fix(desktop): invalidate stale media lookups

Co-authored-by: npub1qvn3cujt28pg06ehlstrxyz6ayzp06t4uc7r566vxwwgrv24hglq9zju0n <03271c724b51c287eb37fc1633105ae90417e975e63c3a6b4c339c81b155ba3e@sprout-oss.stage.blox.sqprod.co>
Signed-off-by: npub1qvn3cujt28pg06ehlstrxyz6ayzp06t4uc7r566vxwwgrv24hglq9zju0n <03271c724b51c287eb37fc1633105ae90417e975e63c3a6b4c339c81b155ba3e@sprout-oss.stage.blox.sqprod.co>

desktop/src/shared/lib/mediaUrl.test.mjs

@@ -5,9 +5,62 @@ import { mediaProxyUrl } from "./mediaUrl.ts";
 
 const HASH = "a".repeat(64);
 
+function deferred() {
+  let resolve;
+  const promise = new Promise((resolvePromise) => {
+    resolve = resolvePromise;
+  });
+  return { promise, resolve };
+}
+
 test("mediaProxyUrl: uses the IPv4 loopback literal for the localhost proxy", () => {
   assert.equal(
     mediaProxyUrl(54321, `${HASH}.png`),
     `http://127.0.0.1:54321/media/${HASH}.png`,
   );
 });
+
+test("resetMediaCaches: ignores relay origin lookups from the previous generation", async () => {
+  const previousWindow = globalThis.window;
+  const staleOrigin = deferred();
+  let relayOriginCalls = 0;
+
+  globalThis.window = {
+    __TAURI_INTERNALS__: {
+      invoke(command) {
+        if (command === "get_media_proxy_port") return Promise.resolve(54321);
+        if (command === "get_relay_http_url") {
+          relayOriginCalls += 1;
+          return relayOriginCalls === 1
+            ? staleOrigin.promise
+            : Promise.resolve("https://active.example");
+        }
+        return Promise.reject(new Error(`Unexpected command: ${command}`));
+      },
+    },
+  };
+
+  try {
+    // A unique URL triggers module-load fetching with the stale relay lookup
+    // still unresolved, matching a cold launch before applyCommunity finishes.
+    const mediaUrl = await import(`./mediaUrl.ts?race=${Date.now()}`);
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    mediaUrl.resetMediaCaches();
+    const activeUrl = `https://active.example/media/${HASH}.png`;
+    mediaUrl.rewriteRelayUrl(activeUrl);
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    // Complete the old lookup after reset. It must not overwrite the active
+    // community origin fetched by the new generation.
+    staleOrigin.resolve("https://stale.example");
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    assert.equal(
+      mediaUrl.rewriteRelayUrl(activeUrl),
+      `http://127.0.0.1:54321/media/${HASH}.png`,
+    );
+  } finally {
+    globalThis.window = previousWindow;
+  }
+});

desktop/src/shared/lib/mediaUrl.ts

@@ -29,6 +29,13 @@ let portPromise: Promise<number | null> | null = null;
 /** Cached relay origin (e.g. "https://buzz-oss.stage.blox.sqprod.co"). */
 let cachedRelayOrigin: string | null = null;
 
+/**
+ * Monotonic cache generation. Async lookups capture the current generation and
+ * may only publish results while it is still current. This prevents a lookup
+ * started for the previous community from repopulating caches after reset.
+ */
+let cacheGeneration = 0;
+
 const POLL_INTERVAL_MS = 100;
 const POLL_TIMEOUT_MS = 5000;
 
@@ -38,20 +45,25 @@ const POLL_TIMEOUT_MS = 5000;
  * Returns the port, or null if the proxy never came up.
  */
 async function fetchProxyPort(): Promise<number | null> {
+  const generation = cacheGeneration;
+
   // Fetch relay origin in parallel — fire-and-forget, no retry needed.
   if (!cachedRelayOrigin) {
     invoke<string>("get_relay_http_url")
       .then((url) => {
-        cachedRelayOrigin = url.replace(/\/+$/, "");
+        if (generation === cacheGeneration) {
+          cachedRelayOrigin = url.replace(/\/+$/, "");
+        }
       })
       .catch(() => {});
   }
 
   const deadline = Date.now() + POLL_TIMEOUT_MS;
-  while (Date.now() < deadline) {
+  while (Date.now() < deadline && generation === cacheGeneration) {
     try {
       const port = await invoke<number>("get_media_proxy_port");
       if (port > 0) {
+        if (generation !== cacheGeneration) return null;
         cachedPort = port;
         return port;
       }
@@ -75,6 +87,7 @@ if (typeof window !== "undefined") {
  * and relay origin for the new community.
  */
 export function resetMediaCaches(): void {
+  cacheGeneration += 1;
   cachedPort = null;
   portPromise = null;
   cachedRelayOrigin = null;