diff --git a/backend/Cargo.lock b/backend/Cargo.lock
index 62c0c34..ba53eac 100644
--- a/backend/Cargo.lock
+++ b/backend/Cargo.lock
@@ -331,6 +331,8 @@ dependencies = [
  "env_logger",
  "futures-util",
  "log",
+ "serde",
+ "serde_json",
  "tokio",
  "tokio-tungstenite",
 ]
@@ -512,6 +514,12 @@ version = "0.1.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "56f7d92ca342cea22a06f2121d944b4fd82af56988c270852495420f961d4ace"
 
+[[package]]
+name = "ryu"
+version = "1.0.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"
+
 [[package]]
 name = "serde"
 version = "1.0.219"
@@ -532,6 +540,18 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "serde_json"
+version = "1.0.143"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d401abef1d108fbd9cbaebc3e46611f4b1021f714a0597a71f41ee463f5f4a5a"
+dependencies = [
+ "itoa",
+ "memchr",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "sha1"
 version = "0.10.6"
diff --git a/backend/Cargo.toml b/backend/Cargo.toml
index 260d543..718984d 100644
--- a/backend/Cargo.toml
+++ b/backend/Cargo.toml
@@ -7,5 +7,7 @@ edition = "2024"
 env_logger = "0.11.8"
 futures-util = "0.3.31"
 log = "0.4.27"
+serde = { version = "1.0.219", features = ["derive"] }
+serde_json = "1.0.143"
 tokio = { version = "1.47.1", features = ["rt-multi-thread", "macros", "net", "time"] }
 tokio-tungstenite = "0.27.0"
diff --git a/backend/src/cell.rs b/backend/src/cell.rs
index 399592b..8f2c9d8 100644
--- a/backend/src/cell.rs
+++ b/backend/src/cell.rs
@@ -1,5 +1,7 @@
 use std::collections::HashSet;
 
+use serde::{Deserialize, Serialize};
+
 use crate::evaluator::*;
 
 #[derive(Clone)]
@@ -49,23 +51,24 @@ impl Cell {
     }
 }
 
-#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub struct CellRef {
-    pub row: i64,
-    pub col: i64,
+    pub row: usize,
+    pub col: usize,
 }
 
 impl CellRef {
+    // Zero indexed
     pub fn new(s: String) -> Result<CellRef, String> {
         let s = s.trim();
-        let mut col: i64 = 0;
+        let mut col: usize = 0;
         let mut i = 0;
 
         // consume leading letters for the column
         for (idx, ch) in s.char_indices() {
             if ch.is_ascii_alphabetic() {
                 let u = ch.to_ascii_uppercase() as u8;
-                let val = (u - b'A' + 1) as i64; // A->1 ... Z->26
+                let val = (u - b'A' + 1) as usize; // A->1 ... Z->26
                 col = col * 26 + val;
                 i = idx + ch.len_utf8();
             } else {
@@ -90,8 +93,11 @@ impl CellRef {
             ));
         }
 
-        if let Ok(row) = row_part.parse::<i64>() {
-            Ok(CellRef { row, col })
+        if let Ok(row) = row_part.parse::<usize>() {
+            Ok(CellRef {
+                row: row - 1,
+                col: col - 1,
+            })
         } else {
             Err(format!("Parse error: invalid row number."))
         }
diff --git a/backend/src/common.rs b/backend/src/common.rs
new file mode 100644
index 0000000..e69de29
diff --git a/backend/src/evaluator.rs b/backend/src/evaluator.rs
index aa95340..4afe1e3 100644
--- a/backend/src/evaluator.rs
+++ b/backend/src/evaluator.rs
@@ -1,7 +1,8 @@
-use crate::cell::{Cell, CellRef};
+use crate::cell::CellRef;
+use crate::grid::Grid;
 use crate::parser::*;
 use crate::tokenizer::Literal;
-use std::collections::{HashMap, HashSet};
+use std::collections::HashSet;
 use std::fmt;
 
 #[derive(Debug, PartialEq, Clone)]
@@ -17,115 +18,58 @@ impl fmt::Display for Eval {
     }
 }
 
-pub struct Evaluator {
-    cells: HashMap<CellRef, Cell>,
+pub fn evaluate(str: String, grid: Option<&Grid>) -> Result<(Eval, HashSet<CellRef>), String> {
+    let (expr, deps) = parse(&str)?;
+
+    match evaluate_expr(&expr, grid) {
+        Ok(it) => Ok((it, deps)),
+        Err(it) => Err(it),
+    }
 }
 
-impl Evaluator {
-    pub fn new() -> Evaluator {
-        return Evaluator {
-            cells: HashMap::new(),
-        };
-    }
-
-    pub fn set_cell(&mut self, cell_ref: CellRef, raw_val: String) -> Result<Eval, String> {
-        if self.cells.contains_key(&cell_ref) && self.cells[&cell_ref].raw() == raw_val {
-            return self.get_cell(cell_ref);
-        }
-
-        let eval: Eval;
-        let deps: HashSet<CellRef>;
-
-        if let Some(c) = raw_val.chars().nth(0)
-            && c == '='
-        {
-            (eval, deps) = self.evaluate(raw_val[1..].to_owned())?;
-            // for dep in deps {}
-        } else {
-            match self.evaluate(raw_val.to_owned()) {
-                Ok(e) => {
-                    (eval, deps) = e;
-                }
-                Err(_) => eval = Eval::Literal(Literal::String(raw_val.to_owned())),
+fn evaluate_expr(expr: &Expr, grid: Option<&Grid>) -> Result<Eval, String> {
+    let res = match expr {
+        Expr::Literal(lit) => Eval::Literal(lit.clone()),
+        Expr::CellRef(re) => {
+            if let Some(g) = grid {
+                g.get_cell(re.to_owned())?
+            } else {
+                return Err("Evaluation error: Found cell reference but no grid.".into());
             }
         }
+        Expr::Infix { op, lhs, rhs } => {
+            let lval = evaluate_expr(lhs, grid)?;
+            let rval = evaluate_expr(rhs, grid)?;
 
