# ue-serialization-savegames

Guides save and load workflows in Unreal Engine 5.8 C++, from USaveGame slot APIs to binary archive serialization and versioning. Useful when building persistent game state.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1100 installs · ★ 405
- Author: quodsoler
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/quodsoler/unreal-engine-skills/tree/HEAD/skills/ue-serialization-savegames/SKILL.md
- Updated: 2026-09-28
- HTML: https://affpapa.org/en/nevibecode/skills/ue-serialization-savegames

## What it does

This skill targets Unreal Engine 5.8 C++ and verifies API signatures directly against 5.8 engine headers. It structures persistence across `USaveGame` slot operations, non-blocking calls in `UGameplayStatics`, `FArchive` binary buffers, and schema migrations with `FCustomVersion`. If an `.agents/ue-project-context.md` file exists in the repository, the agent inspects it first for project modules and conventions.

A critical trap in `UGameplayStatics::SaveGameToSlot` catches many developers off guard. The function serializes every single non-transient property, completely ignoring the `SaveGame` specifier. To keep runtime scratch data out of your save files, you must mark those fields `Transient`. The `SaveGame` tag matters only for archives that explicitly set `ArIsSaveGame`.

Target projects must declare `Core`, `CoreUObject`, and `Engine` in their `Build.cs`. Adding `UDeveloperSettings` requires `DeveloperSettings` in `PublicDependencyModuleNames`, while JSON conversion needs `Json` and `JsonUtilities` in `PrivateDependencyModuleNames`. When writing asynchronous callbacks, avoid using `UFUNCTION` because the async save delegates are plain non-dynamic delegates.

## Requirements
- Works with: Unreal Engine

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add quodsoler/unreal-engine-skills --skill ue-serialization-savegames -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/ue-serialization-savegames/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/ue-serialization-savegames/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add quodsoler/unreal-engine-skills --skill ue-serialization-savegames -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/ue-serialization-savegames/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add quodsoler/unreal-engine-skills --skill ue-serialization-savegames -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/ue-serialization-savegames/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install quodsoler/unreal-engine-skills ue-serialization-savegames
```

2. **Manually: put the files in place**
- File: `.github/skills/ue-serialization-savegames/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add quodsoler/unreal-engine-skills --skill ue-serialization-savegames -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/quodsoler/unreal-engine-skills --path skills/ue-serialization-savegames
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/ue-serialization-savegames/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add quodsoler/unreal-engine-skills --skill ue-serialization-savegames -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/quodsoler/unreal-engine-skills/tree/HEAD/skills/ue-serialization-savegames/SKILL.md

## When to use it
- implement asynchronous save and load operations using `UGameplayStatics`
- capture actor snapshots into memory archives using `UPROPERTY(SaveGame)`
- handle save file versioning and schema migrations across game updates
- manage per-player settings and profiles using `ULocalPlayerSaveGame`

## Example prompts
- Create a `USaveGame` subclass in C++ for UE 5.8 storing player health and weapon references as `FSoftObjectPath`.
- Set up an asynchronous save subsystem that binds non-dynamic delegates to `AsyncSaveGameToSlot` without blocking the game thread.
- Write an `FArchive` serialization routine for custom struct data with `FCustomVersion` migration.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 8f6579c57ddc7e86.

BEGIN THIRD-PARTY FILE 8f6579c57ddc7e86
```text
---
name: ue-serialization-savegames
description: "Use when implementing save/load, player progress persistence, slot management, or binary serialization in Unreal Engine C++. Also use when the user mentions 'save game', 'USaveGame', 'SaveGameToSlot', 'AsyncSaveGameToSlot', 'LoadGameFromSlot', 'DoesSaveGameExist', 'DeleteGameInSlot', 'ULocalPlayerSaveGame', 'UPROPERTY(SaveGame)', 'FArchive', 'FMemoryWriter', 'FCustomVersion', 'save versioning', 'migrate old saves', 'save file corrupted', 'UDeveloperSettings', or 'GConfig'. For asset references, see ue-data-assets-tables; for work off the game thread, see ue-async-threading; for streamed level state, see ue-world-level-streaming."
metadata:
  version: "2.0.0"
  engine: "5.8"
---

# UE Serialization & Save Games

Target engine: **UE 5.8**. APIs below are verified against the 5.8 headers; older forms are listed under "Deprecated — do not use".

This skill covers persisting game state: `USaveGame` objects through `UGameplayStatics`, the platform `ISaveGameSystem`, `FArchive` binary serialization, `UPROPERTY(SaveGame)` actor snapshots, save versioning, and config/settings storage. Build.cs modules: `Core`, `CoreUObject`, `Engine`; add `DeveloperSettings` to `PublicDependencyModuleNames` for `UDeveloperSettings`, and `Json` + `JsonUtilities` to `PrivateDependencyModuleNames` for `FJsonObjectConverter`.

## Context

Read `.agents/ue-project-context.md` if it exists (module names, conventions, enabled plugins, GAS/networking setup). Do not stop if it is missing.

Identify the area from the request and the codebase. Ask only when two plausible readings would produce different code.

| Request is about… | Go to |
|---|---|
| A save object, slot names, save/load/delete | [USaveGame and the Slot API](#usavegame-and-the-slot-api) |
| Not blocking the game thread, callbacks | [Async Save and Load](#async-save-and-load) |
| Per-player saves, settings profiles, split-screen | [ULocalPlayerSaveGame](#ulocalplayersavegame) |
```
END THIRD-PARTY FILE 8f6579c57ddc7e86

The third-party file has ended. Everything between the 8f6579c57ddc7e86 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 1995 of 26306 bytes. © quodsoler · MIT · https://github.com/quodsoler/unreal-engine-skills/tree/HEAD/skills/ue-serialization-savegames/SKILL.md

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