diff --git a/.Rbuildignore b/.Rbuildignore
index 232504f..28b2d85 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -22,3 +22,6 @@
 ^\.jules(/.*)?$
 ^\.trivyignore\.yaml$
 ^trivy\.yaml$
+^\.semgrepignore$
+^test_dummy\.R$
+^test_validation\.R$
diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index a8207a4..1108d62 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -1,4 +1,21 @@
+# Sentinel Journal
+
 ## 2024-07-12 - Fix missing parameter validations
-**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.
+
+**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 - Fix integer overflow coercion vulnerability in readline input validation
+
+**Vulnerability:** Weak regex `^[0-9]+$` allows excessive numeric strings that
+coerce to `NA` inside `as.integer()`, which can lead to unhandled process crashes.
+**Learning:** `readline()` validation should strictly match exact expected bounds
+for interactive prompts instead of open-ended digit validation to prevent
+integer overflow coercion.
+**Prevention:** Strictly match against exact expected values (e.g., `^[12]$`)
+instead of unbounded digit classes when validating user inputs mapped to integers.
diff --git a/R/aFIPC.R b/R/aFIPC.R
index 6254651..918e19b 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-autoFIPC.R b/tests/testthat/test-autoFIPC.R
index 13cecd9..c1be0b3 100644
--- a/tests/testthat/test-autoFIPC.R
+++ b/tests/testthat/test-autoFIPC.R
@@ -89,3 +89,24 @@ test_that("autoFIPC validates input types securely", {
     "Security Error: tryEM must be a single non-NA logical value"
   )
 })
+
+test_that("binary prompt choices reject overflow and malformed values", {
+  expect_identical(aFIPC:::parseBinaryChoice("1"), 1L)
+  expect_identical(aFIPC:::parseBinaryChoice("2"), 2L)
+
+  invalid_values <- list(
+    "0",
+    "3",
+    "01",
+    "2147483648",
+    paste0(strrep("9", 10000L)),
+    "1\n2",
+    "",
+    NA_character_,
+    c("1", "2"),
+    1
+  )
+  for (value in invalid_values) {
+    expect_identical(aFIPC:::parseBinaryChoice(value), NA_integer_)
+  }
+})