diff --git a/AGENTS.md b/AGENTS.md
index c45f361..f1d8c48 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -84,7 +84,7 @@ Each component adds one `Entry` in `gallery/demos_<category>.go`: ID, Name, Zh,
 
 ## Deploy
 
-- `npm run deploy` in `web/` (clean tree only): builds, uploads a Worker version, runs Playwright on its preview URL, promotes it to 100%, runs Playwright on https://8bitmygoui.zhangyanghaha0407.workers.dev.
+- `npm run deploy` in `web/` (clean tree only) ships in two steps, because a rollout serves old and new versions side by side for a while. Step one promotes the live `index.html` with the new files beside the live ones; step two uploads the new page with both file sets, runs Playwright on its preview URL, promotes it, and runs Playwright on https://8bitmygoui.zhangyanghaha0407.workers.dev. A page from either build then finds its files on either version.
 - Rollback: `npx wrangler rollback <version-id>` in `web/`; `npx wrangler deployments list` shows versions.
 - Scripts and wasm sit under `a/`, named by content hash, and `_headers` makes them immutable; `index.html` revalidates. Never cache a path whose content can change.
 
diff --git a/web/deploy.sh b/web/deploy.sh
index 2f824df..55ff6e8 100755
--- a/web/deploy.sh
+++ b/web/deploy.sh
@@ -1,36 +1,60 @@
 #!/bin/sh
-# Uploads a version, tests its preview URL, then promotes it.
+# Ships files first, then the page: no build misses a file.
 set -eu
 cd "$(dirname "$0")"
+site=https://8bitmygoui.zhangyanghaha0407.workers.dev
 if [ -n "$(git status --porcelain)" ]; then
   echo "deploy: commit first; each version names its commit" >&2
   exit 1
 fi
-./build.sh
-rev=$(git rev-parse --short HEAD)
-out=$(npx wrangler versions upload --message "$rev")
-echo "$out"
-id=$(echo "$out" | sed -n 's/^Worker Version ID: //p')
-preview=$(echo "$out" | sed -n 's/^Version Preview URL: //p')
-if [ -z "$id" ] || [ -z "$preview" ]; then
-  echo "deploy: wrangler printed no version id or preview URL" >&2
-  exit 1
-fi
-BASE_URL=$preview npx playwright test
-npx wrangler versions deploy "$id@100%" --yes --message "$rev"
-site=$(echo "$preview" | sed 's#https://[0-9a-f]*-#https://#')
-main=$(sed -n 's#.*src="\(a/main\.[0-9a-f]*\.js\)".*#\1#p' dist/index.html)
-tries=0
-until curl -fs "$site/" | grep -q "$main"; do
-  tries=$((tries + 1))
-  if [ "$tries" -ge 30 ]; then
-    echo "deploy: $site still serves an older build than $main" >&2
+# patient runs a check every 2 s for a minute.
+patient() {
+  tries=0
+  until "$@"; do
+    tries=$((tries + 1))
+    if [ "$tries" -ge 30 ]; then
+      echo "deploy: gave up waiting for: $*" >&2
+      exit 1
+    fi
+    sleep 2
+  done
+}
+# upload makes a version from the assets in $1.
+upload() {
+  out=$(npx wrangler versions upload --assets "$1" --message "$2")
+  echo "$out" >&2
+  id=$(echo "$out" | sed -n 's/^Worker Version ID: //p')
+  preview=$(echo "$out" | sed -n 's/^Version Preview URL: //p')
+  if [ -z "$id" ] || [ -z "$preview" ]; then
+    echo "deploy: wrangler printed no version id or preview URL" >&2
     exit 1
   fi
-  sleep 2
+}
+./build.sh
+rev=$(git rev-parse --short HEAD)
+main=$(sed -n 's#.*src="\(a/main\.[0-9a-f]*\.js\)".*#\1#p' dist/index.html)
+stage=$(mktemp -d)
+trap 'rm -rf "$stage"' EXIT
+# The live build's files ride along, for pages already open.
+if ! curl -fs "$site/" -o "$stage/index.html"; then
+  echo "deploy: cannot read the live page at $site" >&2
+  exit 1
+fi
+for f in $(sed -n 's#.*src="\(a/[^"]*\)".*#\1#p' "$stage/index.html"); do
+  curl -fs "$site/$f" -o "dist/$f"
 done
-# A first fetch warms the edge before the browser tests.
-wasm=$(sed -n "s#.*fetch('\\(a/app\\.[0-9a-f]*\\.wasm\\)').*#\\1#p" dist/a/main.*.js)
-curl -fs --max-time 120 -o /dev/null "$site/$wasm"
+old=$(sed -n 's#.*src="\(a/main\.[0-9a-f]*\.js\)".*#\1#p' "$stage/index.html")
+wasm=$(sed -n "s#.*fetch('\\(a/app\\.[0-9a-f]*\\.wasm\\)').*#\\1#p" "dist/$old")
+curl -fs --max-time 300 "$site/$wasm" -o "dist/$wasm"
+cp -R dist/a dist/_headers "$stage/"
+# Step one: the live page, with the new files beside it.
+upload "$stage" "$rev files"
+npx wrangler versions deploy "$id@100%" --yes --message "$rev files"
+patient curl -fs -o /dev/null "$site/$main"
+# Step two: the new page, tested on its preview first.
+upload ./dist "$rev"
+BASE_URL=$preview npx playwright test
+npx wrangler versions deploy "$id@100%" --yes --message "$rev"
+patient sh -c "curl -fs '$site/' | grep -q '$main'"
 BASE_URL=$site npx playwright test
 echo "deploy: $rev live at $site (version $id)"