diff --git a/Cargo.lock b/Cargo.lock
index 9963e89..ac1ca02 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -358,6 +358,15 @@ version = "0.1.1"
 dependencies = [
  "anyhow",
  "clap",
+ "herkos-core",
+ "wat",
+]
+
+[[package]]
+name = "herkos-core"
+version = "0.1.1"
+dependencies = [
+ "anyhow",
  "heck",
  "wasmparser 0.227.1",
  "wat",
@@ -376,7 +385,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "criterion",
- "herkos",
+ "herkos-core",
  "herkos-runtime",
  "wat",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index f44aa1f..40baed4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,8 +1,12 @@
 [workspace]
 resolver = "2"
-members = ["crates/herkos-runtime", "crates/herkos", "crates/herkos-tests"]
+members = ["crates/herkos-runtime", "crates/herkos-core", "crates/herkos", "crates/herkos-tests"]
 
-exclude = ["examples/c-to-wasm-to-rust", "examples/inter-module-lending"]
+exclude = [
+    "examples/c-to-wasm-to-rust",
+    "examples/inter-module-lending",
+    "examples/herkos-bootstrap",
+]
 
 [workspace.dependencies]
 anyhow = "1"
diff --git a/crates/herkos-core/Cargo.toml b/crates/herkos-core/Cargo.toml
new file mode 100644
index 0000000..ea1d2f2
--- /dev/null
+++ b/crates/herkos-core/Cargo.toml
@@ -0,0 +1,23 @@
+[package]
+name = "herkos-core"
+version = "0.1.1"
+edition = "2021"
+description = "Compile-Time Memory Isolation via WebAssembly and Rust Transpilation — core library"
+license = "Apache-2.0"
+repository = "https://github.com/arnoox/herkos"
+homepage = "https://github.com/arnoox/herkos"
+authors = ["Arnaud Riess"]
+keywords = ["webassembly", "wasm", "transpiler", "rust", "isolation"]
+categories = ["wasm", "development-tools::build-utils"]
+readme = "../../README.md"
+
+[lib]
+crate-type = ["rlib", "cdylib"]
+
+[dependencies]
+wasmparser = { workspace = true }
+anyhow = { workspace = true }
+heck = { workspace = true }
+
+[dev-dependencies]
+wat = { workspace = true }
diff --git a/crates/herkos/src/backend/mod.rs b/crates/herkos-core/src/backend/mod.rs
similarity index 100%
rename from crates/herkos/src/backend/mod.rs
rename to crates/herkos-core/src/backend/mod.rs
diff --git a/crates/herkos/src/backend/safe.rs b/crates/herkos-core/src/backend/safe.rs
similarity index 100%
rename from crates/herkos/src/backend/safe.rs
rename to crates/herkos-core/src/backend/safe.rs
diff --git a/crates/herkos-core/src/c_ffi.rs b/crates/herkos-core/src/c_ffi.rs
new file mode 100644
index 0000000..192cfdd
--- /dev/null
+++ b/crates/herkos-core/src/c_ffi.rs
@@ -0,0 +1,126 @@
+//! C FFI interface for the herkos transpiler.
+//!
+//! This module exports C-compatible functions for transpiling WebAssembly binaries.
+//! The caller is responsible for freeing allocated memory using `herkos_free`.
+
+use std::os::raw::{c_char, c_int, c_uchar};
+use std::ptr;
+use std::slice;
+
+use crate::{transpile, TranspileOptions};
+
+/// Result structure for C FFI calls
+#[repr(C)]
+pub struct HerkosResult {
+    /// Pointer to the output Rust string (must be freed with herkos_free)
+    pub output: *mut c_char,
+    /// Length of the output string in bytes (not including null terminator)
+    pub output_len: usize,
+    /// Error code: 0 on success, non-zero on failure
+    pub error_code: c_int,
+    /// Error message (null if no error)
+    pub error_msg: *mut c_char,
+}
+
+/// Error codes
+const HERKOS_OK: c_int = 0;
+const HERKOS_ERROR_TRANSPILE: c_int = 1;
+const HERKOS_ERROR_INVALID_INPUT: c_int = 2;
+
+/// Transpile WebAssembly bytes to Rust source code using default options.
+///
+/// # Arguments
+/// * `wasm_bytes` - Pointer to the WebAssembly binary data
+/// * `wasm_len` - Length of the WebAssembly binary in bytes
+///
+/// # Returns
+/// A `HerkosResult` struct containing:
+/// - `output`: Pointer to allocated Rust source code (must be freed with `herkos_free`)
