diff --git a/crates/nu-protocol/src/engine/call.rs b/crates/nu-protocol/src/engine/call.rs
new file mode 100644
index 0000000000..cfaa7d2cca
--- /dev/null
+++ b/crates/nu-protocol/src/engine/call.rs
@@ -0,0 +1,16 @@
+use crate::{ast, ir, Span};
+
+/// This is a HACK to help [`Command`](super::Command) support both the old AST evaluator and the
+/// new IR evaluator at the same time. It should be removed once we are satisfied with the new
+/// evaluator.
+#[derive(Debug, Clone)]
+pub struct Call<'a> {
+    pub head: Span,
+    inner: CallImpl<'a>,
+}
+
+#[derive(Debug, Clone)]
+enum CallImpl<'a> {
+    Ast(&'a ast::Call),
+    Ir(ir::Call<'a>),
+}
diff --git a/crates/nu-protocol/src/engine/mod.rs b/crates/nu-protocol/src/engine/mod.rs
index 814049a9ce..a93ed600cb 100644
--- a/crates/nu-protocol/src/engine/mod.rs
+++ b/crates/nu-protocol/src/engine/mod.rs
@@ -1,4 +1,5 @@
 mod cached_file;
+mod call;
 mod call_info;
 mod capture_block;
 mod command;
@@ -15,6 +16,7 @@ mod variable;
 
 pub use cached_file::CachedFile;
 
+pub use call::*;
 pub use call_info::*;
 pub use capture_block::*;
 pub use command::*;
diff --git a/crates/nu-protocol/src/ir/call.rs b/crates/nu-protocol/src/ir/call.rs
new file mode 100644
index 0000000000..0bec7acc44
--- /dev/null
+++ b/crates/nu-protocol/src/ir/call.rs
@@ -0,0 +1,148 @@
+use crate::{PipelineData, RegId, ShellError, Span, Value};
+
+use super::{CallArg, Instruction};
+
+/// Contains the information for a call being made to a declared command.
+#[derive(Debug, Clone)]
+pub struct Call<'a> {
+    pub registers: &'a [PipelineData],
+    pub call_args: &'a [CallArg],
+    pub instruction: &'a Instruction,
+    pub head: &'a Span,
+}
+
+#[derive(Clone, Copy)]
+enum ArgRef<'a> {
+    Positional(&'a Value),
+    Named(&'a str, Option<&'a Value>),
+    Spread(&'a Value),
+}
+
+impl<'a> ArgRef<'a> {
+    fn span(self) -> Span {
+        match self {
+            ArgRef::Positional(v) => v.span(),
+            // FIXME: Named without value needs a span!
+            ArgRef::Named(_, v) => v.map(|v| v.span()).unwrap_or(Span::unknown()),
+            ArgRef::Spread(v) => v.span(),
+        }
+    }
+}
+
+impl<'a> Call<'a> {
+    fn call_args(&self) -> impl Iterator<Item = &CallArg> {
+        let Instruction::Call {
+            args_start,
+            args_len,
+            ..
+        } = *self.instruction
+        else {
+            panic!("self.instruction is not Call")
+        };
+        self.call_args[args_start..(args_start + args_len)].iter()
+    }
+
+    fn get_reg_val(&self, reg_id: RegId) -> &Value {
+        match &self.registers[reg_id.0 as usize] {
+            PipelineData::Value(value, _) => value,
+            other => panic!("value in register {reg_id} for argument was not collected: {other:?}"),
+        }
+    }
+
+    fn arg_refs(&self) -> impl Iterator<Item = ArgRef<'_>> {
+        self.call_args().map(|arg| match arg {
+            CallArg::Positional(r) => ArgRef::Positional(self.get_reg_val(*r)),
+            CallArg::Spread(r) => ArgRef::Spread(self.get_reg_val(*r)),
+            CallArg::Flag(name) => ArgRef::Named(&name, None),
+            CallArg::Named(name, r) => ArgRef::Named(&name, Some(self.get_reg_val(*r))),
+        })
+    }
+
+    /// The span encompassing the arguments
+    ///
+    /// If there are no arguments the span covers where the first argument would exist
+    ///
+    /// If there are one or more arguments the span encompasses the start of the first argument to
+    /// end of the last argument
+    pub fn arguments_span(&self) -> Span {
+        let past = self.head.past();
+
+        let start = self
+            .arg_refs()
+            .next()
+            .map(|a| a.span())
+            .unwrap_or(past)
+            .start;
+        let end = self.arg_refs().last().map(|a| a.span()).unwrap_or(past).end;
+
+        Span::new(start, end)
+    }
+
+    pub fn named_len(&self) -> usize {
+        self.call_args()
+            .filter(|arg| matches!(arg, CallArg::Named(..) | CallArg::Flag(..)))
+            .count()
+    }
+
+    pub fn named_iter(&self) -> impl Iterator<Item = (&str, Option<&Value>)> {
+        self.arg_refs().filter_map(|arg| match arg {
+            ArgRef::Named(name, value) => Some((name, value)),
+            _ => None,
+        })
+    }
+
+    pub fn get_named_arg(&self, flag_name: &str) -> Option<&Value> {
+        self.arg_refs().find_map(|arg| match arg {
+            ArgRef::Named(name, value) if name == flag_name => value,
+            _ => None,
+        })
+    }
+
+    pub fn positional_len(&self) -> usize {
+        self.call_args()
+            .filter(|arg| matches!(arg, CallArg::Positional(..)))
+            .count()
+    }
+
+    pub fn positional_iter(&self) -> impl Iterator<Item = &Value> {
+        self.arg_refs().filter_map(|arg| match arg {
+            ArgRef::Positional(value) => Some(value),
+            _ => None,
+        })
+    }
+
+    pub fn positional_nth(&self, index: usize) -> Option<&Value> {
+        self.positional_iter().nth(index)
+    }
+
+    pub fn rest_iter(&self) -> impl Iterator<Item = &Value> {
+        self.arg_refs().filter_map(|arg| match arg {
+            ArgRef::Spread(value) => Some(value),
+            _ => None,
+        })
+    }
+
+    pub fn rest_iter_flattened(&self) -> Result<Vec<Value>, ShellError> {
+        let mut acc = vec![];
+        for rest_val in self.rest_iter() {
+            match rest_val {
+                Value::List { vals, .. } => acc.extend(vals.iter().cloned()),
+                Value::Error { error, .. } => return Err(ShellError::clone(error)),
+                _ => {
+                    return Err(ShellError::CannotSpreadAsList {
+                        span: rest_val.span(),
+                    })
+                }
+            }
+        }
+        Ok(acc)
+    }
+
+    pub fn span(&self) -> Span {
+        let mut span = *self.head;
+        for arg in self.arg_refs() {
+            span.end = span.end.max(arg.span().end);
+        }
+        span
+    }
+}
diff --git a/crates/nu-protocol/src/ir/mod.rs b/crates/nu-protocol/src/ir/mod.rs
index 76b095b35c..c77061ee15 100644
--- a/crates/nu-protocol/src/ir/mod.rs
+++ b/crates/nu-protocol/src/ir/mod.rs
@@ -6,7 +6,10 @@ use crate::{
 
 use serde::{Deserialize, Serialize};
 
+mod call;
 mod display;
+
+pub use call::Call;
 pub use display::{FmtInstruction, FmtIrBlock};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]