Roblox FastFlags guide for Sober

Verified, safe, and allowlisted FastFlags for the Sober client on Linux.

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Table of contents

• What is Sober?
• What are FastFlags?
• Confirmed active FFlags
  • Rendering and performance
  • Stability and VRAM
  • UI and environment
• Configuration presets
  • Preset 1: Low-end / VRAM crash fix
  • Preset 2: Balanced / mid-range
  • Preset 3: Maximum graphics fidelity
• Detailed technical topics
• Uncapping framerates
• Security and anti-cheat risks
• Deprecated FFlags
• Disclaimer and sources

What is Sober?

Sober is a compatibility layer that runs the Roblox Android application (APK) natively on Linux desktops. It is distributed as a Flatpak (org.vinegarhq.Sober) and uses Vulkan as its primary rendering backend, with OpenGL as a fallback. Configuration is managed through ~/.var/app/org.vinegarhq.Sober/config/sober/config.json. You can also open the settings menu graphically using the command flatpak run org.vinegarhq.Sober config or by right-clicking Sober in your application menu and selecting Settings.

What are FastFlags?

FastFlags (FFlags) are internal Roblox engine variables that control rendering, UI, stability, and other settings. Since September 29, 2025, Roblox enforces a strict allowlist: only a small subset of flags can be overridden locally via configuration files. Any flag not on the allowlist is ignored by the client.

Important

This guide only covers flags confirmed to be on the current allowlist. Flags from older community guides may no longer work.

Confirmed active FFlags

Rendering and performance

These flags control geometry detail, anti-aliasing, lighting, and grass rendering distance.

Flag Name	Type	Value Range	What It Does
DFIntCSGLevelOfDetailSwitchingDistance	int	0 - 1000	Master LOD culling distance for CSG models. Lower = better FPS.
DFIntCSGLevelOfDetailSwitchingDistanceL12	int	0 - 1000	LOD distance for Graphics Quality 1 to 2.
DFIntCSGLevelOfDetailSwitchingDistanceL23	int	0 - 1000	LOD distance for Graphics Quality 2 to 3.
DFIntCSGLevelOfDetailSwitchingDistanceL34	int	0 - 1000	LOD distance for Graphics Quality 3 to 4.
FIntDebugForceMSAASamples	int	1, 2, 4	Forces MSAA anti-aliasing (smoother edges, costs GPU).
DFIntDebugFRMQualityLevelOverride	int	0 - 21	Overrides the graphics level slider (goes beyond default 1 to 10).
FIntFRMMaxGrassDistance	int	0 - 1000	Max render distance for terrain grass. Set to 0 to disable grass.
FIntFRMMinGrassDistance	int	0 - 1000	Min distance where grass starts rendering.
DFFlagDebugPauseVoxelizer	bool	true / false	Disables voxel lighting.
FFlagDebugSkyGray	bool	true / false	Overrides skybox color to gray and removes atmospheric stars.
FFlagDebugGraphicsPreferVulkan	bool	true / false	Prefers Vulkan for rendering.
FFlagDebugGraphicsPreferOpenGL	bool	true / false	Prefers OpenGL for rendering.

Stability and VRAM

These flags help prevent out-of-memory crashes, especially on GPUs with limited VRAM.

Flag Name	Type	Value Range	What It Does
DFFlagTextureQualityOverrideEnabled	bool	true / false	Enables manual control over texture resolution.
DFIntTextureQualityOverride	int	0 - 3	Sets texture quality (0 = lowest, 3 = max).

Warning

Setting DFIntTextureQualityOverride to 3 on GPUs with 4 GB VRAM or less often causes an instant RBXCRASH: OutOfMemory crash. Use 2 or 1 for stability.

UI and environment

Minor flags that affect visual comfort and interface behavior.

Flag Name	Type	Value Range	What It Does
FIntGrassMovementReducedMotionFactor	bool	true / false	Reduces motion for grass animations. (Note: Uses FInt name prefix but expects boolean true/false).

