diff --git a/R/search.R b/R/search.R
index 02ac2c2..3b1320b 100644
--- a/R/search.R
+++ b/R/search.R
@@ -120,3 +120,41 @@ cog_gov_search <- function(name = NULL, state = NULL, type = NULL) {
   WV = "54", WI = "55", WY = "56",
   AS = "60", GU = "66", MP = "69", PR = "72", VI = "78"
 )
+
+# Validate basket-mode inputs. Returns a list with normalized character
+# vectors `name`, `state`, `type`, all of length n = length(name).
+# `state` and `type` of length 1 are recycled; lengths must be 1 or n
+# otherwise. NULL state/type become a vector of NA_character_.
+#' @noRd
+.validate_basket_args <- function(name, state, type) {
+  if (!is.character(name)) {
+    cli::cli_abort("`name` must be a character vector.")
+  }
+  n <- length(name)
+
+  state_norm <- if (is.null(state)) {
+    rep(NA_character_, n)
+  } else if (length(state) == 1L) {
+    rep(as.character(state), n)
+  } else if (length(state) == n) {
+    as.character(state)
+  } else {
+    cli::cli_abort(
+      "`state` must be length 1 or {n} (length of `name`); got {length(state)}."
+    )
+  }
+
+  type_norm <- if (is.null(type)) {
+    rep(NA_character_, n)
+  } else if (length(type) == 1L) {
+    rep(as.character(type), n)
+  } else if (length(type) == n) {
+    as.character(type)
+  } else {
+    cli::cli_abort(
+      "`type` must be length 1 or {n} (length of `name`); got {length(type)}."
+    )
+  }
+
+  list(name = name, state = state_norm, type = type_norm)
+}
diff --git a/tests/testthat/test-search.R b/tests/testthat/test-search.R
index ddc3ffa..ea19a5f 100644
--- a/tests/testthat/test-search.R
+++ b/tests/testthat/test-search.R
@@ -72,3 +72,67 @@ test_that("cog_gov_search with no filters returns full registry", {
   r <- cog_gov_search()
   expect_gt(nrow(r), 1000L)
 })
+
+# ---- basket mode internal helpers ----
+
+test_that(".validate_basket_args recycles state from length 1", {
+  out <- uscogdata:::.validate_basket_args(
+    name  = c("Broward", "San Diego", "Austin"),
+    state = "FL",
+    type  = NULL
+  )
+  expect_equal(out$name,  c("Broward", "San Diego", "Austin"))
+  expect_equal(out$state, c("FL", "FL", "FL"))
+  expect_equal(out$type,  c(NA_character_, NA_character_, NA_character_))
+})
+
+test_that(".validate_basket_args recycles type from length 1", {
+  out <- uscogdata:::.validate_basket_args(
+    name  = c("San Diego", "Oakland"),
+    state = "CA",
+    type  = "city"
+  )
+  expect_equal(out$type, c("city", "city"))
+})
+
+test_that(".validate_basket_args accepts per-row state and type", {
+  out <- uscogdata:::.validate_basket_args(
+    name  = c("Broward", "San Diego"),
+    state = c("FL", "CA"),
+    type  = c(NA, "city")
+  )
+  expect_equal(out$state, c("FL", "CA"))
+  expect_equal(out$type,  c(NA_character_, "city"))
+})
+
+test_that(".validate_basket_args rejects length-mismatched state", {
+  expect_error(
+    uscogdata:::.validate_basket_args(
+      name  = c("Broward", "San Diego", "Austin"),
+      state = c("FL", "CA"),
+      type  = NULL
+    ),
+    regexp = "must be length 1 or 3"
+  )
+})
+
+test_that(".validate_basket_args rejects length-mismatched type", {
+  expect_error(
+    uscogdata:::.validate_basket_args(
+      name  = c("Broward", "San Diego"),
+      state = "FL",
+      type  = c("county", "city", "city")
+    ),
+    regexp = "must be length 1 or 2"
+  )
+})
+
+test_that(".validate_basket_args allows NULL state and type", {
+  out <- uscogdata:::.validate_basket_args(
+    name  = c("Broward", "San Diego"),
+    state = NULL,
+    type  = NULL
+  )
+  expect_equal(out$state, c(NA_character_, NA_character_))
+  expect_equal(out$type,  c(NA_character_, NA_character_))
+})