diff --git a/bootstrap/src/host/mod.rs b/bootstrap/src/host/mod.rs
index d4958bb9..1b1ab80c 100644
--- a/bootstrap/src/host/mod.rs
+++ b/bootstrap/src/host/mod.rs
@@ -17,7 +17,9 @@ pub mod csr_map;
 pub mod driver;
 pub mod irq;
 pub mod mmio;
+pub mod serial;
 
 pub use driver::{BitnetDriver, CsrSnapshot, DriverError};
 pub use irq::{IrqCallback, IrqCounters, IrqDrivenDriver, IrqHandler, IrqSource, ServiceReport};
 pub use mmio::{MmioOp, MmioRecord, MockMmio};
+pub use serial::{Deserializer, SerialError, Serializer};
diff --git a/bootstrap/src/host/serial.rs b/bootstrap/src/host/serial.rs
new file mode 100644
index 00000000..4457bd1f
--- /dev/null
+++ b/bootstrap/src/host/serial.rs
@@ -0,0 +1,292 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum SerialError {
+    EndOfBuffer { need: usize, have: usize },
+    Overflow { capacity: usize, requested: usize },
+}
+
+impl std::fmt::Display for SerialError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            SerialError::EndOfBuffer { need, have } => {
+                write!(f, "end of buffer: need {need}, have {have}")
+            }
+            SerialError::Overflow { capacity, requested } => {
+                write!(f, "overflow: capacity {capacity}, requested {requested}")
+            }
+        }
+    }
+}
+
+impl std::error::Error for SerialError {}
+
+#[derive(Debug, Clone)]
+pub struct Serializer {
+    buf: Vec<u8>,
+}
+
+impl Serializer {
+    pub fn new(capacity: usize) -> Self {
+        Self {
+            buf: Vec::with_capacity(capacity),
+        }
+    }
+
+    pub fn write_u8(&mut self, v: u8) {
+        self.buf.push(v);
+    }
+
+    pub fn write_u16_le(&mut self, v: u16) {
+        self.buf.extend_from_slice(&v.to_le_bytes());
+    }
+
+    pub fn write_u32_le(&mut self, v: u32) {
+        self.buf.extend_from_slice(&v.to_le_bytes());
+    }
+
+    pub fn write_u64_le(&mut self, v: u64) {
+        self.buf.extend_from_slice(&v.to_le_bytes());
+    }
+
+    pub fn write_bytes(&mut self, data: &[u8]) {
+        self.buf.extend_from_slice(data);
+    }
+
+    pub fn write_cstr(&mut self, s: &str) {
+        self.buf.extend_from_slice(s.as_bytes());
+        self.buf.push(0);
+    }
+
+    pub fn len(&self) -> usize {
+        self.buf.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.buf.is_empty()
+    }
+
+    pub fn into_bytes(self) -> Vec<u8> {
+        self.buf
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        &self.buf
+    }
+
+    pub fn clear(&mut self) {
+        self.buf.clear();
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Deserializer<'a> {
+    data: &'a [u8],
+    pos: usize,
+}
+
+impl<'a> Deserializer<'a> {
+    pub fn new(data: &'a [u8]) -> Self {
+        Self { data, pos: 0 }
+    }
+
+    pub fn remaining(&self) -> usize {
+        self.data.len().saturating_sub(self.pos)
+    }
+
+    pub fn pos(&self) -> usize {
+        self.pos
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.pos >= self.data.len()
+    }
+
+    pub fn read_u8(&mut self) -> Result<u8, SerialError> {
+        if self.remaining() < 1 {
+            return Err(SerialError::EndOfBuffer { need: 1, have: self.remaining() });
+        }
+        let v = self.data[self.pos];
+        self.pos += 1;
+        Ok(v)
+    }
+
+    pub fn read_u16_le(&mut self) -> Result<u16, SerialError> {
+        if self.remaining() < 2 {
+            return Err(SerialError::EndOfBuffer { need: 2, have: self.remaining() });
+        }
+        let v = u16::from_le_bytes([self.data[self.pos], self.data[self.pos + 1]]);
+        self.pos += 2;
+        Ok(v)
+    }
+
+    pub fn read_u32_le(&mut self) -> Result<u32, SerialError> {
+        if self.remaining() < 4 {
+            return Err(SerialError::EndOfBuffer { need: 4, have: self.remaining() });
+        }
+        let v = u32::from_le_bytes([
+            self.data[self.pos],
+            self.data[self.pos + 1],
+            self.data[self.pos + 2],
+            self.data[self.pos + 3],
+        ]);
+        self.pos += 4;
+        Ok(v)
+    }
+
+    pub fn read_u64_le(&mut self) -> Result<u64, SerialError> {
+        if self.remaining() < 8 {
+            return Err(SerialError::EndOfBuffer { need: 8, have: self.remaining() });
+        }
+        let bytes: [u8; 8] = self.data[self.pos..self.pos + 8].try_into().unwrap();
+        let v = u64::from_le_bytes(bytes);
