType.Release, "rel-key", ShareChannel.Embed, anonId: null);
+
+        var ev = await _context.ShareEvents.SingleAsync();
+        Assert.That(ev.TargetType, Is.EqualTo(ShareTargetType.Release));
+        Assert.That(ev.TargetKey, Is.EqualTo("rel-key"));
+        Assert.That(ev.Channel, Is.EqualTo(ShareChannel.Embed));
+        Assert.That(ev.AnonId, Is.Null);
+    }
+}

DeepDrftTests/PlayTrackerTests.cs

@@ -0,0 +1,205 @@
+using DeepDrftModels.Enums;
+using DeepDrftPublic.Client.Services;
+
+namespace DeepDrftTests;
+
+/// <summary>
+/// Unit tests for the Phase 16 play-session tracker (<see cref="PlayTracker"/>): the engagement-floor
+/// gate (§1d / D2 — ≥3s OR ≥5% of duration, whichever smaller) and the three-bucket completion
+/// classification (§1a / D1 — partial &lt;30%, sampled 30–80%, complete &gt;80%), exercised behind a
+/// fake sink so the logic is tested with no player or JS interop — the seam the spec calls out as
+/// testable. Also covers the high-water (seek-backward) and idempotent-close invariants.
+/// </summary>
+[TestFixture]
+public class PlayTrackerTests
+{
+    // Captures emitted plays so assertions read the (key, bucket) the tracker classified.
+    private sealed class FakeSink : IPlayEventSink
+    {
+        public List<(string Key, PlayBucket Bucket)> Emitted { get; } = new();
+        public void EmitPlay(string trackEntryKey, PlayBucket bucket) => Emitted.Add((trackEntryKey, bucket));
+    }
+
+    private FakeSink _sink = null!;
+    private PlayTracker _tracker = null!;
+
+    [SetUp]
+    public void SetUp()
+    {
+        _sink = new FakeSink();
+        _tracker = new PlayTracker(_sink);
+    }
+
+    // Drive a full session: open, set duration, advance to a high-water position, close.
+    private void PlaySession(string key, double duration, double highWater)
+    {
+        _tracker.OnPlaybackStarted(key);
+        _tracker.SetDuration(duration);
+        _tracker.OnProgress(highWater);
+        _tracker.Close();
+    }
+
+    // --- Engagement floor (§1d / D2) ---
+
+    // A long track floors on the 3-second wall (3s < 5% of 200s = 10s): under 3s sends nothing.
+    [Test]
+    public void Close_LongTrackUnderThreeSeconds_SendsNothing()
+    {
+        PlaySession("t", duration: 200, highWater: 2.5);
+        Assert.That(_sink.Emitted, Is.Empty);
+    }
+
+    // The same long track at exactly the 3-second floor crosses it and records a (partial) play.
+    [Test]
+    public void Close_LongTrackAtThreeSecondFloor_RecordsPlay()
+    {
+        PlaySession("t", duration: 200, highWater: 3.0);
+        Assert.That(_sink.Emitted, Has.Count.EqualTo(1));
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Partial));
+    }
+
+    // A short clip floors on the percentage (5% of 40s = 2s < 3s): 1.5s is below 2s → nothing.
+    [Test]
+    public void Close_ShortClipUnderFivePercent_SendsNothing()
+    {
+        PlaySession("t", duration: 40, highWater: 1.5);
+        Assert.That(_sink.Emitted, Is.Empty);
+    }
+
+    // The same short clip at the 5%-of-duration floor (2s) crosses it and records.
+    [Test]
+    public void Close_ShortClipAtFivePercentFloor_RecordsPlay()
+    {
+        PlaySession("t", duration: 40, highWater: 2.0);
+        Assert.That(_sink.Emitted, Has.Count.EqualTo(1));
+    }
+
+    // --- Bucket classification (§1a / D1) ---
+
+    // [floor, 30%) → partial. 60/200 = 30% is the boundary, so 59.9/200 (just under) is partial.
+    [Test]
+    public void Close_UnderThirtyPercent_ClassifiesPartial()
+    {
+        PlaySession("t", duration: 200, highWater: 50);   // 25%
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Partial));
+    }
+
+    // Exactly 30% is the start of the sampled band [30%, 80%].
+    [Test]
+    public void Close_AtThirtyPercent_ClassifiesSampled()
+    {
+        PlaySession("t", duration: 200, highWater: 60);   // 30%
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Sampled));
+    }
+
+    // Mid-band is sampled.