Configuration presets

Copy one of the presets below and paste it into your Sober configuration file:

~/.var/app/org.vinegarhq.Sober/config/sober/config.json

Preset 1: Low-end / VRAM crash fix

For GPUs with less than 4 GB VRAM, integrated graphics, or systems experiencing OutOfMemory crashes.

{
  "enable_hidpi": false,
  "fflags": {
    "DFFlagTextureQualityOverrideEnabled": true,
    "DFIntTextureQualityOverride": 1,
    "DFIntCSGLevelOfDetailSwitchingDistance": 100,
    "DFIntCSGLevelOfDetailSwitchingDistanceL12": 75,
    "DFIntCSGLevelOfDetailSwitchingDistanceL23": 100,
    "DFIntCSGLevelOfDetailSwitchingDistanceL34": 150,
    "FIntFRMMaxGrassDistance": 0,
    "FIntGrassMovementReducedMotionFactor": true
  }
}

Preset 2: Balanced / mid-range

For mid-tier GPUs (GTX 1650, RX 580 class) with 4 to 6 GB VRAM. Good balance between visuals and performance.

{
  "enable_hidpi": false,
  "fflags": {
    "DFFlagTextureQualityOverrideEnabled": true,
    "DFIntTextureQualityOverride": 2,
    "DFIntCSGLevelOfDetailSwitchingDistance": 400,
    "DFIntCSGLevelOfDetailSwitchingDistanceL12": 200,
    "DFIntCSGLevelOfDetailSwitchingDistanceL23": 350,
    "DFIntCSGLevelOfDetailSwitchingDistanceL34": 500,
    "FIntDebugForceMSAASamples": 2,
    "FIntFRMMaxGrassDistance": 200,
    "FIntGrassMovementReducedMotionFactor": true
  }
}

Preset 3: Maximum graphics fidelity

For high-end systems with 8 GB+ VRAM. Forces maximum detail, anti-aliasing, and texture quality.

{
  "enable_hidpi": true,
  "fflags": {
    "DFFlagTextureQualityOverrideEnabled": true,
    "DFIntTextureQualityOverride": 3,
    "DFIntCSGLevelOfDetailSwitchingDistance": 1000,
    "DFIntCSGLevelOfDetailSwitchingDistanceL34": 1000,
    "FIntDebugForceMSAASamples": 4,
    "DFIntDebugFRMQualityLevelOverride": 21
  }
}

Tip

You can mix and match flags between presets. For example, use the Balanced LOD distances with Maximum texture quality if your GPU has enough VRAM but struggles with geometry.

Detailed technical topics

Level of detail (LOD) and geometry scaling

Roblox maps often use complex Constructive Solid Geometry (CSG) unions. Rendering these at far distances puts heavy load on both CPU and GPU.

By lowering DFIntCSGLevelOfDetailSwitchingDistance (e.g., to 150), you force the game to swap complex models for low-polygon versions closer to the camera. This increases framerates without changing physical collision hitboxes: objects still behave the same, but look simpler from far away.

The tiered variants (L12, L23, L34) let you fine-tune this per graphics quality level, so lower quality settings cull more aggressively.

VRAM allocation and out-of-memory (OOM) crashes

Sober runs the Roblox Android binary inside a Linux Flatpak environment. The Android binary assumes a shared mobile memory model, which differs from how desktop Linux GPU drivers handle VRAM.

When the engine requests maximum quality textures, it can quickly exhaust dedicated GPU VRAM. On Windows desktop, drivers spill excess data into system RAM. On Linux (especially with proprietary NVIDIA drivers), this fallback does not work reliably, causing an instant RBXCRASH: OutOfMemory crash.

To fix this, set DFFlagTextureQualityOverrideEnabled to true and DFIntTextureQualityOverride to 2 (medium) or 1 (low). This forces the engine to request smaller textures from the server, keeping VRAM usage within safe limits.

Graphics APIs: Vulkan vs. OpenGL

Graphics API selection can be configured via config.json or FFlags (FFlagDebugGraphicsPreferVulkan / FFlagDebugGraphicsPreferOpenGL).