-        self.cells
-            .insert(cell_ref, Cell::new(eval.clone(), raw_val));
-        Ok(eval)
-    }
-
-    // pub fn get_cell(&mut self, cell_ref: CellRef) -> Result<(String, Eval), String> {
-    pub fn get_cell(&mut self, cell_ref: CellRef) -> Result<Eval, String> {
-        if !self.cells.contains_key(&cell_ref) {
-            return Err(format!("Cell at {:?} not found.", cell_ref));
-        }
-
-        let cell = &self.cells[&cell_ref];
-
-        // Ok((cell.raw(), cell.eval()))
-        Ok(cell.eval())
-    }
-
-    pub fn add_cell_dep(&mut self, cell_ref: CellRef, dep_ref: CellRef) -> Result<(), String> {
-        if !self.cells.contains_key(&cell_ref) {
-            return Err(format!("Cell at {:?} not found.", cell_ref));
-        }
-
-        if let Some(cell) = self.cells.get_mut(&cell_ref) {
-            cell.add_i_dep(dep_ref);
-        }
-
-        Ok(())
-    }
-
-    pub fn evaluate(&mut self, str: String) -> Result<(Eval, HashSet<CellRef>), String> {
-        let (expr, deps) = parse(&str)?;
-
-        match self.evaluate_expr(&expr) {
-            Ok(it) => Ok((it, deps)),
-            Err(it) => Err(it),
-        }
-    }
-
-    fn evaluate_expr(&mut self, expr: &Expr) -> Result<Eval, String> {
-        let res = match expr {
-            Expr::Literal(lit) => Eval::Literal(lit.clone()),
-            Expr::CellRef(re) => self.get_cell(re.to_owned())?,
-            Expr::Infix { op, lhs, rhs } => {
-                let lval = self.evaluate_expr(lhs)?;
-                let rval = self.evaluate_expr(rhs)?;
-
-                match op {
-                    InfixOp::ADD => eval_add(&lval, &rval)?,
-                    InfixOp::SUB => eval_sub(&lval, &rval)?,
-                    InfixOp::MUL => eval_mul(&lval, &rval)?,
-                    InfixOp::DIV => eval_div(&lval, &rval)?,
-                    _ => return Err(format!("Evaluation error: Unsupported operator {:?}", op)),
-                }
+            match op {
+                InfixOp::ADD => eval_add(&lval, &rval)?,
+                InfixOp::SUB => eval_sub(&lval, &rval)?,
+                InfixOp::MUL => eval_mul(&lval, &rval)?,
+                InfixOp::DIV => eval_div(&lval, &rval)?,
+                _ => return Err(format!("Evaluation error: Unsupported operator {:?}", op)),
             }
-            Expr::Prefix { op, expr } => {
-                let val = self.evaluate_expr(expr)?;
+        }
+        Expr::Prefix { op, expr } => {
+            let val = evaluate_expr(expr, grid)?;
 
-                match op {
-                    PrefixOp::POS => eval_pos(&val)?,
-                    PrefixOp::NEG => eval_neg(&val)?,
-                    PrefixOp::NOT => eval_not(&val)?,
-                    _ => return Err(format!("Evaluation error: Unsupported operator {:?}", op)),
-                }
+            match op {
+                PrefixOp::POS => eval_pos(&val)?,
+                PrefixOp::NEG => eval_neg(&val)?,
+                PrefixOp::NOT => eval_not(&val)?,
+                // _ => return Err(format!("Evaluation error: Unsupported operator {:?}", op)),
             }
-            Expr::Group(g) => self.evaluate_expr(g)?,
-            it => return Err(format!("Evaluation error: Unsupported expression {:?}", it)),
-        };
+        }
+        Expr::Group(g) => evaluate_expr(g, grid)?,
+        it => return Err(format!("Evaluation error: Unsupported expression {:?}", it)),
+    };
 
-        Ok(res)
-    }
+    Ok(res)
 }
 
 fn eval_add(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
     match (lval, rval) {
         (Eval::Literal(a), Eval::Literal(b)) => {
-            if let Some(res) = eval_numeric_infix(a, b, |x, y| x + y, |x, y| x + y) {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x + y) {
                 return Ok(Eval::Literal(res));
             }
 
@@ -144,7 +88,7 @@ fn eval_add(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
 fn eval_sub(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
     match (lval, rval) {
         (Eval::Literal(a), Eval::Literal(b)) => {
-            if let Some(res) = eval_numeric_infix(a, b, |x, y| x - y, |x, y| x - y) {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x - y) {
                 return Ok(Eval::Literal(res));
             }
 
@@ -155,7 +99,7 @@ fn eval_sub(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
 fn eval_mul(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
     match (lval, rval) {
         (Eval::Literal(a), Eval::Literal(b)) => {
-            if let Some(res) = eval_numeric_infix(a, b, |x, y| x * y, |x, y| x * y) {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x * y) {
                 return Ok(Eval::Literal(res));
             }
 
@@ -166,15 +110,15 @@ fn eval_mul(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
 fn eval_div(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
     match (lval, rval) {
         (Eval::Literal(a), Eval::Literal(b)) => {
-            if let (Literal::Integer(_), Literal::Integer(y)) = (a, b) {
-                if *y == 0 {
+            if let (Literal::Number(_), Literal::Number(y)) = (a, b) {
+                if *y == 0f64 {
                     return Err(
                         "Evaluation error: integers attempted to divide by zero.".to_string()
                     );
                 }
             }
 
-            if let Some(res) = eval_numeric_infix(a, b, |x, y| x / y, |x, y| x / y) {
+            if let Some(res) = eval_numeric_infix(a, b, |x, y| x / y) {
                 return Ok(Eval::Literal(res));
             }
 
@@ -183,41 +127,23 @@ fn eval_div(lval: &Eval, rval: &Eval) -> Result<Eval, String> {
     }
 }
 
-fn eval_numeric_infix<FInt, FDouble>(
-    lhs: &Literal,
-    rhs: &Literal,
-    int_op: FInt,
-    double_op: FDouble,
-) -> Option<Literal>
-where
-    FInt: Fn(i64, i64) -> i64,
-    FDouble: Fn(f64, f64) -> f64,
-{
+fn eval_numeric_infix(lhs: &Literal, rhs: &Literal, op: fn(f64, f64) -> f64) -> Option<Literal> {
     match (lhs, rhs) {
-        (Literal::Integer(a), Literal::Integer(b)) => Some(Literal::Integer(int_op(*a, *b))),
-        (Literal::Double(a), Literal::Double(b)) => Some(Literal::Double(double_op(*a, *b))),
-        (Literal::Integer(a), Literal::Double(b)) => {
-            Some(Literal::Double(double_op(*a as f64, *b)))
-        }
-        (Literal::Double(a), Literal::Integer(b)) => {
-            Some(Literal::Double(double_op(*a, *b as f64)))
-        }
+        (Literal::Number(a), Literal::Number(b)) => Some(Literal::Number(op(*a, *b))),
         _ => None,
     }
 }
 
 fn eval_pos(val: &Eval) -> Result<Eval, String> {
     match val {
-        Eval::Literal(Literal::Integer(it)) => Ok(Eval::Literal(Literal::Integer(*it))),
-        Eval::Literal(Literal::Double(it)) => Ok(Eval::Literal(Literal::Double(*it))),
+        Eval::Literal(Literal::Number(it)) => Ok(Eval::Literal(Literal::Number(*it))),
         _ => Err("Evaluation error: expected numeric type for POS function.".to_string()),
     }
 }
 
