perf: cache un-hashed static assets under /img and /logo

next.config.js

@@ -25,10 +25,26 @@ const nextConfig = {
   transpilePackages: ["jose"],
   serverExternalPackages: ["@duckdb/node-api"],
   async headers() {
+    // ponytail: un-hashed filenames under public/, so `immutable` is unsafe —
+    // a redeploy has to be able to replace these in place. An hour of freshness
+    // drops the per-navigation revalidation round-trip without stranding a
+    // stale asset for long.
+    const staticAssets = [
+      {
+        source: "/:dir(img|logo)/:path*",
+        headers: [
+          {
+            key: "Cache-Control",
+            value: "public, max-age=3600, stale-while-revalidate=604800",
+          },
+        ],
+      },
+    ];
     if (process.env.STAGE === "prod") {
-      return [];
+      return staticAssets;
     }
     return [
+      ...staticAssets,
       {
         source: "/:path*",
         headers: [

next.config.test.ts

@@ -1,5 +1,20 @@
 import nextConfig from "./next.config.js";
 
+const STATIC_ASSET_RULE = {
+  source: "/:dir(img|logo)/:path*",
+  headers: [
+    {
+      key: "Cache-Control",
+      value: "public, max-age=3600, stale-while-revalidate=604800",
+    },
+  ],
+};
+
+const NOINDEX_RULE = {
+  source: "/:path*",
+  headers: [{ key: "X-Robots-Tag", value: "noindex, nofollow" }],
+};
+
 describe("next.config headers()", () => {
   const originalStage = process.env.STAGE;
 
@@ -14,28 +29,26 @@ describe("next.config headers()", () => {
   test("non-prod stage emits noindex header on all paths", async () => {
     process.env.STAGE = "dev";
     const result = await nextConfig.headers!();
-    expect(result).toEqual([
-      {
-        source: "/:path*",
-        headers: [{ key: "X-Robots-Tag", value: "noindex, nofollow" }],
-      },
-    ]);
+    expect(result).toEqual([STATIC_ASSET_RULE, NOINDEX_RULE]);
   });
 
-  test("prod stage emits no header overrides", async () => {
+  test("prod stage emits no noindex override", async () => {
     process.env.STAGE = "prod";
     const result = await nextConfig.headers!();
-    expect(result).toEqual([]);
+    expect(result).toEqual([STATIC_ASSET_RULE]);
   });
 
   test("missing STAGE defaults to noindex", async () => {
     delete process.env.STAGE;
     const result = await nextConfig.headers!();
-    expect(result).toEqual([
-      {
-        source: "/:path*",
-        headers: [{ key: "X-Robots-Tag", value: "noindex, nofollow" }],
-      },
-    ]);
+    expect(result).toEqual([STATIC_ASSET_RULE, NOINDEX_RULE]);
+  });
+
+  test("static assets stay cacheable in every stage", async () => {
+    for (const stage of ["prod", "dev"]) {
+      process.env.STAGE = stage;
+      const result = await nextConfig.headers!();
+      expect(result).toContainEqual(STATIC_ASSET_RULE);
+    }
   });
 });