diff --git a/crates/kind-derive/src/subst.rs b/crates/kind-derive/src/subst.rs
index 10cdfb1f..05fbd462 100644
--- a/crates/kind-derive/src/subst.rs
+++ b/crates/kind-derive/src/subst.rs
@@ -291,9 +291,9 @@ impl<'a> Visitor for Subst<'a> {
             ExprKind::SeqRecord(sec) => {
                 use kind_tree::concrete::SeqOperation::*;
 
-                self.visit_ident(&mut sec.ident[0]);
+                self.visit_ident(&mut sec.name);
 
-                self.visit_expr(&mut sec.typ_);
+                self.visit_expr(&mut sec.typ);
 
                 match &mut sec.operation {
                     Set(expr) => self.visit_expr(expr),
diff --git a/crates/kind-parser/src/expr.rs b/crates/kind-parser/src/expr.rs
index a742a301..63ec9233 100644
--- a/crates/kind-parser/src/expr.rs
+++ b/crates/kind-parser/src/expr.rs
@@ -879,6 +879,46 @@ impl<'a> Parser<'a> {
         }
     }
 
+    pub fn parse_seq(&mut self) -> Result<Box<Expr>, SyntaxDiagnostic> {
+        let start = self.range();
+
+        self.eat_variant(Token::Bang)?;
+
+        let typ = self.parse_atom()?;
+
+        let name = self.parse_id()?;
+
+        let mut fields = vec![];
+
+        let mut end = self.range();
+
+        while let Token::Dot = &self.get() {
+            self.advance();
+            end = self.range();
+            fields.push(self.parse_id()?);
+        }
+
+        let operation = if self.check_and_eat(Token::Eq) {
+            SeqOperation::Set(self.parse_expr(false)?)
+        } else if self.check_and_eat(Token::AtEq) {
+            SeqOperation::Mut(self.parse_expr(false)?)
+        } else {
+            SeqOperation::Get
+        };
+
+        Ok(Box::new(Expr {
+            data: ExprKind::SeqRecord(
+                SeqRecord {
+                    typ,
+                    name,
+                    fields,
+                    operation,
+                }
+            ),
+            range: start.mix(end),
+        }))
+    }
+
     /// The infinite hell of else ifs. But it's the most readable way
     /// to check if the queue of tokens match a pattern as we need
     /// some looakhead tokens.
@@ -904,6 +944,8 @@ impl<'a> Parser<'a> {
             self.parse_pi_or_lambda(false)
         } else if self.is_sigma_type() {
             self.parse_sigma_type()
+        } else if self.check_actual(Token::Bang) {
+            self.parse_seq()
         } else if self.check_actual(Token::Tilde) {
             self.parse_erased()
         } else {
diff --git a/crates/kind-parser/src/lexer/mod.rs b/crates/kind-parser/src/lexer/mod.rs
index 4c9bf2c4..cb410502 100644
--- a/crates/kind-parser/src/lexer/mod.rs
+++ b/crates/kind-parser/src/lexer/mod.rs
@@ -175,7 +175,20 @@ impl<'a> Lexer<'a> {
                 ';' => self.single_token(Token::Semi, start),
                 '$' => self.single_token(Token::Dollar, start),
                 ',' => self.single_token(Token::Comma, start),
-                '+' => self.single_token(Token::Plus, start),
+                '+' => {
+                    self.next_char();
+                    match self.peekable.peek() {
+                        Some('=') => self.single_token(Token::PlusEq, start),
+                        _ => (Token::Plus, self.mk_range(start)),
+                    }
+                }
+                '@' => {
+                    self.next_char();
+                    match self.peekable.peek() {
+                        Some('=') => self.single_token(Token::AtEq, start),
+                        _ => (Token::At, self.mk_range(start)),
+                    }
+                }
                 '-' => {
                     self.next_char();
                     match self.peekable.peek() {
diff --git a/crates/kind-parser/src/lexer/tokens.rs b/crates/kind-parser/src/lexer/tokens.rs
index fe140da8..4a21bb06 100644
--- a/crates/kind-parser/src/lexer/tokens.rs
+++ b/crates/kind-parser/src/lexer/tokens.rs
@@ -75,6 +75,10 @@ pub enum Token {
     BangEq,
     Bang,
 
