text: add workaround for AJDA-1935 to improve Streamlit health check handling

Author: hosekpeter

internal/pkg/service/appsproxy/proxy/pagewriter/pagewriter.go

@@ -62,7 +62,11 @@ func (pw *Writer) MountAssets(mux *http.ServeMux) {
 }
 
 func (pw *Writer) writePage(w http.ResponseWriter, req *http.Request, page string, status int, data any) {
-	// Streamlit health checks expect plain text responses, not HTML
+	// WORKAROUND for AJDA-1935: Return plain text for Streamlit health checks.
+	// Streamlit displays error responses in a modal that doesn't properly render HTML,
+	// resulting in broken/escaped HTML being shown to users. This returns plain text
+	// for known Streamlit internal endpoints to provide a better user experience.
+	// See IsStreamlitHealthCheck() for full documentation and limitations.
 	if IsStreamlitHealthCheck(req.URL.Path) {
 		plainText := renderPlainText(page, status)
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")

internal/pkg/service/appsproxy/proxy/pagewriter/pathutil.go

@@ -2,6 +2,20 @@ package pagewriter
 
 import "strings"
 
+// IsStreamlitHealthCheck detects Streamlit health check endpoints.
+//
+// WORKAROUND: This is a temporary solution for AJDA-1935 to prevent broken HTML
+// from being displayed in Streamlit's error modal when the app is starting or unavailable.
+// Streamlit makes health check requests to these endpoints and renders the response
+// in an error dialog, which doesn't properly handle HTML responses.
+//
+// Limitations:
+//   - This approach is Streamlit-specific and does not scale to other frameworks
+//   - Only covers /_stcore/health and /_stcore/host-config endpoints
+//   - Other Streamlit internal endpoints (e.g., /_stcore/stream) are not covered
+//
+// Long-term solution: Modify Streamlit to properly handle HTML error responses
+// or provide a query parameter for clients to request plain text format.
 func IsStreamlitHealthCheck(path string) bool {
 	return strings.HasSuffix(path, "/_stcore/health") || strings.HasSuffix(path, "/_stcore/host-config")
 }