diff --git a/crates/jacquard-common/src/bos.rs b/crates/jacquard-common/src/bos.rs
index e23263ce..aa2076b7 100644
--- a/crates/jacquard-common/src/bos.rs
+++ b/crates/jacquard-common/src/bos.rs
@@ -189,6 +189,72 @@ impl<'a> Bos<str> for CowStr<'a> {
 /// for strings of 22 bytes or fewer.
 pub type DefaultStr = SmolStr;
 
+/// Construct `S` from either a borrowed `&'de str` or an owned `SmolStr`.
+///
+/// Validated string types (Handle, Did, Nsid, etc.) may need to normalise input during
+/// deserialization (e.g. lowercasing handles). The normalisation always produces a `SmolStr`,
+/// but when the input is already valid the deserializer wants to borrow directly from the
+/// input buffer. This trait provides the two construction paths so that a single custom
+/// deserialize visitor can produce any backing type.
+pub trait StrConsumer<'de, 'r>: Bos<str> + Sized {
+    /// Construct from a borrowed string slice (zero-copy path).
+    fn from_borrowed_str(s: &'de str) -> Self;
+
+    /// Construct from an owned `SmolStr` (normalisation/allocation path).
+    fn from_smolstr(s: &'r SmolStr) -> Self;
+}
+
+impl<'de, 'r> StrConsumer<'de, 'r> for SmolStr {
+    #[inline]
+    fn from_borrowed_str(s: &'de str) -> Self {
+        SmolStr::new(s)
+    }
+
+    #[inline]
+    fn from_smolstr(s: &'r SmolStr) -> Self {
+        s.clone()
+    }
+}
+
+impl<'de, 'r> StrConsumer<'de, 'r> for String {
+    #[inline]
+    fn from_borrowed_str(s: &'de str) -> Self {
+        s.into()
+    }
+
+    #[inline]
+    fn from_smolstr(s: &'r SmolStr) -> Self {
+        s.clone().into()
+    }
+}
+
+impl<'de, 'r> StrConsumer<'de, 'r> for &'de str
+where
+    'r: 'de,
+{
+    #[inline]
+    fn from_borrowed_str(s: &'de str) -> Self {
+        s
+    }
+
+    #[inline]
+    fn from_smolstr(s: &'r SmolStr) -> Self {
+        s.as_str()
+    }
+}
+
+impl<'de, 'r> StrConsumer<'de, 'r> for CowStr<'de> {
+    #[inline]
+    fn from_borrowed_str(s: &'de str) -> Self {
+        CowStr::Borrowed(s)
+    }
+
+    #[inline]
+    fn from_smolstr(s: &'r SmolStr) -> Self {
+        CowStr::Owned(s.clone())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/jacquard-common/src/lib.rs b/crates/jacquard-common/src/lib.rs
index 3d050eea..069fd4dc 100644
--- a/crates/jacquard-common/src/lib.rs
+++ b/crates/jacquard-common/src/lib.rs
@@ -214,7 +214,7 @@ pub use spin::Lazy;
 
 pub use cowstr::CowStr;
 pub use into_static::IntoStatic;
-pub use bos::{Bos, BorrowOrShare, DefaultStr};
+pub use bos::{Bos, BorrowOrShare, DefaultStr, StrConsumer};
 
 /// A copy-on-write immutable string type that uses [`smol_str::SmolStr`] for
 /// the "owned" variant.