NEO-47: perk unlock engine, PerkState persistence, and tests

Add V004 perk tables, in-memory/Postgres stores, PerkUnlockEngine (tier-1 branch
pick, path-auto tier-2 unlocks), level-up hook in skill XP grants, and AAA tests.
Bruno docs note internal perk reevaluation on level-up (HTTP in NEO-48).

bruno/neon-sprawl-server/skill-progression/Post skill progression grant.bru

@@ -7,6 +7,7 @@ meta {
 docs {
   NEO-38: single skill XP grant + allowlist + level-up metadata; see server README.
   NEO-40: same contract; server adds comment-only telemetry hook markers (no request/response change).
+  NEO-47: on level-up, server re-evaluates mastery perk unlocks internally (no JSON change until NEO-48 perk-state HTTP).
   E2.M2 tracking row in docs/decomposition/modules/documentation_and_implementation_alignment.md lists NEO-40 landed with plan + manual QA links.
 }
 

docs/plans/NEO-47-implementation-plan.md

@@ -52,11 +52,11 @@ So “mutually exclusive per tier” applies to **tier 1’s pick**; tier 2 is
 
 ## Acceptance criteria checklist
 
-- [ ] `IPlayerPerkStateStore` with in-memory + Postgres path (migration) mirroring skill progression pattern.
-- [ ] Unlock engine reads catalog + skill level; emits internal `PerkUnlockEvent` when perks unlock.
-- [ ] Branch pick per tier is **mutually exclusive** where a tier requires a pick; stable deny `reasonCode` on invalid picks.
-- [ ] Level-up path (after `SkillProgressionGrantOperations`) triggers re-evaluation for affected skill.
-- [ ] Unit/integration tests (AAA): eligibility, branch select, deny paths.
+- [x] `IPlayerPerkStateStore` with in-memory + Postgres path (migration) mirroring skill progression pattern.
+- [x] Unlock engine reads catalog + skill level; emits internal `PerkUnlockEvent` when perks unlock.
+- [x] Branch pick per tier is **mutually exclusive** where a tier requires a pick; stable deny `reasonCode` on invalid picks.
+- [x] Level-up path (after `SkillProgressionGrantOperations`) triggers re-evaluation for affected skill.
+- [x] Unit/integration tests (AAA): eligibility, branch select, deny paths.
 
 ## Technical approach
 

server/NeonSprawl.Server.Tests/Game/Interaction/SalvageActivityDeniedRegistryWebApplicationFactory.cs

@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using Npgsql;
@@ -25,7 +26,11 @@ public sealed class SalvageActivityDeniedRegistryWebApplicationFactory : WebAppl
         var skillsDir = SkillCatalogPathResolution.TryDiscoverSkillsDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/skills from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var masteryDir = MasteryCatalogPathResolution.TryDiscoverMasteryDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/mastery from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
+        builder.UseSetting("Content:MasteryDirectory", masteryDir);
 
         builder.ConfigureTestServices(services =>
         {
@@ -35,6 +40,7 @@ public sealed class SalvageActivityDeniedRegistryWebApplicationFactory : WebAppl
                 if (d.ServiceType == typeof(IPositionStateStore) ||
                     d.ServiceType == typeof(IPlayerHotbarLoadoutStore) ||
                     d.ServiceType == typeof(IPlayerSkillProgressionStore) ||
+                    d.ServiceType == typeof(IPlayerPerkStateStore) ||
                     d.ServiceType == typeof(TimeProvider) ||
                     d.ServiceType == typeof(IPlayerAbilityCooldownStore) ||
                     d.ServiceType == typeof(ISkillDefinitionRegistry) ||
@@ -52,6 +58,7 @@ public sealed class SalvageActivityDeniedRegistryWebApplicationFactory : WebAppl
             services.AddSingleton<IPositionStateStore, InMemoryPositionStateStore>();
             services.AddSingleton<IPlayerHotbarLoadoutStore, InMemoryPlayerHotbarLoadoutStore>();
             services.AddSingleton<IPlayerSkillProgressionStore, InMemoryPlayerSkillProgressionStore>();
+            services.AddSingleton<IPlayerPerkStateStore, InMemoryPlayerPerkStateStore>();
             services.AddSingleton<IPlayerAbilityCooldownStore, InMemoryPlayerAbilityCooldownStore>();
             services.AddSingleton<ISkillDefinitionRegistry, SalvageActivityDeniedSkillRegistry>();
         });

server/NeonSprawl.Server.Tests/Game/Mastery/PerkStatePersistenceIntegrationTests.cs

@@ -0,0 +1,85 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using NeonSprawl.Server.Game.Mastery;
+using NeonSprawl.Server.Game.PositionState;
+using NeonSprawl.Server.Game.Skills;
+using NeonSprawl.Server.Tests.Game.PositionState;
+using Npgsql;
+using Xunit;
+
+namespace NeonSprawl.Server.Tests.Game.Mastery;
+
+[Collection("Postgres integration")]
+public sealed class PerkStatePersistenceIntegrationTests(PostgresIntegrationHarness harness)
+{
+    private PostgresWebApplicationFactory Factory => harness.Factory;
+
+    [RequirePostgresFact]
+    public async Task BranchPickAndUnlock_ShouldPersistAcrossNewFactory()
+    {
+        // Arrange
+        await ResetPerkTablesAsync();
+        const string playerId = "dev-local-1";
+        using (var scope = Factory.Services.CreateScope())
+        {
+            var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
+            var engine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
+            Assert.True(xpStore.TryApplyXpDelta(playerId, "salvage", 450, out _, out _));
+            Assert.True(engine.TrySelectBranch(playerId, "salvage", 1, "scrap_efficiency").Success);
+            _ = engine.ReevaluateAfterLevelUp(playerId, "salvage", newLevel: 4);
+        }
+
+        // Act
+        PerkStateSnapshot snapshot;
+        await using (var secondFactory = new PostgresWebApplicationFactory())
+        {
+            using var scope = secondFactory.Services.CreateScope();
+            var perkStore = scope.ServiceProvider.GetRequiredService<IPlayerPerkStateStore>();
+            snapshot = perkStore.GetSnapshot(playerId);
+        }
+
+        // Assert
+        Assert.Equal("scrap_efficiency", snapshot.BranchPicksBySkillId["salvage"][1]);
+        Assert.Contains("salvage_scrap_efficiency_1", snapshot.UnlockedPerkIds);
+    }
+
+    private async Task ResetPerkTablesAsync()
+    {
+        var cs = Environment.GetEnvironmentVariable("ConnectionStrings__NeonSprawl");
+        if (string.IsNullOrWhiteSpace(cs))
+        {
+            throw new InvalidOperationException("ConnectionStrings__NeonSprawl is not set.");
+        }
+
+        _ = Factory.Services;
+        var options = Factory.Services.GetRequiredService<IOptions<GamePositionOptions>>().Value;
+
+        var positionDdlPath = Path.Combine(AppContext.BaseDirectory, "db", "migrations", "V001__player_position.sql");
+        var perkDdlPath = Path.Combine(AppContext.BaseDirectory, "db", "migrations", "V004__player_perk_state.sql");
+        if (!File.Exists(positionDdlPath) || !File.Exists(perkDdlPath))
+        {
+            throw new FileNotFoundException("Test DDL for perk persistence not found.");
+        }
+
+        var positionDdl = await File.ReadAllTextAsync(positionDdlPath);
+        var perkDdl = await File.ReadAllTextAsync(perkDdlPath);
+        await using var conn = new NpgsqlConnection(cs);
+        await conn.OpenAsync();
+        await using (var applyPosition = new NpgsqlCommand(positionDdl, conn))
+        {
+            await applyPosition.ExecuteNonQueryAsync();
+        }
+
+        await using (var truncate = new NpgsqlCommand("TRUNCATE player_position CASCADE;", conn))
+        {
+            await truncate.ExecuteNonQueryAsync();
+        }
+
+        PostgresPositionBootstrap.SeedDevPlayer(conn, options);
+
+        await using (var applyPerk = new NpgsqlCommand(perkDdl, conn))
+        {
+            await applyPerk.ExecuteNonQueryAsync();
+        }
+    }
+}