+    PlusEq,
+    AtEq,
+    At,
+
     HashHash,
     Hash,
 
@@ -181,6 +185,9 @@ impl fmt::Display for Token {
             Token::With => write!(f, "with"),
             Token::Return => write!(f, "return"),
             Token::Ask => write!(f, "ask"),
+            Token::PlusEq => write!(f, "+="),
+            Token::AtEq => write!(f, "@="),
+            Token::At => write!(f, "@"),
         }
     }
 }
diff --git a/crates/kind-pass/src/desugar/expr.rs b/crates/kind-pass/src/desugar/expr.rs
index b18c0bac..6e7859f2 100644
--- a/crates/kind-pass/src/desugar/expr.rs
+++ b/crates/kind-pass/src/desugar/expr.rs
@@ -1,6 +1,6 @@
 use kind_span::{Locatable, Range};
 use kind_tree::concrete::{self, expr, Literal, TopLevel};
-use kind_tree::desugared::{self};
+use kind_tree::desugared::{self, Expr};
 use kind_tree::symbol::{Ident, QualifiedIdent};
 
 use crate::diagnostic::{PassDiagnostic, Sugar};
@@ -79,7 +79,78 @@ impl<'a> DesugarState<'a> {
         range: Range,
         sub: &expr::SeqRecord,
     ) -> Box<desugared::Expr> {
-        todo!()
+        use concrete::SeqOperation::*;
+
+        let typ = self.desugar_expr(&sub.typ);
+
+        let mut value = vec![];
+        self.desugar_record_field_sequence(&mut value, typ, &sub.fields);
+
+        match &sub.operation {
+            Set(expr) => {
+                let value_ident = Ident::generate("_value");
+                let expr = self.desugar_expr(&expr);
+
+                let mut result = value.iter().rfold(expr, |acc, (name, field)| {
+                    let name = name.add_segment(field.to_str()).add_segment("mut");
+                    self.mk_desugared_ctr(
+                        range,
+                        name,
+                        vec![Expr::var(value_ident.clone()), Expr::lambda(range.clone(), value_ident.clone(), acc, false)],
+                        false,
+                    )
+                });
+
+                match &mut result.data {
+                    desugared::ExprKind::Ctr { args, .. } => {
+                        if let desugared::ExprKind::Var { name } = &mut args[0].data {
+                            *name = sub.name.clone()
+                        }
+                    },
+                    _ => ()
+                }
+
+                result
+            },
+            Mut(expr) => {
+                let value_ident = Ident::generate("_value");
+                let expr = self.desugar_expr(&expr);
+    
+                let mut result = value.iter().rfold(expr, |acc, (name, field)| {
+                    let name = name.add_segment(field.to_str()).add_segment("mut");
+                    Expr::lambda(name.range.clone(), value_ident.clone(), self.mk_desugared_ctr(
+                        range,
+                        name,
+                        vec![Expr::var(value_ident.clone()), acc],
+                        false,
+                    ), false)
+                });
+
+                let mut result = match result.data {
+                    desugared::ExprKind::Lambda { body, .. } => {
+                        body
+                    }
+                    _ => panic!()
+                };
+
+                match &mut result.data {
+                    desugared::ExprKind::Ctr { args, .. } => {
+                        if let desugared::ExprKind::Var { name } = &mut args[0].data {
+                            *name = sub.name.clone()
+                        }
+                    },
+                    _ => ()
+                }
+
+                result
+            }
+            Get => value
+                .iter()
+                .fold(Expr::var(sub.name.clone()), |acc, (name, field)| {
+                    let name = name.add_segment(field.to_str()).add_segment("get");
+                    self.mk_desugared_ctr(range, name, vec![acc], false)
+                }),
+        }
     }
 
     pub(crate) fn desugar_sttm(
diff --git a/crates/kind-pass/src/desugar/mod.rs b/crates/kind-pass/src/desugar/mod.rs
index 5dfd1361..5316c412 100644
--- a/crates/kind-pass/src/desugar/mod.rs
+++ b/crates/kind-pass/src/desugar/mod.rs
@@ -23,6 +23,7 @@ pub mod attributes;
 pub mod destruct;
 pub mod expr;
 pub mod top_level;
+pub mod record_field;
 
