Reuse the open PWA window when an emailed link launches the app

[ralyodio]

The same fix just shipped for rssamplifier.com (profullstack/rssamplifier.com#154), applied here.

The problem

Clicking the sign-in link in an email opens the installed PWA in a new window every time instead of reusing the one already open.

Why

src/app/api/auth/magic/route.ts builds the magic link from the site's own origin(), so every click is an in-scope launch of p0dcasters. src/app/manifest.ts named no launch_handler, which leaves the browser on auto — and auto opens a new app window per launch.

For a magic link this is the worst shape the bug takes: the session cookie is set in whichever window opened the link, so you end up signed in inside a window you did not open, while the window you were already using sits there signed out, looking like the link failed.

The fix

launch_handler: {
  client_mode: ["navigate-existing", "auto"],
},

navigate-existing hands the launch to the most recently used app window and navigates it, so the link lands where you are already looking and the cookie is set in the window you were using. auto trails it for browsers that do not know the first value, and for when no window is open yet.

MetadataRoute.Manifest in Next 15.5 types this natively (client_mode: ClientModeEnum | ClientModeEnum[], with both values in the enum), so no cast or escape hatch is needed.

What did not need changing

Unlike rssamplifier, no service worker bump. public/sw.js here precaches nothing and never caches the manifest, so there is no stale copy for a version sweep to evict.

Compatibility

Chromium 110+ honours it. Safari and Firefox ignore launch_handler and keep their current behaviour. iOS home-screen installs open email links in Safari rather than the app either way.

Testing

• npx tsc --noEmit passes (exit 0)
• pnpm build succeeds
• The generated manifest was checked, not just the source — .next/server/app/manifest.webmanifest.body contains "launch_handler":{"client_mode":["navigate-existing","auto"]}

🤖 Generated with Claude Code

https://claude.ai/code/session_013FR5zDT4DGJAmwDb6oVZ6n