server/NeonSprawl.Server.Tests/Game/Mastery/PerkUnlockEngineTests.cs

@@ -0,0 +1,189 @@
+using System.Net.Http.Json;
+using Microsoft.Extensions.DependencyInjection;
+using NeonSprawl.Server.Game.Mastery;
+using NeonSprawl.Server.Game.Skills;
+using Xunit;
+
+namespace NeonSprawl.Server.Tests.Game.Mastery;
+
+public sealed class PerkUnlockEngineTests
+{
+    private const string DevPlayer = "dev-local-1";
+    private const string SalvageSkill = "salvage";
+    private const string ScrapBranch = "scrap_efficiency";
+    private const string BulkBranch = "bulk_haul";
+    private const string ScrapPerk = "salvage_scrap_efficiency_1";
+    private const string BulkPerk = "salvage_bulk_haul_1";
+
+    private static (PerkUnlockEngine Engine, IPlayerSkillProgressionStore XpStore, IPlayerPerkStateStore PerkStore) CreateEngine(
+        InMemoryWebApplicationFactory factory)
+    {
+        var scope = factory.Services.CreateScope();
+        return (
+            scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>(),
+            scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>(),
+            scope.ServiceProvider.GetRequiredService<IPlayerPerkStateStore>());
+    }
+
+    [Fact]
+    public async Task TrySelectBranch_AtSalvageLevel2_ShouldRecordPick_WithoutUnlockingTier2Perks()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, perkStore) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 100, out _, out _));
+
+        // Act
+        var outcome = engine.TrySelectBranch(DevPlayer, SalvageSkill, tierIndex: 1, ScrapBranch);
+
+        // Assert
+        Assert.True(outcome.Success);
+        Assert.Null(outcome.ReasonCode);
+        Assert.Empty(outcome.Events);
+        var snap = perkStore.GetSnapshot(DevPlayer);
+        Assert.Equal(ScrapBranch, snap.BranchPicksBySkillId[SalvageSkill][1]);
+        Assert.DoesNotContain(ScrapPerk, snap.UnlockedPerkIds);
+        Assert.DoesNotContain(BulkPerk, snap.UnlockedPerkIds);
+    }
+
+    [Fact]
+    public async Task TrySelectBranch_WhenLevelTooLow_ShouldDenyWithLevelTooLow()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, _, _) = CreateEngine(factory);
+
+        // Act
+        var outcome = engine.TrySelectBranch(DevPlayer, SalvageSkill, tierIndex: 1, ScrapBranch);
+
+        // Assert
+        Assert.False(outcome.Success);
+        Assert.Equal(PerkUnlockReasonCodes.LevelTooLow, outcome.ReasonCode);
+    }
+
+    [Fact]
+    public async Task TrySelectBranch_WhenBranchAlreadyChosen_ShouldDenyWithBranchAlreadyChosen()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, _) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 100, out _, out _));
+        Assert.True(engine.TrySelectBranch(DevPlayer, SalvageSkill, 1, ScrapBranch).Success);
+
+        // Act
+        var outcome = engine.TrySelectBranch(DevPlayer, SalvageSkill, tierIndex: 1, BulkBranch);
+
+        // Assert
+        Assert.False(outcome.Success);
+        Assert.Equal(PerkUnlockReasonCodes.BranchAlreadyChosen, outcome.ReasonCode);
+    }
+
+    [Fact]
+    public async Task TrySelectBranch_WhenBranchUnknown_ShouldDenyWithUnknownBranch()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, _) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 100, out _, out _));
+
+        // Act
+        var outcome = engine.TrySelectBranch(DevPlayer, SalvageSkill, tierIndex: 1, "not_a_branch");
+
+        // Assert
+        Assert.False(outcome.Success);
+        Assert.Equal(PerkUnlockReasonCodes.UnknownBranch, outcome.ReasonCode);
+    }
+
+    [Fact]
+    public async Task TrySelectBranch_OnPathAutoTier2_ShouldDenyWithTierBranchNotSelectable()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, _) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 450, out _, out _));
+        Assert.True(engine.TrySelectBranch(DevPlayer, SalvageSkill, 1, ScrapBranch).Success);
+
+        // Act
+        var outcome = engine.TrySelectBranch(DevPlayer, SalvageSkill, tierIndex: 2, ScrapBranch);
+
+        // Assert
+        Assert.False(outcome.Success);
+        Assert.Equal(PerkUnlockReasonCodes.TierBranchNotSelectable, outcome.ReasonCode);
+    }
+
+    [Fact]
+    public async Task ReevaluateAfterLevelUp_AtLevel4WithTier1Pick_ShouldUnlockScrapPerkOnly()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, perkStore) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 450, out _, out _));
+        Assert.True(engine.TrySelectBranch(DevPlayer, SalvageSkill, 1, ScrapBranch).Success);
+
+        // Act
+        var outcome = engine.ReevaluateAfterLevelUp(DevPlayer, SalvageSkill, newLevel: 4);
+
+        // Assert
+        var perk = Assert.Single(outcome.Events);
+        Assert.Equal(ScrapPerk, perk.PerkId);
+        Assert.Equal(PerkUnlockSource.LevelUp, perk.Source);
+        var snap = perkStore.GetSnapshot(DevPlayer);
+        Assert.Contains(ScrapPerk, snap.UnlockedPerkIds);
+        Assert.DoesNotContain(BulkPerk, snap.UnlockedPerkIds);
+    }
+
+    [Fact]
+    public async Task ReevaluateAfterLevelUp_WhenCalledTwice_ShouldBeIdempotent()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        _ = factory.CreateClient();
+        var (engine, xpStore, perkStore) = CreateEngine(factory);
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 450, out _, out _));
+        Assert.True(engine.TrySelectBranch(DevPlayer, SalvageSkill, 1, ScrapBranch).Success);
+        _ = engine.ReevaluateAfterLevelUp(DevPlayer, SalvageSkill, newLevel: 4);
+
+        // Act
+        var second = engine.ReevaluateAfterLevelUp(DevPlayer, SalvageSkill, newLevel: 4);
+
+        // Assert
+        Assert.Empty(second.Events);
+        var snap = perkStore.GetSnapshot(DevPlayer);
+        Assert.Single(snap.UnlockedPerkIds);
+    }
+
+    [Fact]
+    public async Task PostSkillProgressionGrant_AfterTier1PickAndLevel4Xp_ShouldUnlockPerkViaHook()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        var client = factory.CreateClient();
+        using var scope = factory.Services.CreateScope();
+        var engine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
+        var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
+        var perkStore = scope.ServiceProvider.GetRequiredService<IPlayerPerkStateStore>();
+        Assert.True(xpStore.TryApplyXpDelta(DevPlayer, SalvageSkill, 100, out _, out _));
+        Assert.True(engine.TrySelectBranch(DevPlayer, SalvageSkill, 1, ScrapBranch).Success);
+        var grant = new SkillProgressionGrantRequest
+        {
+            SchemaVersion = SkillProgressionGrantRequest.CurrentSchemaVersion,
+            SkillId = SalvageSkill,
+            Amount = 350,
+            SourceKind = "activity",
+        };
+
+        // Act
+        var response = await client.PostAsJsonAsync($"/game/players/{DevPlayer}/skill-progression", grant);
+
+        // Assert
+        Assert.True(response.IsSuccessStatusCode);
+        var snap = perkStore.GetSnapshot(DevPlayer);
+        Assert.Contains(ScrapPerk, snap.UnlockedPerkIds);
+    }
+}

server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardDeniedRegistryWebApplicationFactory.cs

