<img src="data/icons/org.chaser.Chaser.svg" align="left" width="64" height="64" alt="Chaser icon">

Chaser

CI

A GTK4 launcher and manager for Sober, the way to play Roblox on Linux. What Bloxstrap is on Windows.

Sober runs the x86-64 Android build of Roblox natively, which sidesteps the Hyperion anti-cheat that closed off Wine. It is deliberately a minimal runtime, and VinegarHQ leaves the launcher and config layer to the community. Chaser is that layer: profiles, a FastFlag catalog, performance presets, launch orchestration and config backups, without touching the runtime or the Roblox client.

Features

• Launch writes the active profile to Sober first, so what you see is what runs.
• First-run onboarding checks the Sober install and sets a starting preset.
• Profiles: named bundles of graphics mode, renderer, GameMode, RPC, HiDPI and

gamepad toggles, FastFlags and launch environment.

• Presets: Competitive FPS, Balanced, Cinematic, and Potato for weak GPUs -

all built only from flags the client actually honours.

• FastFlag catalog built from Roblox's official allowlist, risk-tagged, with a

raw JSON editor.

• Every flag validated against the engine's own symbols: Chaser tells you which

of your flags are live, which the client ignores, and which are not real flags at all. chaser doctor audits your live config.

• Import shared FastFlag presets with the invented flags stripped out.
• Play history parsed from Sober's logs: place, universe, server instance and

how long each visit lasted.

• Registers as a roblox:// link handler, so a Play link from the website

applies your active profile before handing off to Sober.

• Performance page: apply a preset, toggle MangoHud, set environment variables.
• Sober's JSONC config.json is parsed with its comment header and unmanaged

keys preserved, written atomically, and backed up before every change to ~/.config/chaser/backups, keeping the newest 20.

• GTK4 and libadwaita. No Electron, no web view.
• CLI with everything the GUI does.

Requirements

• Sober via Flatpak:

flatpak install flathub org.vinegarhq.Sober

• GTK4 4.14 or newer and libadwaita 1.5 or newer (Ubuntu 24.04, Fedora 40, or

anything later)

• Rust, to build from source

Install

Flatpak

Take chaser.flatpak from the latest release:

flatpak install --user ./chaser.flatpak
flatpak run org.chaser.Chaser        # or launch Chaser from the app menu

Or build it:

flatpak install flathub org.gnome.Sdk//49 org.gnome.Platform//49 org.freedesktop.Sdk.Extension.rust-stable//25.08
flatpak-builder --user --install --force-clean build-dir packaging/org.chaser.Chaser.yml

From source

git clone https://github.com/PointOfPressure/chaser.git
cd chaser
# build deps on Debian/Ubuntu/Zorin:
sudo apt install libgtk-4-dev libadwaita-1-dev
cargo build --release

Binaries land in target/release/: chaser-gui is the app, chaser the CLI. Run in place with ./target/release/chaser-gui, or install:

sudo install -Dm755 target/release/chaser-gui /usr/local/bin/chaser-gui
sudo install -Dm755 target/release/chaser /usr/local/bin/chaser
install -Dm644 data/org.chaser.Chaser.desktop ~/.local/share/applications/org.chaser.Chaser.desktop
install -Dm644 data/icons/org.chaser.Chaser.svg ~/.local/share/icons/hicolor/scalable/apps/org.chaser.Chaser.svg

CLI

chaser status              # Sober install + active profile
chaser init                # create the built-in presets
chaser profiles            # list profiles (* = active)
chaser apply <slug>        # write a profile into Sober's config
chaser launch [--profile <slug>] [--dry-run] [uri]
chaser config [--path]     # print Sober's parsed config
chaser fflags              # list the curated FastFlag catalog
chaser sessions            # play history: place, universe, server, duration
chaser doctor              # audit Sober's FastFlags: live, ignored, or fake
chaser import <file>       # merge a shared FastFlag preset, dropping fakes

How it works

Chaser does not touch the Roblox client or Sober's runtime. It:

1. reads and writes ~/.var/app/org.vinegarhq.Sober/config/sober/config.json,

Sober's own settings surface including its fflags object, preserving the // !!! STOP !!! header and any keys it does not understand;

1. backs the file up before each write, and writes atomically via temp file and

rename;

1. launches Sober with flatpak run org.vinegarhq.Sober, injecting environment

through --env=.

Chaser also ships a hidden desktop entry that claims x-scheme-handler/roblox, so a Play link from the Roblox website can route through Chaser: it applies the active profile, then hands the URI to Sober. Sober claims the same scheme, so pick whichever you want as the default handler:

xdg-mime default org.chaser.Chaser.handler.desktop x-scheme-handler/roblox
xdg-mime default org.vinegarhq.Sober.desktop x-scheme-handler/roblox   # to undo

FastFlags

Since 29 September 2025 the Roblox client honours only the flags on [Roblox's published allowlist][allowlist] - eighteen of them. Everything else set through a config file is silently ignored: no error, no warning, it simply does nothing.

That is why most FastFlag guides no longer work, and why a good share of the flags traded around in presets were never real names to begin with.

Chaser checks every flag against two independent dumps of the Roblox engine's own symbols before it reaches Sober, and reports one of four verdicts:

chaser doctor audits what is actually in your Sober config right now:

$ chaser doctor
Auditing 9 FastFlags in ~/.var/app/org.vinegarhq.Sober/config/sober/config.json

  FAKE     DFFlagDebugRenderForceTechnologyVoxel  = true   no such flag in any Roblox build
  LIVE     DFFlagTextureQualityOverrideEnabled    = true
  LIVE     DFIntDebugFRMQualityLevelOverride      = 1
  IGNORED  DFIntTaskSchedulerTargetFps            = 60     not on Roblox's allowlist
  LIVE     DFIntTextureQualityOverride            = 0
  FAKE     FFlagDisablePostFx                     = true   no such flag in any Roblox build

  4 live, 1 ignored, 4 not real.
  5 of 9 flags in this config do nothing.

chaser import preset.json merges a preset someone sent you, dropping the invented flags rather than writing them into your profile. --all keeps them.

Where the ground truth comes from

Two sources, because neither alone is enough:

• core/data/flags.txt - every flag symbol in an unstripped Roblox Studio

build, as PREFIX:Name. The only source that knows a flag's prefix, so it is what catches FFlag/DFFlag mix-ups.

• core/data/player-flags.txt - bare flag names from a current Player

client offset dump, covering the ~1500 flags newer than that Studio build.

A flag is treated as real if either source knows it. The allowlist overrides both: a platform-specific entry missing from a dump is still allowlisted, and is never reported as fabricated.

Why other tools claim thousands of modifiable flags

Because they do not use the config file. Windows tools that advertise ~14,000 modifiable flags write values straight into the running client's memory using dumped offsets, which sidesteps the allowlist entirely. That is a different mechanism with different risks, it is Windows-only, and Chaser does not do it. Through a config file - the only route Sober offers - the allowlist is the whole truth.

[allowlist]: https://devforum.roblox.com/t/allowlist-for-local-client-configuration-via-fast-flags/3966569

Not affiliated

An unofficial community project, not affiliated with Roblox or VinegarHQ. It edits Sober's configuration and launches it. It does not modify the Roblox client, load modified APKs, or attempt to bypass anti-cheat.

License

MIT, see LICENSE.