diff --git a/easel/bin/pack.mjs b/easel/bin/pack.mjs
index 561144a479..340b858e54 100755
--- a/easel/bin/pack.mjs
+++ b/easel/bin/pack.mjs
@@ -42,11 +42,18 @@ for (const entry of INCLUDE) {
 }
 
 mkdirSync(dirname(OUT), { recursive: true });
-// --no-mac-metadata and a fixed mtime keep the tarball byte-stable across
-// machines, so a rebuild that changed nothing does not look like a new release.
+// BSD tar (macOS) understands --no-mac-metadata; GNU tar (the box this actually
+// packs on) does not and refuses the whole command. Probe once rather than
+// branching on platform, since the tar in PATH is the thing that matters and it
+// is not always the one the platform implies.
+let extraFlags = [];
+try {
+  execFileSync("tar", ["--no-mac-metadata", "--version"], { stdio: "ignore" });
+  extraFlags = ["--no-mac-metadata", "--no-xattrs"];
+} catch {}
+
 execFileSync("tar", [
-  "--no-mac-metadata",
-  "--no-xattrs",
+  ...extraFlags,
   "-czf", OUT,
   "-C", EASEL,
   ...INCLUDE,
diff --git a/lith/Caddyfile b/lith/Caddyfile
index 47f6d982d4..d85706da4e 100644
--- a/lith/Caddyfile
+++ b/lith/Caddyfile
@@ -736,12 +736,13 @@
     # install line is read aloud and typed by hand more often than it is copied.
     @easel_install {
         host prompt.ac aesthetic.computer
-        path /easel.sh /easel.tar.gz
+        path /easel.sh /easel.tar.gz /easel.json
     }
     handle @easel_install {
         root * /opt/ac/system/public
         header /easel.sh Content-Type "text/plain; charset=utf-8"
         header /easel.tar.gz Content-Type "application/gzip"
+        header /easel.json Content-Type "application/json"
         # A stale installer is worse than a slow one: it points at a tarball
         # that may no longer be there.
         header Cache-Control "public, max-age=300"