diff --git a/build-rg34xxsp.sh b/build-rg34xxsp.sh
index efa9db73..44dbac4c 100755
--- a/build-rg34xxsp.sh
+++ b/build-rg34xxsp.sh
@@ -202,6 +202,11 @@ export LD_LIBRARY_PATH="$GAMEDIR/libs.aarch64:${LD_LIBRARY_PATH:-}"
 export SDL_GAMECONTROLLERCONFIG="${sdl_controllerconfig:-}"
 # Mali / H700: prefer GLES where available
 export LOVE_GRAPHICS_USE_OPENGLES="${LOVE_GRAPHICS_USE_OPENGLES:-1}"
+# Same GPU class as a phone, but getOS() here says "Linux", so the Android
+# gate (issue #136) would not fire on its own: refuse GBC FX explicitly.
+# Hides the OPTIONS row, pins the level to OFF, and heals a level already
+# persisted in options.lua.
+export POKEPORT_GBCFX="${POKEPORT_GBCFX:-0}"
 
 $ESUDO chmod a+x ./bin/love.aarch64 2>/dev/null || chmod a+x ./bin/love.aarch64
 $ESUDO chmod 666 /dev/uinput 2>/dev/null || true
@@ -292,6 +297,13 @@ Native LÖVE 11.5 port of gen1recomp for Anbernic RG34XXSP on
 
 In-game controls use the normal PortMaster / SDL pad map (rebind under OPTIONS → CONTROLS).
 
+### Display options
+
+GBC FX is disabled on this device (the H700's Mali GPU compiles that present
+pass and then shows a black frame), so the OPTIONS row is hidden. COLORS,
+TILT, ZOOM, VOID FILL and MAX FPS all work. To try it anyway, launch with
+`POKEPORT_GBCFX=1`.
+
 ### First run
 
 Stock OS has no zenity file picker. Put the `.gb` in `lovegame/`, then press
diff --git a/docs/anbernic-rg34xxsp.md b/docs/anbernic-rg34xxsp.md
index 8e41d4f5..4081f4bc 100644
--- a/docs/anbernic-rg34xxsp.md
+++ b/docs/anbernic-rg34xxsp.md
@@ -55,6 +55,16 @@ In-game controls use the normal PortMaster / SDL pad map, rebindable under
 
 ## Notes
 
+**GBC FX is off on this device.** The launcher exports `POKEPORT_GBCFX=0`,
+which hides the GBC FX row from OPTIONS, pins the level to OFF, and clears a
+level carried over in an `options.lua` from another machine. The H700's Mali
+GPU is in the same class as the phone GPUs that compile that present pass and
+then show a black frame (issue #136), and `love.system.getOS()` reports
+`"Linux"` here, so the Android gate would not have caught it. Every other
+display option — COLORS, TILT, ZOOM, VOID FILL, MAX FPS — works normally. If
+your device turns out to handle the pass, launch with `POKEPORT_GBCFX=1` to
+put the row back.
+
 The pack bundles the LÖVE 11.5 aarch64 runtime from
 [PortMaster](https://portmaster.games/), so the device does not need a
 separate `love_11.5` runtime download on first launch. The launcher resolves
diff --git a/docs/new-features.md b/docs/new-features.md
index e07b9805..4ff64e88 100644
--- a/docs/new-features.md
+++ b/docs/new-features.md
@@ -129,6 +129,14 @@ It runs as a final present pass after world + UI composite in
 ([github.com/mattakins/Pixel_Transparency](https://github.com/mattakins/Pixel_Transparency)).
 Default OFF; persisted as `save.options.gbcfx`.
 
