# Part 0 — why the tab bar rendered unstyled through the public address

**Measured 2026-10-15 ~19:55 CEST from DooPlex (Hungary, so the geo rule passes). Nothing was changed.**

## Verdict: (a) a cache — and the mechanism is named

Not (b): **exactly one box runs 0.315.0 and it runs the registry's current image.**

| Box | pinned tag | status |
|---|---|---|
| demo-hp guest 9201 | `felhom-controller:0.315.0` | Up, healthy |
| demo-hp guest 9202 | `felhom-controller:0.314.0` | Up, healthy |
| felhom-pve (N100) guest 9201 | `felhom-controller:0.314.0` | Up, healthy |
| c11-appliance (Tester 1) | unreachable from DooPlex right now | — |

- demo-hp 9201's running image: `gitea.dooplex.hu/admin/felhom-controller@sha256:8887343011d64a2da9c65674a777a099708315063e3abc7c9463c03151dff041`
- The registry's current `0.315.0`: `sha256:8887343011d64a2da9c65674a777a099708315063e3abc7c9463c03151dff041` — **identical**.
- The **global floor is `0.314.0`** (read from the hub's `/configuration`), so no box could have taken
  0.315.0 by itself; the one that has it was deployed by hand. Tester 1 therefore cannot be on a
  stale 0.315.0 even though it is off right now.

## The four facts that make a cache the cause

1. **The stylesheet URL does not change between builds.** `layout.html` L12 asks for
   `/static/style.css?v={{.Version}}` → `?v=0.315.0` for all **three different** 0.315.0 builds
   (`e66d466`, `fe0228c`, `db52f5a`). The first of those had no `.app-tabs` rules at all.
2. **The origin offers no validator.** `serveCSSHandler` (`server.go:1130`) sets only
   `Cache-Control: public, max-age=3600`. Measured on the box: **ETag present = 0, Last-Modified
   present = 0.** With neither, no client and no edge can revalidate a copy — it can only expire.
3. **Cloudflare caches this URL and extends the browser's TTL.** Three requests in a row:
   `cf-cache-status: HIT`, `age: 99 → 100`, and `cache-control: public, max-age=14400` — Cloudflare
   rewrites the origin's 1 hour to **4 hours for the browser**.
4. **Cloudflare held a stale entry for that exact URL.** The very first request of the session returned
   `cf-cache-status: EXPIRED` — which only happens when the edge *has* an entry that has aged past its
   TTL. Having no validator, it had to refetch the whole body.

## What is true right now, and the honest caveat

Origin, edge and box agree byte-for-byte (`sha256 c1774f63daf65c56` both sides) and all contain the
`.app-tabs` rules. The page itself is never cached (`cf-cache-status: DYNAMIC`); only the stylesheet is.

**The caveat, stated rather than glossed:** the specific stale object is no longer observable — the
first probe of this session forced its revalidation, which is exactly what `EXPIRED` records. So I
cannot produce a `HIT` whose body lacks `.app-tabs`. What is shown is every precondition for it, the
proof that an aged entry existed, and the elimination of the only other candidate (b).

## Why this authorises Part 1.2

The fix is not "purge the cache" — that hides the cause and returns at the next build. The fix is that
**the stylesheet's address changes with every build**, so no cache at any layer (browser, Cloudflare,
or anything between) can serve a previous build's CSS under an address the new build still asks for.
`Cache-Control` stays as it is: the new URL is the fix, not a shorter cache.

Part 1.1 removes the precondition entirely — a version number can only be pushed once, so two
different images can never share a number again.