diff --git a/.Rbuildignore b/.Rbuildignore
index 1c85620..b85d639 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -15,3 +15,5 @@
 ^registered_agents\.json$
 ^task_agent_mapping\.json$
 ^\.gitleaks\.toml$
+^\.jules$
+^\.jules/.*
diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..755d06c
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2024-06-27 - [Infinite Recursion DoS in Non-Interactive Environments]
+**Vulnerability:** The legacy `readline()` prompts use unbounded recursion on invalid inputs, causing a C stack overflow (DoS) when executed in headless/CI environments.
+**Learning:** Automated/non-interactive execution environments supply `""` or `EOF` to `readline()`, which fails validation regexes and triggers the infinite recursion loop.
+**Prevention:** Always wrap interactive prompts with `interactive()` checks and provide safe, deterministic default fallbacks for headless execution.
diff --git a/R/aFIPC.R b/R/aFIPC.R
index b6a9e6c..da61777 100644
--- a/R/aFIPC.R
+++ b/R/aFIPC.R
@@ -74,6 +74,8 @@ autoFIPC <-
       data.frame(cbind(newformCommonItemNames, oldformCommonItemNames))
 
     checkCorrect <- function() {
+      # Security fix: Prevent infinite recursion DoS in non-interactive environments
+      if (!interactive()) return(1L)
       n <- readline(prompt = "Is it correct? (1: Yes 2: No) : ")
       if (!grepl("^[0-9]+$", n)) {
         return(checkCorrect())
@@ -99,6 +101,8 @@ autoFIPC <-
       oldformYDataK <- oldformYData
       if (itemtype == '3PL' && length(oldformBILOGprior) == 0) {
         checkoldformBILOGprior <- function() {
+          # Security fix: Prevent infinite recursion DoS in non-interactive environments
+          if (!interactive()) return(1L)
           n <-
             readline(
               prompt = "Do you want to use default BILOG-MG priors for oldform Data? (1: Yes 2: No) : "
@@ -310,6 +314,8 @@ autoFIPC <-
       newformXDataK <- newformXData
       if (itemtype == '3PL' && length(newformBILOGprior) == 0) {
         checknewformBILOGprior <- function() {
+          # Security fix: Prevent infinite recursion DoS in non-interactive environments
+          if (!interactive()) return(1L)
           n <-
             readline(
               prompt = "Do you want to use default BILOG-MG priors for newform Data? (1: Yes 2: No) : "