• By default, Sober uses Vulkan for optimal performance.
• If you experience graphic artifacts, black screens, or startup crashes (common on older GPUs or hybrid laptop setups), Vinegar documentation recommends running flatpak run org.vinegarhq.Sober config in your terminal and selecting Force Legacy Rendering (or setting "use_opengl": true in config.json).

Asset overlay (custom textures and cursors)

Sober allows replacing game assets via the asset_overlay directory located at: ~/.var/app/org.vinegarhq.Sober/data/sober/asset_overlay

Files placed here take priority over standard Roblox assets upon restarting the app. The directory structure mirrors packages/*/com.roblox.client/base.apk/assets.

Example for custom mouse cursors:

~/.var/app/org.vinegarhq.Sober/data/sober/asset_overlay
└── content
    └── textures
        └── Cursors
            └── KeyboardMouse
                ├── ArrowCursor.png
                ├── ArrowFarCursor.png
                └── IBeamCursor.png

To revert changes, clear the files from asset_overlay.

Fullscreen (F11) and exit controls

The in-game fullscreen toggle in Roblox does not function on mobile Android builds. On Sober, press F11 to enter or exit fullscreen mode. Sober remembers the fullscreen state across launches.

To close the app automatically upon leaving an experience, add "close_on_leave": true to your config.json.

Uncapping framerates

The DFIntTaskSchedulerTargetFps FastFlag no longer works because Roblox removed it from the allowlist. To change your framerate cap, edit the XML settings file directly.

Steps:

1. Launch any Roblox experience on Sober to generate the config files.
2. Close the client completely.
3. Navigate to ~/.var/app/org.vinegarhq.Sober/data/sober/appData/.
4. Open GlobalBasicSettings_13.xml in a text editor.
5. Find the line: <int name="FramerateCap">60</int>
6. Change 60 to your target framerate (e.g., 144, 240) or 0 to uncap.
7. Save, close, and relaunch Roblox.

Note

Close Roblox before editing this file. The client overwrites this file on exit, so any changes made while the game is running will be lost.

Security and anti-cheat risks

Roblox uses the Hyperion (Byfron) anti-cheat system. Configuring allowlisted FFlags in config.json is safe. Attempting to bypass the allowlist is not.

Caution

The following actions carry a high risk of permanent account or hardware bans. Do not attempt them.

• Cache file manipulation (IxpSettings.json): Injecting unauthorized flags into cache files and setting them to read-only is detected as tampering by Hyperion.
• Memory editing: Using tools to force-load disallowed flags (such as physics timestep manipulation via DFIntTimestepArbiterThresholdCFLThou or texture bypasses for wallhacks) triggers automated bans.
• Allowlist bypass programs: Programs or launch arguments designed to circumvent the FFlag filter are classified as exploits.

Deprecated FFlags

These flags were popular in older guides, but Roblox removed them from the allowlist. Adding them to config.json has no effect because the client ignores them.

Flag	Why It's Deprecated
DFIntTaskSchedulerTargetFps	Replaced by editing GlobalBasicSettings_13.xml.
FFlagTaskSchedulerLimitTargetFpsTo2402	Removed from the allowlist.
DFIntConnectionMTUSize	Network tuning flags are blocked.
FFlagDebugDisableTelemetryEphemeralCounter	Telemetry suppression is blocked.
FFlagAdServiceEnabled	Ad service toggling is blocked.
FFlagMovePrerender	Thread manipulation flags are blocked.
DFIntDebugDynamicRenderKiloPixels	Render resolution scaling was vetoed by Roblox engineering.

Disclaimer and sources

Note

Roblox Corporation maintains the FFlag allowlist, which may change with future client updates. This guide is accurate as of July 2026. Always verify against official sources before deploying configurations.

Official sources:

• Allowlist for local client configuration via Fast Flags on the Roblox DevForum
• Sober Configuration Tips & Tricks from Vinegar Documentation