diff --git a/R/aFIPC.R b/R/aFIPC.R
index 62546519..389c6ab2 100644
--- a/R/aFIPC.R
+++ b/R/aFIPC.R
@@ -86,8 +86,10 @@ autoFIPC <-
 
     if (!is.character(itemtype)) stop('Security Error: itemtype must be a character vector')
     nItems <- NA_integer_
-    if (is.data.frame(newformXData) || is.matrix(newformXData)) nItems <- ncol(as.data.frame(newformXData))
-    else if (is.data.frame(oldformYData) || is.matrix(oldformYData)) nItems <- ncol(as.data.frame(oldformYData))
+    # Optimization: Use ncol() directly instead of coercing to data.frame to avoid O(N) memory allocation and copy overhead
+    if (is.data.frame(newformXData) || is.matrix(newformXData)) nItems <- ncol(newformXData)
+    # Optimization: Use ncol() directly instead of coercing to data.frame to avoid O(N) memory allocation and copy overhead
+    else if (is.data.frame(oldformYData) || is.matrix(oldformYData)) nItems <- ncol(oldformYData)
     if (!is.na(nItems) && !(length(itemtype) == 1 || length(itemtype) == nItems)) stop(sprintf('Security Error: itemtype must be length 1 or length %d (number of items).', nItems))
 
     # boolean parameter validation
diff --git a/tests/testthat/test-ncol_optimization.R b/tests/testthat/test-ncol_optimization.R
new file mode 100644
index 00000000..a9433d39
--- /dev/null
+++ b/tests/testthat/test-ncol_optimization.R
@@ -0,0 +1,35 @@
+test_that("ncol() optimization correctly determines number of items from matrix", {
+  # Test the newformXData path explicitly.
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = matrix(c(1, 2), nrow = 1, dimnames = list(NULL, c("A", "B"))),
+      oldformYData = data.frame(A=2, B=3),
+      newformCommonItemNames = c('A'),
+      oldformCommonItemNames = c('A'),
+      itemtype = c("2PL", "2PL", "2PL")
+    ),
+    "Security Error: itemtype must be length 1 or length 2 \\(number of items\\)."
+  )
+
+  # Test the oldformYData path explicitly.
+  # We construct an S4 SingleGroupClass from mirt using mock data but provide sufficient
+  # parameters to prevent mirt from crashing during internal check inside `aFIPC`.
+
+  dummy_data <- matrix(sample(c(0, 1), 100, replace=TRUE), 20, 5)
+  colnames(dummy_data) <- paste0("Item", 1:5)
+
+  suppressMessages(suppressWarnings({
+    real_mirt_model <- mirt::mirt(dummy_data, 1, itemtype = "2PL", TOL = 0.5, verbose=FALSE)
+  }))
+
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = real_mirt_model,
+      oldformYData = matrix(c(1, 2, 3), nrow = 1, dimnames = list(NULL, c("A", "B", "C"))),
+      newformCommonItemNames = c('A'),
+      oldformCommonItemNames = c('A'),
+      itemtype = c("2PL", "2PL")
+    ),
+    "Security Error: itemtype must be length 1 or length 3 \\(number of items\\)."
+  )
+})