+/// - `output_len`: Length of the output string in bytes
+/// - `error_code`: 0 on success, non-zero on error
+/// - `error_msg`: Null on success, error message string on failure
+///
+/// # Safety
+/// - The caller must ensure `wasm_bytes` points to valid memory of at least `wasm_len` bytes
+/// - The returned `output` pointer must be freed using `herkos_free`
+/// - The returned `error_msg` pointer (if not null) must be freed using `herkos_free`
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+#[no_mangle]
+pub extern "C" fn herkos_transpile(wasm_bytes: *const c_uchar, wasm_len: usize) -> HerkosResult {
+    // Validate input pointers
+    if wasm_bytes.is_null() {
+        let msg = "wasm_bytes pointer is null";
+        return HerkosResult {
+            output: ptr::null_mut(),
+            output_len: 0,
+            error_code: HERKOS_ERROR_INVALID_INPUT,
+            error_msg: allocate_string(msg),
+        };
+    }
+
+    if wasm_len == 0 {
+        let msg = "wasm_len is 0";
+        return HerkosResult {
+            output: ptr::null_mut(),
+            output_len: 0,
+            error_code: HERKOS_ERROR_INVALID_INPUT,
+            error_msg: allocate_string(msg),
+        };
+    }
+
+    // Convert raw pointer to safe slice
+    let wasm_slice = unsafe { slice::from_raw_parts(wasm_bytes, wasm_len) };
+
+    // Use default transpilation options
+    let options = TranspileOptions::default();
+
+    // Perform transpilation
+    match transpile(wasm_slice, &options) {
+        Ok(rust_code) => {
+            let output = allocate_string(&rust_code);
+            let output_len = rust_code.len();
+            HerkosResult {
+                output,
+                output_len,
+                error_code: HERKOS_OK,
+                error_msg: ptr::null_mut(),
+            }
+        }
+        Err(e) => {
+            let error_msg = format!("{:#}", e);
+            HerkosResult {
+                output: ptr::null_mut(),
+                output_len: 0,
+                error_code: HERKOS_ERROR_TRANSPILE,
+                error_msg: allocate_string(&error_msg),
+            }
+        }
+    }
+}
+
+/// Free memory allocated by herkos functions.
+///
+/// # Arguments
+/// * `ptr` - Pointer to memory allocated by herkos (e.g., output from `herkos_transpile`)
+///
+/// # Safety
+/// - The pointer must have been returned by a herkos function
+/// - The pointer must not have been freed already
+/// - After calling this function, the pointer must not be used
+#[allow(clippy::not_unsafe_ptr_arg_deref)]
+#[no_mangle]
+pub extern "C" fn herkos_free(ptr: *mut c_char) {
+    if !ptr.is_null() {
+        unsafe {
+            let _ = std::ffi::CString::from_raw(ptr);
+        }
+    }
+}
+
+/// Helper function to allocate a Rust string as C-compatible memory
+fn allocate_string(s: &str) -> *mut c_char {
+    match std::ffi::CString::new(s) {
+        Ok(cstring) => cstring.into_raw(),
+        Err(_) => ptr::null_mut(),
+    }
+}
diff --git a/crates/herkos/src/codegen/constructor.rs b/crates/herkos-core/src/codegen/constructor.rs
similarity index 100%
rename from crates/herkos/src/codegen/constructor.rs
rename to crates/herkos-core/src/codegen/constructor.rs
diff --git a/crates/herkos/src/codegen/export.rs b/crates/herkos-core/src/codegen/export.rs
similarity index 100%
rename from crates/herkos/src/codegen/export.rs
rename to crates/herkos-core/src/codegen/export.rs
diff --git a/crates/herkos/src/codegen/function.rs b/crates/herkos-core/src/codegen/function.rs
similarity index 100%
rename from crates/herkos/src/codegen/function.rs
rename to crates/herkos-core/src/codegen/function.rs
diff --git a/crates/herkos/src/codegen/instruction.rs b/crates/herkos-core/src/codegen/instruction.rs
