diff --git a/tools/dev-deploy/Caddyfile.dev b/tools/dev-deploy/Caddyfile.dev
index eb949a1..b882736 100644
--- a/tools/dev-deploy/Caddyfile.dev
+++ b/tools/dev-deploy/Caddyfile.dev
@@ -13,6 +13,23 @@
     @frontend host www.galaxy.lan
     handle @frontend {
         root * /srv/galaxy-ui
+
+        # SvelteKit emits hash-named JS/CSS chunks under
+        # `_app/immutable/`; the file name changes whenever the
+        # content changes, so the browser can cache them forever.
+        # Without an explicit Cache-Control, Caddy falls back to
+        # heuristic caching that revalidates on every reload —
+        # measurably slow on Safari + the long-lived dev stack
+        # when the cache is warm. Everything else (index.html
+        # fallback, env.js, version.json, core.wasm,
+        # wasm_exec.js, favicon.svg) must revalidate so a fresh
+        # deploy lands without the user having to clear the
+        # cache by hand.
+        @immutable path /_app/immutable/*
+        header @immutable Cache-Control "public, max-age=31536000, immutable"
+        @dynamic not path /_app/immutable/*
+        header @dynamic Cache-Control "no-cache, must-revalidate"
+
         try_files {path} /index.html
         file_server
         encode zstd gzip
diff --git a/tools/dev-deploy/Caddyfile.prod b/tools/dev-deploy/Caddyfile.prod
index 5784c28..45895f1 100644
--- a/tools/dev-deploy/Caddyfile.prod
+++ b/tools/dev-deploy/Caddyfile.prod
@@ -5,6 +5,16 @@
 
 www.galaxy.com {
     root * /srv/galaxy-ui
+
+    # Mirrors the cache policy `Caddyfile.dev` documents in detail:
+    # SvelteKit's hash-named `_app/immutable/*` is safe to cache
+    # forever; everything else must revalidate so a deploy reaches
+    # the browser without a manual cache clear.
+    @immutable path /_app/immutable/*
+    header @immutable Cache-Control "public, max-age=31536000, immutable"
+    @dynamic not path /_app/immutable/*
+    header @dynamic Cache-Control "no-cache, must-revalidate"
+
     try_files {path} /index.html
     file_server
     encode zstd gzip