diff --git a/R/aaa-auto.R b/R/aaa-auto.R
index 022e5b9128..cd706e2578 100644
--- a/R/aaa-auto.R
+++ b/R/aaa-auto.R
@@ -189,9 +189,9 @@ neighbors_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -314,16 +314,16 @@ get_eid_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -381,16 +381,16 @@ get_all_eids_between_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -419,9 +419,9 @@ incident_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2481,16 +2481,16 @@ are_adjacent_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   v1 <- as_igraph_vs(graph, v1)
-  if (length(v1) == 0) {
+  if (length(v1) != 1) {
     cli::cli_abort(
-      "{.arg v1} must specify at least one vertex",
+      "{.arg v1} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   v2 <- as_igraph_vs(graph, v2)
-  if (length(v2) == 0) {
+  if (length(v2) != 1) {
     cli::cli_abort(
-      "{.arg v2} must specify at least one vertex",
+      "{.arg v2} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2515,16 +2515,16 @@ are_connected_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   v1 <- as_igraph_vs(graph, v1)
-  if (length(v1) == 0) {
+  if (length(v1) != 1) {
     cli::cli_abort(
-      "{.arg v1} must specify at least one vertex",
+      "{.arg v1} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   v2 <- as_igraph_vs(graph, v2)
-  if (length(v2) == 0) {
+  if (length(v2) != 1) {
     cli::cli_abort(
-      "{.arg v2} must specify at least one vertex",
+      "{.arg v2} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2758,16 +2758,16 @@ get_shortest_path_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2807,16 +2807,16 @@ get_shortest_path_bellman_ford_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2865,16 +2865,16 @@ get_shortest_path_dijkstra_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2924,16 +2924,16 @@ get_shortest_path_astar_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -2982,9 +2982,9 @@ get_shortest_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3024,9 +3024,9 @@ get_all_shortest_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3152,9 +3152,9 @@ get_shortest_paths_dijkstra_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3204,9 +3204,9 @@ get_shortest_paths_bellman_ford_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3256,9 +3256,9 @@ get_all_shortest_paths_dijkstra_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3469,9 +3469,9 @@ get_all_simple_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3523,16 +3523,16 @@ get_k_shortest_paths_impl <- function(
   }
   k <- as.numeric(k)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3574,16 +3574,16 @@ get_widest_path_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   to <- as_igraph_vs(graph, to)
-  if (length(to) == 0) {
+  if (length(to) != 1) {
     cli::cli_abort(
-      "{.arg to} must specify at least one vertex",
+      "{.arg to} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3632,9 +3632,9 @@ get_widest_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   from <- as_igraph_vs(graph, from)
-  if (length(from) == 0) {
+  if (length(from) != 1) {
     cli::cli_abort(
-      "{.arg from} must specify at least one vertex",
+      "{.arg from} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -3795,9 +3795,9 @@ subcomponent_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -6236,9 +6236,9 @@ pseudo_diameter_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   start_vid <- as_igraph_vs(graph, start_vid)
-  if (length(start_vid) == 0) {
+  if (length(start_vid) != 1) {
     cli::cli_abort(
-      "{.arg start_vid} must specify at least one vertex",
+      "{.arg start_vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -6276,9 +6276,9 @@ pseudo_diameter_dijkstra_impl <- function(
     weights <- NULL
   }
   start_vid <- as_igraph_vs(graph, start_vid)
-  if (length(start_vid) == 0) {
+  if (length(start_vid) != 1) {
     cli::cli_abort(
-      "{.arg start_vid} must specify at least one vertex",
+      "{.arg start_vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -6349,9 +6349,9 @@ random_walk_impl <- function(
     weights <- NULL
   }
   start <- as_igraph_vs(graph, start)
-  if (length(start) == 0) {
+  if (length(start) != 1) {
     cli::cli_abort(
-      "{.arg start} must specify at least one vertex",
+      "{.arg start} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -6404,9 +6404,9 @@ random_edge_walk_impl <- function(
     weights <- NULL
   }
   start <- as_igraph_vs(graph, start)
-  if (length(start) == 0) {
+  if (length(start) != 1) {
     cli::cli_abort(
-      "{.arg start} must specify at least one vertex",
+      "{.arg start} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -6665,9 +6665,9 @@ bfs_simple_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
-  if (length(root) == 0) {
+  if (length(root) != 1) {
     cli::cli_abort(
-      "{.arg root} must specify at least one vertex",
+      "{.arg root} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -7716,9 +7716,9 @@ layout_star_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   center <- as_igraph_vs(graph, center)
-  if (length(center) == 0) {
+  if (length(center) != 1) {
     cli::cli_abort(
-      "{.arg center} must specify at least one vertex",
+      "{.arg center} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -10414,16 +10414,16 @@ write_graph_dimacs_flow_impl <- function(
   check_string(outstream)
 