@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using Npgsql;
@@ -25,7 +26,11 @@ public sealed class MissionRewardDeniedRegistryWebApplicationFactory : WebApplic
         var skillsDir = SkillCatalogPathResolution.TryDiscoverSkillsDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/skills from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var masteryDir = MasteryCatalogPathResolution.TryDiscoverMasteryDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/mastery from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
+        builder.UseSetting("Content:MasteryDirectory", masteryDir);
 
         builder.ConfigureTestServices(services =>
         {
@@ -35,6 +40,7 @@ public sealed class MissionRewardDeniedRegistryWebApplicationFactory : WebApplic
                 if (d.ServiceType == typeof(IPositionStateStore) ||
                     d.ServiceType == typeof(IPlayerHotbarLoadoutStore) ||
                     d.ServiceType == typeof(IPlayerSkillProgressionStore) ||
+                    d.ServiceType == typeof(IPlayerPerkStateStore) ||
                     d.ServiceType == typeof(TimeProvider) ||
                     d.ServiceType == typeof(IPlayerAbilityCooldownStore) ||
                     d.ServiceType == typeof(ISkillDefinitionRegistry) ||
@@ -52,6 +58,7 @@ public sealed class MissionRewardDeniedRegistryWebApplicationFactory : WebApplic
             services.AddSingleton<IPositionStateStore, InMemoryPositionStateStore>();
             services.AddSingleton<IPlayerHotbarLoadoutStore, InMemoryPlayerHotbarLoadoutStore>();
             services.AddSingleton<IPlayerSkillProgressionStore, InMemoryPlayerSkillProgressionStore>();
+            services.AddSingleton<IPlayerPerkStateStore, InMemoryPlayerPerkStateStore>();
             services.AddSingleton<IPlayerAbilityCooldownStore, InMemoryPlayerAbilityCooldownStore>();
             services.AddSingleton<ISkillDefinitionRegistry, MissionRewardDeniedSkillRegistry>();
         });

server/NeonSprawl.Server.Tests/Game/Skills/MissionRewardSkillXpGrantTests.cs

@@ -2,6 +2,7 @@ using System.Linq;
 using System.Net;
 using System.Net.Http.Json;
 using Microsoft.Extensions.DependencyInjection;
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using Xunit;
@@ -23,6 +24,7 @@ public sealed class MissionRewardSkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
         MissionRewardSkillXpGrant.GrantFromMissionReward(
@@ -31,7 +33,8 @@ public sealed class MissionRewardSkillXpGrantTests
             TestMissionRewardXp,
             registry,
             xpStore,
-            levelCurve);
+            levelCurve,
+            perkEngine);
 
         // Assert
         var totals = xpStore.GetXpTotals("dev-local-1");
@@ -55,6 +58,7 @@ public sealed class MissionRewardSkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
         MissionRewardSkillXpGrant.GrantFromMissionReward(
@@ -63,7 +67,8 @@ public sealed class MissionRewardSkillXpGrantTests
             TestMissionRewardXp,
             registry,
             xpStore,
-            levelCurve);
+            levelCurve,
+            perkEngine);
         var snapshot = await client.GetAsync("/game/players/dev-local-1/skill-progression");
 
         // Assert
@@ -84,6 +89,7 @@ public sealed class MissionRewardSkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
         MissionRewardSkillXpGrant.GrantFromMissionReward(
@@ -92,7 +98,8 @@ public sealed class MissionRewardSkillXpGrantTests
             TestMissionRewardXp,
             registry,
             xpStore,
-            levelCurve);
+            levelCurve,
+            perkEngine);
 
         // Assert — deny returns before TryApplyXpDelta; salvage row must not appear in stored XP map.
         var totals = xpStore.GetXpTotals("dev-local-1");

server/NeonSprawl.Server.Tests/Game/Skills/RefineActivityDeniedRegistryWebApplicationFactory.cs

@@ -6,6 +6,7 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Time.Testing;
 using NeonSprawl.Server.Game.AbilityInput;
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using Npgsql;
@@ -25,7 +26,11 @@ public sealed class RefineActivityDeniedRegistryWebApplicationFactory : WebAppli
         var skillsDir = SkillCatalogPathResolution.TryDiscoverSkillsDirectory(AppContext.BaseDirectory)
             ?? throw new InvalidOperationException(
                 "Could not discover repo content/skills from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
+        var masteryDir = MasteryCatalogPathResolution.TryDiscoverMasteryDirectory(AppContext.BaseDirectory)
+            ?? throw new InvalidOperationException(
+                "Could not discover repo content/mastery from AppContext.BaseDirectory; run tests from the neon-sprawl clone.");
         builder.UseSetting("Content:SkillsDirectory", skillsDir);
+        builder.UseSetting("Content:MasteryDirectory", masteryDir);
 
         builder.ConfigureTestServices(services =>
         {
@@ -35,6 +40,7 @@ public sealed class RefineActivityDeniedRegistryWebApplicationFactory : WebAppli
                 if (d.ServiceType == typeof(IPositionStateStore) ||
                     d.ServiceType == typeof(IPlayerHotbarLoadoutStore) ||
                     d.ServiceType == typeof(IPlayerSkillProgressionStore) ||
+                    d.ServiceType == typeof(IPlayerPerkStateStore) ||
                     d.ServiceType == typeof(TimeProvider) ||
                     d.ServiceType == typeof(IPlayerAbilityCooldownStore) ||
                     d.ServiceType == typeof(ISkillDefinitionRegistry) ||
@@ -52,6 +58,7 @@ public sealed class RefineActivityDeniedRegistryWebApplicationFactory : WebAppli
             services.AddSingleton<IPositionStateStore, InMemoryPositionStateStore>();
             services.AddSingleton<IPlayerHotbarLoadoutStore, InMemoryPlayerHotbarLoadoutStore>();
             services.AddSingleton<IPlayerSkillProgressionStore, InMemoryPlayerSkillProgressionStore>();
+            services.AddSingleton<IPlayerPerkStateStore, InMemoryPlayerPerkStateStore>();
             services.AddSingleton<IPlayerAbilityCooldownStore, InMemoryPlayerAbilityCooldownStore>();
             services.AddSingleton<ISkillDefinitionRegistry, RefineActivityDeniedSkillRegistry>();
         });

server/NeonSprawl.Server.Tests/Game/Skills/RefineActivitySkillXpGrantTests.cs

@@ -2,6 +2,7 @@ using System.Linq;
 using System.Net;
 using System.Net.Http.Json;
 using Microsoft.Extensions.DependencyInjection;
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using Xunit;
@@ -21,9 +22,15 @@ public sealed class RefineActivitySkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
-        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine("dev-local-1", registry, xpStore, levelCurve);
+        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine(
+            "dev-local-1",
+            registry,
+            xpStore,
+            levelCurve,
+            perkEngine);
 
