Fix two bugs: SPA-routing page load failure and stale service worker

fetchPageFile now rejects text/html responses so servers with SPA routing
(e.g. Cloudflare Pages with /* /index.html 200) no longer trick the renderer
into treating a fallback index.html as a found markdown file. Category-variant
pages (page.current.md with no plain page.md) now fall through correctly to
their variant URL.

mdcms build now writes a self-unregistering service-worker.js when pwa: no,
evicting any stale caching worker left over from a previous pwa: yes build.
manifest.json is also removed when pwa: no.

https://claude.ai/code/session_01Xs5GyREFhjWxhS1UhW2wA8

app/index.html

@@ -1135,11 +1135,19 @@ body {
     if (b) b.remove();
   }
 
+  function _isMdResponse(r) {
+    // Reject HTML responses — servers with SPA routing (e.g. Cloudflare Pages with
+    // "/* /index.html 200") return index.html with 200 for missing files, which would
+    // be mistaken for a found markdown file.
+    const ct = r.headers.get('content-type') || '';
+    return !ct.startsWith('text/html');
+  }
+
   async function fetchPageFile(conceptualFile) {
     // conceptualFile like "pages/foo.md". Returns { ok, text, resolvedFile } or { ok: false }.
     if (!categoriesUse) {
       const r = await fetch(conceptualFile);
-      if (r.ok) return { ok: true, text: await r.text(), resolvedFile: conceptualFile };
+      if (r.ok && _isMdResponse(r)) return { ok: true, text: await r.text(), resolvedFile: conceptualFile };
       return { ok: false };
     }
     const base = conceptualFile.replace(/\.md$/, '');
@@ -1169,7 +1177,7 @@ body {
       if (seen.has(url)) continue;
       seen.add(url);
       const r = await fetch(url);
-      if (r.ok) return { ok: true, text: await r.text(), resolvedFile: url };
+      if (r.ok && _isMdResponse(r)) return { ok: true, text: await r.text(), resolvedFile: url };
     }
     return { ok: false };
   }

docs/knownbugs.md

@@ -6,6 +6,26 @@ Bugs that have been identified but not yet fixed. Fixed bugs are moved to the re
 
 ## Fixed in development (not yet released)
 
+### Category-variant pages fail to load on servers with SPA routing
+
+**Symptom:** On Cloudflare Pages (and any other server configured to serve `index.html` with HTTP 200 for missing paths), clicking a nav item whose page only exists as a category-variant file (e.g. `page.current.md`, no plain `page.md`) showed garbled content — the raw HTML of `index.html` rendered as markdown, with the site's `<title>` text visible in the content area.
+
+**Root cause:** `fetchPageFile` tried the base filename (`pages/page.md`) first. Servers with SPA routing return this with HTTP 200 (serving `index.html`), so `r.ok` was true and the function returned without trying the actual variant file (`pages/page.current.md`).
+
+**Fix:** `fetchPageFile` now checks the `Content-Type` response header and skips any response with `text/html`, continuing to the next candidate URL.
+
+---
+
+### Stale service worker not removed when `pwa: no`
+
+**Symptom:** After changing a site from `pwa: yes` to `pwa: no` and rebuilding, the old service worker remained active in browsers that had previously visited the site. Cached responses from the old build continued to be served.
+
+**Root cause:** `mdcms build` stopped generating PWA files when `pwa: no`, but `index.html` unconditionally registers `service-worker.js` on every page load. With no new SW to replace it, the old worker stayed installed indefinitely.
+
+**Fix:** `mdcms build` now writes a self-unregistering stub `service-worker.js` when `pwa: no`. On the visitor's next visit, the browser installs the stub which immediately calls `self.registration.unregister()`, evicting the stale worker. `manifest.json` is also deleted if present.
+
+---
+
 ### `config.yml` YAML parse errors were silently swallowed
 
 **Symptom:** A malformed `config.yml` (e.g. a stray tab character, which YAML forbids as a token starter) caused `read_config` to catch the `YAMLError` and return an empty dict. The build would proceed with no config — categories disabled, no default category code — producing a `nav.yml` that omitted `variants` fields and listed category variant files (e.g. `page.current.md`) as plain pages. Pages with category variants would not appear in the sidebar.

docs/unreleased.md

@@ -43,6 +43,22 @@ A rebuild is required for existing sites to pick up the change.
 
