diff --git a/src/api/factory.rs b/src/api/factory.rs
index 6fec49e..693c179 100644
--- a/src/api/factory.rs
+++ b/src/api/factory.rs
@@ -2,7 +2,7 @@
 //!
 //! a helper trait that any string container can implement, which generates opseqs
 //!
-//! an OperationFactory trait implementation is provided for String, but plugin developers 
+//! an OperationFactory trait implementation is provided for `String` and `Arc<str>`, but plugin developers 
 //! should implement their own operation factory interfacing directly with the editor 
 //! buffer when possible.
 
@@ -93,16 +93,6 @@ pub fn op_effective_range(op: &OperationSeq) -> Range<u64> {
 /// assert_eq!(factory, "from scratch");
 /// # Ok::<(), codemp::ot::OTError>(())
 /// ```
-///
-/// use [OperationFactory::canc] to remove characters at index, but backwards
-///
-/// ```rust
-/// # use codemp::api::OperationFactory;
-/// # let mut factory = String::from("from scratch");
-/// factory = factory.canc(12, 8).apply(&factory)?;
-/// assert_eq!(factory, "from");
-/// # Ok::<(), codemp::ot::OTError>(())
-/// ```
 pub trait OperationFactory {
 	/// the current content of the buffer
 	fn content(&self) -> String;
@@ -160,16 +150,6 @@ pub trait OperationFactory {
 		out.retain(len - (pos+count));
 		out
 	}
-
-	/// delete n characters backwards at given position
-	fn canc(&self, pos: u64, count: u64) -> OperationSeq {
-		let mut out = OperationSeq::default();
-		let len = self.content().len() as u64;
-		out.retain(pos - count);
-		out.delete(count);
-		out.retain(len - pos);
-		out
-	}
 }
 
 impl OperationFactory for String {
@@ -177,3 +157,9 @@ impl OperationFactory for String {
 		self.clone()
 	}
 }
+
+impl OperationFactory for std::sync::Arc<str> {
+	fn content(&self) -> String {
+		self.to_string()
+	}
+}
diff --git a/src/instance.rs b/src/instance.rs
index 3582b22..d89bc5e 100644
--- a/src/instance.rs
+++ b/src/instance.rs
@@ -166,7 +166,7 @@ pub mod sync {
 		}
 	
 		/// return a reference to contained tokio runtime, to spawn tasks on
-		pub fn rt(&self) -> &Handle { &self.runtime.handle() }
+		pub fn rt(&self) -> &Handle { self.runtime.handle() }
 	
 		/// connect and store a client session, threadsafe and sync version of [crate::client::Client::new]
 		pub fn connect(&self, addr: &str) -> Result<(), Error> {