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11238,9 +11238,9 @@ rooted_product_impl <- function(
   ensure_igraph(g1)
   ensure_igraph(g2)
   root <- as_igraph_vs(g2, root)
-  if (length(root) == 0) {
+  if (length(root) != 1) {
     cli::cli_abort(
-      "{.arg root} must specify at least one vertex",
+      "{.arg root} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11292,16 +11292,16 @@ maxflow_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11344,16 +11344,16 @@ maxflow_value_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11506,16 +11506,16 @@ st_mincut_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11558,16 +11558,16 @@ st_mincut_value_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11602,16 +11602,16 @@ st_vertex_connectivity_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11663,16 +11663,16 @@ st_edge_connectivity_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11716,16 +11716,16 @@ edge_disjoint_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11750,16 +11750,16 @@ vertex_disjoint_paths_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11822,9 +11822,9 @@ dominator_tree_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   root <- as_igraph_vs(graph, root)
-  if (length(root) == 0) {
+  if (length(root) != 1) {
     cli::cli_abort(
-      "{.arg root} must specify at least one vertex",
+      "{.arg root} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11858,16 +11858,16 @@ all_st_cuts_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -11898,16 +11898,16 @@ all_st_mincuts_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   source <- as_igraph_vs(graph, source)
-  if (length(source) == 0) {
+  if (length(source) != 1) {
     cli::cli_abort(
-      "{.arg source} must specify at least one vertex",
+      "{.arg source} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
   target <- as_igraph_vs(graph, target)
-  if (length(target) == 0) {
+  if (length(target) != 1) {
     cli::cli_abort(
-      "{.arg target} must specify at least one vertex",
+      "{.arg target} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -13438,9 +13438,9 @@ fundamental_cycles_impl <- function(
   ensure_igraph(graph)
   if (!is.null(start)) {
     start <- as_igraph_vs(graph, start)
-    if (length(start) == 0) {
+    if (length(start) != 1) {
       cli::cli_abort(
-        "{.arg start} must specify at least one vertex",
+        "{.arg start} must specify exactly one vertex",
         call = rlang::caller_env()
       )
     }
@@ -13719,9 +13719,9 @@ random_spanning_tree_impl <- function(
   ensure_igraph(graph)
   if (!is.null(vid)) {
     vid <- as_igraph_vs(graph, vid)
-    if (length(vid) == 0) {
+    if (length(vid) != 1) {
       cli::cli_abort(
-        "{.arg vid} must specify at least one vertex",
+        "{.arg vid} must specify exactly one vertex",
         call = rlang::caller_env()
       )
     }
@@ -13870,9 +13870,9 @@ deterministic_optimal_imitation_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -13954,9 +13954,9 @@ roulette_wheel_imitation_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -13996,9 +13996,9 @@ stochastic_imitation_impl <- function(
   # Argument checks
   ensure_igraph(graph)
   vid <- as_igraph_vs(graph, vid)
-  if (length(vid) == 0) {
+  if (length(vid) != 1) {
     cli::cli_abort(
-      "{.arg vid} must specify at least one vertex",
+      "{.arg vid} must specify exactly one vertex",
       call = rlang::caller_env()
     )
   }
@@ -14151,9 +14151,9 @@ vertex_path_from_edge_path_impl <- function(
   ensure_igraph(graph)
   if (!is.null(start)) {
     start <- as_igraph_vs(graph, start)
-    if (length(start) == 0) {
+    if (length(start) != 1) {
       cli::cli_abort(
-        "{.arg start} must specify at least one vertex",
+        "{.arg start} must specify exactly one vertex",
         call = rlang::caller_env()
       )
     }
diff --git a/tests/testthat/_snaps/aaa-auto.md b/tests/testthat/_snaps/aaa-auto.md
index a34e62e8c4..5a5919e393 100644
--- a/tests/testthat/_snaps/aaa-auto.md
+++ b/tests/testthat/_snaps/aaa-auto.md
@@ -11820,13 +11820,21 @@
       Error in `ensure_igraph()`:
       ! Must provide a graph object (provided `NULL`).
 
