# There is no ISR on Cloudflare

> For agents: start with the [agent guide](https://ratstack.sh/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

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There is no SvelteKit `isr` switch for the Cloudflare adapter. [That configuration belongs to adapter-vercel](https://svelte.dev/docs/kit/adapter-vercel).

[Vercel ISR](https://vercel.com/docs/incremental-static-regeneration) stores generated content and regenerates it. [Kit #661](https://github.com/sveltejs/kit/issues/661) asks for a general regeneration feature.

The title names this adapter boundary. It does not claim that Cloudflare cannot cache rendered pages.

[Workers Cache](https://blog.cloudflare.com/workers-cache/) puts a cache in front of a Worker entrypoint. Its [stale-while-revalidate behavior](https://developers.cloudflare.com/workers/cache/) serves a stale response while the Worker refreshes it.

## What our bake-off proves

We compare three local candidates:

- A static-assets gateway.
- A SvelteKit prerender gateway.
- A Workers Cache entrypoint.

The cache candidate mints a marker inside the rendering entrypoint. Repeated identical requests do not reuse it.

An assets response carries `CF-Cache-Status: HIT`. That proves asset-cache reuse, not rendering-entrypoint reuse. The selected Miniflare implementation does not implement Workers Cache handling.

The cache candidate's home-page Markdown timings are:

| Request                                            | Local time |
| -------------------------------------------------- | ---------- |
| Cold: first application request in a fresh runtime | 8.25 ms    |
| Warm: median of 20 sequential requests             | 1.69 ms    |

**What to notice:** Neither number measures an edge cache HIT.

The check does not prove:

- Stale-while-revalidate.
- Purge.
- Representation isolation across Workers Cache HITs.

Accepting the configuration is not a cache proof.

## What we choose

We choose [static assets](https://github.com/joelhooks/rat-stack/commit/a337a96). [`apps/mischief/src/static-assets.ts`](https://github.com/joelhooks/rat-stack/blob/main/apps/mischief/src/static-assets.ts) serves separate HTML and Markdown assets. The dynamic signup page stays outside that path.

See [Worker init runs twice](/lore/init-runs-twice) for another boundary a local check can miss.

## Sources

1. [SvelteKit Vercel adapter](https://svelte.dev/docs/kit/adapter-vercel)
   Primary source. SvelteKit Vercel adapter Accessed 2026-10-02.

2. [Vercel ISR](https://vercel.com/docs/incremental-static-regeneration)
   Primary source. Vercel ISR Accessed 2026-10-02.

3. [Add incremental static regeneration](https://github.com/sveltejs/kit/issues/661)
   GitHub. Add incremental static regeneration Accessed 2026-10-02.

4. [Workers Cache announcement](https://blog.cloudflare.com/workers-cache/)
   Primary source. Workers Cache announcement Accessed 2026-10-02.

5. [Workers Cache documentation](https://developers.cloudflare.com/workers/cache/)
   Primary source. Workers Cache documentation Accessed 2026-10-02.

6. [apps/mischief/src/static-assets.ts](https://github.com/joelhooks/rat-stack/blob/main/apps/mischief/src/static-assets.ts)
   GitHub. apps/mischief/src/static-assets.ts Accessed 2026-10-02.

7. [Serve static assets through Effect HTTP composition](https://github.com/joelhooks/rat-stack/commit/a337a96)
   GitHub. Serve static assets through Effect HTTP composition Accessed 2026-10-02.

## Linked from

- Agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms.txt)

- Change log → What changed in the files served here, newest first. → [Read page](https://ratstack.sh/log)

- Full agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms-full.txt)

- log.md → The generated change log as Markdown. → [Read page](https://ratstack.sh/log.md)

- Rat Stack lore | rat-stack → Short, source-grounded notes on the ideas and decisions behind rat-stack. → [Read page](https://ratstack.sh/lore)