diff --git a/internal/machine/caddyconfig/caddyfile.go b/internal/machine/caddyconfig/caddyfile.go
index c73aa9e8..a2e05ddf 100644
--- a/internal/machine/caddyconfig/caddyfile.go
+++ b/internal/machine/caddyconfig/caddyfile.go
@@ -114,6 +114,8 @@ func (g *CaddyfileGenerator) Generate(ctx context.Context, records []store.Conta
 	}
 
 	upstreams := serviceUpstreams(containers)
+	// Track validation errors for reporting.
+	var configErrors []string
 
 	// Find the 'caddy' service container on this machine. Use the most recent one if multiple exist.
 	var caddyCtr *api.ServiceContainer
@@ -136,6 +138,8 @@ func (g *CaddyfileGenerator) Generate(ctx context.Context, records []store.Conta
 		if err != nil {
 			g.log.Error("Failed to render template directives in user-defined global Caddy config, skipping it.",
 				"service", caddyCtr.ServiceName(), "container", caddyCtr.ID, "err", err)
+			configErrors = append(configErrors,
+				fmt.Sprintf("service '%s': failed to render template: %v", caddyCtr.ServiceName(), err))
 		} else {
 			caddyfileCandidate := fmt.Sprintf("# User-defined global config from service '%s'.\n%s\n\n%s",
 				caddyCtr.ServiceName(), renderedConfig, caddyfile)
@@ -143,6 +147,8 @@ func (g *CaddyfileGenerator) Generate(ctx context.Context, records []store.Conta
 			if err = g.validator.Validate(ctx, caddyfileCandidate); err != nil {
 				g.log.Error("User-defined global Caddy config is invalid, skipping it.",
 					"service", caddyCtr.ServiceName(), "container", caddyCtr.ID, "err", err)
+				configErrors = append(configErrors,
+					fmt.Sprintf("service '%s': validation failed: %v", caddyCtr.ServiceName(), err))
 			} else {
 				caddyfile = caddyfileCandidate
 			}
@@ -186,6 +192,8 @@ func (g *CaddyfileGenerator) Generate(ctx context.Context, records []store.Conta
 		if err != nil {
 			g.log.Error("Failed to render template directives in user-defined Caddy config for service, skipping it.",
 				"service", serviceName, "err", err)
+			configErrors = append(configErrors,
+				fmt.Sprintf("service '%s': failed to render template: %v", serviceName, err))
 			continue
 		}
 
@@ -194,15 +202,21 @@ func (g *CaddyfileGenerator) Generate(ctx context.Context, records []store.Conta
 		if err = g.validator.Validate(ctx, caddyfileCandidate); err != nil {
 			g.log.Error("User-defined Caddy config for service is invalid, skipping it.",
 				"service", serviceName, "err", err)
+			configErrors = append(configErrors, fmt.Sprintf("service '%s': validation failed: %v", serviceName, err))
 		} else {
 			caddyfile = caddyfileCandidate
 		}
 	}
 
-	// TODO: add ac omment with invalid configs and their validation errors:
-	//  # Skipped invalid configs:
-	//  # - Service 'api': Template error in x-caddy
-	//  # - Service 'web': Invalid Caddyfile syntax
+	// Append error summary as comment if there were any invalid configs.
+	if len(configErrors) > 0 {
+		errorsComment := "# Skipped invalid user-defined configs:\n"
+		for _, e := range configErrors {
+			errorsComment += fmt.Sprintf("# - %s\n", e)
+		}
+
+		caddyfile += "\n" + errorsComment
+	}
 
 	return caddyfileHeader + "\n" + caddyfile, nil
 }
diff --git a/internal/machine/caddyconfig/caddyfile_test.go b/internal/machine/caddyconfig/caddyfile_test.go
index f7cba036..f027fd35 100644
--- a/internal/machine/caddyconfig/caddyfile_test.go
+++ b/internal/machine/caddyconfig/caddyfile_test.go
@@ -297,7 +297,10 @@ bad.config.com {
 					time.Now(),
 				),
 			},
-			want: caddyfileBase,
+			want: caddyfileBase + `
+# Skipped invalid user-defined configs:
+# - service 'bad-service': validation failed: invalid config detected
+`,
 		},
 		{
 			name: "service with invalid config template is skipped",
@@ -313,7 +316,10 @@ bad.template.com {
 					time.Now(),
 				),
 			},
-			want: caddyfileBase,
+			want: caddyfileBase + `
+# Skipped invalid user-defined configs:
+# - service 'bad-template': failed to render template: parse config as Go template: template: Caddyfile:3: unexpected "}" in operand
+`,
 		},
 		{
 			name: "caddy service with invalid global config is skipped",
@@ -329,7 +335,10 @@ localhost {
 					time.Now(),
 				),
 			},
-			want: caddyfileBase,
+			want: caddyfileBase + `
+# Skipped invalid user-defined configs:
+# - service 'caddy': validation failed: invalid config detected
+`,
 		},
 		{
 			name: "caddy service on different machine is ignored",
@@ -389,6 +398,9 @@ api.example.com {
 web.example.com {
 	reverse_proxy web:3000
 }
+
+# Skipped invalid user-defined configs:
+# - service 'invalid-svc': validation failed: invalid config detected
 `,
 		},
 		{
@@ -756,6 +768,63 @@ gateway.example.com {
 web-v2.example.com {
 	reverse_proxy 10.210.1.3:8080 10.210.3.3:8080 10.210.2.3:8080
 }
+
+# Skipped invalid user-defined configs:
+# - service 'invalid': validation failed: invalid config detected
+`,
+		},
+		{
+			name: "multiple errors: invalid global, template error, and validation error",
+			containers: []store.ContainerRecord{
+				newContainerRecordWithCaddyConfig(
+					"caddy",
+					"10.210.0.1",
+					`# test:invalid
+{
+	invalid global
+}`,
+					"test-machine-id",
+					time.Now(),
+				),
+				newContainerRecordWithCaddyConfig(
+					"broken-template",
+					"10.210.0.2",
+					`broken.example.com {
+	reverse_proxy {{upstreams "missing
+}`,
+					"test-machine-id",
+					time.Now(),
+				),
+				newContainerRecordWithCaddyConfig(
+					"invalid",
+					"10.210.0.3",
+					`# test:invalid
+invalid.example.com {
+	respond "Invalid config"
+}`,
+					"test-machine-id",
+					time.Now(),
+				),
+				newContainerRecordWithCaddyConfig(
+					"valid",
+					"10.210.0.4",
+					`valid.example.com {
+	respond "Valid config"
+}`,
+					"test-machine-id",
+					time.Now(),
+				),
+			},
+			want: caddyfileBase + `
+# User-defined config for service 'valid'.
+valid.example.com {
+	respond "Valid config"
+}
+
+# Skipped invalid user-defined configs:
+# - service 'caddy': validation failed: invalid config detected
+# - service 'broken-template': failed to render template: parse config as Go template: template: Caddyfile:2: unterminated quoted string
+# - service 'invalid': validation failed: invalid config detected
 `,
 		},
 	}