SaveInstanceFetch

A smart SaveInstance tool that saves Roblox games the way they actually look — working terrain, unions, media, decompiled scripts, and asset recovery.

Fork of UniversalSynSaveInstance focused on visual accuracy and ease of use. No extra dependencies — load straight from GitHub raw.

Usage

Paste this into your executor:

--!nocheck
local Params = {
    RepoURL = "https://raw.githubusercontent.com/achmdfzn/SaveInstanceFetch/main/",
    Prepass = "prepass",
}

local Loader = loadstring(game:HttpGet(Params.RepoURL .. Params.Prepass .. ".luau", true), Params.Prepass)
assert(Loader, "[SaveInstanceFetch] failed to compile prepass loader (check your connection / RepoURL)")
local prepass = Loader()

local Options = {}        -- saveinstance options — see docs/option.md
local PrepassOptions = {} -- optional — PersistentCache and RepoURL default sensibly

prepass(Options, PrepassOptions)

The two [Error] lines your editor shows (could be nil on loadstring, Unknown global 'game') are just the type-checker not knowing the executor environment — the script runs fine. The --!nocheck header silences them, and the assert turns a failed download into a clear message instead of a nil call crash.

Wait until you see [saveinstance] Saved!, then check your executor's workspace folder:

• *.rbxlx — the save file (open in Roblox Studio)
• saveinstance_assets/ — downloaded assets, ready to drag-drop into Studio (when DownloadAssets = true)
• saveinstance-capabilities.txt / saveinstance-verify.txt / saveinstance-assets.txt — diagnostics

Privacy note: when an executor lacks a native decompiler, scripts are decompiled via the third-party lua.expert API — script bytecode is sent off-device. Set noscripts = true to skip decompiling entirely.

Common tweaks

Goal	Add to Options
Full union mesh + terrain on StreamingEnabled maps	FullUnionTerrainSupport = true
Recover private meshes to .obj (Blender / Studio)	ExportObj = true, SetStreaming = true
Save the map only, skip decompile	noscripts = true
Skip instances by name / tag	IgnoreNamePatterns = {"^Camera$"} / IgnoreTags = {"EditorOnly"}
Save ONLY tagged instances	SaveOnlyTags = {"SaveMe"}
Reset a stale decompile cache	PrepassOptions.ClearCache = true
Pin to a specific version	PrepassOptions.PinVersion = "1.5.0"
Load from the dev channel	PrepassOptions.Channel = "dev"
Force a fresh download (skip update check)	PrepassOptions.CheckForUpdates = false

Full option reference: docs/option.md.

PrepassOptions

The second argument to prepass(Options, PrepassOptions) controls the loader itself — downloading, caching, update checks, and version pinning. All are optional and default sensibly.

Option	Default	Description
RepoURL	raw.githubusercontent.com/achmdfzn/SaveInstanceFetch/main/	Base URL the loader fetches saveinstance.luau, version.txt, and CHANGELOG.md from.
ScriptName	"saveinstance"	Name of the main script to load from RepoURL.
Channel	nil	Repo branch to load from (e.g. "main", "dev"). Built on top of RepoBase.
Ref	nil	Explicit branch/tag to load from; overrides Channel.
PinVersion	nil	Refuse to run unless the loaded version matches (e.g. "1.5.0"). Guards against unexpected main changes.
PersistentCache	true	Reuse decompiled scripts from disk across runs (skips repeat API calls).
CacheDir	"saveinstance_decompile_cache"	Workspace folder for the decompile cache.
ClearCache	false	Wipe the decompile cache before this run.
CacheMainScript	true	Keep the last good saveinstance.luau on disk and fall back to it if a download fails or returns a bad body.
MainScriptCacheFile	"saveinstance_source_cache.luau"	Workspace file for the main-script fallback copy.
CheckForUpdates	true	Fetch version.txt and log when a newer version is published.
ShowChangelog	true	When an update is found, print the top of the remote CHANGELOG.md.
VerifyHash	true	If version.txt publishes a hash, verify the downloaded source matches before running it.

Prepass behavior toggles

These control how the decompile prepass runs, separate from the loader/cache settings above.

Option	Default	Description
UseSaveInstancePrepass	false	Use saveinstance.luau's built-in DecompilePrepass instead of the loader's own hook-based prepass. Wires PrepassConcurrency, PrepassRateGap, and PrepassApiUrl from the loader's rate settings.
MaxScripts	nil	Cap the number of scripts to decompile (maps to Options.PrepassMaxScripts). Only applied when UseSaveInstancePrepass = true.
SkipPrepass	false	Skip the decompile prepass entirely — no scripts are decompiled, but saveinstance still runs (scripts stay empty).
SkipSaveInstance	false	Run the prepass only and return without invoking saveinstance. Useful for warming the decompile cache.
MaxInFlight	8	How many decompile requests run at once. Kept low so mobile / low-RAM executors don't run out of memory. Raise it (e.g. 20) on a strong PC executor for more speed.
RequestsPerMinute	600	Rate cap for decompile requests. Lower it if the API rate-limits you; raise it for speed on a fast connection.
NoProgressUI	false	Disable the on-screen Drawing progress bar. Set true on executors whose Drawing implementation is incomplete or crash-prone (e.g. some Xeno / Solara builds). The prepass detects a broken Drawing automatically, but this forces it off.

Troubleshooting

The executor force-closes / crashes mid-save. Two common causes:

Crash during the decompile progress bar (especially Xeno / Solara). The on-screen progress bar uses the Drawing API, which is incomplete on some executors. The loader now probes Drawing and guards every frame, but if it still crashes, turn the bar off:

local PrepassOptions = { NoProgressUI = true }

Crash from memory / too many requests (mobile, low-RAM). Lower concurrency and cap how many scripts are decompiled:

local PrepassOptions = {
    NoProgressUI = true,   -- also skip the Drawing UI to be safe
    MaxInFlight = 3,       -- fewer simultaneous requests = less memory
    RequestsPerMinute = 300,
    MaxScripts = 200,      -- decompile at most 200 scripts
}

To skip decompiling entirely (map/assets only — lightest possible run), set Options.noscripts = true or PrepassOptions.SkipPrepass = true.

Executor compatibility

Executor	Terrain	Union Mesh	Scripts
Synapse / Wave	Yes	Yes	Yes
Volt	Yes	Yes	Yes (native decompiler)
Fluxus	Yes	Partial	Yes
Xeno / Solara	No	No	Yes

No gethiddenproperty (Xeno/Solara) means terrain & union mesh can't be saved. Check saveinstance-capabilities.txt after a run for your executor's support.

Files

• saveinstance.luau — main serializer (terrain, unions, decompile, export)
• prepass.luau — loader/wrapper: caches decompile to disk, hooks decompile, verifies + loads saveinstance
• docs/option.md — full option reference
• version.txt — current published version (checked by the loader for updates)
• CHANGELOG.md — what changed per release
• ROADMAP.md — planned work
• moonwave.toml — Moonwave documentation config

Credits

Builds on UniversalSynSaveInstance, USSI Prepass, lua.expert, and SaveInstance 420 Edition.