diff --git a/tools/attack/adv-accept/src/main.rs b/tools/attack/adv-accept/src/main.rs
index 0cee33df7..7505e0443 100644
--- a/tools/attack/adv-accept/src/main.rs
+++ b/tools/attack/adv-accept/src/main.rs
@@ -584,10 +584,23 @@ mod gap {
 
 fn gap_cmd(args: &[String]) {
     let get = |k: &str, d: &str| -> String { args.windows(2).find(|w| w[0] == k).map(|w| w[1].clone()).unwrap_or_else(|| d.to_string()) };
-    let seeds: Vec<u64> = get("--seeds", "2").split(',').map(|x| x.parse().unwrap()).collect();
+    let seeds: Vec<u64> = if args.windows(2).any(|w| w[0] == "--seeds") { get("--seeds", "2").split(',').map(|x| x.parse().unwrap()).collect() } else { Vec::new() };
     let day: u64 = get("--day", "20730").parse().unwrap();
     let threads: usize = get("--threads", "32").parse().unwrap();
     let zero = args.iter().any(|a| a == "--plant") && get("--plant", "") == "zero-dataset";
+    // `--hex <epoch hex>:<era hex>:<label>` (repeatable): a program named by its raw 32-byte seeds, as a pack or a
+    // sibling lane names it, through the same chain draw (Epoch::chain_program, class v4)
+    for w in args.windows(2) {
+        if w[0] == "--hex" {
+            let parts: Vec<&str> = w[1].split(':').collect();
+            let epoch = unhex(parts[0]).expect("epoch hex");
+            let era = unhex(parts.get(1).copied().unwrap_or(parts[0])).expect("era hex");
+            let label = parts.get(2).copied().unwrap_or("hex-program").to_string();
+            let p = Epoch::chain_program(&epoch, Some(&era), ProgramClass::V4, &label);
+            println!("gap: hex program {label}: epoch {} era {}", hex(&epoch), hex(&era));
+            gap::run(&p, day, threads, zero);
+        }
+    }
     for k in seeds {
         let p = if k == 1 {
             let g = unhex(GENESIS_HEX).unwrap();