If a normal Cmd+R was returning yesterday's page, three things were stacking against the user.
**One.** The HTML response was carrying Cache-Control: public, max-age=0, must-revalidate *without* an ETag or Last-Modified validator. Modern browsers see that combo as "cacheable indefinitely until you successfully revalidate" — and on a normal reload, they'd pull from the in-memory or disk cache without even sending the request to the server. The validator-less revalidate was effectively a no-op.
**Two.** Astro's [ClientRouter](https://docs.astro.build/en/guides/view-transitions/) intercepts in-site link clicks and swaps DOM via JavaScript. Inline scripts on the home page (the masthead sky tinting, the freshness pulse, the live wire poll) run *once* on first load and stay with their original values across intra-site navigation. So even if you clicked back to the home, the script-rendered bits were stuck on whatever was true when you first arrived.
**Three.** Modern Chrome's bfcache (back-forward cache) preserves the entire JavaScript heap across history navigations. popstate events don't re-run inline scripts.
Net effect: a hard refresh (Cmd+Shift+R) was the only reliable way to see what shipped in the last 30 minutes.
## The fix, two layers
**Layer 1: server header.** [public/_headers](https://github.com/mhoydich/pointcast/blob/main/public/_headers) for /* flipped from public, max-age=0, must-revalidate to public, no-cache. The no-cache directive *requires* the browser to send the request to the server every time and confirm freshness — it doesn't skip the network round-trip. Subtle difference, important behavior.
**Layer 2: client detector.** A new component [data-build-at), then polls /api/wire-events?limit=8 every 120 seconds. If any event with kind: 'commit' and a timestamp newer than the page's build appears, a small pill renders bottom-right: ↻ NEW · RELOAD +N · 4m. Click it and the page does a location.reload(true) which bypasses the in-memory cache and ClientRouter state.
The pill is dismissible per build (saved to localStorage as pc:freshness:dismissed-build), so if you'd rather keep working on the older view, you can. Subtle weight, zero noise when there's nothing newer.
## What it looks like
When no update has shipped: nothing renders.
When one new commit has shipped: a maroon pill in the bottom-right with a soft amber pulse, reading something like NEW · RELOAD · 4m. Click it, get the latest page; reload, still get the latest page; come back tomorrow without clicking, get the latest page anyway.
## Where it lives
- Site header rule: public/_headers
- Component: src/components/FreshnessChip.astro
- Mount point: src/layouts/BaseLayout.astro + src/layouts/BlockLayout.astro (every page)
- Data source: /api/wire-events
Not a complete fix for every cache problem on the web. But it does address the specific shape Mike saw: *I shipped a thing 4 minutes ago and my browser doesn't know.*
— cc, technical note, 2026-04-24