         // Assert
         var totals = xpStore.GetXpTotals("dev-local-1");
@@ -47,9 +54,15 @@ public sealed class RefineActivitySkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
-        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine("dev-local-1", registry, xpStore, levelCurve);
+        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine(
+            "dev-local-1",
+            registry,
+            xpStore,
+            levelCurve,
+            perkEngine);
         var snapshot = await client.GetAsync("/game/players/dev-local-1/skill-progression");
 
         // Assert
@@ -70,9 +83,15 @@ public sealed class RefineActivitySkillXpGrantTests
         var registry = scope.ServiceProvider.GetRequiredService<ISkillDefinitionRegistry>();
         var xpStore = scope.ServiceProvider.GetRequiredService<IPlayerSkillProgressionStore>();
         var levelCurve = scope.ServiceProvider.GetRequiredService<ISkillLevelCurve>();
+        var perkEngine = scope.ServiceProvider.GetRequiredService<PerkUnlockEngine>();
 
         // Act
-        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine("dev-local-1", registry, xpStore, levelCurve);
+        RefineActivitySkillXpGrant.GrantOnSuccessfulCraftOrRefine(
+            "dev-local-1",
+            registry,
+            xpStore,
+            levelCurve,
+            perkEngine);
 
         // Assert — deny returns before TryApplyXpDelta; refine row must not appear in stored XP map.
         var totals = xpStore.GetXpTotals("dev-local-1");

server/NeonSprawl.Server.Tests/InMemoryWebApplicationFactory.cs

@@ -41,6 +41,7 @@ public sealed class InMemoryWebApplicationFactory : WebApplicationFactory<Progra
                 if (d.ServiceType == typeof(IPositionStateStore) ||
                     d.ServiceType == typeof(IPlayerHotbarLoadoutStore) ||
                     d.ServiceType == typeof(IPlayerSkillProgressionStore) ||
+                    d.ServiceType == typeof(IPlayerPerkStateStore) ||
                     d.ServiceType == typeof(TimeProvider) ||
                     d.ServiceType == typeof(IPlayerAbilityCooldownStore) ||
                     d.ServiceType == typeof(NpgsqlDataSource) ||
@@ -58,6 +59,7 @@ public sealed class InMemoryWebApplicationFactory : WebApplicationFactory<Progra
             services.AddSingleton<IPositionStateStore, InMemoryPositionStateStore>();
             services.AddSingleton<IPlayerHotbarLoadoutStore, InMemoryPlayerHotbarLoadoutStore>();
             services.AddSingleton<IPlayerSkillProgressionStore, InMemoryPlayerSkillProgressionStore>();
+            services.AddSingleton<IPlayerPerkStateStore, InMemoryPlayerPerkStateStore>();
             services.AddSingleton<IPlayerAbilityCooldownStore, InMemoryPlayerAbilityCooldownStore>();
         });
     }

server/NeonSprawl.Server/Game/Interaction/InteractionApi.cs

@@ -1,3 +1,4 @@
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 using NeonSprawl.Server.Game.Skills;
 using NeonSprawl.Server.Game.World;
@@ -15,7 +16,8 @@ public static class InteractionApi
         app.MapPost(
             "/game/players/{id}/interact",
             (string id, InteractionRequest? body, IPositionStateStore store,
-                ISkillDefinitionRegistry registry, IPlayerSkillProgressionStore xpStore, ISkillLevelCurve levelCurve) =>
+                ISkillDefinitionRegistry registry, IPlayerSkillProgressionStore xpStore, ISkillLevelCurve levelCurve,
+                PerkUnlockEngine perkUnlockEngine) =>
             {
                 if (body is null || body.SchemaVersion != InteractionRequest.CurrentSchemaVersion)
                 {
@@ -79,7 +81,8 @@ public static class InteractionApi
                         GatherSkillXpConstants.ActivitySourceKind,
                         registry,
                         xpStore,
-                        levelCurve);
+                        levelCurve,
+                        perkUnlockEngine);
                 }
 
                 return Results.Json(

server/NeonSprawl.Server/Game/Mastery/IPlayerPerkStateStore.cs

@@ -0,0 +1,13 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Persisted mastery branch picks and unlocked perks per player (NEO-47).</summary>
+public interface IPlayerPerkStateStore
+{
+    PerkStateSnapshot GetSnapshot(string playerId);
+
+    /// <summary>Fails when pick already exists for <c>(skillId, tierIndex)</c> or player cannot be written.</summary>
+    bool TrySetBranchPick(string playerId, string skillId, int tierIndex, string branchId);
+
+    /// <summary>Adds perks not already unlocked; fails when player cannot be written.</summary>
+    bool TryAddUnlockedPerks(string playerId, IEnumerable<string> perkIds);
+}