 pub struct DesugarState<'a> {
     pub errors: Sender<Box<dyn Diagnostic>>,
diff --git a/crates/kind-pass/src/desugar/record_field.rs b/crates/kind-pass/src/desugar/record_field.rs
new file mode 100644
index 00000000..ded1f45a
--- /dev/null
+++ b/crates/kind-pass/src/desugar/record_field.rs
@@ -0,0 +1,91 @@
+use fxhash::FxHashMap;
+use kind_tree::{
+    concrete::{self, TopLevel},
+    desugared::{self, Expr},
+    symbol::{Ident, QualifiedIdent},
+    telescope::Telescope,
+};
+
+use crate::subst::subst_on_expr;
+
+use super::DesugarState;
+
+impl<'a> DesugarState<'a> {
+    pub fn specialize_on_field(
+        &mut self,
+        typ: Box<desugared::Expr>,
+    ) -> Option<(
+        QualifiedIdent,
+        &Telescope<concrete::Argument>,
+        Telescope<concrete::Argument>,
+        Vec<Box<Expr>>,
+    )> {
+        match typ.data {
+            desugared::ExprKind::Ctr { name, args } => {
+                let Some(TopLevel::RecordType(record)) = self.old_book.entries.get(name.to_str()) else { return None };
+                let entry_constructor = self.old_book.meta.get(
+                    record
+                        .name
+                        .add_segment(record.constructor.to_str())
+                        .to_str(),
+                )?;
+                Some((
+                    name,
+                    &record.parameters,
+                    entry_constructor
+                        .arguments
+                        .clone()
+                        .drop(record.parameters.len()),
+                    args,
+                ))
+            }
+            _ => None,
+        }
+    }
+
+    pub fn desugar_record_field_sequence(
+        &mut self,
+        res: &mut Vec<(QualifiedIdent, Ident)>,
+        typ: Box<desugared::Expr>,
+        fields: &[Ident],
+    ) {
+        if fields.is_empty() {
+            return;
+        }
+
+        if let Some((name, params, record_fields, args)) = self.specialize_on_field(typ.clone()) {
+            if let Some(field) = record_fields
+                .iter()
+                .find(|x| x.name.to_str() == fields[0].to_str())
+            {
+                let key = field.name.clone();
+
+                let pair = params
+                    .iter()
+                    .zip(args)
+                    .map(|(k, v)| (k.name.to_string(), v))
+                    .collect::<FxHashMap<_, _>>();
+
+                let mut val = self.desugar_expr(
+                    &field
+                        .typ
+                        .clone()
+                        .unwrap_or_else(|| concrete::expr::Expr::typ(field.range.clone())),
+                );
+
+
+                subst_on_expr(&mut val, pair);
+
+                println!("{}", val);
+
+                res.push((name, key));
+
+                self.desugar_record_field_sequence(res, val, &fields[1..])
+            } else {
+                panic!("no field")
+            }
+        } else {
+            panic!("no record {}", typ)
+        }
+    }
+}
diff --git a/crates/kind-pass/src/lib.rs b/crates/kind-pass/src/lib.rs
index a7251658..c6a185cc 100644
--- a/crates/kind-pass/src/lib.rs
+++ b/crates/kind-pass/src/lib.rs
@@ -11,3 +11,4 @@ mod diagnostic;
 pub mod expand;
 pub mod inline;
 pub mod unbound;
+pub mod subst;
\ No newline at end of file
diff --git a/crates/kind-pass/src/subst.rs b/crates/kind-pass/src/subst.rs
new file mode 100644
index 00000000..8bca013b
--- /dev/null
+++ b/crates/kind-pass/src/subst.rs
@@ -0,0 +1,61 @@
+use fxhash::FxHashMap;
+use kind_tree::desugared::*;
+
+pub fn subst_on_expr(expr: &mut Expr, substs: FxHashMap<String, Box<Expr>>) {
+    subst(Default::default(), expr, &substs)
+}
+
+fn subst(bindings: im_rc::HashSet<String>, expr: &mut Expr, substs: &FxHashMap<String, Box<Expr>>) {
+    use ExprKind::*;
+
+    match &mut expr.data {
+        Var { name } => {
+            if !bindings.contains(name.to_str()) {
+                if let Some(res) = substs.get(name.to_str()) {
+                    *expr = *res.clone();
+                }
+            }
+        },
+        All { param, typ, body, .. } => {
+            subst(bindings.clone(), typ, substs);
+            let mut on_body = bindings.clone();
+            on_body.insert(param.to_string());
+            subst(on_body.clone(), body, substs);
+        },
+        Lambda { param, body, .. } => {
+            let mut on_body = bindings.clone();
+            on_body.insert(param.to_string());
+            subst(on_body.clone(), body, substs);
+        },
+        App { fun, args } => {
+            subst(bindings.clone(), fun, substs);
+            for arg in args.iter_mut() {
+                subst(bindings.clone(), &mut arg.data, substs);
+            }
+        },
+        Fun { name: _, args } | Ctr { name: _, args } => {
+            for arg in args.iter_mut() {
+                subst(bindings.clone(), arg, substs);
+            }
+        },
+        Let { name, val, next } => {
+            subst(bindings.clone(), val, substs);
+            let mut on_body = bindings.clone();
+            on_body.insert(name.to_string());
+            subst(on_body.clone(), next, substs);
+        },
+        Ann { expr, typ } => {
+            subst(bindings.clone(), expr, substs);
+            subst(bindings.clone(), typ, substs);
+        },
+        Sub { expr, .. } => {
+            subst(bindings.clone(), expr, substs);
+        },
+        Binary { left, right, .. } => {
+            subst(bindings.clone(), left, substs);
+            subst(bindings.clone(), right, substs);
+        },
+        _ => ()
+    }
+}
+
diff --git a/crates/kind-pass/src/unbound/mod.rs b/crates/kind-pass/src/unbound/mod.rs
index 8b2a7051..2398c9f6 100644
--- a/crates/kind-pass/src/unbound/mod.rs
+++ b/crates/kind-pass/src/unbound/mod.rs
@@ -638,9 +638,9 @@ impl Visitor for UnboundCollector {
             ExprKind::SeqRecord(sec) => {
                 use kind_tree::concrete::SeqOperation::*;
 
