From 22769977e3366dff64250509c0185a240ade76b8 Mon Sep 17 00:00:00 2001
From: GitHub Actions <actions@github.com>
Date: Sat, 21 Mar 2026 02:12:24 +0000
Subject: [PATCH] fix: clarify that advanced_config requires Caddy JSON, not
 Caddyfile syntax

---
 .../internal/api/handlers/proxy_host_handler.go    |  4 ++--
 frontend/src/components/ProxyHostForm.tsx          | 14 +++++++++++++-
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/backend/internal/api/handlers/proxy_host_handler.go b/backend/internal/api/handlers/proxy_host_handler.go
index dc73a462..6149e47d 100644
--- a/backend/internal/api/handlers/proxy_host_handler.go
+++ b/backend/internal/api/handlers/proxy_host_handler.go
@@ -358,7 +358,7 @@ func (h *ProxyHostHandler) Create(c *gin.Context) {
 	if host.AdvancedConfig != "" {
 		var parsed any
 		if err := json.Unmarshal([]byte(host.AdvancedConfig), &parsed); err != nil {
-			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid advanced_config JSON: " + err.Error()})
+			c.JSON(http.StatusBadRequest, gin.H{"error": "advanced_config must be valid Caddy JSON (not Caddyfile syntax). See https://caddyserver.com/docs/json/ for the correct format."})
 			return
 		}
 		parsed = caddy.NormalizeAdvancedConfig(parsed)
@@ -586,7 +586,7 @@ func (h *ProxyHostHandler) Update(c *gin.Context) {
 		if v != "" && v != host.AdvancedConfig {
 			var parsed any
 			if err := json.Unmarshal([]byte(v), &parsed); err != nil {
-				c.JSON(http.StatusBadRequest, gin.H{"error": "invalid advanced_config JSON: " + err.Error()})
+				c.JSON(http.StatusBadRequest, gin.H{"error": "advanced_config must be valid Caddy JSON (not Caddyfile syntax). See https://caddyserver.com/docs/json/ for the correct format."})
 				return
 			}
 			parsed = caddy.NormalizeAdvancedConfig(parsed)
diff --git a/frontend/src/components/ProxyHostForm.tsx b/frontend/src/components/ProxyHostForm.tsx
index 19d7f246..0a77144f 100644
--- a/frontend/src/components/ProxyHostForm.tsx
+++ b/frontend/src/components/ProxyHostForm.tsx
@@ -1388,11 +1388,23 @@ export default function ProxyHostForm({ host, onSubmit, onCancel }: ProxyHostFor
               id="advanced-config"
               value={formData.advanced_config}
               onChange={e => setFormData(prev => ({ ...prev, advanced_config: e.target.value }))}
-              placeholder="Additional Caddy directives..."
+              placeholder='{"handler": "headers", "request": {"set": {"X-Custom": ["value"]}}}'
               rows={4}
               className="w-full bg-gray-900 border border-gray-700 rounded-lg px-4 py-2 text-white font-mono text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
             />
             </div>
+            <p className="mt-1.5 text-xs text-gray-500">
+              Accepts{' '}
+              <a
+                href="https://caddyserver.com/docs/json/"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="text-blue-400 hover:underline"
+              >
+                Caddy JSON
+              </a>
+              {' '}format only — not Caddyfile syntax.
+            </p>
           </div>
 
           {/* Enabled Toggle */}