server/NeonSprawl.Server/Game/Mastery/InMemoryPlayerPerkStateStore.cs

@@ -0,0 +1,131 @@
+using System.Collections.Concurrent;
+using Microsoft.Extensions.Options;
+using NeonSprawl.Server.Game.PositionState;
+
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Thread-safe in-memory perk state; seeds the configured dev player (NEO-47).</summary>
+public sealed class InMemoryPlayerPerkStateStore(IOptions<GamePositionOptions> options) : IPlayerPerkStateStore
+{
+    private readonly ConcurrentDictionary<string, PlayerPerkState> byPlayer = CreateInitialMap(options.Value);
+
+    private readonly ConcurrentDictionary<string, object> playerLocks = new(StringComparer.OrdinalIgnoreCase);
+
+    private static ConcurrentDictionary<string, PlayerPerkState> CreateInitialMap(GamePositionOptions o)
+    {
+        var id = NormalizePlayerId(o.DevPlayerId);
+        var map = new ConcurrentDictionary<string, PlayerPerkState>(StringComparer.OrdinalIgnoreCase);
+        map[id] = new PlayerPerkState();
+        return map;
+    }
+
+    /// <inheritdoc />
+    public PerkStateSnapshot GetSnapshot(string playerId)
+    {
+        var key = NormalizePlayerId(playerId);
+        if (key.Length == 0 || !byPlayer.TryGetValue(key, out var inner))
+        {
+            return PerkStateSnapshot.Empty;
+        }
+
+        lock (playerLocks.GetOrAdd(key, _ => new object()))
+        {
+            return inner.ToSnapshot();
+        }
+    }
+
+    /// <inheritdoc />
+    public bool TrySetBranchPick(string playerId, string skillId, int tierIndex, string branchId)
+    {
+        var key = NormalizePlayerId(playerId);
+        var sid = skillId.Trim();
+        var bid = branchId.Trim();
+        if (key.Length == 0 || sid.Length == 0 || bid.Length == 0 || tierIndex < 1
+            || !byPlayer.TryGetValue(key, out var inner))
+        {
+            return false;
+        }
+
+        lock (playerLocks.GetOrAdd(key, _ => new object()))
+        {
+            if (inner.HasBranchPick(sid, tierIndex))
+            {
+                return false;
+            }
+
+            inner.SetBranchPick(sid, tierIndex, bid);
+            return true;
+        }
+    }
+
+    /// <inheritdoc />
+    public bool TryAddUnlockedPerks(string playerId, IEnumerable<string> perkIds)
+    {
+        var key = NormalizePlayerId(playerId);
+        if (key.Length == 0 || !byPlayer.TryGetValue(key, out var inner))
+        {
+            return false;
+        }
+
+        lock (playerLocks.GetOrAdd(key, _ => new object()))
+        {
+            foreach (var raw in perkIds)
+            {
+                var pid = raw.Trim();
+                if (pid.Length == 0)
+                {
+                    continue;
+                }
+
+                inner.AddUnlockedPerk(pid);
+            }
+
+            return true;
+        }
+    }
+
+    private static string NormalizePlayerId(string? playerId)
+    {
+        var t = playerId?.Trim();
+        if (string.IsNullOrEmpty(t))
+        {
+            return string.Empty;
+        }
+
+        return t.ToLowerInvariant();
+    }
+
+    private sealed class PlayerPerkState
+    {
+        private readonly Dictionary<string, Dictionary<int, string>> branchPicks = new(StringComparer.Ordinal);
+
+        private readonly HashSet<string> unlockedPerks = new(StringComparer.Ordinal);
+
+        public bool HasBranchPick(string skillId, int tierIndex) =>
+            branchPicks.TryGetValue(skillId, out var tiers) && tiers.ContainsKey(tierIndex);
+
+        public void SetBranchPick(string skillId, int tierIndex, string branchId)
+        {
+            if (!branchPicks.TryGetValue(skillId, out var tiers))
+            {
+                tiers = new Dictionary<int, string>();
+                branchPicks[skillId] = tiers;
+            }
+
+            tiers[tierIndex] = branchId;
+        }
+
+        public void AddUnlockedPerk(string perkId) => unlockedPerks.Add(perkId);
+
+        public PerkStateSnapshot ToSnapshot()
+        {
+            var bySkill = new Dictionary<string, IReadOnlyDictionary<int, string>>(StringComparer.Ordinal);
+            foreach (var (skillId, tiers) in branchPicks)
+            {
+                bySkill[skillId] = new Dictionary<int, string>(tiers);
+            }
+
+            return new PerkStateSnapshot(bySkill, new HashSet<string>(unlockedPerks, StringComparer.Ordinal));
+        }
+    }
+}

server/NeonSprawl.Server/Game/Mastery/PerkBranchSelectOutcome.cs

@@ -0,0 +1,8 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Result of <see cref="PerkUnlockEngine.TrySelectBranch"/> (NEO-47).</summary>
+public sealed record PerkBranchSelectOutcome(
+    bool Success,
+    string? ReasonCode,
+    IReadOnlyList<PerkUnlockEvent> Events,
+    PerkStateSnapshot Snapshot);

server/NeonSprawl.Server/Game/Mastery/PerkReevaluationOutcome.cs

@@ -0,0 +1,6 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Result of <see cref="PerkUnlockEngine.ReevaluateAfterLevelUp"/> (NEO-47).</summary>
+public sealed record PerkReevaluationOutcome(
+    IReadOnlyList<PerkUnlockEvent> Events,
+    PerkStateSnapshot Snapshot);

server/NeonSprawl.Server/Game/Mastery/PerkStateServiceCollectionExtensions.cs

@@ -0,0 +1,24 @@
+using NeonSprawl.Server.Game.PositionState;
+using NeonSprawl.Server.Game.Skills;
+
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Registers perk state persistence and unlock engine (NEO-47).</summary>
+public static class PerkStateServiceCollectionExtensions
+{
+    public static IServiceCollection AddPerkStateStore(this IServiceCollection services, IConfiguration configuration)
+    {
+        var cs = configuration.GetConnectionString(PositionStateServiceCollectionExtensions.NeonSprawlConnectionStringName);
+        if (!string.IsNullOrWhiteSpace(cs))
+        {
+            services.AddSingleton<IPlayerPerkStateStore, PostgresPlayerPerkStateStore>();
+        }
+        else
+        {
+            services.AddSingleton<IPlayerPerkStateStore, InMemoryPlayerPerkStateStore>();
+        }
+
+        services.AddSingleton<PerkUnlockEngine>();
+        return services;
+    }
+}

server/NeonSprawl.Server/Game/Mastery/PerkStateSnapshot.cs

@@ -0,0 +1,33 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Read model for one player's perk state (NEO-47).</summary>
+public sealed class PerkStateSnapshot
+{
+    public static PerkStateSnapshot Empty { get; } = new(
+        new Dictionary<string, IReadOnlyDictionary<int, string>>(StringComparer.Ordinal),
+        new HashSet<string>(StringComparer.Ordinal));
+
+    public PerkStateSnapshot(
+        IReadOnlyDictionary<string, IReadOnlyDictionary<int, string>> branchPicksBySkillId,
+        IReadOnlySet<string> unlockedPerkIds)
+    {
+        BranchPicksBySkillId = branchPicksBySkillId;
+        UnlockedPerkIds = unlockedPerkIds;
+    }
+
+    /// <summary><c>skillId</c> → <c>tierIndex</c> → <c>branchId</c>.</summary>
+    public IReadOnlyDictionary<string, IReadOnlyDictionary<int, string>> BranchPicksBySkillId { get; }
+
+    public IReadOnlySet<string> UnlockedPerkIds { get; }
+
+    public bool TryGetBranchPick(string skillId, int tierIndex, out string branchId)
+    {
+        branchId = string.Empty;
+        if (!BranchPicksBySkillId.TryGetValue(skillId, out var tiers))
+        {
+            return false;
+        }
+
+        return tiers.TryGetValue(tierIndex, out branchId!);
+    }
+}

