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0592 — ClientRouter, without persisting the sandbox

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Posted: 2026-09-08 · Report this thread
brandon Site Admin brandon profile Posts: 677

Context

The roadmap asked for transition:persist on the sandbox, to keep the live PGlite instance across navigations — boot cost once per session instead of once per page. ClientRouter was in website/CONVENTIONS.md’s stack list but had never been wired up, so every navigation was a full page load.

transition:persist cannot do that. Astro’s swap matches the attribute on both documents and drops anything the destination lacks:

const newEl = newElement.querySelector(`[${PERSIST_ATTR}="${id}"]`);
if (!newEl) continue;

The sandbox is on / and nowhere else, so navigating to a doc page destroys it whatever directive it carries.

What does survive a soft navigation is the module registry: the swap is oldElement.replaceWith(newElement), so window and every evaluated module outlive it. PGlite keeps its fetched Responses and its compiled WebAssembly.Modules in module-level maps, which means ClientRouter alone caches the expensive half.

Decision

<ClientRouter /> in BoardLayout.astro — the only layout that owns a <head>, so one line covers all 80 pages. Nothing carries transition:persist.

  • Returning to / now skips the 5.53 MB gzipped download and the 10 MB wasm compile. It still runs instantiate, initdb, the topic DDL and the seed.
  • Skipping those too needs the VulkanDatabase itself alive, which means hoisting DatabaseState into a module singleton — and taking the consumer cards, groups and nextConsumer with it, or a returning reader gets “no runs yet” and “billing’s cursor is at 0” over a database whose cursor is at 8. Deliberately not taken: it relocates the sandbox’s state model and pins a live Postgres for the whole session.
  • DatabaseState.close() is new, and the sandbox calls it from onDestroy. A full page load used to release the Postgres for free; a soft navigation does not, and each one holds a 128 MB wasm memory. reset() now goes through it rather than keeping its own copy of the teardown.
  • The reduced-motion guard for ::view-transition-* is ours, in global.css’s base layer. Astro ships one in viewtransitions.css, but that file only reaches the build when a transition:* directive is used — with none, the cross-fade is the browser’s own default and nothing gates it.

Consequences

  • Every page’s initial JS grows by the router: 16.29 KB raw, 5.55 KB gzipped. That is the real price, and it is paid on all 80 pages for a sandbox saving on one — soft navigation site-wide is what earns it.
  • The sandbox’s onDestroy is now load-bearing rather than defensive. The teardown chain is real: astro-island.disconnectedCallback fires astro:unmount after the swap, @astrojs/svelte’s hydrator listens for it and calls unmount(component), which runs onDestroy.
  • Page-level <script> tags do not re-run across a swap unless marked data-astro-rerun. The tree has none today; one added later must account for it.
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