diff --git a/.gitignore b/.gitignore
index ceee666..48a69a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,5 +13,7 @@ json.xml
 lib/*.so
 out/
 src/*.o
+src/rust/Cargo.lock
+src/rust/target
 *.swp
 tmp*
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a6448c9..fbfca89 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.10)
-project(fun VERSION 0.37.62 LANGUAGES C)
+project(fun VERSION 0.38.0 LANGUAGES C)
 
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED ON)
@@ -11,11 +11,114 @@ include(${CMAKE_SOURCE_DIR}/cmake/Dependencies.cmake)
 include(${CMAKE_SOURCE_DIR}/cmake/Extensions/Extensions.cmake)
 include(${CMAKE_SOURCE_DIR}/cmake/Targets.cmake)
 
+# --- Always show key build toggles ---
+# Normalize to ENABLED/DISABLED like the "Fun extension summary"
+if(FUN_DEBUG)
+  set(_FUN_DEBUG_STATE "ENABLED")
+else()
+  set(_FUN_DEBUG_STATE "DISABLED")
+endif()
+
+if(FUN_WITH_RUST)
+  set(_FUN_WITH_RUST_STATE "ENABLED")
+else()
+  set(_FUN_WITH_RUST_STATE "DISABLED")
+endif()
+
+message(STATUS "==== Fun build options ====")
+message(STATUS "  FUN_DEBUG: ${_FUN_DEBUG_STATE}")
+message(STATUS "  FUN_WITH_RUST: ${_FUN_WITH_RUST_STATE}")
+message(STATUS "===========================")
+
 # Convenience aggregate target (like 'build' in Makefile)
 add_custom_target(build
   DEPENDS fun fun_test test_opcodes
 )
 
+# --- Rust (Cargo) integration: optionally build and link a staticlib with opcode examples ---
+option(FUN_WITH_RUST "Build and link Rust opcode library" OFF)
+
+if(FUN_WITH_RUST)
+  find_program(CARGO_EXECUTABLE cargo)
+  if(NOT CARGO_EXECUTABLE)
+    message(FATAL_ERROR "FUN_WITH_RUST=ON but 'cargo' not found in PATH")
+  endif()
+
+  set(RUST_CRATE_DIR ${CMAKE_SOURCE_DIR}/src/rust)
+
+  # Map CMake build type to Cargo profile and output path
+  if(CMAKE_BUILD_TYPE STREQUAL "Debug")
+    set(RUST_PROFILE "debug")
+    set(RUST_BUILD_ARGS)
+  else()
+    set(RUST_PROFILE "release")
+    set(RUST_BUILD_ARGS --release)
+  endif()
+
+  # Crate name as per Cargo.toml
+  # Crate name on-disk replaces '-' with '_' in artifact names
+  set(RUST_CRATE_NAME hello-c-world)
+  string(REPLACE "-" "_" RUST_CRATE_BASENAME "${RUST_CRATE_NAME}")
+  set(RUST_LIB_NAME lib${RUST_CRATE_BASENAME}.a)
+  set(RUST_LIB_PATH ${RUST_CRATE_DIR}/target/${RUST_PROFILE}/${RUST_LIB_NAME})
+
+  add_custom_command(
+    OUTPUT ${RUST_LIB_PATH}
+    COMMAND ${CARGO_EXECUTABLE} build ${RUST_BUILD_ARGS}
+    WORKING_DIRECTORY ${RUST_CRATE_DIR}
+    COMMENT "Building Rust static library (${RUST_PROFILE})"
+    VERBATIM
+  )
+
+  add_custom_target(rust_ops_build DEPENDS ${RUST_LIB_PATH})
+
+  add_library(fun_ops STATIC IMPORTED GLOBAL)
+  set_target_properties(fun_ops PROPERTIES
+    IMPORTED_LOCATION ${RUST_LIB_PATH}
+    IMPORTED_LINK_INTERFACE_LANGUAGES C
+  )
+  add_dependencies(fun_ops rust_ops_build)
+
+  # Link Rust ops into the core so executables can call them
+  if(TARGET fun_core)
+    add_dependencies(fun_core rust_ops_build)
+    target_link_libraries(fun_core PRIVATE fun_ops)
+    target_compile_definitions(fun_core PRIVATE FUN_WITH_RUST)
+  endif()
+
+  # Propagate define to test targets that might call Rust
+  if(TARGET test_opcodes)
+    add_dependencies(test_opcodes rust_ops_build)
+    target_link_libraries(test_opcodes PRIVATE fun_ops)
+    target_compile_definitions(test_opcodes PRIVATE FUN_WITH_RUST)
+  endif()
+
+  if(TARGET fun)
+    target_compile_definitions(fun PRIVATE FUN_WITH_RUST)
+  endif()
+endif()
+
+# --- Size optimization for final binaries (Release) ---
+# Enable function/data sectioning for better GC; safe for all configs.
+add_compile_options(-ffunction-sections -fdata-sections)
+
+# Link-time garbage collection and stripping for the main executable in Release
+if(TARGET fun)
+  # Garbage-collect unused sections; also strip symbols (-s) in Release
+  target_link_options(fun PRIVATE
+    $<$<CONFIG:Release>:-Wl,--gc-sections -s>
+  )
+  # Prefer enabling LTO/IPO for Release builds
+  set_property(TARGET fun PROPERTY INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)
+endif()
+
+if(TARGET fun_core)
+  # LTO/IPO for the core library helps the final link DCE more Rust/C glue
+  set_property(TARGET fun_core PROPERTY INTERPROCEDURAL_OPTIMIZATION_RELEASE TRUE)
+  # Ensure objects compiled with sectioning (added globally above) benefit from GC
+  target_link_options(fun_core PRIVATE $<$<CONFIG:Release>:-Wl,--gc-sections>)
+endif()
+
 # Convenience targets: repl, run, threads-demo, ops, examples
 set(FUN_RUN_SCRIPT "" CACHE STRING "Script to run with the 'run' target, e.g. -DFUN_RUN_SCRIPT=examples/strings_test.fun")
 
