diff --git a/core/dr-catalog/examples/catalog_bench.rs b/core/dr-catalog/examples/catalog_bench.rs
index b39d54f..3445995 100644
--- a/core/dr-catalog/examples/catalog_bench.rs
+++ b/core/dr-catalog/examples/catalog_bench.rs
@@ -1,6 +1,6 @@
 //! What the catalog's routine reads cost on a real library, off the GUI.
 //!
-//!   cargo run --release -p dr-catalog --example catalog_bench -- CATALOG.sqlite [FACES_DIR]
+//!   cargo run --release -p dr-catalog --example catalog_bench -- CATALOG.sqlite [FACES_DIR] [--remote PEER.sqlite]
 //!
 //! Times `Catalog::open` — which every worker thread pays, including the
 //! develop view's fetch of each original and each neighbour it prefetches —
@@ -13,6 +13,13 @@
 //! count), whose `library` module is private; their SQL is spelled here as
 //! it is spelled there, and has to be kept in step by hand.
 //!
+//! `--remote` also times a merge with another device's catalog — the
+//! server snapshot — which is the pass where the two disagree: faces one
+//! side found and the other did not, boxes that moved. The merge with a copy
+//! of itself matches every face by its box and never reaches that work. The
+//! first of its runs writes what the peer brought; the rest are the steady
+//! state, so compare two builds from two fresh copies of one catalog.
+//!
 //! The figures are for reading side by side before and after a change; they
 //! are not a gate. Compare the `cpu` column when the machine is busy. The
 //! answers are printed too, so two builds can be checked for agreeing.
@@ -23,7 +30,15 @@ use std::time::{Duration, Instant};
 use dr_catalog::{keywords, rating, schema, Catalog};
 
 fn main() {
-    let args: Vec<String> = std::env::args().skip(1).collect();
+    let mut args: Vec<String> = std::env::args().skip(1).collect();
+    let peer = args.iter().position(|a| a == "--remote").map(|at| {
+        let path = args.get(at + 1).map(PathBuf::from).unwrap_or_else(|| {
+            eprintln!("--remote needs a catalog");
+            std::process::exit(2);
+        });
+        args.drain(at..at + 2);
+        path
+    });
     let Some(path) = args.first().map(PathBuf::from) else {
         eprintln!("usage: catalog_bench CATALOG.sqlite");
         std::process::exit(2);
@@ -117,6 +132,19 @@ fn main() {
     let _ = std::fs::remove_file(&scratch);
     let _ = std::fs::remove_file(&remote);
 
+    if let Some(peer) = &peer {
+        // A copy, so nothing the merge does to its input reaches the file
+        // the caller named.
+        std::fs::copy(peer, &remote).unwrap();
+        let mut first = None;
+        time("merge_remote_catalog (--remote)", 5, || {
+            let report = catalog.merge_remote_catalog(&remote).unwrap();
+            first.get_or_insert(report);
+        });
+        println!("  first pass: {first:?}");
+        let _ = std::fs::remove_file(&remote);
+    }
+
     // The face half of a sync pass, against a copy of the face store: both
     // directions in the steady state, where nothing is new either way.
     if let Some(faces) = args.get(1).map(PathBuf::from) {