 fn eval_neg(val: &Eval) -> Result<Eval, String> {
     match val {
-        Eval::Literal(Literal::Integer(it)) => Ok(Eval::Literal(Literal::Integer(-it))),
-        Eval::Literal(Literal::Double(it)) => Ok(Eval::Literal(Literal::Double(-it))),
+        Eval::Literal(Literal::Number(it)) => Ok(Eval::Literal(Literal::Number(-it))),
         _ => Err("Evaluation error: expected numeric type for NEG function.".to_string()),
     }
 }
diff --git a/backend/src/grid.rs b/backend/src/grid.rs
new file mode 100644
index 0000000..0ae5f62
--- /dev/null
+++ b/backend/src/grid.rs
@@ -0,0 +1,72 @@
+use std::collections::{HashMap, HashSet};
+
+use crate::{
+    cell::{Cell, CellRef},
+    evaluator::{Eval, evaluate},
+    tokenizer::Literal,
+};
+
+pub struct Grid {
+    cells: HashMap<CellRef, Cell>,
+}
+
+impl Grid {
+    pub fn new() -> Grid {
+        return Grid {
+            cells: HashMap::new(),
+        };
+    }
+}
+
+impl Grid {
+    pub fn set_cell(&mut self, cell_ref: CellRef, raw_val: String) -> Result<Eval, String> {
+        if self.cells.contains_key(&cell_ref) && self.cells[&cell_ref].raw() == raw_val {
+            return self.get_cell(cell_ref);
+        }
+
+        let eval: Eval;
+        let deps: HashSet<CellRef>;
+
+        if let Some(c) = raw_val.chars().nth(0)
+            && c == '='
+        {
+            (eval, deps) = evaluate(raw_val[1..].to_owned(), Some(&self))?;
+            // for dep in deps {}
+        } else {
+            match evaluate(raw_val.to_owned(), Some(&self)) {
+                Ok(e) => {
+                    (eval, deps) = e;
+                }
+                Err(_) => eval = Eval::Literal(Literal::String(raw_val.to_owned())),
+            }
+        }
+
+        self.cells
+            .insert(cell_ref, Cell::new(eval.clone(), raw_val));
+        Ok(eval)
+    }
+
+    // pub fn get_cell(&mut self, cell_ref: CellRef) -> Result<(String, Eval), String> {
+    pub fn get_cell(&self, cell_ref: CellRef) -> Result<Eval, String> {
+        if !self.cells.contains_key(&cell_ref) {
+            return Err(format!("Cell at {:?} not found.", cell_ref));
+        }
+
+        let cell = &self.cells[&cell_ref];
+
+        // Ok((cell.raw(), cell.eval()))
+        Ok(cell.eval())
+    }
+
+    pub fn add_cell_dep(&mut self, cell_ref: CellRef, dep_ref: CellRef) -> Result<(), String> {
+        if !self.cells.contains_key(&cell_ref) {
+            return Err(format!("Cell at {:?} not found.", cell_ref));
+        }
+
+        if let Some(cell) = self.cells.get_mut(&cell_ref) {
+            cell.add_i_dep(dep_ref);
+        }
+
+        Ok(())
+    }
+}
diff --git a/backend/src/main.rs b/backend/src/main.rs
index 43323f3..db7f500 100644
--- a/backend/src/main.rs
+++ b/backend/src/main.rs
@@ -1,28 +1,24 @@
 mod cell;
 mod evaluator;
+mod grid;
+mod messages;
 mod parser;
 mod tokenizer;
 
-use futures_util::{SinkExt, StreamExt, TryStreamExt, future};
+use futures_util::{SinkExt, StreamExt, TryStreamExt};
 use log::info;
 use std::{env, io::Error};
 use tokio::net::{TcpListener, TcpStream};
 
-use crate::{cell::CellRef, evaluator::Evaluator};
+use crate::{
+    evaluator::Eval,
+    grid::Grid,
+    messages::{LeadMsg, MsgType},
+};
 
 #[tokio::main]
 async fn main() -> Result<(), Error> {
     env_logger::init();
-    // let mut input = String::new();
-    // io::stdin().read_line(&mut input).expect("Expected input.");
-
-    // let mut ast = parser::parse(&input).unwrap();
-    // println!("{}", ast.pretty());
-    let mut evaluator = Evaluator::new();
-    // // println!("{}", evaluator.evaluate(input).unwrap());
-    // let a1 = CellRef { row: 1, col: 2 };
-    // evaluator.set_cell(a1, input).unwrap();
-    // println!("{:?}", evaluator.get_cell(a1).unwrap());
 
     let addr = env::args()
         .nth(1)
@@ -38,78 +34,8 @@ async fn main() -> Result<(), Error> {
     }
 
     Ok(())
-
-    // println!("CMDS : set <cell_ref>, get <cell_ref>");
-    // loop {
-    //     let mut input = String::new();
-    //     io::stdin().read_line(&mut input).expect("Expected input.");
-    //
-    //     let cmds = ["set", "get"];
-    //     let cmd = &input[0..3];
-    //     if !cmds.iter().any(|c| c == &cmd) {
-    //         println!("{} is an invalid command!", cmd);
-    //         println!("CMDS : set <cell_ref>, get <cell_ref>");
-    //         continue;
-    //     }
-    //
-    //     let rest = &input[4..];
-    //     let mut parts = rest.splitn(2, char::is_whitespace);
-    //
-    //     let raw_ref = parts.next().unwrap_or("").trim(); // cell reference
-    //     let raw_str = parts.next().unwrap_or("").trim(); // rest of the string (value)
-    //     // println!("{} {}", raw_ref, raw_str);
-    //
-    //     if let Ok(cell_ref) = CellRef::new(raw_ref.to_owned()) {
-    //         match cmd {
-    //             "set" => match evaluator.set_cell(cell_ref, raw_str.to_owned()) {
-    //                 Ok(_) => println!("Successfully set cell {} to {}.", raw_ref, raw_str),
-    //                 Err(e) => println!("{}", e),
-    //             },
-    //             "get" => match evaluator.get_cell(cell_ref) {
-    //                 Ok(res) => println!("{:?}", res),
-    //                 Err(e) => println!("{}", e),
-    //             },
-    //             _ => {
-    //                 panic!("Impossible.");
-    //             }
-    //         }
-    //     } else {
-    //         println!("{} is an invalid cell reference!", raw_ref);
-    //         continue;
-    //     }
-    // }
 }
 
-// async fn accept_connection(stream: TcpStream) {
-//     let addr = stream
-//         .peer_addr()
-//         .expect("connected streams should have a peer address");
-//     info!("Peer address: {}", addr);
-//
-//     let ws_stream = tokio_tungstenite::accept_async(stream)
-//         .await
-//         .expect("Error during the websocket handshake occurred");
-//
-//     info!("New WebSocket connection: {}", addr);
-//
-//     let (mut write, mut read) = ws_stream.split();
-//
-//     // We should not forward messages other than text or binary.
-//     while let Some(msg) = read.try_next().await.unwrap_or(None) {
-//         if msg.is_text() || msg.is_binary() {
-//             if let Err(e) = write
-//                 .send(format!("This is a message {}!", msg.to_text().unwrap_or("")).into())
-//                 .await
-//             {
-//                 eprintln!("send error: {}", e);
-//                 break;
-//             }
-//         }
-//     }
-//
-//     info!("Disconnected from {}", addr);
-// }
-
 async fn accept_connection(stream: TcpStream) {
     let addr = stream
         .peer_addr()
@@ -125,56 +51,51 @@ async fn accept_connection(stream: TcpStream) {
     let (mut write, mut read) = ws_stream.split();
 