diff --git a/examples/rust_hello.fun b/examples/rust_hello.fun
new file mode 100644
index 0000000..5cd23d2
--- /dev/null
+++ b/examples/rust_hello.fun
@@ -0,0 +1,32 @@
+#!/usr/bin/env fun
+
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-27
+ */
+
+/*
+ * Rust-backed opcode demo: rust_hello()
+ *
+ * Build instructions:
+ *   - Default builds disable Rust integration.
+ *   - Enable it via: cmake -S . -B build_debug -DFUN_WITH_RUST=ON
+ *   - Then: cmake --build build_debug --target fun
+ *
+ * Run:
+ *   build_debug/fun examples/rust_hello.fun
+ *
+ * Expected output (with FUN_WITH_RUST=ON):
+ *   Hello from Rust ops!
+ *
+ * If built without Rust, calling rust_hello() will raise a runtime error
+ * explaining that Rust integration is disabled.
+ */
+
+print(rust_hello())
diff --git a/src/bytecode.c b/src/bytecode.c
index 80a4ce7..58b62a8 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -206,6 +206,7 @@ static const char *opcode_name(OpCode op) {
         case OP_SIGN: return "SIGN";
         case OP_FMIN: return "FMIN";
         case OP_FMAX: return "FMAX";
+        case OP_RUST_HELLO: return "RUST_HELLO";
         default: return "???";
     }
 }
diff --git a/src/bytecode.h b/src/bytecode.h
index c1b9434..0cb4908 100644
--- a/src/bytecode.h
+++ b/src/bytecode.h
@@ -263,6 +263,9 @@ typedef enum {
     OP_FMIN,              // pops b, a (int/float); pushes fmin(a,b) (NaN handling per C99)
     OP_FMAX,              // pops b, a (int/float); pushes fmax(a,b) (NaN handling per C99)
 