server/NeonSprawl.Server/Game/Mastery/PerkUnlockEngine.cs

@@ -0,0 +1,201 @@
+using NeonSprawl.Server.Game.Skills;
+
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>
+/// Server-authoritative perk unlock evaluation from skill level + branch picks (NEO-47).
+/// Tier rule: all branches have empty <c>perkIds</c> ⇒ explicit pick tier; otherwise path-auto when a prior pick tier exists.
+/// </summary>
+public sealed class PerkUnlockEngine(
+    IMasteryCatalogRegistry catalog,
+    IPlayerPerkStateStore perkStore,
+    IPlayerSkillProgressionStore xpStore,
+    ISkillLevelCurve levelCurve)
+{
+    /// <summary>Selects a branch for a pick tier; unlocks any perks on that branch for the tier.</summary>
+    public PerkBranchSelectOutcome TrySelectBranch(
+        string playerId,
+        string skillIdRaw,
+        int tierIndex,
+        string branchIdRaw)
+    {
+        var snapshot = perkStore.GetSnapshot(playerId);
+        var skillId = skillIdRaw.Trim();
+        var branchId = branchIdRaw.Trim();
+        if (skillId.Length == 0 || branchId.Length == 0)
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.UnknownTrack);
+        }
+
+        if (!catalog.TryGetTrack(skillId, out var track))
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.UnknownTrack);
+        }
+
+        var tier = FindTier(track, tierIndex);
+        if (tier is null)
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.UnknownTier);
+        }
+
+        if (TierIsPathAuto(tier))
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.TierBranchNotSelectable);
+        }
+
+        if (!TierContainsBranch(tier, branchId))
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.UnknownBranch);
+        }
+
+        var level = GetSkillLevel(playerId, track.SkillId);
+        if (level < tier.RequiredLevel)
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.LevelTooLow);
+        }
+
+        if (snapshot.TryGetBranchPick(track.SkillId, tier.TierIndex, out _))
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.BranchAlreadyChosen);
+        }
+
+        if (!perkStore.TrySetBranchPick(playerId, track.SkillId, tier.TierIndex, branchId))
+        {
+            return Deny(snapshot, PerkUnlockReasonCodes.PlayerNotFound);
+        }
+
+        var branch = tier.Branches.First(b => string.Equals(b.BranchId, branchId, StringComparison.Ordinal));
+        var events = UnlockPerks(playerId, track.SkillId, tier.TierIndex, branch.BranchId, branch.PerkIds, PerkUnlockSource.BranchPick);
+        snapshot = perkStore.GetSnapshot(playerId);
+        return new PerkBranchSelectOutcome(true, null, events, snapshot);
+    }
+
+    /// <summary>Unlocks path-auto tier perks after skill level-up (idempotent).</summary>
+    public PerkReevaluationOutcome ReevaluateAfterLevelUp(string playerId, string skillIdRaw, int newLevel)
+    {
+        var allEvents = new List<PerkUnlockEvent>();
+        var skillId = skillIdRaw.Trim();
+        if (skillId.Length == 0 || !catalog.TryGetTrack(skillId, out var track))
+        {
+            return new PerkReevaluationOutcome(allEvents, perkStore.GetSnapshot(playerId));
+        }
+
+        foreach (var tier in track.Tiers.OrderBy(static t => t.TierIndex))
+        {
+            if (tier.RequiredLevel > newLevel || !TierIsPathAuto(tier))
+            {
+                continue;
+            }
+
+            var pathBranchId = GetPathBranchId(perkStore.GetSnapshot(playerId), track, tier);
+            if (pathBranchId is null)
+            {
+                continue;
+            }
+
+            var branch = tier.Branches.FirstOrDefault(b =>
+                string.Equals(b.BranchId, pathBranchId, StringComparison.Ordinal));
+            if (branch is null)
+            {
+                continue;
+            }
+
+            var batch = UnlockPerks(
+                playerId,
+                track.SkillId,
+                tier.TierIndex,
+                branch.BranchId,
+                branch.PerkIds,
+                PerkUnlockSource.LevelUp);
+            allEvents.AddRange(batch);
+        }
+
+        return new PerkReevaluationOutcome(allEvents, perkStore.GetSnapshot(playerId));
+    }
+
+    private PerkBranchSelectOutcome Deny(PerkStateSnapshot snapshot, string reason) =>
+        new(false, reason, [], snapshot);
+
+    private int GetSkillLevel(string playerId, string skillId)
+    {
+        var xpBySkill = xpStore.GetXpTotals(playerId);
+        xpBySkill.TryGetValue(skillId, out var xp);
+        return levelCurve.LevelFromTotalXp(xp);
+    }
+
+    private static MasteryTierRow? FindTier(MasteryTrackRow track, int tierIndex) =>
+        track.Tiers.FirstOrDefault(t => t.TierIndex == tierIndex);
+
+    /// <summary>True when every branch has no perks — player must pick a branch explicitly.</summary>
+    internal static bool TierRequiresExplicitPick(MasteryTierRow tier) =>
+        tier.Branches.All(static b => b.PerkIds.Count == 0);
+
+    internal static bool TierIsPathAuto(MasteryTierRow tier) => !TierRequiresExplicitPick(tier);
+
+    private static bool TierContainsBranch(MasteryTierRow tier, string branchId) =>
+        tier.Branches.Any(b => string.Equals(b.BranchId, branchId, StringComparison.Ordinal));
+
+    /// <summary>Branch id from the highest prior tier that required an explicit pick.</summary>
+    internal static string? GetPathBranchId(PerkStateSnapshot snapshot, MasteryTrackRow track, MasteryTierRow tier)
+    {
+        MasteryTierRow? anchor = null;
+        foreach (var prior in track.Tiers.OrderByDescending(static t => t.TierIndex))
+        {
+            if (prior.TierIndex >= tier.TierIndex)
+            {
+                continue;
+            }
+
+            if (TierRequiresExplicitPick(prior))
+            {
+                anchor = prior;
+                break;
+            }
+        }
+
+        if (anchor is null)
+        {
+            return null;
+        }
+
+        return snapshot.TryGetBranchPick(track.SkillId, anchor.TierIndex, out var bid) ? bid : null;
+    }
+
+    private IReadOnlyList<PerkUnlockEvent> UnlockPerks(
+        string playerId,
+        string skillId,
+        int tierIndex,
+        string branchId,
+        IReadOnlyList<string> perkIds,
+        PerkUnlockSource source)
+    {
+        if (perkIds.Count == 0)
+        {
+            return [];
+        }
+
+        var snapshot = perkStore.GetSnapshot(playerId);
+        var newIds = new List<string>();
+        foreach (var perkId in perkIds)
+        {
+            if (!snapshot.UnlockedPerkIds.Contains(perkId))
+            {
+                newIds.Add(perkId);
+            }
+        }
+
+        if (newIds.Count == 0)
+        {
+            return [];
+        }
+
+        if (!perkStore.TryAddUnlockedPerks(playerId, newIds))
+        {
+            return [];
+        }
+
+        return newIds
+            .Select(pid => new PerkUnlockEvent(playerId, pid, skillId, tierIndex, branchId, source))
+            .ToList();
+    }
+}

server/NeonSprawl.Server/Game/Mastery/PerkUnlockEvent.cs

@@ -0,0 +1,17 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Internal event when a perk becomes unlocked (NEO-47; NEO-49 telemetry).</summary>
+public enum PerkUnlockSource
+{
+    BranchPick,
+    LevelUp,
+}
+
+/// <param name="BranchId">Chosen branch when relevant; null for edge cases without a branch context.</param>
+public sealed record PerkUnlockEvent(
+    string PlayerId,
+    string PerkId,
+    string SkillId,
+    int TierIndex,
+    string? BranchId,
+    PerkUnlockSource Source);

server/NeonSprawl.Server/Game/Mastery/PerkUnlockReasonCodes.cs

@@ -0,0 +1,13 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Stable deny codes for perk branch selection (NEO-47; NEO-48 HTTP).</summary>
+public static class PerkUnlockReasonCodes
+{
+    public const string UnknownTrack = "unknown_track";
+    public const string UnknownTier = "unknown_tier";
+    public const string UnknownBranch = "unknown_branch";
+    public const string LevelTooLow = "level_too_low";
+    public const string BranchAlreadyChosen = "branch_already_chosen";
+    public const string TierBranchNotSelectable = "tier_branch_not_selectable";
+    public const string PlayerNotFound = "player_not_found";
+}

