Environment variables

Variable	Read by	Effect
LUNE_ROBLOX_FFLAGS	Everything that runs or compiles Luau	0 keeps Luau’s default fast flags
LUNE_LUAU_JIT	luneblox run	0, false or off turns native code generation off
LUNEBLOX_CACHE	luneblox build --target	Sets the cache directory
LUNEBLOX_STATE	luneblox repl	Sets the state directory
XDG_CACHE_HOME	luneblox build --target	Base of the cache directory on Linux
XDG_STATE_HOME	luneblox repl	Base of the state directory on Linux
RUST_LOG	Every command	Turns on internal trace logging

The first two keep the LUNE_ prefix. The directory overrides use LUNEBLOX_.

LUNE_ROBLOX_FFLAGS

By default LuneBlox sets Luau’s fast flags to the values the live Roblox client uses. With this variable set to 0, it leaves Luau’s own defaults in place.

Value	Effect
0	Luau’s default flags
Anything else, or unset	Roblox’s flags

LUNE_ROBLOX_FFLAGS=0 luneblox run bench.luau

It is read once per process, before the first Luau VM is created, by luneblox run, the REPL, luneblox build and standalone executables. See Fast flags.

LUNE_LUAU_JIT

luneblox run turns on Luau’s native code generation. This variable turns it off.

Value	Effect
0, false, off	The script runs interpreted
Anything else, or unset	Native code generation is on

The match is exact and case-sensitive: OFF and False leave it on.

LUNE_LUAU_JIT=off luneblox run bench.luau

Only luneblox run reads it. The REPL and standalone executables run with native code generation off whatever its value. See Running scripts.

LUNEBLOX_CACHE

The cache directory, used as given. luneblox build --target keeps downloaded base executables in its target folder.

LUNEBLOX_CACHE=/tmp/luneblox-cache luneblox build tool.luau --target linux-x86_64

The base executable lands in /tmp/luneblox-cache/target/linux-x86_64.

When set, it wins over every other rule, including an existing ~/.luneblox/target. No luneblox segment is appended to it.

LUNEBLOX_STATE

The state directory, used as given. The REPL keeps its history file, .luneblox_history, in it.

LUNEBLOX_STATE=/tmp/luneblox-state luneblox repl

The history is /tmp/luneblox-state/.luneblox_history. When set, it wins over every other rule.

XDG_CACHE_HOME and XDG_STATE_HOME

On Linux, when the LUNEBLOX_ overrides are not set, the cache directory is $XDG_CACHE_HOME/luneblox and the state directory is $XDG_STATE_HOME/luneblox. When the XDG variables are not set, their standard defaults apply: ~/.cache and ~/.local/state.

On macOS and Windows these variables are not read; the platform’s own cache location is used.

Files that already exist in the older home-directory locations keep being used. See Directories for the full order.

Note

None of these four move the type definitions. luneblox setup always writes them to ~/.luneblox/.typedefs/<version>/, because the lune alias in .luaurc points there.

RUST_LOG

luneblox has internal trace logging, written to stderr. It is off unless RUST_LOG sets a level:

RUST_LOG=trace luneblox run script.luau

This is for debugging the runtime itself, such as the order the scheduler resumes threads in. A script does not need it.

Variables for your script

Every environment variable of the process is available to the script in process.env:

--!strict
local process = require("@lune/process")

local port = tonumber(process.env.PORT) or 8080
print(port)

PORT=3000 luneblox run server.luau

See process.