+    // Rust FFI demo opcode(s)
+    OP_RUST_HELLO,        // pushes string returned from Rust (hello world)
+
     /* Notcurses TUI (optional) */
     OP_NC_INIT,           // initializes Notcurses; returns 1 on success, 0 on failure
     OP_NC_SHUTDOWN,       // shuts down Notcurses; returns 0
diff --git a/src/parser.c b/src/parser.c
index e110f68..78da293 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -786,6 +786,13 @@ static int emit_primary(Bytecode *bc, const char *src, size_t len, size_t *pos)
                 free(name);
                 return 1;
             }
+            if (strcmp(name, "rust_hello") == 0) {
+                (*pos)++; /* '(' */
+                if (!consume_char(src, len, pos, ')')) { parser_fail(*pos, "rust_hello expects ()"); free(name); return 0; }
+                bytecode_add_instruction(bc, OP_RUST_HELLO, 0);
+                free(name);
+                return 1;
+            }
             if (strcmp(name, "os_list_dir") == 0) {
                 (*pos)++; /* '(' */
                 if (!emit_expression(bc, src, len, pos)) { parser_fail(*pos, "os_list_dir expects (path)"); free(name); return 0; }
diff --git a/src/rust/Cargo.toml b/src/rust/Cargo.toml
new file mode 100644
index 0000000..a6c7500
--- /dev/null
+++ b/src/rust/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "hello-c-world"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["staticlib"]
+
+[profile.release]
+panic = "abort"
+# Optimize for minimal size
+opt-level = "z"
+codegen-units = 1
+lto = true
+# If Cargo is new enough, this strips symbols from Rust objects
+strip = "symbols"
diff --git a/src/rust/src/lib.rs b/src/rust/src/lib.rs
new file mode 100644
index 0000000..12121ed
--- /dev/null
+++ b/src/rust/src/lib.rs
@@ -0,0 +1,44 @@
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-27
+ */
+
+#![no_std]
+
+#[repr(C)]
+pub struct Vm;
+
+extern "C" {
+    fn vm_pop_i64(vm: *mut Vm) -> i64;
+    fn vm_push_i64(vm: *mut Vm, v: i64);
+}
+
+// Submodule with additional Rust VM math ops (exported via C ABI)
+pub mod vm;
+
+#[no_mangle]
+pub extern "C" fn fun_op_radd(vm: *mut Vm) -> i32 {
+    unsafe {
+        let b = vm_pop_i64(vm);
+        let a = vm_pop_i64(vm);
+        vm_push_i64(vm, a + b);
+    }
+    0
+}
+
+#[no_mangle]
+pub extern "C" fn fun_rust_get_string() -> *const core::ffi::c_char {
+    b"Hello from Rust ops!\0".as_ptr() as *const _
+}
+
+// Minimal panic handler for no_std; abort behavior requested via Cargo profile
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
diff --git a/src/test_opcodes.c b/src/test_opcodes.c
index c6c6e3a..db79283 100644
--- a/src/test_opcodes.c
+++ b/src/test_opcodes.c
@@ -46,6 +46,29 @@ int main() {
     }
 
     vm_clear_output(&vm);
+
+    /* --- Rust FFI demo: call a Rust opcode and string function --- */
+#ifdef FUN_WITH_RUST
+    extern int fun_op_radd(VM *vm);
+    extern const char *fun_rust_get_string(void);
+
+    printf("=== Rust FFI demo ===\n");
+    const char *rs = fun_rust_get_string();
+    if (rs) {
+        printf("Rust says: %s\n", rs);
+    }
+
+    /* prepare stack: push 10 and 32, then call Rust add -> expect 42 */
+    vm_push_i64(&vm, 10);
+    vm_push_i64(&vm, 32);
+    int rc = fun_op_radd(&vm);
+    printf("fun_op_radd rc=%d\n", rc);
+    long long sum = (long long)vm_pop_i64(&vm);
+    printf("Rust op result: %lld\n", sum);
+#else
+    printf("=== Rust FFI demo (disabled; build with -DFUN_WITH_RUST=ON) ===\n");
+#endif
+
     vm_free(&vm);
     bytecode_free(bc);
     return 0;
diff --git a/src/vm.c b/src/vm.c
index 16ac20b..4c78db9 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -466,6 +466,28 @@ static Value pop_value(VM *vm) {
     return vm->stack[vm->sp--]; /* caller owns returned Value */
 }
 