server/NeonSprawl.Server/Game/Mastery/PostgresPerkStateBootstrap.cs

@@ -0,0 +1,39 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>Applies NEO-47 perk state table DDL once per process.</summary>
+public static class PostgresPerkStateBootstrap
+{
+    private static readonly string DdlRelativePath = Path.Combine("db", "migrations", "V004__player_perk_state.sql");
+
+    private static readonly object SchemaGate = new();
+
+    private static int _schemaReady;
+
+    public static void EnsureSchema(Npgsql.NpgsqlDataSource dataSource)
+    {
+        if (Volatile.Read(ref _schemaReady) != 0)
+        {
+            return;
+        }
+
+        lock (SchemaGate)
+        {
+            if (Volatile.Read(ref _schemaReady) != 0)
+            {
+                return;
+            }
+
+            var ddlPath = Path.Combine(AppContext.BaseDirectory, DdlRelativePath);
+            if (!File.Exists(ddlPath))
+            {
+                throw new FileNotFoundException($"NEO-47 DDL not found at '{ddlPath}'.", ddlPath);
+            }
+
+            var ddl = File.ReadAllText(ddlPath);
+            using var conn = dataSource.OpenConnection();
+            using var cmd = new Npgsql.NpgsqlCommand(ddl, conn);
+            cmd.ExecuteNonQuery();
+            Volatile.Write(ref _schemaReady, 1);
+        }
+    }
+}

server/NeonSprawl.Server/Game/Mastery/PostgresPlayerPerkStateStore.cs

@@ -0,0 +1,198 @@
+namespace NeonSprawl.Server.Game.Mastery;
+
+/// <summary>PostgreSQL-backed perk state keyed by normalized player id (NEO-47).</summary>
+public sealed class PostgresPlayerPerkStateStore(Npgsql.NpgsqlDataSource dataSource) : IPlayerPerkStateStore
+{
+    /// <inheritdoc />
+    public PerkStateSnapshot GetSnapshot(string playerId)
+    {
+        var norm = NormalizePlayerId(playerId);
+        if (norm.Length == 0)
+        {
+            return PerkStateSnapshot.Empty;
+        }
+
+        PostgresPerkStateBootstrap.EnsureSchema(dataSource);
+        using var conn = dataSource.OpenConnection();
+
+        var branchPicks = new Dictionary<string, Dictionary<int, string>>(StringComparer.Ordinal);
+        using (var pickCmd = new Npgsql.NpgsqlCommand(
+                   """
+                   SELECT skill_id, tier_index, branch_id
+                   FROM player_mastery_branch_pick
+                   WHERE player_id = @pid;
+                   """,
+                   conn))
+        {
+            pickCmd.Parameters.AddWithValue("pid", norm);
+            using var reader = pickCmd.ExecuteReader();
+            while (reader.Read())
+            {
+                var skillId = reader.GetString(0);
+                var tierIndex = reader.GetInt32(1);
+                var branchId = reader.GetString(2);
+                if (!branchPicks.TryGetValue(skillId, out var tiers))
+                {
+                    tiers = new Dictionary<int, string>();
+                    branchPicks[skillId] = tiers;
+                }
+
+                tiers[tierIndex] = branchId;
+            }
+        }
+
+        var bySkill = new Dictionary<string, IReadOnlyDictionary<int, string>>(StringComparer.Ordinal);
+        foreach (var (skillId, tiers) in branchPicks)
+        {
+            bySkill[skillId] = tiers;
+        }
+
+        var unlocked = new HashSet<string>(StringComparer.Ordinal);
+        using (var perkCmd = new Npgsql.NpgsqlCommand(
+                   """
+                   SELECT perk_id
+                   FROM player_unlocked_perk
+                   WHERE player_id = @pid;
+                   """,
+                   conn))
+        {
+            perkCmd.Parameters.AddWithValue("pid", norm);
+            using var reader = perkCmd.ExecuteReader();
+            while (reader.Read())
+            {
+                unlocked.Add(reader.GetString(0));
+            }
+        }
+
+        return new PerkStateSnapshot(bySkill, unlocked);
+    }
+
+    /// <inheritdoc />
+    public bool TrySetBranchPick(string playerId, string skillId, int tierIndex, string branchId)
+    {
+        var norm = NormalizePlayerId(playerId);
+        var sid = skillId.Trim();
+        var bid = branchId.Trim();
+        if (norm.Length == 0 || sid.Length == 0 || bid.Length == 0 || tierIndex < 1)
+        {
+            return false;
+        }
+
+        PostgresPerkStateBootstrap.EnsureSchema(dataSource);
+        using var conn = dataSource.OpenConnection();
+        using var tx = conn.BeginTransaction();
+        if (!PlayerExists(conn, norm, tx))
+        {
+            tx.Rollback();
+            return false;
+        }
+
+        using (var exists = new Npgsql.NpgsqlCommand(
+                   """
+                   SELECT 1
+                   FROM player_mastery_branch_pick
+                   WHERE player_id = @pid AND skill_id = @sid AND tier_index = @tier
+                   LIMIT 1;
+                   """,
+                   conn,
+                   tx))
+        {
+            exists.Parameters.AddWithValue("pid", norm);
+            exists.Parameters.AddWithValue("sid", sid);
+            exists.Parameters.AddWithValue("tier", tierIndex);
+            if (exists.ExecuteScalar() is not null)
+            {
+                tx.Rollback();
+                return false;
+            }
+        }
+
+        using var insert = new Npgsql.NpgsqlCommand(
+            """
+            INSERT INTO player_mastery_branch_pick (player_id, skill_id, tier_index, branch_id, updated_at)
+            VALUES (@pid, @sid, @tier, @bid, now());
+            """,
+            conn,
+            tx);
+        insert.Parameters.AddWithValue("pid", norm);
+        insert.Parameters.AddWithValue("sid", sid);
+        insert.Parameters.AddWithValue("tier", tierIndex);
+        insert.Parameters.AddWithValue("bid", bid);
+        insert.ExecuteNonQuery();
+        tx.Commit();
+        return true;
+    }
+
+    /// <inheritdoc />
+    public bool TryAddUnlockedPerks(string playerId, IEnumerable<string> perkIds)
+    {
+        var norm = NormalizePlayerId(playerId);
+        if (norm.Length == 0)
+        {
+            return false;
+        }
+
+        var toAdd = new List<string>();
+        foreach (var raw in perkIds)
+        {
+            var pid = raw.Trim();
+            if (pid.Length > 0)
+            {
+                toAdd.Add(pid);
+            }
+        }
+
+        if (toAdd.Count == 0)
+        {
+            return true;
+        }
+
+        PostgresPerkStateBootstrap.EnsureSchema(dataSource);
+        using var conn = dataSource.OpenConnection();
+        using var tx = conn.BeginTransaction();
+        if (!PlayerExists(conn, norm, tx))
+        {
+            tx.Rollback();
+            return false;
+        }
+
+        foreach (var perkId in toAdd)
+        {
+            using var upsert = new Npgsql.NpgsqlCommand(
+                """
+                INSERT INTO player_unlocked_perk (player_id, perk_id, unlocked_at)
+                VALUES (@pid, @perk, now())
+                ON CONFLICT (player_id, perk_id) DO NOTHING;
+                """,
+                conn,
+                tx);
+            upsert.Parameters.AddWithValue("pid", norm);
+            upsert.Parameters.AddWithValue("perk", perkId);
+            upsert.ExecuteNonQuery();
+        }
+
+        tx.Commit();
+        return true;
+    }
+
+    private static bool PlayerExists(Npgsql.NpgsqlConnection conn, string playerIdNormalized, Npgsql.NpgsqlTransaction tx)
+    {
+        using var cmd = new Npgsql.NpgsqlCommand(
+            "SELECT 1 FROM player_position WHERE player_id = @pid LIMIT 1;",
+            conn,
+            tx);
+        cmd.Parameters.AddWithValue("pid", playerIdNormalized);
+        return cmd.ExecuteScalar() is not null;
+    }
+
+    private static string NormalizePlayerId(string? playerId)
+    {
+        var t = playerId?.Trim();
+        if (string.IsNullOrEmpty(t))
+        {
+            return string.Empty;
+        }
+
+        return t.ToLowerInvariant();
+    }
+}

server/NeonSprawl.Server/Game/Skills/MissionRewardSkillXpGrant.cs

@@ -1,3 +1,5 @@
+using NeonSprawl.Server.Game.Mastery;
+
 namespace NeonSprawl.Server.Game.Skills;
 