+    [Test]
+    public void Close_MidBand_ClassifiesSampled()
+    {
+        PlaySession("t", duration: 200, highWater: 120);  // 60%
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Sampled));
+    }
+
+    // Exactly 80% is the inclusive top of the sampled band — still sampled, not complete.
+    [Test]
+    public void Close_AtEightyPercent_ClassifiesSampled()
+    {
+        PlaySession("t", duration: 200, highWater: 160);  // 80%
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Sampled));
+    }
+
+    // Past 80% is complete.
+    [Test]
+    public void Close_OverEightyPercent_ClassifiesComplete()
+    {
+        PlaySession("t", duration: 200, highWater: 190);  // 95%
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Complete));
+    }
+
+    // A full listen classifies complete, and the high-water is clamped (never over 100%).
+    [Test]
+    public void Close_FullListen_ClassifiesComplete()
+    {
+        PlaySession("t", duration: 200, highWater: 200);
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Complete));
+    }
+
+    // --- High-water invariant (§1d: seeks never lower the mark) ---
+
+    // Seeking backward after reaching the end still classifies complete — the max position wins.
+    [Test]
+    public void Close_SeekBackwardAfterEnd_StaysComplete()
+    {
+        _tracker.OnPlaybackStarted("t");
+        _tracker.SetDuration(200);
+        _tracker.OnProgress(190);   // reached 95%
+        _tracker.OnProgress(20);    // seek back to 10% — must NOT lower the high-water
+        _tracker.Close();
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Complete));
+    }
+
+    // --- Session lifecycle ---
+
+    // Carries the track key the session opened with through to the emitted event.
+    [Test]
+    public void Close_RecordsTheOpenedTrackKey()
+    {
+        PlaySession("the-entry-key", duration: 100, highWater: 90);
+        Assert.That(_sink.Emitted[0].Key, Is.EqualTo("the-entry-key"));
+    }
+
+    // Close is idempotent — a second close (e.g. organic end after the unload beacon already fired) emits nothing further.
+    [Test]
+    public void Close_CalledTwice_EmitsOnce()
+    {
+        PlaySession("t", duration: 100, highWater: 90);
+        _tracker.Close();
+        Assert.That(_sink.Emitted, Has.Count.EqualTo(1));
+    }
+
+    // A session with no duration ever set (header never parsed) has no fraction to classify → nothing.
+    [Test]
+    public void Close_WithoutDuration_SendsNothing()
+    {
+        _tracker.OnPlaybackStarted("t");
+        _tracker.OnProgress(30);
+        _tracker.Close();
+        Assert.That(_sink.Emitted, Is.Empty);
+    }
+
+    // Progress before any session opens is ignored (no open session to advance), so a later open+close
+    // starts the high-water from zero.
+    [Test]
+    public void OnProgress_BeforeOpen_IsIgnored()
+    {
+        _tracker.OnProgress(150);
+        PlaySession("t", duration: 200, highWater: 10);   // 5% — partial
+        Assert.That(_sink.Emitted[0].Bucket, Is.EqualTo(PlayBucket.Partial));
+    }
+
+    // Opening a new session while one is still open closes (and records) the prior one — a track-switch
+    // that did not route through Close still records the superseded listen. Two complete plays result.
+    [Test]
+    public void OnPlaybackStarted_WhileOpen_ClosesPriorSession()
+    {
+        _tracker.OnPlaybackStarted("first");
+        _tracker.SetDuration(100);
+        _tracker.OnProgress(95);                // first: complete
+        _tracker.OnPlaybackStarted("second");   // supersedes — records first
+        _tracker.SetDuration(100);
+        _tracker.OnProgress(95);                // second: complete
+        _tracker.Close();
+
+        Assert.That(_sink.Emitted.Select(e => e.Key), Is.EqualTo(new[] { "first", "second" }));
+        Assert.That(_sink.Emitted.All(e => e.Bucket == PlayBucket.Complete), Is.True);
+    }
+
+    // A replay (open the same key again after closing) is a second, independent play (§1d).
