Caddyfile

:8080 {
    root * /usr/share/caddy

    encode gzip zstd

    # route forces declaration order so @forbidden and asset handling run
    # before document fallbacks.
    route {
        # Block access to sensitive paths
        @forbidden {
            path /.git/* /node_modules/* /vendor/* /.venv/*
        }
        respond @forbidden 404

        # Requests with a non-HTML extension are assets. They must never
        # fall back to index.html.
        @asset {
            path_regexp \.[A-Za-z0-9]+$
            not path *.html *.htm
        }
        handle @asset {
            file_server
        }

        # Serve real document files directly: the path as-is, then with a
        # .html suffix, then as a directory index.
        @documentFile file {path} {path}.html {path}/index.html
        handle @documentFile {
            rewrite * {http.matchers.file.relative}
            file_server
        }

        # Document-like misses:
        # - If /404.html exists in the site root, treat the site as an MPA
        #   and serve it with a real 404 status.
        # - Otherwise, treat it as a SPA and serve /index.html normally.
        #   Avoid `file_server status 200` here; it also overrides 304/206
        #   generated by http.ServeContent for conditional and range requests.
        @hasMpa404 file /404.html
        handle @hasMpa404 {
            rewrite * /404.html
            # Strip range headers so http.ServeContent always serves the full
            # file; the status 404 override then applies to a clean 200.
            request_header -Range
            request_header -If-Range
            # Fresh requests get an explicit 404; revalidation requests
            # (If-None-Match / If-Modified-Since) reach file_server unmodified
            # so http.ServeContent can return 304 instead of an empty 404.
            @mpa404Fresh {
                not header If-None-Match *
                not header If-Modified-Since *
            }
            route {
                handle @mpa404Fresh {
                    file_server {
                        status 404
                    }
                }
                handle {
                    file_server
                }
            }
        }

        handle {
            rewrite * /index.html
            file_server
        }
    }

    handle_errors 404 {
        @asset {
            path_regexp \.[A-Za-z0-9]+$
            not path *.html *.htm
        }
        handle @asset {
            respond "Not Found" 404
        }
    }

    zeaburextension

    log {
        output stderr
    }
}