similarity index 100%
rename from crates/herkos/src/codegen/instruction.rs
rename to crates/herkos-core/src/codegen/instruction.rs
diff --git a/crates/herkos/src/codegen/mod.rs b/crates/herkos-core/src/codegen/mod.rs
similarity index 100%
rename from crates/herkos/src/codegen/mod.rs
rename to crates/herkos-core/src/codegen/mod.rs
diff --git a/crates/herkos/src/codegen/module.rs b/crates/herkos-core/src/codegen/module.rs
similarity index 100%
rename from crates/herkos/src/codegen/module.rs
rename to crates/herkos-core/src/codegen/module.rs
diff --git a/crates/herkos/src/codegen/traits.rs b/crates/herkos-core/src/codegen/traits.rs
similarity index 100%
rename from crates/herkos/src/codegen/traits.rs
rename to crates/herkos-core/src/codegen/traits.rs
diff --git a/crates/herkos/src/codegen/types.rs b/crates/herkos-core/src/codegen/types.rs
similarity index 100%
rename from crates/herkos/src/codegen/types.rs
rename to crates/herkos-core/src/codegen/types.rs
diff --git a/crates/herkos/src/codegen/utils.rs b/crates/herkos-core/src/codegen/utils.rs
similarity index 100%
rename from crates/herkos/src/codegen/utils.rs
rename to crates/herkos-core/src/codegen/utils.rs
diff --git a/crates/herkos/src/ir/builder/analysis.rs b/crates/herkos-core/src/ir/builder/analysis.rs
similarity index 100%
rename from crates/herkos/src/ir/builder/analysis.rs
rename to crates/herkos-core/src/ir/builder/analysis.rs
diff --git a/crates/herkos/src/ir/builder/assembly.rs b/crates/herkos-core/src/ir/builder/assembly.rs
similarity index 100%
rename from crates/herkos/src/ir/builder/assembly.rs
rename to crates/herkos-core/src/ir/builder/assembly.rs
diff --git a/crates/herkos/src/ir/builder/core.rs b/crates/herkos-core/src/ir/builder/core.rs
similarity index 100%
rename from crates/herkos/src/ir/builder/core.rs
rename to crates/herkos-core/src/ir/builder/core.rs
diff --git a/crates/herkos/src/ir/builder/mod.rs b/crates/herkos-core/src/ir/builder/mod.rs
similarity index 100%
rename from crates/herkos/src/ir/builder/mod.rs
rename to crates/herkos-core/src/ir/builder/mod.rs
diff --git a/crates/herkos/src/ir/builder/translate.rs b/crates/herkos-core/src/ir/builder/translate.rs
similarity index 100%
rename from crates/herkos/src/ir/builder/translate.rs
rename to crates/herkos-core/src/ir/builder/translate.rs
diff --git a/crates/herkos/src/ir/lower_phis.rs b/crates/herkos-core/src/ir/lower_phis.rs
similarity index 100%
rename from crates/herkos/src/ir/lower_phis.rs
rename to crates/herkos-core/src/ir/lower_phis.rs
diff --git a/crates/herkos/src/ir/mod.rs b/crates/herkos-core/src/ir/mod.rs
similarity index 100%
rename from crates/herkos/src/ir/mod.rs
rename to crates/herkos-core/src/ir/mod.rs
diff --git a/crates/herkos/src/ir/types.rs b/crates/herkos-core/src/ir/types.rs
similarity index 99%
rename from crates/herkos/src/ir/types.rs
rename to crates/herkos-core/src/ir/types.rs
index c331e28..d5b75c4 100644
--- a/crates/herkos/src/ir/types.rs
+++ b/crates/herkos-core/src/ir/types.rs
@@ -581,12 +581,11 @@ pub enum UnOp {
     I32WrapI64,    // i64 → i32 (truncate to low 32 bits)
     I64ExtendI32S, // i32 → i64 (sign-extend)
     I64ExtendI32U, // i32 → i64 (zero-extend)
-    // Sign-extension ops (Wasm sign-extension-ops proposal)
-    I32Extend8S,  // sign-extend 8-bit value in i32
-    I32Extend16S, // sign-extend 16-bit value in i32
-    I64Extend8S,  // sign-extend 8-bit value in i64
-    I64Extend16S, // sign-extend 16-bit value in i64
-    I64Extend32S, // sign-extend 32-bit value in i64
+    I32Extend8S,   // i32 → i32 (sign-extend low 8 bits)
+    I32Extend16S,  // i32 → i32 (sign-extend low 16 bits)
+    I64Extend8S,   // i64 → i64 (sign-extend low 8 bits)
+    I64Extend16S,  // i64 → i64 (sign-extend low 16 bits)
+    I64Extend32S,  // i64 → i64 (sign-extend low 32 bits)
 