+    [Test]
+    public void Replay_RecordsTwoPlays()
+    {
+        PlaySession("t", duration: 100, highWater: 95);
+        PlaySession("t", duration: 100, highWater: 95);
+        Assert.That(_sink.Emitted, Has.Count.EqualTo(2));
+    }
+}

DeepDrftTests/ShareTrackerTests.cs

@@ -0,0 +1,94 @@
+using DeepDrftModels.Enums;
+using DeepDrftPublic.Client.Services;
+using Microsoft.AspNetCore.Components;
+using Microsoft.JSInterop;
+using Microsoft.JSInterop.Infrastructure;
+
+namespace DeepDrftTests;
+
+/// <summary>
+/// Unit tests for the Phase 16 share tracker (<see cref="ShareTracker"/>): the per-(target,channel)
+/// debounce (§1b — at most one event per target+channel per 60s window per session). The tracker fires
+/// through a beacon that wraps <see cref="IJSRuntime"/>; the tests use a no-op JS runtime (the send is
+/// fire-and-forget and its outcome is irrelevant) and assert on the debounce decision via the bool the
+/// recorder returns — true when an event fired, false when debounced.
+/// </summary>
+[TestFixture]
+public class ShareTrackerTests
+{
+    // sendBeacon interop is fire-and-forget; the tracker never reads the result, so a no-op runtime that
+    // returns default for any invocation is sufficient to exercise the debounce logic.
+    private sealed class NoopJsRuntime : IJSRuntime
+    {
+        public ValueTask<TValue> InvokeAsync<TValue>(string identifier, object?[]? args)
+            => ValueTask.FromResult<TValue>(default!);
+
+        public ValueTask<TValue> InvokeAsync<TValue>(string identifier, CancellationToken cancellationToken, object?[]? args)
+            => ValueTask.FromResult<TValue>(default!);
+    }
+
+    // Minimal NavigationManager so the tracker can compose the (unused-in-test) beacon URL.
+    private sealed class TestNavigationManager : NavigationManager
+    {
+        public TestNavigationManager() => Initialize("https://deepdrft.test/", "https://deepdrft.test/");
+        protected override void NavigateToCore(string uri, bool forceLoad) { }
+    }
+
+    private ShareTracker _tracker = null!;
+    private readonly DateTimeOffset _t0 = new(2026, 6, 19, 12, 0, 0, TimeSpan.Zero);
+
+    [SetUp]
+    public void SetUp()
+        => _tracker = new ShareTracker(new BeaconInterop(new NoopJsRuntime()), new TestNavigationManager());
+
+    // A copy-link records one share with channel = link.
+    [Test]
+    public void RecordShare_CopyLink_FiresOnce()
+        => Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0), Is.True);
+
+    // A copy-embed records one share with channel = embed — distinct (target,channel) from the link copy.
+    [Test]
+    public void RecordShare_CopyEmbedAfterLink_FiresSeparately()
+    {
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0), Is.True);
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Embed, _t0), Is.True,
+            "embed is a different channel from link — not debounced against it");
+    }
+
+    // An immediate repeat copy of the same (target, channel) within the window is debounced.
+    [Test]
+    public void RecordShare_ImmediateRepeat_IsDebounced()
+    {
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0), Is.True);
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0.AddSeconds(5)), Is.False);
+    }
+
+    // After the 60s window elapses, the same (target, channel) fires again.
+    [Test]
+    public void RecordShare_AfterWindow_FiresAgain()
+    {
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0), Is.True);
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "k", ShareChannel.Link, _t0.AddSeconds(61)), Is.True);
+    }
+
+    // Different targets debounce independently — sharing track A then track B both fire.
+    [Test]
+    public void RecordShare_DifferentTargets_FireIndependently()
+    {
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "a", ShareChannel.Link, _t0), Is.True);
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "b", ShareChannel.Link, _t0), Is.True);
+    }
+
+    // A track key and a release key are distinct targets even if the key string collides.
+    [Test]
+    public void RecordShare_TrackVsRelease_AreDistinctTargets()
+    {
+        Assert.That(_tracker.RecordShare(ShareTargetType.Track, "x", ShareChannel.Link, _t0), Is.True);
+        Assert.That(_tracker.RecordShare(ShareTargetType.Release, "x", ShareChannel.Link, _t0), Is.True);
+    }
+
+    // A blank target key never fires (defensive — the popover guards too).
+    [Test]
+    public void RecordShare_BlankKey_DoesNotFire()
+        => Assert.That(_tracker.RecordShare(ShareTargetType.Track, "  ", ShareChannel.Link, _t0), Is.False);
+}