diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index a8207a48..1796220e 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -2,3 +2,8 @@
 **Vulnerability:** Unvalidated inputs passed to `if()` statements can cause process crashes (`condition has length > 1`) or unexpected coercion vulnerabilities.
 **Learning:** In R, optional boolean parameters that default to `NULL` should be validated using explicit runtime type validation (e.g., `if (!is.null(flag) && (!is.logical(flag) || length(flag) != 1 || is.na(flag)))`).
 **Prevention:** Always implement explicit runtime type validation for optional boolean parameters.
+
+## 2024-07-13 - Integer overflow prevention in interactive prompts
+**Vulnerability:** Input validation using regex `^[0-9]+$` on interactive prompts combined with `as.integer()` allows inputs larger than R's max integer (e.g., `999999999999999999999`) to cause `NA` coercion via integer overflow. This missing value can crash execution when evaluated in an `if()` condition (e.g., `if (confirm != 1)`).
+**Learning:** `grepl("^[0-9]+$")` only checks if characters are digits, but does not enforce bounds checking for the data type it's subsequently parsed into.
+**Prevention:** Strictly validate inputs from `readline()` against specific expected discrete values (e.g., `if (n == "1" || n == "2")`) to explicitly reject any out-of-bounds or malformed entries prior to type coercion.
diff --git a/DESCRIPTION b/DESCRIPTION
index f31d3e1a..c90753c5 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -10,7 +10,7 @@ Description: Automates fixed item parameter linking for test linking under
     the item response theory paradigm using mirt package estimates.
 License: GPL-3 | file LICENSE
 Imports: mirt, methods
-Suggests: testthat (>= 3.0.0)
+Suggests: testthat (>= 3.0.0), mockery
 Encoding: UTF-8
 Config/testthat/edition: 3
 Config/roxygen2/version: 8.0.0
diff --git a/R/aFIPC.R b/R/aFIPC.R
index 62546519..d32d09bd 100644
--- a/R/aFIPC.R
+++ b/R/aFIPC.R
@@ -141,7 +141,7 @@ autoFIPC <-
       }
       for (attempt in seq_len(3)) {
         n <- readline(prompt = "Is it correct? (1: Yes 2: No) : ")
-        if (grepl("^[0-9]+$", n)) {
+        if (n == "1" || n == "2") {
           return(as.integer(n))
         }
       }
@@ -171,7 +171,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for oldform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (n == "1" || n == "2") {
               return(as.integer(n))
             }
           }
@@ -390,7 +390,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for newform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (n == "1" || n == "2") {
               return(as.integer(n))
             }
           }
diff --git a/tests/testthat/test-sentinel-interactive.R b/tests/testthat/test-sentinel-interactive.R
new file mode 100644
index 00000000..88d7a2de
--- /dev/null
+++ b/tests/testthat/test-sentinel-interactive.R
@@ -0,0 +1,18 @@
+test_that("interactive prompts strictly validate input and prevent integer overflow", {
+  df_x <- data.frame(A = c(1,0,1,0), B = c(1,0,1,0))
+  df_y <- data.frame(A = c(1,0,1,0), C = c(1,0,1,0))
+
+  mockery::stub(aFIPC::autoFIPC, "interactive", function() TRUE)
+  mockery::stub(aFIPC::autoFIPC, "readline", mockery::mock("999999999999999999999", "3", "abc", cycle = TRUE))
+
+  expect_error(
+    aFIPC::autoFIPC(
+      newformXData = df_x,
+      oldformYData = df_y,
+      newformCommonItemNames = "A",
+      oldformCommonItemNames = "A",
+      confirmCommonItems = NULL
+    ),
+    "Too many invalid common item confirmation attempts"
+  )
+})