     // Conversions: float → integer (trapping on NaN/overflow)
     I32TruncF32S,
diff --git a/crates/herkos/src/lib.rs b/crates/herkos-core/src/lib.rs
similarity index 96%
rename from crates/herkos/src/lib.rs
rename to crates/herkos-core/src/lib.rs
index 18f3b6a..3c86c44 100644
--- a/crates/herkos/src/lib.rs
+++ b/crates/herkos-core/src/lib.rs
@@ -1,9 +1,10 @@
-//! herkos — WebAssembly to Rust transpiler.
+//! herkos-core — WebAssembly to Rust transpiler.
 //!
 //! This crate provides the core transpilation pipeline that converts WebAssembly
 //! modules into memory-safe Rust source code.
 
 pub mod backend;
+pub mod c_ffi;
 pub mod codegen;
 pub mod ir;
 pub mod optimizer;
@@ -53,7 +54,7 @@ impl Default for TranspileOptions {
 ///
 /// # Example
 /// ```no_run
-/// use herkos::{transpile, TranspileOptions};
+/// use herkos_core::{transpile, TranspileOptions};
 ///
 /// let wasm_bytes = std::fs::read("input.wasm").unwrap();
 /// let options = TranspileOptions::default();
diff --git a/crates/herkos/src/optimizer/dead_blocks.rs b/crates/herkos-core/src/optimizer/dead_blocks.rs
similarity index 100%
rename from crates/herkos/src/optimizer/dead_blocks.rs
rename to crates/herkos-core/src/optimizer/dead_blocks.rs
diff --git a/crates/herkos/src/optimizer/mod.rs b/crates/herkos-core/src/optimizer/mod.rs
similarity index 100%
rename from crates/herkos/src/optimizer/mod.rs
rename to crates/herkos-core/src/optimizer/mod.rs
diff --git a/crates/herkos/src/parser/mod.rs b/crates/herkos-core/src/parser/mod.rs
similarity index 100%
rename from crates/herkos/src/parser/mod.rs
rename to crates/herkos-core/src/parser/mod.rs
diff --git a/crates/herkos-tests/Cargo.toml b/crates/herkos-tests/Cargo.toml
index b7ddd42..6728e31 100644
--- a/crates/herkos-tests/Cargo.toml
+++ b/crates/herkos-tests/Cargo.toml
@@ -13,7 +13,7 @@ herkos-runtime = { path = "../herkos-runtime" }
 [build-dependencies]
 anyhow = { workspace = true }
 wat = { workspace = true }
-herkos = { path = "../herkos" }
+herkos-core = { path = "../herkos-core" }
 
