diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index a8207a48..30e263d4 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -2,3 +2,7 @@
 **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.
+## 2024-09-14 - Fix weak regex validation for readline inputs
+**Vulnerability:** Weak regex `^[0-9]+$` on interactive `readline` inputs allows passing arbitrarily large numbers that exceed the 32-bit integer limit, resulting in coercion to `NA` when passed to `as.integer()` and breaking downstream logic.
+**Learning:** When validating `readline()` inputs intended for `as.integer()` coercion, using unbounded regex like `^[0-9]+$` is a security vulnerability because inputs exceeding the 32-bit integer limit coerce to `NA`.
+**Prevention:** Always use strictly bounded exact-match regex (e.g., `^[12]$`) when parsing integer choices to prevent coercion to `NA`.
diff --git a/R/aFIPC.R b/R/aFIPC.R
index 62546519..918e19b1 100644
--- a/R/aFIPC.R
+++ b/R/aFIPC.R
@@ -141,7 +141,7 @@ autoFIPC <-
       }
       for (attempt in seq_len(3)) {
         n <- readline(prompt = "Is it correct? (1: Yes 2: No) : ")
-        if (grepl("^[0-9]+$", n)) {
+        if (grepl("^[12]$", n)) {
           return(as.integer(n))
         }
       }
@@ -171,7 +171,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for oldform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (grepl("^[12]$", n)) {
               return(as.integer(n))
             }
           }
@@ -390,7 +390,7 @@ autoFIPC <-
               readline(
                 prompt = "Do you want to use default BILOG-MG priors for newform Data? (1: Yes 2: No) : "
               )
-            if (grepl("^[0-9]+$", n)) {
+            if (grepl("^[12]$", n)) {
               return(as.integer(n))
             }
           }
diff --git a/tests/testthat/test-sentinel-validation.R b/tests/testthat/test-sentinel-validation.R
index 900f0ee3..6a027f09 100644
--- a/tests/testthat/test-sentinel-validation.R
+++ b/tests/testthat/test-sentinel-validation.R
@@ -35,3 +35,58 @@ test_that("autoFIPC validates boolean flags for newformBILOGprior, oldformBILOGp
     "Security Error: confirmCommonItems must be a single non-NA logical value or NULL"
   )
 })
+
+test_that("autoFIPC strictly validates readline inputs using exact bounds", {
+  dummy_mod <- function(...) {
+    mod <- new("SingleGroupClass")
+    mod@OptimInfo$converged <- TRUE
+    mod@OptimInfo$secondordertest <- TRUE
+    mod@Data$data <- data.frame(A=1, B=2)
+    return(mod)
+  }
+
+  mockery::stub(autoFIPC, "mirt::mirt", dummy_mod)
+  mockery::stub(autoFIPC, "interactive", function() TRUE)
+  mockery::stub(autoFIPC, "readline", mockery::mock("33333333333", "33333333", "2"))
+
+  expect_error(
+    expect_message(
+      autoFIPC(
+        newformXData = data.frame(A=1, B=2),
+        oldformYData = data.frame(A=1, B=2),
+        newformCommonItemNames = c('A'),
+        oldformCommonItemNames = c('A'),
+        confirmCommonItems = NULL
+      ),
+      "Checking correspond common item names"
+    ),
+    "Please write down pairs correctly"
+  )
+})
+
+test_that("autoFIPC strictly validates oldformBILOGprior and newformBILOGprior using exact bounds", {
+  dummy_mod <- function(...) {
+    mod <- new("SingleGroupClass")
+    mod@OptimInfo$converged <- TRUE
+    mod@OptimInfo$secondordertest <- TRUE
+    mod@Data$data <- data.frame(A=1, B=2)
+    return(mod)
+  }
+
+  mockery::stub(autoFIPC, "mirt::mirt", dummy_mod)
+  mockery::stub(autoFIPC, "interactive", function() TRUE)
+  mockery::stub(autoFIPC, "readline", mockery::mock("1", "3333333", "333333", "3333333", "33333333"))
+
+  expect_error(
+    autoFIPC(
+      newformXData = data.frame(A=1, B=2),
+      oldformYData = data.frame(A=1, B=2),
+      newformCommonItemNames = c('A'),
+      oldformCommonItemNames = c('A'),
+      oldformBILOGprior = NULL,
+      newformBILOGprior = NULL,
+      confirmCommonItems = NULL
+    ),
+    "Too many invalid oldform BILOG prior attempts"
+  )
+})