v0.27.0 — user-configurable app subdomains

Users can now customize the subdomain for each app during deployment
instead of using a fixed value. The deploy page shows an editable text
input with the default pre-filled and the base domain as a suffix.

New "subdomain" deploy field type with DNS-safe format validation,
reserved name blocklist, and uniqueness check across deployed stacks.
Locked after deploy — changing requires Remove + Redeploy.

Backward compatible: InjectMissingFields() auto-fills SUBDOMAIN from
.felhom.yml defaults for existing deployed apps on next sync/restart.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/web/handlers.go

@@ -202,6 +202,21 @@ func (s *Server) stacksHandler(w http.ResponseWriter, r *http.Request) {
 	}
 	data["StorageLabels"] = storageLabels
 
+	// Build effective subdomain lookup (stored env > metadata fallback)
+	subdomains := make(map[string]string)
+	for _, stack := range s.stackMgr.GetStacks() {
+		if stack.Deployed {
+			if appCfg := s.stackMgr.LoadAppConfigByName(stack.Name); appCfg != nil {
+				if sd, ok := appCfg.Env["SUBDOMAIN"]; ok && sd != "" {
+					subdomains[stack.Name] = sd
+					continue
+				}
+			}
+		}
+		subdomains[stack.Name] = stack.Meta.Subdomain
+	}
+	data["Subdomains"] = subdomains
+
 	s.executeTemplate(w, r, "stacks", data)
 }
 
@@ -259,12 +274,7 @@ func (s *Server) deployHandler(w http.ResponseWriter, r *http.Request, name stri
 	if alreadyDeployed && appCfg != nil {
 		for _, f := range meta.AutoGeneratedFields() {
 			if val, ok := appCfg.Env[f.EnvVar]; ok {
-				// For domain fields show the full URL (subdomain.base_domain) as displayed on app cards.
-				if f.Type == "domain" && meta.Subdomain != "" {
-					autoFieldValues[f.EnvVar] = meta.Subdomain + "." + val
-				} else {
-					autoFieldValues[f.EnvVar] = val
-				}
+				autoFieldValues[f.EnvVar] = val
 			}
 		}
 	} else if !alreadyDeployed {
@@ -275,6 +285,10 @@ func (s *Server) deployHandler(w http.ResponseWriter, r *http.Request, name stri
 		}
 	}
 	data["AutoFieldValues"] = autoFieldValues
+	// For deployed apps, pass stored field values so subdomain and other user fields show current values
+	if alreadyDeployed && appCfg != nil {
+		data["DeployedFieldValues"] = appCfg.Env
+	}
 	// Storage paths with free space info for deploy dropdown
 	var deployPaths []DeployStoragePath
 	for _, sp := range s.settings.GetSchedulableStoragePaths() {
@@ -406,6 +420,12 @@ func (s *Server) appDetailHandler(w http.ResponseWriter, r *http.Request, slug s
 		}
 	}
 
+	// Determine effective subdomain (stored env > metadata fallback)
+	effectiveSubdomain := found.Meta.Subdomain
+	if sd, ok := currentValues["SUBDOMAIN"]; ok && sd != "" {
+		effectiveSubdomain = sd
+	}
+
 	data := s.baseData("stacks", found.Meta.DisplayName)
 	data["Stack"] = found
 	data["Meta"] = found.Meta
@@ -414,6 +434,7 @@ func (s *Server) appDetailHandler(w http.ResponseWriter, r *http.Request, slug s
 	data["CurrentValues"] = currentValues
 	data["HasAppInfo"] = found.Meta.HasAppInfo()
 	data["HasOptionalConfig"] = found.Meta.HasOptionalConfig()
+	data["EffectiveSubdomain"] = effectiveSubdomain
 
 	s.executeTemplate(w, r, "app_info", data)
 }