+/* --- C ABI helpers for Rust FFI --- */
+int64_t vm_pop_i64(VM *vm) {
+    Value v = pop_value(vm);
+    int64_t out = 0;
+    if (v.type == VAL_INT) {
+        out = v.i;
+    } else if (v.type == VAL_FLOAT) {
+        out = (int64_t) v.d;
+    } else {
+        fprintf(stderr, "Runtime type error: expected int/float on stack, got %s\n", value_type_name(v.type));
+        free_value(v);
+        exit(1);
+    }
+    /* free any dynamic payload (no-op for int/float) */
+    free_value(v);
+    return out;
+}
+
+void vm_push_i64(VM *vm, int64_t v) {
+    push_value(vm, make_int(v));
+}
+
 static void frame_init(Frame *f) {
     f->fn = NULL;
     f->ip = 0;
@@ -734,6 +756,9 @@ void vm_run(VM *vm, Bytecode *entry) {
             #include "vm/math/isqrt.c"
             #include "vm/math/sign.c"
 
+            /* Rust FFI demo opcode(s) */
+            #include "vm/rust/hello.c"
+
             #include "vm/os/env.c"
             #include "vm/os/env_all.c"
             #include "vm/os/fun_version.c"
diff --git a/src/vm.h b/src/vm.h
index a08a891..0e1d528 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -54,6 +54,9 @@ static const char *opcode_names[] = {
     "SERIAL_OPEN","SERIAL_CONFIG","SERIAL_SEND","SERIAL_RECV","SERIAL_CLOSE",
     "TK_EVAL","TK_RESULT","TK_LOOP","TK_WM_TITLE","TK_LABEL","TK_BUTTON","TK_PACK",
     "TRY_PUSH","TRY_POP","THROW",
+    "FMIN","FMAX",
+    /* Rust FFI demo */
+    "RUST_HELLO",
     /* Notcurses TUI (optional) */
     "NC_INIT","NC_SHUTDOWN","NC_CLEAR","NC_DRAW_TEXT","NC_GETCH"
 };
@@ -143,4 +146,16 @@ static inline int opcode_is_valid(int op) {
     return op >= OP_NOP && op <= OP_NC_GETCH;  // all current opcodes (including optional NC_*)
 }
 
+/* --- Minimal C ABI helpers for FFI (Rust opcode experiments) --- */
+/* Pop an int64 from VM stack (errors if not an int/float); returns integer-converted value. */
+int64_t vm_pop_i64(VM *vm);
+/* Push an int64 onto VM stack. */
+void vm_push_i64(VM *vm, int64_t v);
+
+/* Example Rust-implemented opcode (adds top two ints on stack) */
+int fun_op_radd(VM *vm);
+
+/* Example Rust function returning a demo C string (null-terminated). */
+const char *fun_rust_get_string(void);
+
 #endif
diff --git a/src/vm/rust/hello.c b/src/vm/rust/hello.c
new file mode 100644
index 0000000..709d8c6
--- /dev/null
+++ b/src/vm/rust/hello.c
@@ -0,0 +1,27 @@
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2026-01-27
+ */
+ 
+ /**
+ * Rust FFI demo opcode: OP_RUST_HELLO
+ * When executed, it pushes a hello string returned by Rust onto the VM stack.
+ */
+
+case OP_RUST_HELLO: {
+#ifdef FUN_WITH_RUST
+    const char *s = fun_rust_get_string();
+    if (!s) s = "";
+    push_value(vm, make_string(s));
+#else
+    vm_raise_error(vm, "RUST_HELLO requires FUN_WITH_RUST=ON at build time");
+    push_value(vm, make_nil());
+#endif
+    break;
+}