     // Each connection gets its own evaluator
-    let mut evaluator = Evaluator::new();
+    let mut grid = Grid::new();
 
     while let Some(msg) = read.try_next().await.unwrap_or(None) {
         if msg.is_text() {
-            let input = msg.to_text().unwrap_or("").trim().to_string();
+            let input = msg.to_text().unwrap();
 
-            let cmds = ["set", "get"];
-            let cmd = &input[0..3.min(input.len())]; // avoid panic on short strings
+            if let Ok(req) = serde_json::from_str::<LeadMsg>(&input) {
+                match req.msg_type {
+                    MsgType::Set => {
+                        let Some(cell_ref) = req.cell else { continue };
+                        let Some(raw) = req.raw else { continue };
 
-            if !cmds.iter().any(|c| c == &cmd) {
-                let _ = write
-                    .send(format!("ERR invalid command: {}", input).into())
-                    .await;
-                continue;
-            }
-
-            let rest = input[4..].trim();
-            let mut parts = rest.splitn(2, char::is_whitespace);
-
-            let raw_ref = parts.next().unwrap_or("").trim(); // cell reference
-            let raw_str = parts.next().unwrap_or("").trim(); // rest (value)
-
-            if let Ok(cell_ref) = CellRef::new(raw_ref.to_owned()) {
-                match cmd {
-                    "set" => match evaluator.set_cell(cell_ref.clone(), raw_str.to_owned()) {
-                        Ok(eval) => {
-                            let _ = write.send(format!("{} {}", raw_ref, eval).into()).await;
+                        match grid.set_cell(cell_ref.clone(), raw.to_owned()) {
+                            Ok(eval) => match eval {
+                                Eval::Literal(lit) => {
+                                    let res = LeadMsg {
+                                        msg_type: MsgType::Set,
+                                        cell: Some(cell_ref),
+                                        raw: Some(raw.to_string()),
+                                        eval: Some(lit),
+                                    };
+                                    let _ = write
+                                        .send(serde_json::to_string(&res).unwrap().into())
+                                        .await;
+                                }
+                            },
+                            Err(e) => {
+                                let res = LeadMsg {
+                                    msg_type: MsgType::Error,
+                                    cell: Some(cell_ref),
+                                    raw: Some(e.to_string()),
+                                    eval: None,
+                                };
+                                let _ = write
+                                    .send(serde_json::to_string(&res).unwrap().into())
+                                    .await;
+                            }
                         }
-                        Err(e) => {
-                            let _ = write.send(format!("ERR {}", e).into()).await;
-                        }
-                    },
-                    "get" => match evaluator.get_cell(cell_ref.clone()) {
-                        Ok(res) => {
-                            let _ = write
-                                .send(format!("{} {}", raw_ref, res.to_string()).into())
-                                .await;
-                        }
-                        Err(e) => {
-                            let _ = write.send(format!("ERR {}", e).into()).await;
-                        }
-                    },
+                    }
                     _ => {
-                        let _ = write.send("ERR impossible".into()).await;
+                        continue; // handle other cases
                     }
                 }
             } else {
-                let _ = write
-                    .send(format!("ERR invalid cell reference: {}", raw_ref).into())
-                    .await;
+                continue;
             }
         }
     }
diff --git a/backend/src/messages.rs b/backend/src/messages.rs
new file mode 100644
index 0000000..e9791cc
--- /dev/null
+++ b/backend/src/messages.rs
@@ -0,0 +1,19 @@
+use serde::{Deserialize, Serialize};
+
+use crate::{cell::CellRef, tokenizer::Literal};
+
+#[derive(Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum MsgType {
+    Set,
+    Get,
+    Error,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct LeadMsg {
+    pub msg_type: MsgType,
+    pub cell: Option<CellRef>,
+    pub raw: Option<String>,
+    pub eval: Option<Literal>,
+}
diff --git a/backend/src/parser.rs b/backend/src/parser.rs
index bbb9e16..4c31cd6 100644
--- a/backend/src/parser.rs
+++ b/backend/src/parser.rs
@@ -169,11 +169,9 @@ pub fn _parse(
 ) -> Result<Expr, String> {
     let mut lhs = match input.next() {
         Token::Literal(it) => Expr::Literal(it),
-        Token::Identifier(id) if id == "true" => Expr::Literal(Literal::Boolean(true)),
-        Token::Identifier(id) if id == "false" => Expr::Literal(Literal::Boolean(false)),
-        Token::Paren('(') => {
+        Token::OpenParen => {
             let lhs = _parse(input, 0, deps)?;
-            if input.next() != Token::Paren(')') {
+            if input.next() != Token::CloseParen {
                 return Err(format!("Parse error: expected closing paren."));
             }
             Expr::Group(Box::new(lhs))
@@ -194,14 +192,14 @@ pub fn _parse(
             }
         }
         Token::Identifier(id) => match input.peek() {
-            Token::Paren('(') => {
+            Token::OpenParen => {
                 input.next();
 
                 let mut args: Vec<Expr> = Vec::new();
                 loop {
                     let nxt = input.peek();
 
-                    if nxt == Token::Paren(')') {
+                    if nxt == Token::CloseParen {
                         input.next();
                         break;
                     } else if nxt != Token::Comma && args.len() != 0 {
@@ -286,6 +284,5 @@ pub fn _parse(
         }
     }
 
-
     Ok(lhs)
 }
diff --git a/backend/src/tokenizer.rs b/backend/src/tokenizer.rs
index 547aa2a..794b698 100644
--- a/backend/src/tokenizer.rs
+++ b/backend/src/tokenizer.rs
@@ -1,7 +1,9 @@
-#[derive(Debug, Clone, PartialEq)]
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "type", content = "value")]
 pub enum Literal {
-    Integer(i64),
-    Double(f64),
+    Number(f64),
     Boolean(bool),
     String(String),
 }
@@ -11,7 +13,8 @@ pub enum Token {
     Identifier(String), // Could be a function
     Literal(Literal),
     Operator(char),
-    Paren(char),
+    OpenParen,
+    CloseParen,
     Comma,
     Eof,
 }
@@ -39,29 +42,38 @@ impl Tokenizer {
                         break;
                     }
                 }
-                tokens.push(Token::Identifier(ident));
+                let res = match ident.as_str() {
+                    "true" => Token::Literal(Literal::Boolean(true)),
+                    "false" => Token::Literal(Literal::Boolean(false)),
+                    it => Token::Identifier(it.into()),
+                };
+
+                tokens.push(res);
             } else if c.is_ascii_digit() {
                 // parse number
                 let mut number = String::new();
                 let mut is_decimal = false;
+                let mut is_exp = false;
 
