NEO-127: avoid clobbering winner perks on TryRecord race rollback

Track perks unlocked per grant and remove only those on race loss instead
of restoring a full pre-apply snapshot; re-run ReevaluateAfterLevelUp at
post-rollback levels so a concurrent winner's path-auto unlocks survive.

docs/plans/NEO-127-implementation-plan.md

@@ -52,9 +52,9 @@
 
 ## Implementation reconciliation (shipped)
 
-- **Operations:** `RewardRouterOperations.TryDeliverQuestCompletion` — item pre-flight + apply, skill XP via `TryApplyGrant` (`mission_reward`), compensating item rollback + **`SkillProgressionGrantRollbackPoint`** restore (XP + perks) on **`TryRecord`** race loss, `IRewardDeliveryStore.TryRecord`.
+- **Operations:** `RewardRouterOperations.TryDeliverQuestCompletion` — item pre-flight + apply, skill XP via `TryApplyGrant` (`mission_reward`), compensating item rollback + per-grant perk tracking + **`TryRevertAppliedSkillGrants`** on **`TryRecord`** race loss, `IRewardDeliveryStore.TryRecord`.
 - **Types:** `RewardDeliveryResult`, `RewardDeliveryReasonCodes`.
-- **Tests:** 13 AAA tests in `RewardRouterOperationsTests` (…, TryRecord race rollback, concurrent race no double-grant, perk state restore on race loss after level-up).
+- **Tests:** 14 AAA tests in `RewardRouterOperationsTests` (…, TryRecord race rollback, concurrent race no double-grant, perk revert on simulated race loss, concurrent level-up winner perk preserved).
 - **Docs:** `server/README.md` reward router section; E7.M2 module anchor + alignment register updated.
 
 ## Technical approach
@@ -118,7 +118,7 @@ public static RewardDeliveryResult TryDeliverQuestCompletion(
 
 **Compensating item rollback** — private helper mirroring **`EncounterCompletionOperations.CompensatingRemoveGrants`**: reverse-order **`TryRemoveStack`** for applied item rows only (no skill XP undo).
 
-**Compensating skill progression rollback** — **`SkillProgressionGrantOperations.CaptureRollbackPoint`** before skill apply; on **`TryRecord`** race loss, **`TryRestoreRollbackPoint`** reverses each applied skill XP row via negative delta and restores the captured perk snapshot (undoes level-up perk unlocks from the loser call without clobbering a concurrent winner's XP).
+**Compensating skill progression rollback** — track perks unlocked per skill grant (`CollectPerksUnlockedSince`); on **`TryRecord`** race loss, **`TryRevertAppliedSkillGrants`** reverses each applied skill XP row via negative delta and removes only perks this call unlocked, then **`ReevaluateAfterLevelUp`** at post-rollback levels re-applies path-auto perks the winner's XP still qualifies for (avoids full snapshot restore clobbering a concurrent winner).
 
