diff --git a/electron/affiliateTracking.js b/electron/affiliateTracking.js
index 6f060dd0..cb97c4dc 100644
--- a/electron/affiliateTracking.js
+++ b/electron/affiliateTracking.js
@@ -41,6 +41,10 @@ const FILENAME_ATTRIBUTION_WINDOW_MS =
   Number(process.env.OPENSWARM_AFFILIATE_FILENAME_WINDOW_MS) || 30 * 24 * 60 * 60 * 1000;
 const INSTALLER_HASH_RE =
   /^OpenSwarm(?:-Setup)?-(?:arm64|x64)-([A-Za-z0-9_-]{16,32})(?: \([0-9]+\))?\.(dmg|exe|AppImage)$/i;
+// A file whose mtime is slightly in the future is NOT suspicious: APFS/NTFS
+// keep sub-ms timestamps, and NTP can step the clock backwards between the
+// download and first launch. Only skip files more than a minute ahead.
+const FUTURE_MTIME_TOLERANCE_MS = 60 * 1000;
 
 function getStateFilePath(userDataDir) {
   return path.join(userDataDir, "install.json");
@@ -214,7 +218,7 @@ function recentInstallerHashesInDir(dir, nowMs) {
     try {
       const st = fs.statSync(fullPath);
       const ageMs = nowMs - st.mtimeMs;
-      if (ageMs < 0 || ageMs > FILENAME_ATTRIBUTION_WINDOW_MS) continue;
+      if (ageMs < -FUTURE_MTIME_TOLERANCE_MS || ageMs > FILENAME_ATTRIBUTION_WINDOW_MS) continue;
       out.push({ hash, path: fullPath, mtimeMs: st.mtimeMs });
     } catch (_) {}
   }
diff --git a/electron/affiliateTracking.test.js b/electron/affiliateTracking.test.js
index 8ae98705..c81b8949 100644
--- a/electron/affiliateTracking.test.js
+++ b/electron/affiliateTracking.test.js
@@ -297,6 +297,56 @@ test("filename parser keeps hyphens inside base64url affiliate hash", () => {
   );
 });
 
+test("filename parser covers every stamped artifact shape (mac/win/linux)", () => {
+  const h = "abcDEF1234567890_hash";
+  for (const name of [
+    `OpenSwarm-arm64-${h}.dmg`,          // mac Apple Silicon
+    `OpenSwarm-x64-${h}.dmg`,            // mac Intel
+    `OpenSwarm-Setup-x64-${h}.exe`,      // windows squirrel setup
+    `OpenSwarm-x64-${h}.AppImage`,       // linux x64
+    `OpenSwarm-arm64-${h}.AppImage`,     // linux arm64
+  ]) {
+    assert.equal(affiliateTracking._hashFromInstallerBasename(name), h, name);
+  }
+  // Unstamped artifacts must NOT parse as carrying a hash.
+  for (const name of ["OpenSwarm-arm64.dmg", "OpenSwarm-Setup-x64.exe", "OpenSwarm-x64.AppImage"]) {
+    assert.equal(affiliateTracking._hashFromInstallerBasename(name), null, name);
+  }
+});
+
+test("first launch (win32): stamped setup exe in Downloads binds before welcome URL", async () => {
+  const cloud = await makeMockCloud();
+  try {
+    const userDataDir = makeTempUserDataDir();
+    const shell = makeFakeShell();
+    const hash = "abcDEF1234567890_hash";
+    cloud.filenameHashes.set(hash, "windows-affiliate");
+
+    const downloads = path.join(userDataDir, "Downloads");
+    fs.mkdirSync(downloads, { recursive: true });
+    fs.writeFileSync(path.join(downloads, `OpenSwarm-Setup-x64-${hash}.exe`), "");
+
+    process.env.OPENSWARM_AFFILIATE_LANDING_URL = "https://landing.test";
+    process.env.OPENSWARM_AFFILIATE_CLOUD_URL = cloud.url;
+
+    await affiliateTracking.maybeRunFirstLaunchHandshake({
+      shell,
+      userDataDir,
+      isDev: false,
+      isPackaged: true,
+      platform: "win32",
+      homeDir: userDataDir,
+    });
+
+    assert.equal(shell.opened.length, 0, "filename hash bind skips welcome URL");
+    const state = readJson(path.join(userDataDir, "install.json"));
+    assert.equal(state.ref, "windows-affiliate");
+    assert.equal(state.ref_bind_method, "affiliate_filename_hash");
+  } finally {
+    await cloud.close();
+  }
+});
+
 test("download scan refuses ambiguous stamped installers", () => {
   const userDataDir = makeTempUserDataDir();
   const downloads = path.join(userDataDir, "Downloads");