                 while let Some(&ch) = chars.peek() {
                     if ch.is_ascii_digit() {
                         number.push(ch);
                         chars.next();
-                    } else if ch == '.' && !is_decimal {
+                    } else if ch == '.' && !is_decimal && !is_exp {
                         is_decimal = true;
                         number.push(ch);
                         chars.next();
+                    } else if ch == 'e' && !is_decimal && !is_exp {
+                        is_exp = true;
+                        number.push(ch);
+                        chars.next();
                     } else {
                         break;
                     }
                 }
-                if is_decimal {
-                    tokens.push(Token::Literal(Literal::Double(number.parse().unwrap())))
-                } else {
-                    tokens.push(Token::Literal(Literal::Integer(number.parse().unwrap())))
-                };
+
+                // TODO: REMOVE UNWRAP
+                tokens.push(Token::Literal(Literal::Number(number.parse().unwrap())));
             } else if c == '"' || c == '\'' {
                 // parse string literal
                 let mut string = String::new();
@@ -89,7 +101,11 @@ impl Tokenizer {
                 tokens.push(Token::Operator(c));
                 chars.next();
             } else if "()".contains(c) {
-                tokens.push(Token::Paren(c));
+                if c == '(' {
+                    tokens.push(Token::OpenParen);
+                } else {
+                    tokens.push(Token::CloseParen);
+                }
                 chars.next();
             } else if c == ',' {
                 tokens.push(Token::Comma);
@@ -116,20 +132,140 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_tokenizer() {
-        let raw = "hello hello 1.23 this 5 (1+2)";
-        let expected: Vec<Token> = vec![
-            Token::Identifier("hello".to_string()),
-            Token::Identifier("hello".to_string()),
-            Token::Literal(Literal::Double(1.23)),
-            Token::Identifier("this".to_string()),
-            Token::Literal(Literal::Integer(5)),
-            Token::Paren('('),
-            Token::Literal(Literal::Integer(1)),
+    fn test_single_token() {
+        assert_eq!(
+            Tokenizer::new("1").unwrap().tokens,
+            Vec::from([Token::Literal(Literal::Number(1.0))])
+        );
+        assert_eq!(
+            Tokenizer::new("2.0").unwrap().tokens,
+            Vec::from([Token::Literal(Literal::Number(2.0))])
+        );
+        assert_eq!(
+            Tokenizer::new("\"hello\"").unwrap().tokens,
+            Vec::from([Token::Literal(Literal::String("hello".into()))])
+        );
+        assert_eq!(
+            Tokenizer::new("\'hello\'").unwrap().tokens,
+            Vec::from([Token::Literal(Literal::String("hello".into()))])
+        );
+        assert_eq!(
+            Tokenizer::new("hello").unwrap().tokens,
+            Vec::from([Token::Identifier("hello".into())])
+        );
+        assert_eq!(
+            Tokenizer::new("+").unwrap().tokens,
+            Vec::from([Token::Operator('+')])
+        );
+        assert_eq!(
+            Tokenizer::new(",").unwrap().tokens,
+            Vec::from([Token::Comma])
+        );
+        assert_eq!(
+            Tokenizer::new(")").unwrap().tokens,
+            Vec::from([Token::CloseParen])
+        );
+        assert_eq!(
+            Tokenizer::new("(").unwrap().tokens,
+            Vec::from([Token::OpenParen])
+        );
+    }
+
+    #[test]
+    fn test_token_punctuation() {
+        let mut exp = Vec::from([
+            Token::Comma,
+            Token::CloseParen,
+            Token::Comma,
+            Token::OpenParen,
+        ]);
+        exp.reverse();
+
+        assert_eq!(Tokenizer::new(", ) , (").unwrap().tokens, exp);
+    }
+
+    #[test]
+    fn test_token_operators() {
+        let mut exp = Vec::from([
             Token::Operator('+'),
-            Token::Literal(Literal::Integer(2)),
-            Token::Paren(')'),
+            Token::Operator('-'),
+            Token::Operator('*'),
+            Token::Operator('/'),
+            Token::Operator('^'),
+            Token::Operator('!'),
+            Token::Operator('%'),
+            Token::Operator('&'),
+            Token::Operator('|'),
+        ]);
+        exp.reverse();
+
+        assert_eq!(Tokenizer::new("+-*/^!%&|").unwrap().tokens, exp);
+    }
+
+    #[test]
+    fn test_token_string() {
+        let raw = "\"hello\" \'world\'";
+        let mut expected: Vec<Token> = vec![
+            Token::Literal(Literal::String("hello".into())),
+            Token::Literal(Literal::String("world".into())),
         ];
+        expected.reverse();
+        let t = Tokenizer::new(&raw).unwrap();
+        assert_eq!(t.tokens, expected);
+    }
+
+    #[test]
+    fn test_token_number() {
+        let raw = "123 4.56";
+        let mut expected: Vec<Token> = vec![
+            Token::Literal(Literal::Number(123.0)),
+            Token::Literal(Literal::Number(4.56)),
+        ];
+        expected.reverse();
+        let t = Tokenizer::new(&raw).unwrap();
+        assert_eq!(t.tokens, expected);
+    }
+
+    #[test]
+    fn test_token_boolean() {
+        let raw = "false true";
+        let mut expected: Vec<Token> = vec![
+            Token::Literal(Literal::Boolean(false)),
+            Token::Literal(Literal::Boolean(true)),
+        ];
+        expected.reverse();
+        let t = Tokenizer::new(&raw).unwrap();
+        assert_eq!(t.tokens, expected);
+    }
+
+    #[test]
+    fn test_token_identifier() {
+        let raw = "hello test";
+        let mut expected: Vec<Token> = vec![
+            Token::Identifier("hello".to_string()),
+            Token::Identifier("test".to_string()),
+        ];
+        expected.reverse();
+        let t = Tokenizer::new(&raw).unwrap();
+        assert_eq!(t.tokens, expected);
+    }
+
+    #[test]
+    fn test_token_mix() {
+        let raw = "hello test 1.23 this 5 (1+2)";
+        let mut expected: Vec<Token> = vec![
+            Token::Identifier("hello".to_string()),
+            Token::Identifier("test".to_string()),
+            Token::Literal(Literal::Number(1.23)),
+            Token::Identifier("this".to_string()),
+            Token::Literal(Literal::Number(5.0)),
+            Token::OpenParen,
+            Token::Literal(Literal::Number(1.0)),
+            Token::Operator('+'),
+            Token::Literal(Literal::Number(2.0)),
+            Token::CloseParen,
+        ];
+        expected.reverse();
         let t = Tokenizer::new(&raw).unwrap();
         assert_eq!(t.tokens, expected);
     }
diff --git a/frontend/src/app.css b/frontend/src/app.css
index 05decf4..f7e7bb8 100644
--- a/frontend/src/app.css
+++ b/frontend/src/app.css
@@ -111,6 +111,28 @@
 	--color-sidebar-ring: var(--sidebar-ring);
 }
 