 ---
 
+## Fix: category-variant pages fail to load on servers with SPA routing (e.g. Cloudflare Pages)
+
+When a site uses category-suffixed page files (e.g. `page.current.md`) and is hosted on a server configured with SPA fallback routing (serving `index.html` with HTTP 200 for any unknown path), the renderer's `fetchPageFile` mistook the HTML fallback for a found markdown file. It returned `index.html` content instead of falling through to try the `.current.md` variant. The page rendered the raw HTML of `index.html` as markdown, showing the `<title>` text (`sitename`) in the content area.
+
+`fetchPageFile` now checks the `Content-Type` response header and rejects any response with `text/html`, continuing to the next candidate URL instead.
+
+---
+
+## Fix: stale service worker not removed when `pwa: no`
+
+`index.html` unconditionally registers `service-worker.js` on every page load. When a site switched from `pwa: yes` to `pwa: no`, `mdcms build` stopped generating a new service worker, but the old one remained active in browsers that had visited the site before. The stale worker continued to serve cached responses from the old build.
+
+`mdcms build` now writes a self-unregistering `service-worker.js` when `pwa: no`. On the visitor's next page load, the browser installs this stub worker, which immediately unregisters itself and evicts any previously cached content. `manifest.json` is also removed if present.
+
+---
+
 ## Fix: `config.yml` YAML parse errors now abort the build with a clear message
 
 A malformed `config.yml` (e.g. a stray tab character, which YAML forbids as a token starter) previously caused `read_config` to silently return an empty dict. The build would proceed with no config — categories disabled, no default category code — producing a broken `nav.yml` with wrong filenames and missing `variants` fields, so category-variant pages would not appear in the sidebar.

mdcms.py

@@ -528,6 +528,8 @@ def run_build(site_path: Path):
     pwa_enabled = str(cfg.get("pwa", "no")).lower() in ("yes", "true")
     if pwa_enabled:
         generate_pwa(site_path, cfg)
+    else:
+        cleanup_pwa(site_path)
 
     asset_warnings = validate_assets(site_path, cfg)
     for w in asset_warnings:
@@ -543,6 +545,29 @@ def run_build(site_path: Path):
 
 # ─── PWA generation ───────────────────────────────────────────
 
+def cleanup_pwa(site_path: Path):
+    """When pwa: no, write a self-unregistering service worker and remove manifest.json.
+
+    Browsers keep the previously installed service worker active until a new one is
+    installed. Writing a stub that immediately unregisters itself ensures any stale
+    caching worker is evicted on the next visit after a pwa: yes → pwa: no change.
+    """
+    sw = site_path / "service-worker.js"
+    sw.write_text(
+        "// mdcms: PWA disabled — unregisters any previously installed service worker.\n"
+        "self.addEventListener('install', () => self.skipWaiting());\n"
+        "self.addEventListener('activate', event => {\n"
+        "  event.waitUntil(self.registration.unregister());\n"
+        "});\n",
+        encoding="utf-8",
+    )
+    manifest = site_path / "manifest.json"
+    if manifest.exists():
+        manifest.unlink()
+        click.echo("  Removed manifest.json (pwa: no)")
+    click.echo("  Wrote service-worker.js (self-unregistering stub, pwa: no)")
+
+
 def generate_pwa(site_path: Path, cfg: dict):
     """Generate manifest.json and service-worker.js when pwa: yes."""
     pwa_name      = cfg.get("pwa-name", cfg.get("sitename", "MD-CMS Site"))