diff --git a/programs/roulette.lua b/programs/roulette.lua
index 6984edd..6c1447a 100644
--- a/programs/roulette.lua
+++ b/programs/roulette.lua
@@ -43,16 +43,30 @@ local function findGPU()
 end
 
 local function makeGpuBackend(gpu)
+    -- refreshSize() is async: it schedules the monitor-wall scan on the
+    -- server thread and returns immediately.  Poll until blocksX or
+    -- blocksY grows, or we time out (2 s).
     gpu.refreshSize()
-    -- Try a high per-block resolution; older/cheaper GPU tiers may cap
-    -- this so fall back if it errors.
+    local pw, ph, bx, by, sb
+    local deadline = os.clock() + 2
+    repeat
+        sleep(0.1)
+        pw, ph, bx, by, sb = gpu.getSize()
+    until ((bx or 0) > 1 or (by or 0) > 1) or os.clock() >= deadline
+
+    -- If still 1x1 try once more after a longer wait, then proceed anyway.
+    if (bx or 0) <= 1 and (by or 0) <= 1 then
+        sleep(0.5)
+        pw, ph, bx, by, sb = gpu.getSize()
+    end
+
+    -- Try a high per-block resolution; fall back if GPU tier caps it.
     local trySizes = { 64, 32, 16, 8 }
     for _, s in ipairs(trySizes) do
         if pcall(gpu.setSize, s) then break end
     end
-
-    -- getSize() returns: pixelW, pixelH, blocksX, blocksY, sizePerBlock
-    local pw, ph, bx, by, sb = gpu.getSize()
+    -- Re-read size after setSize (pixel dimensions change).
+    pw, ph, bx, by, sb = gpu.getSize()
     print(("[roulette] GPU pixel size: %sx%s  blocks: %sx%s  per-block: %s")
         :format(tostring(pw), tostring(ph), tostring(bx), tostring(by), tostring(sb)))