+---
+
+    Code
+      get_eid_impl(graph = g, from = c(1, 2), to = 2)
+    Condition
+      Error:
+      ! `from` must specify exactly one vertex
+
 ---
 
     Code
       get_eid_impl(graph = g, from = 1, to = integer(0))
     Condition
       Error:
-      ! `to` must specify at least one vertex
+      ! `to` must specify exactly one vertex
 
 # community_voronoi_impl basic
 
diff --git a/tests/testthat/_snaps/flow.md b/tests/testthat/_snaps/flow.md
index add2f35391..61e2886e0f 100644
--- a/tests/testthat/_snaps/flow.md
+++ b/tests/testthat/_snaps/flow.md
@@ -4,7 +4,7 @@
       st_cuts(g_path, source = "a", target = NULL)
     Condition
       Error in `st_cuts()`:
-      ! `target` must specify at least one vertex
+      ! `target` must specify exactly one vertex
 
 ---
 
@@ -12,7 +12,7 @@
       st_cuts(g_path, source = NULL, target = "a")
     Condition
       Error in `st_cuts()`:
-      ! `source` must specify at least one vertex
+      ! `source` must specify exactly one vertex
 
 ---
 
@@ -20,7 +20,7 @@
       st_min_cuts(g_path, source = "a", target = NULL)
     Condition
       Error in `st_min_cuts()`:
-      ! `target` must specify at least one vertex
+      ! `target` must specify exactly one vertex
 
 ---
 
@@ -28,7 +28,7 @@
       st_min_cuts(g_path, source = NULL, target = "a")
     Condition
       Error in `st_min_cuts()`:
-      ! `source` must specify at least one vertex
+      ! `source` must specify exactly one vertex
 
 # vertex_connectivity error works
 
diff --git a/tests/testthat/test-aaa-auto.R b/tests/testthat/test-aaa-auto.R
index 02ec2db379..0fc4aa57ed 100644
--- a/tests/testthat/test-aaa-auto.R
+++ b/tests/testthat/test-aaa-auto.R
@@ -11982,6 +11982,13 @@ test_that("get_eid_impl errors", {
     to = 2
   ))
 
+  # Test error when from or to is not exactly one vertex
+  expect_snapshot_igraph_error(get_eid_impl(
+    graph = g,
+    from = c(1, 2),
+    to = 2
+  ))
+
   expect_snapshot_igraph_error(get_eid_impl(
     graph = g,
     from = 1,
diff --git a/tools/stimulus/types-RR.yaml b/tools/stimulus/types-RR.yaml
index 8f523c8f39..256959693a 100644
--- a/tools/stimulus/types-RR.yaml
+++ b/tools/stimulus/types-RR.yaml
@@ -196,9 +196,9 @@ VERTEX:
     CALL: '%I% - 1'
     INCONV: |-
         %I% <- as_igraph_vs(%I1%, %I%)
-        if (length(%I%) == 0) {
+        if (length(%I%) != 1) {
           cli::cli_abort(
-            "{.arg %I%} must specify at least one vertex",
+            "{.arg %I%} must specify exactly one vertex",
             call = rlang::caller_env()
           )
         }
@@ -229,9 +229,9 @@ VERTEX_ROOT:
     CALL: '%I% - 1'
     INCONV: |-
         %I% <- as_igraph_vs(%I1%, %I%)
-        if (length(%I%) == 0) {
+        if (length(%I%) != 1) {
           cli::cli_abort(
-            "{.arg %I%} must specify at least one vertex",
+            "{.arg %I%} must specify exactly one vertex",
             call = rlang::caller_env()
           )
         }