+        self.pos += 8;
+        Ok(v)
+    }
+
+    pub fn read_bytes(&mut self, len: usize) -> Result<&'a [u8], SerialError> {
+        if self.remaining() < len {
+            return Err(SerialError::EndOfBuffer { need: len, have: self.remaining() });
+        }
+        let slice = &self.data[self.pos..self.pos + len];
+        self.pos += len;
+        Ok(slice)
+    }
+
+    pub fn read_cstr(&mut self) -> Result<&'a str, SerialError> {
+        let start = self.pos;
+        while self.pos < self.data.len() && self.data[self.pos] != 0 {
+            self.pos += 1;
+        }
+        if self.pos >= self.data.len() {
+            return Err(SerialError::EndOfBuffer { need: 1, have: 0 });
+        }
+        let s = std::str::from_utf8(&self.data[start..self.pos]).unwrap_or("");
+        self.pos += 1;
+        Ok(s)
+    }
+
+    pub fn skip(&mut self, len: usize) -> Result<(), SerialError> {
+        if self.remaining() < len {
+            return Err(SerialError::EndOfBuffer { need: len, have: self.remaining() });
+        }
+        self.pos += len;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn serializer_u8() {
+        let mut s = Serializer::new(16);
+        s.write_u8(0xAB);
+        assert_eq!(s.as_slice(), &[0xAB]);
+    }
+
+    #[test]
+    fn serializer_u16_le() {
+        let mut s = Serializer::new(16);
+        s.write_u16_le(0x1234);
+        assert_eq!(s.as_slice(), &[0x34, 0x12]);
+    }
+
+    #[test]
+    fn serializer_u32_le() {
+        let mut s = Serializer::new(16);
+        s.write_u32_le(0x12345678);
+        assert_eq!(s.as_slice(), &[0x78, 0x56, 0x34, 0x12]);
+    }
+
+    #[test]
+    fn serializer_u64_le() {
+        let mut s = Serializer::new(16);
+        s.write_u64_le(0x0102030405060708);
+        assert_eq!(s.as_slice(), &[0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01]);
+    }
+
+    #[test]
+    fn serializer_cstr() {
+        let mut s = Serializer::new(16);
+        s.write_cstr("hello");
+        assert_eq!(s.as_slice(), b"hello\0");
+    }
+
+    #[test]
+    fn deserializer_u8() {
+        let mut d = Deserializer::new(&[0xAB]);
+        assert_eq!(d.read_u8().unwrap(), 0xAB);
+    }
+
+    #[test]
+    fn deserializer_u16_le() {
+        let mut d = Deserializer::new(&[0x34, 0x12]);
+        assert_eq!(d.read_u16_le().unwrap(), 0x1234);
+    }
+
+    #[test]
+    fn deserializer_u32_le() {
+        let mut d = Deserializer::new(&[0x78, 0x56, 0x34, 0x12]);
+        assert_eq!(d.read_u32_le().unwrap(), 0x12345678);
+    }
+
+    #[test]
+    fn deserializer_u64_le() {
+        let mut d = Deserializer::new(&[0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01]);
+        assert_eq!(d.read_u64_le().unwrap(), 0x0102030405060708);
+    }
+
+    #[test]
+    fn roundtrip() {
+        let mut s = Serializer::new(32);
+        s.write_u8(1);
+        s.write_u16_le(0x1234);
+        s.write_u32_le(0xDEADBEEF);
+        s.write_u64_le(0xCAFEBABE_DEADBEEF);
+        let bytes = s.into_bytes();
+        let mut d = Deserializer::new(&bytes);
+        assert_eq!(d.read_u8().unwrap(), 1);
+        assert_eq!(d.read_u16_le().unwrap(), 0x1234);
+        assert_eq!(d.read_u32_le().unwrap(), 0xDEADBEEF);
+        assert_eq!(d.read_u64_le().unwrap(), 0xCAFEBABE_DEADBEEF);
+    }
+
+    #[test]
+    fn read_bytes() {
+        let data = b"hello";
+        let mut d = Deserializer::new(data);
+        assert_eq!(d.read_bytes(3).unwrap(), b"hel");
+        assert_eq!(d.remaining(), 2);
+    }
+
+    #[test]
+    fn read_cstr() {
+        let data = b"hello\0world";
+        let mut d = Deserializer::new(data);
+        assert_eq!(d.read_cstr().unwrap(), "hello");
+        assert_eq!(d.remaining(), 5);
+    }
+
+    #[test]
+    fn end_of_buffer() {
+        let data = [0x01];
+        let mut d = Deserializer::new(&data);
+        d.read_u8().unwrap();
+        let err = d.read_u8().unwrap_err();
+        assert!(matches!(err, SerialError::EndOfBuffer { .. }));
+    }
+
+    #[test]
+    fn skip() {
+        let data = [0x01, 0x02, 0x03, 0x04];
+        let mut d = Deserializer::new(&data);
+        d.skip(2).unwrap();
+        assert_eq!(d.read_u8().unwrap(), 0x03);
+    }
+
+    #[test]
+    fn error_display() {
+        let e = SerialError::EndOfBuffer { need: 4, have: 2 };
+        assert!(e.to_string().contains("4"));
+    }
+}