 [dev-dependencies]
 criterion = "0.8.2"
diff --git a/crates/herkos-tests/build.rs b/crates/herkos-tests/build.rs
index 045ebc0..c2fcef9 100644
--- a/crates/herkos-tests/build.rs
+++ b/crates/herkos-tests/build.rs
@@ -1,5 +1,5 @@
 use anyhow::{Context, Result};
-use herkos::{transpile, TranspileOptions};
+use herkos_core::{transpile, TranspileOptions};
 use std::env;
 use std::fs;
 use std::path::{Path, PathBuf};
diff --git a/crates/herkos-tests/data/wat/conversions.wat b/crates/herkos-tests/data/wat/conversions.wat
index bf4731e..8ddb18e 100644
--- a/crates/herkos-tests/data/wat/conversions.wat
+++ b/crates/herkos-tests/data/wat/conversions.wat
@@ -35,6 +35,26 @@
   (func (param i32) (result f32)
     local.get 0
     f32.reinterpret_i32)
+  ;; i32.extend8_s: sign-extend from i8
+  (func (param i32) (result i32)
+    local.get 0
+    i32.extend8_s)
+  ;; i32.extend16_s: sign-extend from i16
+  (func (param i32) (result i32)
+    local.get 0
+    i32.extend16_s)
+  ;; i64.extend8_s: sign-extend i64 from i8
+  (func (param i64) (result i64)
+    local.get 0
+    i64.extend8_s)
+  ;; i64.extend16_s: sign-extend i64 from i16
+  (func (param i64) (result i64)
+    local.get 0
+    i64.extend16_s)
+  ;; i64.extend32_s: sign-extend i64 from i32
+  (func (param i64) (result i64)
+    local.get 0
+    i64.extend32_s)
   (export "wrap_i64" (func 0))
   (export "extend_i32_s" (func 1))
   (export "extend_i32_u" (func 2))
@@ -43,4 +63,9 @@
   (export "demote_f64" (func 5))
   (export "promote_f32" (func 6))
   (export "reinterpret_f32" (func 7))
-  (export "reinterpret_i32" (func 8)))
+  (export "reinterpret_i32" (func 8))
+  (export "extend8_s" (func 9))
+  (export "extend16_s" (func 10))
+  (export "i64_extend8_s" (func 11))
+  (export "i64_extend16_s" (func 12))
+  (export "i64_extend32_s" (func 13)))
diff --git a/crates/herkos-tests/tests/numeric_ops.rs b/crates/herkos-tests/tests/numeric_ops.rs
index 9b33974..ef54f54 100644
--- a/crates/herkos-tests/tests/numeric_ops.rs
+++ b/crates/herkos-tests/tests/numeric_ops.rs
@@ -168,6 +168,65 @@ fn test_i64_extend_i32_u() {
     );
 }
 