+:root {
+	--sidebar: oklch(0.985 0 0);
+	--sidebar-foreground: oklch(0.145 0 0);
+	--sidebar-primary: oklch(0.205 0 0);
+	--sidebar-primary-foreground: oklch(0.985 0 0);
+	--sidebar-accent: oklch(0.97 0 0);
+	--sidebar-accent-foreground: oklch(0.205 0 0);
+	--sidebar-border: oklch(0.922 0 0);
+	--sidebar-ring: oklch(0.708 0 0);
+}
+
+.dark {
+	--sidebar: oklch(0.205 0 0);
+	--sidebar-foreground: oklch(0.985 0 0);
+	--sidebar-primary: oklch(0.488 0.243 264.376);
+	--sidebar-primary-foreground: oklch(0.985 0 0);
+	--sidebar-accent: oklch(0.269 0 0);
+	--sidebar-accent-foreground: oklch(0.985 0 0);
+	--sidebar-border: oklch(1 0 0 / 10%);
+	--sidebar-ring: oklch(0.439 0 0);
+}
+
 @layer base {
 	* {
 		@apply border-border outline-ring/50;
diff --git a/frontend/src/lib/components/grid/cell-header.svelte b/frontend/src/lib/components/grid/cell-header.svelte
index e654e08..87ed670 100644
--- a/frontend/src/lib/components/grid/cell-header.svelte
+++ b/frontend/src/lib/components/grid/cell-header.svelte
@@ -18,7 +18,7 @@
 		val: string;
 		active: boolean;
 		resizeable?: boolean;
-		direction?: 'col' | 'row';
+		direction?: 'col' | 'row' | 'blank';
 	} = $props();
 
 	// --- Drag Logic ---
@@ -62,7 +62,12 @@
 <div
 	style:width
 	style:height
-	class={clsx('placeholder group relative bg-background p-1 dark:bg-input/30', { active })}
+	class={clsx('placeholder group relative bg-background p-1', {
+		active,
+		col: direction === 'col',
+		row: direction === 'row',
+		blank: direction === 'blank'
+	})}
 >
 	<span class="pointer-events-none flex h-full w-full items-center justify-center select-none">
 		{val}
@@ -88,20 +93,34 @@
 		background-color: var(--color-background);
 	}
 
+	.placeholder.blank {
+		border: 1px solid var(--input);
+	}
+
+	.placeholder.blank,
+	.placeholder.row {
+		border-left: none;
+	}
+
+	.placeholder.blank,
+	.placeholder.col {
+		border-top: none;
+	}
+
 	.active {
-		border: 1px solid var(--color-primary);
 		background-color: color-mix(in oklab, var(--color-primary) 80%, var(--color-background) 80%);
+		font-weight: bold;
+		/* border: 1px solid var(--color-primary); */
 	}
 
 	/* --- Resizer Styles --- */
 	.resizer {
 		position: absolute;
-		/* Make it easier to grab */
-		z-index: 10;
 		/* Subtle visual cue, becomes more visible on hover */
 		background-color: var(--color-primary);
 		opacity: 0;
 		transition: opacity 0.1s ease-in-out;
+		z-index: 60;
 	}
 
 	/* Style for vertical (column) resizing */
@@ -113,7 +132,6 @@
 		height: 100%;
 	}
 
-	/* Style for horizontal (row) resizing */
 	.resizer-row {
 		cursor: row-resize;
 		bottom: -5px;
diff --git a/frontend/src/lib/components/grid/cell.svelte b/frontend/src/lib/components/grid/cell.svelte
index e835991..36b88a1 100644
--- a/frontend/src/lib/components/grid/cell.svelte
+++ b/frontend/src/lib/components/grid/cell.svelte
@@ -3,6 +3,7 @@
 	import clsx from 'clsx';
 
 	let {
+		cla = '',
 		width = '80px',
 		height = '30px',
 		raw_val = $bindable(''),
@@ -13,10 +14,11 @@
 		active = false,
 		editing = false
 	}: {
+		cla?: string;
 		width?: string;
 		height?: string;
 		raw_val?: string;
-		val?: number | string | undefined;
+		val?: LiteralValue | undefined;
 		onmousedown?: (e: MouseEvent) => void;
 		startediting?: () => void;
 		stopediting?: () => void;
@@ -51,9 +53,8 @@
 	<div use:autofocusWithin onkeydown={handleKeydown}>
 		<Input
 			style="width: {width}; height: {height}"
-			class="relative rounded-none p-1
-             !transition-none delay-0 duration-0
-             focus:z-20"
+			class="relative rounded-none p-1 !transition-none delay-0 duration-0
+			focus:z-20 focus:shadow-[0_0_0_1px_var(--color-primary)] focus:outline-none"
 			onblur={(e) => {
 				raw_val = (e.target as HTMLInputElement).value;
 				stopediting();
@@ -66,7 +67,7 @@
 		{onmousedown}
 		style:width
 		style:height
-		class={clsx('placeholder bg-background p-1 dark:bg-input/30', { active, 'z-20': active })}
+		class={clsx('placeholder bg-background p-1', { active }, cla)}
 	>
 		{#if raw_val !== '' || val !== ''}
 			<span class="pointer-events-none select-none">
@@ -89,6 +90,7 @@
 	}
 
 	.active {
+		z-index: 20;
 		border: 1px solid var(--color-primary);
 		outline: 1px solid var(--color-primary);
 	}
diff --git a/frontend/src/lib/components/grid/grid.svelte b/frontend/src/lib/components/grid/grid.svelte
index 5b5c98d..425ae6d 100644
--- a/frontend/src/lib/components/grid/grid.svelte
+++ b/frontend/src/lib/components/grid/grid.svelte
@@ -3,84 +3,57 @@
 	import Cell from '$lib/components/grid/cell.svelte';
 	import { onDestroy, onMount } from 'svelte';
 	import CellHeader from './cell-header.svelte';
-	import {
-		refFromStr,
-		splitErrorString,
-		colToStr,
-		refFromPos,
-		type CellData,
-		type CellValue
-	} from './utils';
+	import { colToStr, refToStr, type CellT } from './utils';
+	import clsx from 'clsx';
 
 	let {
-		socket
+		socket,
+		class: className = ''
 	}: {
+		class?: string;
 		socket: WebSocket;
 	} = $props();
 
 	socket.onmessage = (msg: MessageEvent) => {
-		const input = msg.data.toString().trim();
-
-		if (input.startsWith('ERR')) {
-			let split = splitErrorString(input);
-			toast.error(split[0], {
-				description: split[1]
-			});
+		let res: LeadMsg;
 
+		try {
+			res = JSON.parse(msg.data);
+			console.log(res);
+		} catch (err) {
+			console.error('Failed to parse LeadMsg:', err);
 			return;
 		}
 
