fix(web): mark static assets no-cache to stop CDN version skew

src/web/server.test.ts

@@ -397,6 +397,23 @@ describe("startWebServer", () => {
       expect(res.headers.get("content-length")).toBe(String(Buffer.byteLength(body)));
     });
 
+    // /app.js and index.html ship at fixed, unhashed paths and every deploy
+    // overwrites them in place, so a cache that serves either past its
+    // freshness window can pair a new index.html with a stale app.js (or vice
+    // versa) after a deploy. That mismatch is exactly what broke
+    // tl.reccd.stream: a CDN in front cached /app.js under its default
+    // Browser Cache TTL while index.html (no explicit header) went stale too,
+    // and the two drifted apart until the cache expired. no-cache forces a
+    // revalidation (in practice a refetch, since nothing here emits an
+    // ETag/Last-Modified) on every request rather than letting an
+    // intermediary reuse a stale copy.
+    it("marks static assets no-cache so a CDN cannot pair a stale bundle with a fresh index.html", async () => {
+      const base = await start({ staticDir: assets() });
+      const [index, appJs] = await Promise.all([fetch(`${base}/`), fetch(`${base}/app.js`)]);
+      expect(index.headers.get("cache-control")).toBe("no-cache");
+      expect(appJs.headers.get("cache-control")).toBe("no-cache");
+    });
+
     // resolveAssetPath proves containment but not that the target is a file, so
     // without the isFile() check this streams a directory and dies with EISDIR
     // *after* the 200 header is out — a hang or a truncated body, not a 404.

src/web/server.ts

@@ -590,7 +590,11 @@ export async function startWebServer(
         }
         const wrote = await writeWebResponse(
           res,
-          { status: 200, filePath: asset, headers: { "Content-Type": contentTypeFor(asset) } },
+          {
+            status: 200,
+            filePath: asset,
+            headers: { "Content-Type": contentTypeFor(asset), "Cache-Control": "no-cache" },
+          },
           log,
         );
         log(`${method} ${urlPath} -> ${wrote}`);
@@ -667,9 +671,22 @@ export async function startWebServer(
       // directory is answered 404 in there, and logging 200 regardless made
       // every asset failure read as a success — which defeats the point of
       // warning about missing assets at all.
+      // No cache validator (ETag/Last-Modified) is generated here, so
+      // "no-cache" in practice means every request refetches — that is the
+      // point. app.js and index.html both live at fixed, unhashed paths that
+      // a deploy overwrites in place, and a downstream cache (browser or
+      // CDN) that serves either past its freshness window can pair a fresh
+      // index.html with a stale app.js. That drift is exactly what broke
+      // tl.reccd.stream: the DOM index.html expected no longer matched what
+      // the cached bundle's listeners were wired for, so an
+      // addEventListener call landed on a null element.
       const wrote = await writeWebResponse(
         res,
-        { status: 200, filePath: file, headers: { "Content-Type": contentTypeFor(file) } },
+        {
+          status: 200,
+          filePath: file,
+          headers: { "Content-Type": contentTypeFor(file), "Cache-Control": "no-cache" },
+        },
         log,
       );
       log(`${method} ${urlPath} -> ${wrote}`);