+#[test]
+fn test_i32_extend8_s() {
+    let mut conversions_mod = conversions::new().unwrap();
+    // Sign-extend from i8 to i32
+    assert_eq!(conversions_mod.extend8_s(0x42).unwrap(), 0x42);
+    assert_eq!(conversions_mod.extend8_s(0xFF).unwrap(), -1); // 0xFF as i8 = -1
+    assert_eq!(conversions_mod.extend8_s(0x7F).unwrap(), 127); // 0x7F as i8 = 127
+    assert_eq!(conversions_mod.extend8_s(0x80).unwrap(), -128); // 0x80 as i8 = -128
+}
+
+#[test]
+fn test_i32_extend16_s() {
+    let mut conversions_mod = conversions::new().unwrap();
+    // Sign-extend from i16 to i32
+    assert_eq!(conversions_mod.extend16_s(0x4242).unwrap(), 0x4242);
+    assert_eq!(conversions_mod.extend16_s(0xFFFF).unwrap(), -1); // 0xFFFF as i16 = -1
+    assert_eq!(conversions_mod.extend16_s(0x7FFF).unwrap(), 32767); // max positive i16
+    assert_eq!(conversions_mod.extend16_s(0x8000).unwrap(), -32768); // min negative i16
+}
+
+#[test]
+fn test_i64_extend8_s() {
+    let mut conversions_mod = conversions::new().unwrap();
+    // Sign-extend from i8 to i64
+    assert_eq!(conversions_mod.i64_extend8_s(0x42).unwrap(), 0x42i64);
+    assert_eq!(conversions_mod.i64_extend8_s(0xFF).unwrap(), -1i64); // 0xFF as i8 = -1
+    assert_eq!(conversions_mod.i64_extend8_s(0x7F).unwrap(), 127i64);
+    assert_eq!(conversions_mod.i64_extend8_s(0x80).unwrap(), -128i64);
+}
+
+#[test]
+fn test_i64_extend16_s() {
+    let mut conversions_mod = conversions::new().unwrap();
+    // Sign-extend from i16 to i64
+    assert_eq!(conversions_mod.i64_extend16_s(0x4242).unwrap(), 0x4242i64);
+    assert_eq!(conversions_mod.i64_extend16_s(0xFFFF).unwrap(), -1i64); // 0xFFFF as i16 = -1
+    assert_eq!(conversions_mod.i64_extend16_s(0x7FFF).unwrap(), 32767i64);
+    assert_eq!(conversions_mod.i64_extend16_s(0x8000).unwrap(), -32768i64);
+}
+
+#[test]
+fn test_i64_extend32_s() {
+    let mut conversions_mod = conversions::new().unwrap();
+    // Sign-extend from i32 to i64
+    assert_eq!(
+        conversions_mod.i64_extend32_s(0x42424242).unwrap(),
+        0x42424242i64
+    );
+    assert_eq!(conversions_mod.i64_extend32_s(0xFFFFFFFF).unwrap(), -1i64); // -1 as i32
+    assert_eq!(
+        conversions_mod.i64_extend32_s(0x7FFFFFFF).unwrap(),
+        i32::MAX as i64
+    );
+    assert_eq!(
+        conversions_mod.i64_extend32_s(0x80000000).unwrap(),
+        i32::MIN as i64
+    );
+}
+
 #[test]
 fn test_f64_convert_i32_s() {
     let mut conversions_mod = conversions::new().unwrap();
diff --git a/crates/herkos/Cargo.toml b/crates/herkos/Cargo.toml
index e3a4c30..6af2e93 100644
--- a/crates/herkos/Cargo.toml
+++ b/crates/herkos/Cargo.toml
@@ -12,10 +12,9 @@ categories = ["wasm", "development-tools::build-utils"]
 readme = "../../README.md"
 
 [dependencies]
-wasmparser = { workspace = true }
+herkos-core = { path = "../herkos-core" }
 anyhow = { workspace = true }
 clap = { workspace = true }
-heck = { workspace = true }
 
 [dev-dependencies]
 wat = { workspace = true }
diff --git a/crates/herkos/src/main.rs b/crates/herkos/src/main.rs
index 6670ca6..852bb54 100644
--- a/crates/herkos/src/main.rs
+++ b/crates/herkos/src/main.rs
@@ -1,6 +1,6 @@
 use anyhow::{Context, Result};
 use clap::Parser;
-use herkos::{transpile, TranspileOptions};
+use herkos_core::{transpile, TranspileOptions};
 use std::fs;
 use std::path::PathBuf;
 
diff --git a/crates/herkos/tests/e2e.rs b/crates/herkos/tests/e2e.rs
index 95efdf1..87b2f28 100644
--- a/crates/herkos/tests/e2e.rs
+++ b/crates/herkos/tests/e2e.rs
@@ -3,7 +3,7 @@
 //! These tests verify the complete pipeline: Wasm → IR → Rust source.
 
 use anyhow::{Context, Result};
-use herkos::{transpile, TranspileOptions};
+use herkos_core::{transpile, TranspileOptions};
 
 /// Helper to transpile WAT source to Rust code.
 fn transpile_wat(wat_source: &str) -> Result<String> {