-		let strRef: string | undefined;
-		let evalStr: string | undefined;
-
-		// Case 1: "Cell D4 = Integer(4)"
-		let match = input.match(/^Cell\s+([A-Z]+\d+)\s*=\s*(.+)$/);
-		if (match) {
-			[, strRef, evalStr] = match;
-		}
-
-		// Case 2: "D6 String("hello")" or "E9 Double(4.0)"
-		if (!match) {
-			match = input.match(/^([A-Z]+\d+)\s+(.+)$/);
-			if (match) {
-				[, strRef, evalStr] = match;
+		switch (res.msg_type) {
+			case 'error': {
+				toast.error('Error', {
+					description: res.raw
+				});
+				break;
+			}
+			case 'set': {
+				if (res.cell === undefined) {
+					console.error('Expected cell ref for SET response from server.');
+					return;
+				} else if (res.eval === undefined) {
+					console.error('Expected cell value for SET response from server.');
+					return;
+				}
+				setCellVal(res.cell.row, res.cell.col, res.eval.value);
+				break;
 			}
-		}
-
-		if (!strRef || !evalStr) {
-			console.warn('Unrecognized message:', input);
-			return;
-		}
-
-		console.log(`Cell: ${strRef}`);
-		console.log(`Eval: ${evalStr}`);
-
-		let { row, col } = refFromStr(strRef);
-
-		// Parse eval types
-		if (evalStr.startsWith('Integer(')) {
-			const num = parseInt(evalStr.match(/^Integer\(([-\d]+)\)$/)?.[1] ?? 'NaN', 10);
-			console.log(`Parsed integer:`, num);
-			setCellVal(row, col, num);
-		} else if (evalStr.startsWith('Double(')) {
-			const num = parseFloat(evalStr.match(/^Double\(([-\d.]+)\)$/)?.[1] ?? 'NaN');
-			console.log(`Parsed double:`, num);
-			setCellVal(row, col, num);
-		} else if (evalStr.startsWith('String(')) {
-			const str = evalStr.match(/^String\("(.+)"\)$/)?.[1];
-			console.log(`Parsed string:`, str);
-			setCellVal(row, col, str);
 		}
 	};
 
-	let rows = 100;
-	let cols = 60;
+	let rows = 50;
+	let cols = 40;
 
 	let default_row_height = '30px';
 	let default_col_width = '80px';
 
 	// Only store touched cells
-	let grid_vals: Record<string, CellData> = $state({});
+	let grid_vals: Record<string, CellT> = $state({});
 	let row_heights: Record<number, string> = $state({});
 	let col_widths: Record<number, string> = $state({});
 
@@ -136,7 +109,7 @@
 		}
 	};
 	const getCellVal = (i: number, j: number) => getCell(i, j)?.val ?? undefined;
-	const setCellVal = (i: number, j: number, val: CellValue) => {
+	const setCellVal = (i: number, j: number, val: LiteralValue) => {
 		if (grid_vals[key(i, j)] === undefined) {
 			console.warn('Cell raw value was undefined but recieved eval.');
 		} else {
@@ -144,20 +117,22 @@
 		}
 	};
 
-	const setCell = (i: number, j: number, v: string | undefined) => {
+	const setCell = (row: number, col: number, v: string | undefined) => {
 		// ignore “no value” so we don’t create keys on mount
-		if (v == null || v === '') delete grid_vals[key(i, j)];
+		if (v == null || v === '') delete grid_vals[key(row, col)];
 		else {
-			setCellRaw(i, j, v);
-			console.log(i, j);
-			socket.send(`set ${refFromPos(i, j).str} ${v}`);
+			setCellRaw(row, col, v);
+
+			let msg: LeadMsg = {
+				msg_type: 'set',
+				cell: { row, col },
+				raw: v
+			};
+
+			socket.send(JSON.stringify(msg));
 		}
 	};
 
-	// $effect(() => {
-	// 	$inspect(grid_vals);
-	// });
-
 	function handleCellInteraction(i: number, j: number, e: MouseEvent) {
 		if (editing_cell) {
 			// Get the actual input element that's being edited
@@ -170,7 +145,7 @@
 				e.preventDefault();
 
 				// --- This is the same reference-inserting logic as before ---
-				const ref = refFromPos(i, j).str;
+				const ref = refToStr(i, j);
 				if (el) {
 					const { selectionStart, selectionEnd } = el;
 					const before = el.value.slice(0, selectionStart ?? 0);
@@ -202,15 +177,18 @@
 	});
 </script>
 
-<div class="grid-wrapper relative max-h-[100vh] max-w-full overflow-auto">
-	<div class="sticky top-0 z-40 flex w-fit">
-		<div class="sticky top-0 left-0 z-50">
+<div
+	class={clsx('grid-wrapper relative h-full min-h-0 max-w-full min-w-0 overflow-auto', className)}
+>
+	<div class="sticky top-0 flex w-fit" style="z-index: {rows + 70}">
+		<div class="sticky top-0 left-0" style="z-index: {rows + 70}">
 			<CellHeader
 				resizeable={false}
 				height={default_row_height}
 				width={default_col_width}
 				val=""
 				active={false}
+				direction="blank"
 			/>
 		</div>
 
@@ -226,8 +204,8 @@
 		{/each}
 	</div>
 	{#each Array(rows) as _, i}
-		<div class="flex w-fit">
-			<div class="sticky left-0 z-30 flex w-fit">
+		<div class="relative flex w-fit">
+			<div class="sticky left-0 flex w-fit" style="z-index: {rows - i + 40}">
 				<CellHeader
 					direction="row"
 					width={default_col_width}
diff --git a/frontend/src/lib/components/grid/messages.d.ts b/frontend/src/lib/components/grid/messages.d.ts
new file mode 100644
index 0000000..224614b
--- /dev/null
+++ b/frontend/src/lib/components/grid/messages.d.ts
@@ -0,0 +1,19 @@
+interface LeadMsg {
+	msg_type: 'set' | 'get' | 'error';
+	cell?: CellRef;
+	raw?: string;
+	eval?: Literal;
+}
+
+interface CellRef {
+	row: number;
+	col: number;
+}
+
+type LiteralType = 'Number' | 'Boolean' | 'String';
+type LiteralValue = number | string | boolean;
+
+interface Literal {
+	type: LiteralType;
+	value: LiteralValue;
+}
diff --git a/frontend/src/lib/components/grid/utils.ts b/frontend/src/lib/components/grid/utils.ts
index 3152c16..bf5b806 100644
--- a/frontend/src/lib/components/grid/utils.ts
+++ b/frontend/src/lib/components/grid/utils.ts
@@ -1,14 +1,6 @@
-export type CellValue = number | string | undefined;
-
-export interface CellData {
+export interface CellT {
 	raw_val: string;
-	val: CellValue;
-}
-
-export interface CellRef {
-	row: number;
-	col: number;
-	str: string;
+	val: LiteralValue | undefined;
 }
 
 /**
@@ -26,7 +18,7 @@ export function refFromStr(ref: string): CellRef {
 	}
 
 	const row = parseInt(rowStr, 10);
-	return { row: row - 1, col: col - 1, str: ref };
+	return { row: row - 1, col: col - 1 };
 }
 