-                self.visit_expr(&mut sec.typ_);
+                self.visit_expr(&mut sec.typ);
 
-                self.visit_ident(&mut sec.ident[0]);
+                self.visit_ident(&mut sec.name);
 
                 match &mut sec.operation {
                     Set(expr) => self.visit_expr(expr),
diff --git a/crates/kind-tree/src/concrete/expr.rs b/crates/kind-tree/src/concrete/expr.rs
index 978a40e1..a1b76867 100644
--- a/crates/kind-tree/src/concrete/expr.rs
+++ b/crates/kind-tree/src/concrete/expr.rs
@@ -145,8 +145,9 @@ pub enum SeqOperation {
 
 #[derive(Clone, Debug)]
 pub struct SeqRecord {
-    pub typ_: Box<Expr>,
-    pub ident: Vec<Ident>,
+    pub typ: Box<Expr>,
+    pub name: Ident,
+    pub fields: Vec<Ident>,
     pub operation: SeqOperation
 }
 
@@ -592,7 +593,7 @@ impl Display for Expr {
             Hole => write!(f, "_"),
             SeqRecord(rec) => {
                 use SeqOperation::*;
-                write!(f, "(!({}) {}", rec.typ_, rec.ident.iter().map(|x| x.to_str()).collect::<Vec<_>>().join(","))?;
+                write!(f, "(!({}) {} {}", rec.typ, rec.name, rec.fields.iter().map(|x| format!(".{}", x.to_str())).collect::<Vec<_>>().join(","))?;
                 match &rec.operation {
                     Set(expr) => write!(f, "+= {})", expr),
                     Mut(expr) => write!(f, "@= {})", expr),
diff --git a/crates/kind-tree/src/concrete/visitor.rs b/crates/kind-tree/src/concrete/visitor.rs
index d0e9e2be..e840550c 100644
--- a/crates/kind-tree/src/concrete/visitor.rs
+++ b/crates/kind-tree/src/concrete/visitor.rs
@@ -492,6 +492,15 @@ pub fn walk_expr<T: Visitor>(ctx: &mut T, expr: &mut Expr) {
         ExprKind::Hole => {}
         ExprKind::Subst(subst) => ctx.visit_substitution(subst),
         ExprKind::Match(matcher) => ctx.visit_match(matcher),
-        ExprKind::SeqRecord(_) => todo!(),
+        ExprKind::SeqRecord(seq) => {
+            ctx.visit_ident(&mut seq.name);
+            ctx.visit_expr(&mut seq.typ);
+
+            match &mut seq.operation {
+                SeqOperation::Set(expr) => ctx.visit_expr(expr),
+                SeqOperation::Mut(expr) => ctx.visit_expr(expr),
+                SeqOperation::Get => (),
+            }
+        },
     }
 }