diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index bc5c6e1..057690c 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -12,3 +12,8 @@
 **Vulnerability:** Raw `stop()` and `warning()` calls without `call. = FALSE` in `llcont.R` and `vuongtest.R` exposed execution stack/call details when raised.
 **Learning:** While some instances of `stop()` inside `tryCatch()` were previously fixed to hide the call stack, other standalone exceptions and warnings still leaked call context. Security must be consistently applied across the entire codebase.
 **Prevention:** Always set `call. = FALSE` when using `stop()` or `warning()` to enforce a secure-by-default boundary and prevent internal execution paths from being disclosed to the end user.
+
+## 2026-08-07 - Add input validation for exported functions
+**Vulnerability:** Unvalidated arguments passed to exported functions (`vuongtest` and `icci`) could bypass top-level `stop(..., call. = FALSE)` safeguards and trigger raw R errors deep inside internal logic, leaking internal execution contexts.
+**Learning:** In R codebases, exported functions must explicitly validate argument types, lengths, and bounds (e.g., `length(x) == 1`, `match.arg()`) to fail securely and avoid information disclosure.
+**Prevention:** Always strictly validate the type, length, and bounds of user inputs at the very beginning of exported functions, using `stop(..., call. = FALSE)` to securely halt execution on invalid input.
diff --git a/R/icci.R b/R/icci.R
index f22278a..6a1eb1d 100644
--- a/R/icci.R
+++ b/R/icci.R
@@ -65,6 +65,10 @@
 #' @export
 icci <- function(object1, object2, conf.level=.95, ll1=llcont, ll2=llcont) {
 
+  if (!is.numeric(conf.level) || length(conf.level) != 1 || is.na(conf.level) || conf.level <= 0 || conf.level >= 1) {
+    stop("Argument 'conf.level' must be a single numeric value between 0 and 1.", call. = FALSE)
+  }
+
   ## check objects, issue warnings/errors, get classes/calls
   obinfo <- check.obj(object1, object2)
   callA <- obinfo$callA; classA <- obinfo$classA
diff --git a/R/vuongtest.R b/R/vuongtest.R
index 2bdfbf6..69dfbf1 100644
--- a/R/vuongtest.R
+++ b/R/vuongtest.R
@@ -96,7 +96,12 @@
 #' @importMethodsFrom lavaan coef fitted logLik vcov
 #' @importFrom methods slotNames
 #' @export
-vuongtest <- function(object1, object2, nested=FALSE, adj="none", ll1=llcont, ll2=llcont, score1=NULL, score2=NULL, vc1=vcov, vc2=vcov) {
+vuongtest <- function(object1, object2, nested=FALSE, adj=c("none", "aic", "bic"), ll1=llcont, ll2=llcont, score1=NULL, score2=NULL, vc1=vcov, vc2=vcov) {
+
+  if (!is.logical(nested) || length(nested) != 1 || is.na(nested)) {
+    stop("Argument 'nested' must be a single logical value.", call. = FALSE)
+  }
+  adj <- match.arg(adj)
 
   ## check objects, issue warnings/errors, get classes/calls
   obinfo <- check.obj(object1, object2)