diff --git a/_config.ts b/_config.ts
index 3a812fc9..ab25571d 100644
--- a/_config.ts
+++ b/_config.ts
@@ -368,25 +368,21 @@ async function buildFileTree(
 }
 
 async function writeFileTree() {
-  const RAW = 0x55;
-
-  // Stamp the built SW with a unique build ID so the browser always detects a
-  // SW update on each build, not just when the SW source itself changes.
-  // Do this before buildFileTree (and before brotli's stale-sidecar cleanup)
-  // so the stamped version is the one captured in the tree CID.  Also delete
-  // any brotli'd copy of the *un*stamped SW so Caddy's precompressed-br
-  // serving never delivers it to the browser's update checker.
   const swDist = "./dist/service-worker.js";
+
+  // Remove stale brotli'd SW so Caddy never serves the old compressed version
+  // while the plain file has been updated.
   try {
     Deno.removeSync(`${swDist}.br`);
   } catch { /* already gone */ }
-  const swSource = Deno.readTextFileSync(swDist)
-    .replace(/\n\/\/ @build \S+\n$/, "");
-  const swStamped = `${swSource}\n// @build ${crypto.randomUUID()}\n`;
-  Deno.writeTextFileSync(swDist, swStamped);
 
   const tree = await buildFileTree("dist/");
 
+  // The SW is not included in its own embedded tree — the browser manages the
+  // SW lifecycle independently and never fetches it through the SW's handler.
+  delete tree["service-worker.js"];
+  delete tree["service-worker.js.br"];
+
   // Remove any .br sidecar that is older than its plain counterpart — this
   // catches cases where brotli compression did not re-run after an asset
   // changed (e.g. incremental afterUpdate builds), so the server falls back
@@ -405,23 +401,24 @@ async function writeFileTree() {
     } catch { /* .br sidecar doesn't exist — nothing to do */ }
   }
 
-  tree["service-worker.js"] = await createCID(
-    RAW,
-    new TextEncoder().encode(swStamped),
-  );
-
-  // Exclude file-tree.json from its own contents (self-referential).
-  delete tree["file-tree.json"];
-  delete tree["file-tree.json.br"];
-
   const sorted = Object.fromEntries(
     Object.keys(tree).sort().map((k) => [k, tree[k]]),
   );
 
-  Deno.writeTextFileSync(
-    "./dist/file-tree.json",
-    JSON.stringify(sorted, null, 2),
-  );
+  // Inject the file tree into the compiled SW and stamp with a build ID so
+  // the browser always detects an update on each build.
+  //
+  // The placeholder "__FILE_TREE__" may survive as-is or may be folded by
+  // esbuild into `JSON.parse("__FILE_TREE__")` → `"__FILE_TREE__"`. Both
+  // patterns are replaced with the actual object literal so that `FILE_TREE`
+  // is always an object in the running SW, never a string.
+  const treeJson = JSON.stringify(sorted);
+  const swSource = Deno.readTextFileSync(swDist)
+    .replace(/\n\/\/ @build \S+\n$/, "")
+    .replace('JSON.parse("__FILE_TREE__")', () => treeJson)
+    .replace('"__FILE_TREE__"', () => treeJson);
+  const swStamped = `${swSource}\n// @build ${crypto.randomUUID()}\n`;
+  Deno.writeTextFileSync(swDist, swStamped);
 }
 
 site.addEventListener("afterBuild", writeFileTree);
diff --git a/specs/service-worker/SPEC.md b/specs/service-worker/SPEC.md
index eda916db..5d1f8c43 100644
--- a/specs/service-worker/SPEC.md
+++ b/specs/service-worker/SPEC.md
@@ -4,7 +4,7 @@
 
 - It must be able to serve every resource offline that has been requested before.
 - Every file must be cached by CID.
-- The `dist` contains a file tree in the form of a JSON file which maps the path to the correct CID for the latest version.
+- The file tree (a map of path → CID for file) is embedded directly in the service worker at build time. Because every build produces a new service worker, the embedded tree is always current.
 - Every new build means a new service worker.
 - All pages must use the same code.
 - When a new service worker is available, install and activate it immediately, while still making sure all pages are on the same service worker. This is done through sending a `{ type: "sw-activated" }` message to the client, on which they must reload the page.
diff --git a/src/service-worker.js b/src/service-worker.js
index 5cc3a7b6..ab0f6870 100644
--- a/src/service-worker.js
+++ b/src/service-worker.js
@@ -2,9 +2,8 @@
 
 import { create as createCid } from "./common/cid.js";
 
-const fileTreePromise = fetch("./file-tree.json", { cache: "no-cache" })
-  .then((r) => /** @type {Promise<Record<string, string>>} */ (r.json()))
-  .catch(() => null);
+/** @type {Record<string, string>} */
+const FILE_TREE = JSON.parse("__FILE_TREE__");
 
 /** Media content types to ignore */
 const MEDIA_CONTENT_TYPE = /^(audio|video)\//;
@@ -145,17 +144,15 @@ async function openCaches() {
 }
 
 /**
- * Looks up a pathname in the pre-built file tree and returns its CID, or
- * `undefined` if the entry is absent or the tree failed to load.
+ * Looks up a pathname in the embedded file tree and returns its CID, or
+ * `undefined` if the entry is absent.
  *
  * @param {string} pathname - e.g. "/components/foo.js"
- * @returns {Promise<string | undefined>}
+ * @returns {string | undefined}
  */
-async function cidFromTree(pathname) {
-  const tree = await fileTreePromise;
-  if (!tree) return undefined;
+function cidFromTree(pathname) {
   const key = pathname.replace(/^\//, "");
-  return tree[key];
+  return FILE_TREE[key];
 }
 
 /**
@@ -227,7 +224,7 @@ async function lookup(request) {
 async function handleFetch(request) {
   if (navigator.onLine) {
     const { pathname } = new URL(request.url);
-    const cid = await cidFromTree(pathname);
+    const cid = cidFromTree(pathname);
     if (cid !== undefined) {
       const { content } = await openCaches();
       const cached = await content.match(cidUrl(cid));