Lua errors

Lua errors use values with a stable code, readable message, optional detail, and optional cause. The complete API, value type, and native code catalogue are in the mux.error package reference.

Use raised errors for contract violations such as invalid arguments, dead handles, and limits. For a failure the caller is expected to recover from, return nil, err instead.

local ok, err = mux.error.pcall(function()
  mux.error.raise(
    mux.error.codes.state.value_too_large,
    "state value exceeds 4096 bytes",
    { limit = 4096 }
  )
end)
if not ok and err:is(mux.error.codes.state) then
  mux.world.pemit(ctx.enactor, err.message)
end

Plain strings remain supported for existing scripts. Authors can build their own checked symbols with mux.error.namespace:

local codes = mux.error.namespace("cargo", { "full", "bay.locked" })
mux.error.raise(codes.full, "the cargo bay is full")

See Error for fields, matching, cause chains, and callback reporting. See mux.error.codes for the native constants, including mux.unavailable.checking for operations that cannot run during @lua/check and btech.failed for BattleTech script failures.