+Mobile GPUs often compile the pass but present a black frame, so Android and
+iOS hide the row entirely, pin the level to OFF, and rewrite a level already
+persisted in `options.lua` (issue #136). `POKEPORT_GBCFX` overrides that
+decision either way, same tri-state as `POKEPORT_TOUCH`: `=0` refuses the
+effect, `=1` forces it available. The Anbernic handheld pack exports `0` from
+its launcher because the device reports `"Linux"` while its GPU is in the
+phone class (see [Anbernic RG34XXSP](anbernic-rg34xxsp.md)).
+
 ## Peer-to-peer link play (lua-enet)
 
 Trades and link battles connect two copies of the game directly over
diff --git a/src/render/GBCFX.lua b/src/render/GBCFX.lua
index 0a05db7f..c2788a2a 100644
--- a/src/render/GBCFX.lua
+++ b/src/render/GBCFX.lua
@@ -25,7 +25,16 @@ local shader -- false = unavailable (headless / no shader support)
 -- Mobile GPUs often compile this pass but present a black frame, and the
 -- level persists in options.lua -- soft-bricking the APK until a manual
 -- edit (issue #136).  Desktop is unchanged; Android/iOS refuse the effect.
+--
+-- POKEPORT_GBCFX overrides the platform default either way ("1" force on,
+-- "0" force off), same tri-state as POKEPORT_TOUCH.  Handheld packs whose
+-- GPU is in the same class as a phone's but whose getOS() says "Linux" set
+-- it to 0 in their launcher (build-rg34xxsp.sh); it also lets a desktop
+-- checkout exercise the unsupported path without stubbing love.system.
 function GBCFX.isSupported()
+  local env = os.getenv("POKEPORT_GBCFX")
+  if env == "1" then return true end
+  if env == "0" then return false end
   if not love or not love.system or not love.system.getOS then return true end
   local osName = love.system.getOS()
   return osName ~= "Android" and osName ~= "iOS"
diff --git a/tests/parity_gbcfx.lua b/tests/parity_gbcfx.lua
index 996c20ab..891008e6 100644
--- a/tests/parity_gbcfx.lua
+++ b/tests/parity_gbcfx.lua
@@ -121,5 +121,51 @@ end
 check(not hasGbc, "Options menu omits GBC FX on Android")
 love.system = prevSystem
 
+-- POKEPORT_GBCFX overrides the platform default both ways.  Handheld packs
+-- (build-rg34xxsp.sh) export 0 because their getOS() says "Linux" while the
+-- GPU is phone class; 1 is the escape hatch if a device turns out to cope.
+local prevEnv = os.getenv("POKEPORT_GBCFX")
+local realGetenv = os.getenv
+local stubEnv
+os.getenv = function(name)
+  if name == "POKEPORT_GBCFX" then return stubEnv end
+  return realGetenv(name)
+end
+
+stubEnv = "0"
+check(not GBCFX.isSupported(), "POKEPORT_GBCFX=0 refuses GBC FX on desktop")
+GBCFX.setLevel(3)
+eq(GBCFX.level, 0, "setLevel forces OFF under POKEPORT_GBCFX=0")
+local handheldOpts = { gbcfx = 4 }
+check(GBCFX.applyOptions(handheldOpts) == true,
+      "applyOptions reports a cleared level under POKEPORT_GBCFX=0")
+eq(handheldOpts.gbcfx, 0, "applyOptions heals a persisted level on a handheld")
+check(not GBCFX.active(), "active() is false under POKEPORT_GBCFX=0")
+
+local omHandheld = OptionsMenu.new({
+  data = { rulesets = {}, constants = {} },
+  save = { options = {} },
+  stack = { pop = function() end },
+  input = { wasPressed = function() return false end },
+  modStatus = { available = {} },
+})
+hasGbc = false
+for _, row in ipairs(omHandheld.rows) do
+  if row.id == "gbcfx" then hasGbc = true end
+end
+check(not hasGbc, "Options menu omits GBC FX under POKEPORT_GBCFX=0")
+
+-- "1" wins over the Android gate, so the override is a real two-way door.
+stubEnv = "1"
+love.system = { getOS = function() return "Android" end }
+check(GBCFX.isSupported(), "POKEPORT_GBCFX=1 forces GBC FX on despite Android")
+love.system = prevSystem
+
+stubEnv = nil
+check(GBCFX.isSupported(), "unset POKEPORT_GBCFX falls back to the OS check")
+os.getenv = realGetenv
+eq(os.getenv("POKEPORT_GBCFX"), prevEnv, "os.getenv restored")
+GBCFX.setLevel(0)
+
 -- === summary ===
 S.finish()