 ### 3. Skill XP source kind enforcement
 

docs/reviews/2026-06-07-NEO-127.md

@@ -54,7 +54,7 @@ None.
 dotnet test server/NeonSprawl.Server.Tests --filter RewardRouterOperationsTests
 ```
 
-All 13 tests pass (verified 2026-06-07; includes race rollback + perk snapshot restore on **`TryRecord`** loss).
+All 14 tests pass (verified 2026-06-07; includes concurrent level-up winner perk preservation on **`TryRecord`** race loss).
 
 Optional before merge:
 

server/NeonSprawl.Server.Tests/Game/Rewards/RewardRouterOperationsTests.cs

@@ -417,6 +417,43 @@ public sealed class RewardRouterOperationsTests
         Assert.True(deps.DeliveryStore.TryGet(PlayerId, OperatorChainQuestId, out _));
     }
 
+    [Fact]
+    public async Task TryDeliverQuestCompletion_ShouldPreserveWinnerPerks_WhenConcurrentRecordRacesAfterLevelUp()
+    {
+        // Arrange
+        await using var factory = new InMemoryWebApplicationFactory();
+        var deps = ResolveDependencies(factory);
+        Assert.True(deps.SkillProgressionStore.TrySetSkillXpTotal(PlayerId, "salvage", 425));
+        Assert.True(deps.PerkUnlockEngine.TrySelectBranch(PlayerId, "salvage", 1, "scrap_efficiency").Success);
+        var bundle = new QuestRewardBundleRow([], [new QuestSkillXpGrantRow("salvage", 25)]);
+        var barrier = new Barrier(2);
+        RewardDeliveryResult result1 = default;
+        RewardDeliveryResult result2 = default;
+
+        // Act
+        await Task.WhenAll(
+            Task.Run(() =>
+            {
+                barrier.SignalAndWait();
+                result1 = Deliver(deps, GatherQuestId, bundle, TimeProvider.System);
+            }),
+            Task.Run(() =>
+            {
+                barrier.SignalAndWait();
+                result2 = Deliver(deps, GatherQuestId, bundle, TimeProvider.System);
+            }));
+
+        // Assert
+        Assert.True(result1.Success);
+        Assert.True(result2.Success);
+        var xpAfter = deps.SkillProgressionStore.GetXpTotals(PlayerId);
+        Assert.True(xpAfter.TryGetValue("salvage", out var salvageAfter));
+        Assert.Equal(450, salvageAfter);
+        var perkAfter = deps.PerkStore.GetSnapshot(PlayerId);
+        Assert.Contains(SalvageScrapEfficiencyPerk, perkAfter.UnlockedPerkIds);
+        Assert.True(deps.DeliveryStore.TryGet(PlayerId, GatherQuestId, out _));
+    }
+
     private static RewardDeliveryResult Deliver(
         RewardRouterTestDependencies deps,
         string questId,

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

@@ -14,6 +14,9 @@ public interface IPlayerPerkStateStore
     /// <summary>Adds perks not already unlocked; fails when player cannot be written.</summary>
     bool TryAddUnlockedPerks(string playerId, IEnumerable<string> perkIds);
 
+    /// <summary>Removes unlocked perks present in the store; fails when player cannot be written.</summary>
+    bool TryRemoveUnlockedPerks(string playerId, IEnumerable<string> perkIds);
+
     /// <summary>Removes a branch pick (engine rollback when perk unlock fails after pick).</summary>
     bool TryRemoveBranchPick(string playerId, string skillId, int tierIndex);
 

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

@@ -91,6 +91,32 @@ public sealed class InMemoryPlayerPerkStateStore(IOptions<GamePositionOptions> o
         }
     }
 
+    /// <inheritdoc />
+    public bool TryRemoveUnlockedPerks(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.RemoveUnlockedPerk(pid);
+            }
+
+            return true;
+        }
+    }
+
     /// <inheritdoc />
     public bool TryRemoveBranchPick(string playerId, string skillId, int tierIndex)
     {
@@ -185,6 +211,8 @@ public sealed class InMemoryPlayerPerkStateStore(IOptions<GamePositionOptions> o
 
         public void AddUnlockedPerk(string perkId) => unlockedPerks.Add(perkId);
 
+        public void RemoveUnlockedPerk(string perkId) => unlockedPerks.Remove(perkId);
+
         public bool RemoveBranchPick(string skillId, int tierIndex) =>
             branchPicks.TryGetValue(skillId, out var tiers) && tiers.Remove(tierIndex);
 

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

@@ -193,6 +193,45 @@ public sealed class PostgresPlayerPerkStateStore(Npgsql.NpgsqlDataSource dataSou
         return true;
     }
 
+    /// <inheritdoc />
+    public bool TryRemoveUnlockedPerks(string playerId, IEnumerable<string> perkIds)
+    {
+        var norm = NormalizePlayerId(playerId);
