Add cache headers to nginx config

Browsers were heuristically caching the site and the compiled /output
modules because no Cache-Control header was sent; with files dating
from a 2023 deploy, cached clients could be considered fresh for
months. no-cache makes browsers revalidate via ETag: unchanged files
cost a 304, changed files are re-downloaded immediately.

Matches the configuration applied to the live server on 2026-07-05.
Also updates the changelog entries to reference this PR.

Author: thomashoneyman

CHANGELOG.md

@@ -11,9 +11,10 @@ New features:
 Bugfixes:
 
 Other improvements:
-- Bump the Stackage resolver from `lts-20.9` to `lts-20.26` (GHC 9.2.5 → 9.2.8), the newest snapshot compatible with `purescript-0.15.15` (#320 by @thomashoneyman)
-- Modernize the server build: `cabal-version: 2.4`, build with `-Wall -Werror` (with attendant cleanup in `server/Main.hs`), remove unused dependencies and the redundant `Setup.hs` (#320 by @thomashoneyman)
-- Speed up CI server builds by removing the `-j1` limit; runners have had 4 vCPUs and 16GB of RAM for years (#320 by @thomashoneyman)
+- Bump the Stackage resolver from `lts-20.9` to `lts-20.26` (GHC 9.2.5 → 9.2.8), the newest snapshot compatible with `purescript-0.15.15` (#322 by @thomashoneyman)
+- Modernize the server build: `cabal-version: 2.4`, build with `-Wall -Werror` (with attendant cleanup in `server/Main.hs`), remove unused dependencies and the redundant `Setup.hs` (#322 by @thomashoneyman)
+- Speed up CI server builds by removing the `-j1` limit; runners have had 4 vCPUs and 16GB of RAM for years (#322 by @thomashoneyman)
+- Serve the site and the compiled `/output` modules with `Cache-Control: no-cache` so browsers revalidate via ETag instead of heuristically caching a stale client for months after a deploy (#322 by @thomashoneyman)
 
 ## [v2026-07-05.1](https://github.com/purescript/trypurescript/releases/tag/v2026-07-05.1)
 

deploy/nginx.conf

@@ -44,6 +44,10 @@ server {
 
     location / {
       root /var/www/trypurescript/public;
+      # Always revalidate (cheap ETag 304s): the HTML references the bundle by
+      # a fixed name, so without this browsers heuristically cache the site
+      # and can serve a stale client for months after a deploy.
+      add_header Cache-Control "no-cache";
     }
 
 }
@@ -86,6 +90,10 @@ server {
     # match to ensure that we only serve JS files.
     location ~ ^/output/(.+\.js)$ {
       add_header Access-Control-Allow-Origin *;
+      # Module URLs are generated by the compiler and change content when the
+      # package set or compiler changes; revalidate so browsers never mix
+      # modules from different deploys.
+      add_header Cache-Control "no-cache";
       alias /var/www/trypurescript/staging/.psci_modules/$1;
     }
 }