hassio-addons/komga/rootfs/etc/nginx/servers/ingress.conf

server {
    listen %%interface%%:%%port%% default_server;

    client_max_body_size 0;

    # Home Assistant opens the ingress panel at <ingress_entry>/ and forwards it
    # as / , but Komga only answers below its servlet context path (/komga), so
    # bounce the panel there. absolute_redirect off keeps the Location relative
    # to the HA host instead of nginx's own listen address.
    location = / {
        absolute_redirect off;
        return 302 %%ingress_entry%%/komga/;
    }

    location / {
        add_header Access-Control-Allow-Origin *;
        proxy_connect_timeout 30m;
        proxy_send_timeout 30m;
        proxy_read_timeout 30m;
        proxy_pass http://127.0.0.1:25600;

        # Komga pushes live events over SSE (/komga/sse/v1/events), which must
        # not be buffered or the UI stops refreshing until the buffer fills
        proxy_buffering off;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;

        # Spring redirects /komga to /komga/ ; the Location it produces is
        # absolute against the upstream address, so rewrite it back onto the
        # ingress path (the second rule covers an already relative Location).
        absolute_redirect off;
        proxy_redirect http://127.0.0.1:25600/ %%ingress_entry%%/;
        proxy_redirect / %%ingress_entry%%/;

        # Komga scopes its cookies to the servlet context path
        # (Set-Cookie: ...; Path=/komga). The browser lives under the ingress
        # entry, so such a cookie is never sent back : login succeeds, then
        # every following request arrives anonymous and Komga answers 401.
        proxy_cookie_path /komga %%ingress_entry%%/komga;
        proxy_cookie_path / %%ingress_entry%%/;

        # Komga renders its index page with Thymeleaf @{...} link expressions,
        # so every asset url and window.resourceBaseUrl carry the context path
        # (/komga). Ingress strips its own prefix before forwarding, so the
        # browser needs that prefix added back. Only text/html is rewritten
        # (the nginx default for sub_filter_types) : the SPA derives its api
        # origin and router base from resourceBaseUrl at runtime, so json
        # responses and book pages stream through untouched.
        proxy_set_header Accept-Encoding "";
        sub_filter_once off;
        sub_filter "/komga" "%%ingress_entry%%/komga";

        # The epub/divina reader fetches a Readium manifest whose links Komga
        # builds with ServletUriComponentsBuilder.fromCurrentContextPath(), so
        # they are fully absolute against the upstream address nginx talks to
        # (http://127.0.0.1:25600/komga). Rewriting them to a root relative
        # ingress path also fixes the scheme : Home Assistant may be served over
        # https, and an absolute http:// link would be blocked as mixed content.
        # Only the json/xml document types are added here, so book pages are
        # never scanned.
        sub_filter "http://127.0.0.1:25600/komga" "%%ingress_entry%%/komga";

        # Komga opens the reader with window.open(url, '_blank'). In the Home
        # Assistant companion apps the ingress panel is a webview, which hands
        # such a popup to an external browser : that browser carries no ingress
        # session cookie, so Home Assistant answers 401 before Komga is even
        # reached. Turn that popup into a navigation of the panel itself, but
        # only for the call shape Komga uses (name _blank, no feature string)
        # and only for http(s) urls below window.resourceBaseUrl. That leaves
        # the OAuth2 login popup (window.open(url, 'oauth2Login', '<features>'),
        # which needs its own window), blob urls and links out of Komga alone,
        # and if Komga ever stopped setting resourceBaseUrl the popup is left
        # untouched rather than widened to the whole Home Assistant origin,
        # which ingress shares. Anchored on the single page app mount point :
        # both Komga ui shells carry it once, and only a book served as
        # text/html rather than the xhtml the epub spec mandates could collide
        # with it -- the same exposure the /komga filter above already has, and
        # Komga sends script-src 'none' on that endpoint.
        sub_filter "<div id=\"app\">" "<script>(function(){var o=window.open;window.open=function(u,n,f){try{var b=window.resourceBaseUrl;if(u&&n==='_blank'&&!f&&b){if(b.slice(-1)!=='/')b+='/';var t=new URL(u,location.href);if((t.protocol==='http:'||t.protocol==='https:')&&t.origin===location.origin&&t.pathname.indexOf(b)===0){location.assign(t.href);return window}}}catch(e){}return o.apply(window,arguments)}})();</script><div id=\"app\">";

        sub_filter_types application/json application/webpub+json
                         application/divina+json application/opds+json
                         application/atom+xml;
    }
}