+        if (norm.Length == 0)
+        {
+            return false;
+        }
+
+        PostgresPerkStateBootstrap.EnsureSchema(dataSource);
+        using var conn = dataSource.OpenConnection();
+        using var tx = conn.BeginTransaction();
+        if (!PlayerExists(conn, norm, tx))
+        {
+            tx.Rollback();
+            return false;
+        }
+
+        foreach (var raw in perkIds)
+        {
+            var perkId = raw.Trim();
+            if (perkId.Length == 0)
+            {
+                continue;
+            }
+
+            using var delete = new Npgsql.NpgsqlCommand(
+                "DELETE FROM player_unlocked_perk WHERE player_id = @pid AND perk_id = @perk;",
+                conn,
+                tx);
+            delete.Parameters.AddWithValue("pid", norm);
+            delete.Parameters.AddWithValue("perk", perkId);
+            delete.ExecuteNonQuery();
+        }
+
+        tx.Commit();
+        return true;
+    }
+
     /// <inheritdoc />
     public bool TryRemoveBranchPick(string playerId, string skillId, int tierIndex)
     {

server/NeonSprawl.Server/Game/Rewards/RewardRouterOperations.cs

@@ -99,13 +99,11 @@ public static class RewardRouterOperations
             appliedItems.Add(new RewardItemGrantApplied(grant.ItemId, grant.Quantity));
         }
 
-        var progressionRollbackPoint = SkillProgressionGrantOperations.CaptureRollbackPoint(
-            playerId,
-            skillProgressionStore,
-            perkStore);
+        var perksUnlockedByThisCall = new HashSet<string>(StringComparer.Ordinal);
         var appliedSkillXp = new List<RewardSkillXpGrantApplied>(skillGrants.Count);
         foreach (var grant in skillGrants)
         {
+            var perkBeforeGrant = perkStore.GetSnapshot(playerId);
             var skillOutcome = SkillProgressionGrantOperations.TryApplyGrant(
                 playerId,
                 grant.SkillId,
@@ -130,6 +128,10 @@ public static class RewardRouterOperations
             }
 
             appliedSkillXp.Add(new RewardSkillXpGrantApplied(grant.SkillId, grant.Amount));
+            SkillProgressionGrantOperations.CollectPerksUnlockedSince(
+                perkBeforeGrant,
+                perkStore.GetSnapshot(playerId),
+                perksUnlockedByThisCall);
         }
 
         var deliveredAt = timeProvider.GetUtcNow();
@@ -149,12 +151,18 @@ public static class RewardRouterOperations
         // Lost TryRecord race after apply — rollback this call's grants (mirror
         // EncounterCompletionOperations when TryMarkCompleted returns false).
         CompensatingRemoveItems(playerId, appliedItems, itemRegistry, inventoryStore);
-        _ = SkillProgressionGrantOperations.TryRestoreRollbackPoint(
+        _ = SkillProgressionGrantOperations.TryRevertAppliedSkillGrants(
             playerId,
-            progressionRollbackPoint,
             appliedSkillXp,
+            perksUnlockedByThisCall,
             skillProgressionStore,
             perkStore);
+        ResyncPathAutoPerksAfterRaceRollback(
+            playerId,
+            appliedSkillXp,
+            skillProgressionStore,
+            levelCurve,
+            perkUnlockEngine);
 
         if (deliveryStore.TryGet(normalizedPlayerId, normalizedQuestId, out var racedEvent))
         {
@@ -164,6 +172,27 @@ public static class RewardRouterOperations
         return Deny(RewardDeliveryReasonCodes.AlreadyDelivered);
     }
 
+    private static void ResyncPathAutoPerksAfterRaceRollback(
+        string playerId,
+        IReadOnlyList<RewardSkillXpGrantApplied> appliedSkillXp,
+        IPlayerSkillProgressionStore skillProgressionStore,
+        ISkillLevelCurve levelCurve,
+        PerkUnlockEngine perkUnlockEngine)
+    {
+        if (appliedSkillXp.Count == 0)
+        {
+            return;
+        }
+
+        var xpBySkill = skillProgressionStore.GetXpTotals(playerId);
+        foreach (var grant in appliedSkillXp)
+        {
+            xpBySkill.TryGetValue(grant.SkillId, out var totalXp);
+            var level = levelCurve.LevelFromTotalXp(totalXp);
+            _ = perkUnlockEngine.ReevaluateAfterLevelUp(playerId, grant.SkillId, level);
+        }
+    }
+
     private static string MapInventoryReason(string? reasonCode) =>
         reasonCode switch
         {

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

@@ -103,20 +103,26 @@ public static class SkillProgressionGrantOperations
