diff --git a/dashboard/src/relay.rs b/dashboard/src/relay.rs
index e7e7af00789b6b65bb151dfa11ea84bae0b896d7..1f5572bdbcef7ab2ac44efa4587353c045306736 100644
--- a/dashboard/src/relay.rs
+++ b/dashboard/src/relay.rs
@@ -359,7 +359,7 @@ fn schema(method: &str) -> Option<Value> {
             json!([]),
         ),
         "read_thread" => (
-            json!({"provider":provider,"thread_id":id,"limit":{"type":"integer","minimum":1,"maximum":100,"default":20}}),
+            json!({"provider":provider,"thread_id":id,"cursor":{"type":"string","minLength":1,"maxLength":512},"limit":{"type":"integer","minimum":1,"maximum":100,"default":20}}),
             json!(["provider", "thread_id"]),
         ),
         "send_message" => (
@@ -914,7 +914,10 @@ mod tests {
             command("read_thread", json!({"provider":"claude","thread_id":id})).unwrap()["limit"],
             20
         );
+        assert_eq!(command("read_thread", json!({"provider":"codex","thread_id":id,"cursor":"page"})).unwrap()["cursor"], "page");
         for (method, params) in [
+            ("read_thread", json!({"provider":"codex","thread_id":id,"cursor":""})),
+            ("read_thread", json!({"provider":"codex","thread_id":id,"cursor":"x".repeat(513)})),
             (
                 "read_thread",
                 json!({"provider":"codex","thread_id":"not-a-uuid"}),