diff --git a/bootstrap/src/host/capflags.rs b/bootstrap/src/host/capflags.rs
new file mode 100644
index 00000000..5e08bcd8
--- /dev/null
+++ b/bootstrap/src/host/capflags.rs
@@ -0,0 +1,222 @@
+pub const CAP_INFERENCE: u32 = 1 << 0;
+pub const CAP_DMA: u32 = 1 << 1;
+pub const CAP_IRQ: u32 = 1 << 2;
+pub const CAP_TERNARY: u32 = 1 << 3;
+pub const CAP_CRC32: u32 = 1 << 4;
+pub const CAP_SCATTER_GATHER: u32 = 1 << 5;
+pub const CAP_WEIGHT_VALIDATION: u32 = 1 << 6;
+pub const CAP_MULTI_LAYER: u32 = 1 << 7;
+pub const CAP_DEBUG_CSR: u32 = 1 << 8;
+pub const CAP_WATCHDOG: u32 = 1 << 9;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct CapFlags(u32);
+
+impl CapFlags {
+    pub const fn none() -> Self {
+        Self(0)
+    }
+
+    pub const fn all() -> Self {
+        Self(0x03FF)
+    }
+
+    pub const fn from_bits(bits: u32) -> Self {
+        Self(bits)
+    }
+
+    pub const fn bits(self) -> u32 {
+        self.0
+    }
+
+    pub const fn has(self, cap: u32) -> bool {
+        (self.0 & cap) != 0
+    }
+
+    pub const fn set(mut self, cap: u32) -> Self {
+        self.0 |= cap;
+        self
+    }
+
+    pub const fn clear(mut self, cap: u32) -> Self {
+        self.0 &= !cap;
+        self
+    }
+
+    pub const fn is_empty(self) -> bool {
+        self.0 == 0
+    }
+
+    pub fn count(self) -> u32 {
+        self.0.count_ones()
+    }
+
+    pub fn missing(self, required: CapFlags) -> CapFlags {
+        CapFlags(required.0 & !self.0)
+    }
+
+    pub fn satisfies(self, required: CapFlags) -> bool {
+        (self.0 & required.0) == required.0
+    }
+
+    pub fn names(self) -> Vec<&'static str> {
+        let mut result = Vec::new();
+        if self.has(CAP_INFERENCE) { result.push("inference"); }
+        if self.has(CAP_DMA) { result.push("dma"); }
+        if self.has(CAP_IRQ) { result.push("irq"); }
+        if self.has(CAP_TERNARY) { result.push("ternary"); }
+        if self.has(CAP_CRC32) { result.push("crc32"); }
+        if self.has(CAP_SCATTER_GATHER) { result.push("scatter_gather"); }
+        if self.has(CAP_WEIGHT_VALIDATION) { result.push("weight_validation"); }
+        if self.has(CAP_MULTI_LAYER) { result.push("multi_layer"); }
+        if self.has(CAP_DEBUG_CSR) { result.push("debug_csr"); }
+        if self.has(CAP_WATCHDOG) { result.push("watchdog"); }
+        result
+    }
+}
+
+impl std::fmt::Display for CapFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let names = self.names();
+        if names.is_empty() {
+            write!(f, "none")
+        } else {
+            write!(f, "{}", names.join("|"))
+        }
+    }
+}
+
+impl std::fmt::Binary for CapFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:010b}", self.0)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct CapabilityError {
+    pub missing: CapFlags,
+}
+
+impl std::fmt::Display for CapabilityError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "missing capabilities: {}", self.missing)
+    }
+}
+
+impl std::error::Error for CapabilityError {}
+
+pub fn check_capabilities(have: CapFlags, need: CapFlags) -> Result<(), CapabilityError> {
+    let missing = have.missing(need);
+    if missing.is_empty() {
+        Ok(())
+    } else {
+        Err(CapabilityError { missing })
+    }
+}
+
+pub const BASE_CAPABILITIES: CapFlags = CapFlags::none()
+    .set(CAP_INFERENCE)
+    .set(CAP_TERNARY)
+    .set(CAP_CRC32);
+
+pub const FULL_CAPABILITIES: CapFlags = CapFlags::all();
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn none_is_empty() {
+        assert!(CapFlags::none().is_empty());
