diff --git a/internal/config/config_stdin_test.go b/internal/config/config_stdin_test.go
index 15f243b70..17985547c 100644
--- a/internal/config/config_stdin_test.go
+++ b/internal/config/config_stdin_test.go
@@ -439,7 +439,6 @@ func TestConvertStdinServerConfig_HTTPServerNoDockerArgs(t *testing.T) {
 		Entrypoint:     "/ignored",
 		EntrypointArgs: []string{"ignored"},
 		Args:           []string{"--ignored"},
-		Mounts:         []string{"/ignored:/ignored"},
 		Env: map[string]string{
 			"IGNORED": "ignored",
 		},
diff --git a/internal/config/validation.go b/internal/config/validation.go
index 66bb1a52d..ff663eff3 100644
--- a/internal/config/validation.go
+++ b/internal/config/validation.go
@@ -144,12 +144,16 @@ func validateStandardServerConfig(name string, server *StdinServerConfig, jsonPa
 		}
 	}
 
-	// For HTTP servers, url is required
+	// For HTTP servers, url is required and mounts are not allowed
 	if server.Type == "http" {
 		if server.URL == "" {
 			logValidation.Printf("Validation failed: HTTP server missing url field, name=%s", name)
 			return rules.MissingRequired("url", "HTTP", jsonPath, "Add a 'url' field (e.g., \"https://example.com/mcp\")")
 		}
+		if len(server.Mounts) > 0 {
+			logValidation.Printf("Validation failed: HTTP server has mounts field, name=%s", name)
+			return rules.UnsupportedField("mounts", "mounts are only supported for stdio (containerized) servers", jsonPath, "Remove the 'mounts' field from HTTP server configuration; mounts only apply to stdio servers")
+		}
 	}
 
 	logValidation.Printf("Server config validation passed: name=%s", name)
diff --git a/internal/config/validation_test.go b/internal/config/validation_test.go
index d3c75c852..53cc1ad6c 100644
--- a/internal/config/validation_test.go
+++ b/internal/config/validation_test.go
@@ -284,6 +284,16 @@ func TestValidateStdioServer(t *testing.T) {
 			},
 			shouldErr: false,
 		},
+		{
+			name: "http server with mounts should be rejected (T-CFG-019)",
+			server: &StdinServerConfig{
+				Type:   "http",
+				URL:    "https://example.com/mcp",
+				Mounts: []string{"/host/path:/container/path:ro"},
+			},
+			shouldErr: true,
+			errorMsg:  "mounts are only supported for stdio",
+		},
 		{
 			name: "empty type defaults to stdio with container",
 			server: &StdinServerConfig{