 /// <summary>
@@ -15,7 +17,8 @@ public static class MissionRewardSkillXpGrant
         int amount,
         ISkillDefinitionRegistry registry,
         IPlayerSkillProgressionStore xpStore,
-        ISkillLevelCurve levelCurve)
+        ISkillLevelCurve levelCurve,
+        PerkUnlockEngine perkUnlockEngine)
     {
         _ = SkillProgressionGrantOperations.TryApplyGrant(
             playerId,
@@ -24,6 +27,7 @@ public static class MissionRewardSkillXpGrant
             MissionRewardSkillXpConstants.MissionRewardSourceKind,
             registry,
             xpStore,
-            levelCurve);
+            levelCurve,
+            perkUnlockEngine);
     }
 }

server/NeonSprawl.Server/Game/Skills/RefineActivitySkillXpGrant.cs

@@ -1,3 +1,5 @@
+using NeonSprawl.Server.Game.Mastery;
+
 namespace NeonSprawl.Server.Game.Skills;
 
 /// <summary>
@@ -13,7 +15,8 @@ public static class RefineActivitySkillXpGrant
         string playerId,
         ISkillDefinitionRegistry registry,
         IPlayerSkillProgressionStore xpStore,
-        ISkillLevelCurve levelCurve)
+        ISkillLevelCurve levelCurve,
+        PerkUnlockEngine perkUnlockEngine)
     {
         _ = SkillProgressionGrantOperations.TryApplyGrant(
             playerId,
@@ -22,6 +25,7 @@ public static class RefineActivitySkillXpGrant
             RefineSkillXpConstants.ActivitySourceKind,
             registry,
             xpStore,
-            levelCurve);
+            levelCurve,
+            perkUnlockEngine);
     }
 }

server/NeonSprawl.Server/Game/Skills/SkillProgressionGrantOperations.cs

@@ -1,3 +1,5 @@
+using NeonSprawl.Server.Game.Mastery;
+
 namespace NeonSprawl.Server.Game.Skills;
 
 /// <summary>Shared NEO-38 skill XP grant apply (used by HTTP POST and NEO-41 gather interact hook).</summary>
@@ -14,7 +16,8 @@ public static class SkillProgressionGrantOperations
         string sourceKindRaw,
         ISkillDefinitionRegistry registry,
         IPlayerSkillProgressionStore xpStore,
-        ISkillLevelCurve levelCurve)
+        ISkillLevelCurve levelCurve,
+        PerkUnlockEngine perkUnlockEngine)
     {
         static SkillProgressionGrantResponse Deny(SkillProgressionSnapshotResponse snapshot, string reason) =>
             new()
@@ -80,6 +83,14 @@ public static class SkillProgressionGrantOperations
                 });
         }
 
+        if (levelUps.Count > 0)
+        {
+            foreach (var levelUp in levelUps)
+            {
+                _ = perkUnlockEngine.ReevaluateAfterLevelUp(playerId, levelUp.SkillId, levelUp.NewLevel);
+            }
+        }
+
         var afterSnapshot = SkillProgressionSnapshotApi.BuildSnapshot(playerId, registry, xpStore, levelCurve);
         return new SkillProgressionGrantApplyOutcome(
             SkillProgressionGrantApplyKind.Granted,

server/NeonSprawl.Server/Game/Skills/SkillProgressionSnapshotApi.cs

@@ -1,3 +1,4 @@
+using NeonSprawl.Server.Game.Mastery;
 using NeonSprawl.Server.Game.PositionState;
 
 namespace NeonSprawl.Server.Game.Skills;
@@ -31,7 +32,8 @@ public static class SkillProgressionSnapshotApi
         app.MapPost(
             "/game/players/{id}/skill-progression",
             (string id, SkillProgressionGrantRequest? body, IPositionStateStore positions,
-                ISkillDefinitionRegistry registry, IPlayerSkillProgressionStore xpStore, ISkillLevelCurve levelCurve) =>
+                ISkillDefinitionRegistry registry, IPlayerSkillProgressionStore xpStore, ISkillLevelCurve levelCurve,
+                PerkUnlockEngine perkUnlockEngine) =>
             {
                 if (body is null || body.SchemaVersion != SkillProgressionGrantRequest.CurrentSchemaVersion)
                 {
@@ -51,7 +53,8 @@ public static class SkillProgressionSnapshotApi
                     body.SourceKind,
                     registry,
                     xpStore,
-                    levelCurve);
+                    levelCurve,
+                    perkUnlockEngine);
 
                 return outcome.Kind switch
                 {

server/NeonSprawl.Server/Program.cs

@@ -9,6 +9,7 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddPositionStateStore(builder.Configuration);
 builder.Services.AddHotbarLoadoutStore(builder.Configuration);
 builder.Services.AddSkillProgressionStore(builder.Configuration);
+builder.Services.AddPerkStateStore(builder.Configuration);
 builder.Services.AddAbilityCooldownStore();
 builder.Services.AddSingleton<IPlayerTargetLockStore, InMemoryPlayerTargetLockStore>();
 builder.Services.AddSkillDefinitionCatalog(builder.Configuration);

server/db/migrations/V004__player_perk_state.sql

@@ -0,0 +1,19 @@
+-- NEO-47: per-player mastery branch picks and unlocked perk ids.
+CREATE TABLE IF NOT EXISTS player_mastery_branch_pick (
+    player_id TEXT NOT NULL REFERENCES player_position(player_id) ON DELETE CASCADE,
+    skill_id TEXT NOT NULL,
+    tier_index INTEGER NOT NULL CHECK (tier_index >= 1),
+    branch_id TEXT NOT NULL,
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    PRIMARY KEY (player_id, skill_id, tier_index)
+);
+
+CREATE TABLE IF NOT EXISTS player_unlocked_perk (
+    player_id TEXT NOT NULL REFERENCES player_position(player_id) ON DELETE CASCADE,
+    perk_id TEXT NOT NULL,
+    unlocked_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    PRIMARY KEY (player_id, perk_id)
+);
+
+COMMENT ON TABLE player_mastery_branch_pick IS 'Mutually exclusive branch picks per mastery tier (NEO-47); tier 1 pick drives path-auto tier unlocks.';
+COMMENT ON TABLE player_unlocked_perk IS 'Unlocked perk ids for a player (NEO-47); additive, idempotent per perk_id.';