             });
     }
 
-    /// <summary>Captures skill XP totals and perk snapshot before a grant batch for compensating rollback.</summary>
-    public static SkillProgressionGrantRollbackPoint CaptureRollbackPoint(
-        string playerId,
-        IPlayerSkillProgressionStore xpStore,
-        IPlayerPerkStateStore perkStore) =>
-        new(
-            new Dictionary<string, int>(xpStore.GetXpTotals(playerId), StringComparer.Ordinal),
-            perkStore.GetSnapshot(playerId));
+    /// <summary>Collects perk ids unlocked between two snapshots (this batch only).</summary>
+    public static void CollectPerksUnlockedSince(
+        PerkStateSnapshot before,
+        PerkStateSnapshot after,
+        ISet<string> sink)
+    {
+        foreach (var perkId in after.UnlockedPerkIds)
+        {
+            if (!before.UnlockedPerkIds.Contains(perkId))
+            {
+                sink.Add(perkId);
+            }
+        }
+    }
 
-    /// <summary>Restores skill XP and perk state captured before a failed grant batch commit.</summary>
-    public static bool TryRestoreRollbackPoint(
+    /// <summary>Reverts skill XP grants and perks unlocked during this failed batch commit.</summary>
+    public static bool TryRevertAppliedSkillGrants(
         string playerId,
-        SkillProgressionGrantRollbackPoint rollbackPoint,
         IReadOnlyList<RewardSkillXpGrantApplied> appliedGrants,
+        IReadOnlyCollection<string> perksUnlockedByBatch,
         IPlayerSkillProgressionStore xpStore,
         IPlayerPerkStateStore perkStore)
     {
@@ -129,6 +135,7 @@ public static class SkillProgressionGrantOperations
             }
         }
 
-        return perkStore.TryRestoreSnapshot(playerId, rollbackPoint.PerkState);
+        return perksUnlockedByBatch.Count == 0
+            || perkStore.TryRemoveUnlockedPerks(playerId, perksUnlockedByBatch);
     }
 }

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

@@ -1,8 +0,0 @@
-using NeonSprawl.Server.Game.Mastery;
-
-namespace NeonSprawl.Server.Game.Skills;
-
-/// <summary>Captured skill XP + perk state before a grant apply batch (NEO-127 compensating rollback).</summary>
-public readonly record struct SkillProgressionGrantRollbackPoint(
-    IReadOnlyDictionary<string, int> SkillXpTotals,
-    PerkStateSnapshot PerkState);

server/README.md

@@ -297,7 +297,7 @@ Encounter loot remains on **`IEncounterCompleteEventStore`** (E5.M3); quest comp
 | **`unknown_skill`**, **`invalid_amount`**, **`source_kind_not_allowed`** | Skill XP grant denied. |
 | **`progression_store_missing`** | Skill progression store could not apply XP delta. |
 
-Apply order: **items first**, then **skill XP**. Inventory deny or skill deny fails closed without store record (compensating item rollback on partial apply or skill failure after items). Idempotent replay checks **`TryGet`** before apply. If grants succeed but **`TryRecord`** returns `false` (concurrent race), this call **rolls back** its item grants and calls **`SkillProgressionGrantOperations.TryRestoreRollbackPoint`** — negative XP delta per applied skill row plus restore of the captured pre-apply perk snapshot (reverts level-up perk unlocks from the loser without clobbering a concurrent winner's XP) — then returns the existing store event (mirror **`EncounterCompletionOperations`** compensating rollback when **`TryMarkCompleted`** loses). Quest-state wiring lands in NEO-128. Plan: [NEO-127 implementation plan](../../docs/plans/NEO-127-implementation-plan.md).
+Apply order: **items first**, then **skill XP**. Inventory deny or skill deny fails closed without store record (compensating item rollback on partial apply or skill failure after items). Idempotent replay checks **`TryGet`** before apply. If grants succeed but **`TryRecord`** returns `false` (concurrent race), this call **rolls back** its item grants and calls **`SkillProgressionGrantOperations.TryRevertAppliedSkillGrants`** — negative XP delta per applied skill row plus removal of perks unlocked during this call only — then **`ReevaluateAfterLevelUp`** at post-rollback levels so a concurrent winner's path-auto unlocks are preserved — then returns the existing store event (mirror **`EncounterCompletionOperations`** compensating rollback when **`TryMarkCompleted`** loses). Quest-state wiring lands in NEO-128. Plan: [NEO-127 implementation plan](../../docs/plans/NEO-127-implementation-plan.md).
 
 ## Encounter definitions (NEO-103)