## What
`Dictionary<K,V>.Remove` and `HashSet<T>.Remove` do not bump the collection's version, so removing an entry during a `foreach` does not invalidate the enumerator. A number of loops were still paying for a `PooledRefQueue`/`PooledRefList` to collect keys and drain them in a second pass. This drops those guards.
## Why it's safe
Verified against .NET 10.0.10 rather than taken on trust, since the documented guarantee covers only `Dictionary<TKey,TValue>.Remove` while several of these call sites are `HashSet<T>` or enumerate `.Keys`/`.Values`:
| Case | Result |
|---|---|
| `Dictionary` foreach + `Remove` | safe, all entries visited |
| `Dictionary.Keys` / `.Values` foreach + `Remove` | safe, all entries visited |
| `HashSet` foreach + `Remove` | safe, all entries visited |
| `Dictionary` foreach + `Remove` **then `Add`** | throws `InvalidOperationException` |
Reflection on `_version` confirms the mechanism: neither `Dictionary.Remove` nor `HashSet.Remove` touches it. Because `Remove` never bumps the version, the `Keys` and `Values` enumerators are just as safe as the dictionary's own, even though only `Dictionary.Remove` documents the behaviour. No entries were skipped in any case.
The `HashSet` half is confirmed by [stephentoub on dotnet/dotnet-api-docs#8177](https://github.com/dotnet/dotnet-api-docs/issues/8177#issuecomment-1167251052): *"Both HashSet and Dictionary have been improved to support removal during enumeration. The docs may just benefit from updating."* The gap is in the documentation, not the runtime.
`Remove` followed by `Add` in the same enumeration still throws. That is the line this PR does not cross.
## Guards removed
`VisibilityList`, `ChampionTitleSystem`, `Channel`, `BombingRun`, `Ruleset`, `PuzzleChest`, `RaceChangeGump`, `StepCache`, `PlayerMurderSystem`, `VirtueSystem`, `ProjectedItem`, `StaminaSystem`, `AIGroupMovement`, `PromotedGuard`, `AutoDenylist`, `LoginAllowlist`, `AntiMacroSystem`, `DetectHidden`.
Both collection kinds are covered: `Dictionary` (including loops over `.Keys` and `.Values`) and `HashSet` (`ProjectedItem._active`, `PlayerMurderSystem._contextTerms`, `StaminaSystem._resetHash`). In `StaminaSystem.ResetTimer` the `Count == queue.Count → Clear()` branch goes away with the queue — it only existed to avoid paying for N individual removes.
Where the collection supports it, `Contains` + `Remove` and `TryGetValue` + `Remove` also collapse into a single lookup (`if (list.Remove(x))`, `if (m_Pending.Remove(ns, out var state))`).
`Utility.Tidy<K,V>` keeps its two branches: when `K` is serializable the value is not inspected, otherwise the value is. Only the serializable side may be cast, so `Dictionary<Mobile, int>` and `Dictionary<Mobile, string>` stay valid.
## Deliberately unchanged
**`BaseCreature.LoyaltyTimer.OnTick`** keeps its deferred-delete queue. Removing from `World.Mobiles` while enumerating it is safe, but `Mobile.Delete()` is not a `Remove` — it runs `OnDelete`/`OnAfterDelete`, the `OnParentDeleted` cascade over the creature's pack, `DropHolding()`, and region and guild callbacks. Anything in that surface that constructs a `Mobile` is an `Add` into the dictionary being enumerated, which does invalidate it. `BaseHire.PayTimer.OnTick` has the same shape and is likewise untouched.
**Spatial-query buffers** — `GuardedRegion.CallGuards`, `Thunderstorm`, `Exorcism`, `LeverPuzzleController`, `BaseCreature.TeleportPets` — are a different hazard. They buffer the result of a range query because the drain moves or harms mobiles, which mutates sectors mid-enumeration.
**Re-entrant drains.** The `_users` sets in `Firebomb` and the explosion, conflagration and confusion-blast potions look like this pattern but are not: the loop collects, `Clear()`s, and only then runs `Target.Cancel` on each, which can re-enter. `AnimalTrainer` enumerates `pm.Stabled` and drains through `RemoveStabled`, which nulls the `Stabled` field once it empties — safe for an in-flight enumerator, which holds the set reference rather than the field, but subtle enough not to be worth inlining on a cold path.
## Verification
`dotnet build` clean with 0 warnings; 810 Server and 684 UOContent tests pass.
### Summary
* Makes mount stamina significantly faster.
* Reduces absolute reset from 24 hours to 4 hours.
* Adds Pub 46+ Ethereal stamina where the stamina is global to all mounts for the player
* Removes serialization of stamina entirely because it's ok if it gets reset during shard restarts.
### Summary
- [X] Fixed a bug where entity persistence was serialized out of order, causing world corruption.
- [X] Fixed LastSerialized not being utilized properly and dangling references still becoming an issue.
- [X] Added a new `GenericEntityPersistence<T>` type to encapsulate `ISerializable` serialization.
- [X] Removing the custom logic and moved Items, Mobiles, Guilds, and Accounts to GenericEntityPersistence.
- [X] Changed serialization to use the singleton pattern to reduce calling methods from stored variables.
## Overhaul to Stamina (Overweight) System
### Added configurations
```json
{
"settings": {
"stamina.enableMountStamina": "True",
"stamina.cannotMoveWhenFatigued": "True",
"stamina.stonesPerOverweightLoss": "25",
"stamina.stonesOverweightAllowance": "4",
"stamina.baseOverweightLoss": "5",
"stamina.additionalLossWhenBelow": "0.1",
"stamina.mountLastMoveStepsReset": "01:00:00:00",
"stamina.enableMountStamina": "True",
"stamina.useMountStaminaOnlyWhenOverloaded": "False",
},
}
```
- `stamina.cannotMoveWhenFatigued` - By default, Pre-AOS expansions will outright block a player if they are fatigued. A player is fatigued when they run out of stamina by any mechanism.
- `stamina.stonesPerOverweightLoss` - The amount of stamina lost for every X stones above overweight. Example, if a person is overweight 28 stones overweight, then there there is 1 additional stamina. 28 / 25 = 1 (no decimals, no rounding)
- `stamina.stonesOverweightAllowance` - The number of stones allowed before overweight penalties take affect. This _does not_ substract from the overweight stones calculation.
- `stamina.baseOverweightLoss` - The base amount of stamina loss for being overweight. While running, the final amount is multiplied by 2. If mount stamina is turned off, then the final amount is divided by 3 while mounted.
### Mount stamina
Mounts have a new property `StepsMax` to determine the maximum steps they can take before being fatigued. To regain steps, the player _must stay on the mount and not move_ (per OSI). The gain rates are configurable. If a mount is dismounted, or the player logs off, the mount is considered inactive and mounts regain all of their steps after _24 hours_.
### Changes to player stamina
Players now have a proper inactivity time reset for their steps. If a player is idle for 16 seconds (including logging off, or the server being offline), then the steps counter is rest.
### Developer Notes
- `StepsTaken` - This field has been removed. It was not serialized and could not be used reliably. If a developer was using it, then the recommendation is to build a mechanism to track total steps another way.
- `IHasStamina` - This new interface was added and currently `IMount` and `PlayerMobile` are valid types.
Important: Entities that are sent to the StaminaSystem for tracking (mounts, players, or something else), must be an `ISerializable` to be serialized properly. If they are not, then the serialization system will record a null, and nothing will be deserialized upon world load. No errors will be given.
