diff --git a/forth.h b/forth.h
index 608cbbc..dd781a0 100644
--- a/forth.h
+++ b/forth.h
@@ -11,6 +11,43 @@
 // Configuration (all hard limits removed)
 #define MAX_NAME_LEN 31
 
+/* Portable panic hook. Override for bare-metal reset/handling. */
+#ifndef forth_panic
+#define forth_panic() do { for (;;) ; } while (0)
+#endif
+
+/* Portable I/O hooks. Define FORTH_CUSTOM_IO before including this header
+ * to provide bare-metal UART (or other) implementations. */
+#ifndef FORTH_CUSTOM_IO
+#define forth_putchar(c) putchar(c)
+#define forth_getchar() getchar()
+#define forth_printf(...) printf(__VA_ARGS__)
+#define forth_fflush() fflush(stdout)
+#endif
+
+/* Static memory sizes (override before including forth.h) */
+#ifndef FORTH_DATA_STACK_SIZE
+#define FORTH_DATA_STACK_SIZE 128
+#endif
+#ifndef FORTH_RET_STACK_SIZE
+#define FORTH_RET_STACK_SIZE 128
+#endif
+#ifndef FORTH_COMPILE_STACK_SIZE
+#define FORTH_COMPILE_STACK_SIZE 64
+#endif
+#ifndef FORTH_COMPILE_BUF_SIZE
+#define FORTH_COMPILE_BUF_SIZE 256
+#endif
+#ifndef FORTH_USER_MEM_CELLS
+#define FORTH_USER_MEM_CELLS (1024 * 1024)
+#endif
+#ifndef FORTH_MAX_WORDS
+#define FORTH_MAX_WORDS 256
+#endif
+#ifndef FORTH_MAX_WORD_BODY_CELLS
+#define FORTH_MAX_WORD_BODY_CELLS 4096
+#endif
+
 #define F_IMMEDIATE (1 << 7)
 #define F_HIDDEN    (1 << 6)