+        assert_eq!(CapFlags::none().count(), 0);
+    }
+
+    #[test]
+    fn all_has_ten() {
+        assert_eq!(CapFlags::all().count(), 10);
+    }
+
+    #[test]
+    fn set_and_has() {
+        let caps = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        assert!(caps.has(CAP_INFERENCE));
+        assert!(caps.has(CAP_DMA));
+        assert!(!caps.has(CAP_IRQ));
+    }
+
+    #[test]
+    fn clear() {
+        let caps = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA).clear(CAP_INFERENCE);
+        assert!(!caps.has(CAP_INFERENCE));
+        assert!(caps.has(CAP_DMA));
+    }
+
+    #[test]
+    fn satisfies() {
+        let need = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        let have = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA).set(CAP_IRQ);
+        assert!(have.satisfies(need));
+        assert!(!need.satisfies(have));
+    }
+
+    #[test]
+    fn missing() {
+        let have = CapFlags::none().set(CAP_INFERENCE);
+        let need = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        let miss = have.missing(need);
+        assert!(miss.has(CAP_DMA));
+        assert!(!miss.has(CAP_INFERENCE));
+    }
+
+    #[test]
+    fn names() {
+        let caps = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        let names = caps.names();
+        assert_eq!(names, vec!["inference", "dma"]);
+    }
+
+    #[test]
+    fn display() {
+        let caps = CapFlags::none().set(CAP_INFERENCE);
+        assert_eq!(caps.to_string(), "inference");
+        assert_eq!(CapFlags::none().to_string(), "none");
+    }
+
+    #[test]
+    fn check_ok() {
+        let have = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        let need = CapFlags::none().set(CAP_INFERENCE);
+        check_capabilities(have, need).unwrap();
+    }
+
+    #[test]
+    fn check_missing() {
+        let have = CapFlags::none().set(CAP_INFERENCE);
+        let need = CapFlags::none().set(CAP_INFERENCE).set(CAP_DMA);
+        let err = check_capabilities(have, need).unwrap_err();
+        assert!(err.missing.has(CAP_DMA));
+        assert!(err.to_string().contains("dma"));
+    }
+
+    #[test]
+    fn from_bits_roundtrip() {
+        let caps = CapFlags::from_bits(CAP_INFERENCE | CAP_TERNARY);
+        assert!(caps.has(CAP_INFERENCE));
+        assert!(caps.has(CAP_TERNARY));
+        assert_eq!(caps.bits(), CAP_INFERENCE | CAP_TERNARY);
+    }
+
+    #[test]
+    fn base_capabilities() {
+        assert!(BASE_CAPABILITIES.has(CAP_INFERENCE));
+        assert!(BASE_CAPABILITIES.has(CAP_TERNARY));
+        assert!(BASE_CAPABILITIES.has(CAP_CRC32));
+        assert!(!BASE_CAPABILITIES.has(CAP_DMA));
+    }
+
+    #[test]
+    fn binary_format() {
+        let caps = CapFlags::from_bits(0x03);
+        assert_eq!(format!("{:b}", caps), "0000000011");
+    }
+}
diff --git a/bootstrap/src/host/mod.rs b/bootstrap/src/host/mod.rs
index d4958bb9..962b0d1c 100644
--- a/bootstrap/src/host/mod.rs
+++ b/bootstrap/src/host/mod.rs
@@ -13,11 +13,13 @@
 // write `use t27c::host::{BitnetDriver, MockMmio, DriverError};`.
 // ============================================================================
 
+pub mod capflags;
 pub mod csr_map;
 pub mod driver;
 pub mod irq;
 pub mod mmio;
 
+pub use capflags::{check_capabilities, CapFlags, CapabilityError, BASE_CAPABILITIES, FULL_CAPABILITIES};
 pub use driver::{BitnetDriver, CsrSnapshot, DriverError};
 pub use irq::{IrqCallback, IrqCounters, IrqDrivenDriver, IrqHandler, IrqSource, ServiceReport};
 pub use mmio::{MmioOp, MmioRecord, MockMmio};