 /**
@@ -47,27 +39,6 @@ export function colToStr(col: number): string {
 /**
  * Zero indexed | A1 == {row: 0, col: 0};
  */
-export function refFromPos(row: number, col: number): CellRef {
-	return { row, col, str: colToStr(col) + (row + 1).toString() };
-}
-
-export function splitErrorString(errorString: string) {
-	// Remove the "ERR " prefix.
-	const content = errorString.substring(4);
-
-	// Find the index of the first colon.
-	const colonIndex = content.indexOf(':');
-
-	// If no colon is found, return the whole content as the first element.
-	if (colonIndex === -1) {
-		return [content.trim(), ''];
-	}
-
-	// Extract the part before the colon (the error type).
-	const errorType = content.substring(0, colonIndex).trim();
-
-	// Extract the part after the colon (the error message).
-	const errorMessage = content.substring(colonIndex + 1).trim();
-
-	return [errorType, errorMessage];
+export function refToStr(row: number, col: number): string {
+	return colToStr(col) + (row + 1).toString();
 }
diff --git a/frontend/src/lib/components/ui/lead-sidebar/lead-sidebar.svelte b/frontend/src/lib/components/ui/lead-sidebar/lead-sidebar.svelte
new file mode 100644
index 0000000..81b1c2b
--- /dev/null
+++ b/frontend/src/lib/components/ui/lead-sidebar/lead-sidebar.svelte
@@ -0,0 +1,82 @@
+<script lang="ts">
+	import CalendarIcon from '@lucide/svelte/icons/calendar';
+	import HouseIcon from '@lucide/svelte/icons/house';
+	import InboxIcon from '@lucide/svelte/icons/inbox';
+	import SearchIcon from '@lucide/svelte/icons/search';
+	import SettingsIcon from '@lucide/svelte/icons/settings';
+	import SunIcon from '@lucide/svelte/icons/sun';
+	import MoonIcon from '@lucide/svelte/icons/moon';
+	import * as Sidebar from '$lib/components/ui/sidebar/index.js';
+	import Button from '../button/button.svelte';
+	import { toggleMode } from 'mode-watcher';
+
+	// Menu items.
+	const items = [
+		{
+			title: 'Home',
+			url: '#',
+			icon: HouseIcon
+		},
+		{
+			title: 'Inbox',
+			url: '#',
+			icon: InboxIcon
+		},
+		{
+			title: 'Calendar',
+			url: '#',
+			icon: CalendarIcon
+		},
+		{
+			title: 'Search',
+			url: '#',
+			icon: SearchIcon
+		},
+		{
+			title: 'Settings',
+			url: '#',
+			icon: SettingsIcon
+		}
+	];
+</script>
+
+<Sidebar.Root variant="floating">
+	<Sidebar.Content>
+		<Sidebar.Group>
+			<Sidebar.GroupLabel>
+				<div class="flex w-full items-center justify-between">
+					<div>Lead</div>
+					<Sidebar.Trigger />
+				</div>
+			</Sidebar.GroupLabel>
+			<Sidebar.GroupContent>
+				<Sidebar.Menu>
+					{#each items as item (item.title)}
+						<Sidebar.MenuItem>
+							<Sidebar.MenuButton>
+								{#snippet child({ props })}
+									<a href={item.url} {...props}>
+										<item.icon />
+										<span>{item.title}</span>
+									</a>
+								{/snippet}
+							</Sidebar.MenuButton>
+						</Sidebar.MenuItem>
+					{/each}
+				</Sidebar.Menu>
+			</Sidebar.GroupContent>
+		</Sidebar.Group>
+	</Sidebar.Content>
+
+	<Sidebar.Footer>
+		<Button onclick={toggleMode} variant="ghost" size="icon">
+			<SunIcon
+				class="h-[1.2rem] w-[1.2rem] scale-100 rotate-0 !transition-all dark:scale-0 dark:-rotate-90"
+			/>
+			<MoonIcon
+				class="absolute h-[1.2rem] w-[1.2rem] scale-0 rotate-90 !transition-all dark:scale-100 dark:rotate-0"
+			/>
+			<span class="sr-only">Toggle theme</span>
+		</Button>
+	</Sidebar.Footer>
+</Sidebar.Root>
diff --git a/frontend/src/lib/components/ui/separator/index.ts b/frontend/src/lib/components/ui/separator/index.ts
new file mode 100644
index 0000000..82442d2
--- /dev/null
+++ b/frontend/src/lib/components/ui/separator/index.ts
@@ -0,0 +1,7 @@
+import Root from "./separator.svelte";
+
+export {
+	Root,
+	//
+	Root as Separator,
+};
diff --git a/frontend/src/lib/components/ui/separator/separator.svelte b/frontend/src/lib/components/ui/separator/separator.svelte
new file mode 100644
index 0000000..09d88f4
--- /dev/null
+++ b/frontend/src/lib/components/ui/separator/separator.svelte
@@ -0,0 +1,20 @@
+<script lang="ts">
+	import { Separator as SeparatorPrimitive } from "bits-ui";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: SeparatorPrimitive.RootProps = $props();
+</script>
+
+<SeparatorPrimitive.Root
+	bind:ref
+	data-slot="separator"
+	class={cn(
+		"bg-border shrink-0 data-[orientation=horizontal]:h-px data-[orientation=vertical]:h-full data-[orientation=horizontal]:w-full data-[orientation=vertical]:w-px",
+		className
+	)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sheet/index.ts b/frontend/src/lib/components/ui/sheet/index.ts
new file mode 100644
index 0000000..01d40c8
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/index.ts
@@ -0,0 +1,36 @@
+import { Dialog as SheetPrimitive } from "bits-ui";
+import Trigger from "./sheet-trigger.svelte";
+import Close from "./sheet-close.svelte";
+import Overlay from "./sheet-overlay.svelte";
+import Content from "./sheet-content.svelte";
+import Header from "./sheet-header.svelte";
+import Footer from "./sheet-footer.svelte";
+import Title from "./sheet-title.svelte";
+import Description from "./sheet-description.svelte";
+
+const Root = SheetPrimitive.Root;
+const Portal = SheetPrimitive.Portal;
+
+export {
+	Root,
+	Close,
+	Trigger,
+	Portal,
+	Overlay,
+	Content,
+	Header,
+	Footer,
+	Title,
+	Description,
+	//
+	Root as Sheet,
+	Close as SheetClose,
+	Trigger as SheetTrigger,
+	Portal as SheetPortal,
+	Overlay as SheetOverlay,
+	Content as SheetContent,
+	Header as SheetHeader,
+	Footer as SheetFooter,
+	Title as SheetTitle,
+	Description as SheetDescription,
+};
diff --git a/frontend/src/lib/components/ui/sheet/sheet-close.svelte b/frontend/src/lib/components/ui/sheet/sheet-close.svelte
new file mode 100644
index 0000000..ae382c1
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-close.svelte
@@ -0,0 +1,7 @@
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+
+	let { ref = $bindable(null), ...restProps }: SheetPrimitive.CloseProps = $props();
+</script>
+
+<SheetPrimitive.Close bind:ref data-slot="sheet-close" {...restProps} />
diff --git a/frontend/src/lib/components/ui/sheet/sheet-content.svelte b/frontend/src/lib/components/ui/sheet/sheet-content.svelte
new file mode 100644
index 0000000..856922e
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-content.svelte
@@ -0,0 +1,58 @@
+<script lang="ts" module>
+	import { tv, type VariantProps } from "tailwind-variants";
+	export const sheetVariants = tv({
+		base: "bg-background data-[state=open]:animate-in data-[state=closed]:animate-out fixed z-50 flex flex-col gap-4 shadow-lg transition ease-in-out data-[state=closed]:duration-300 data-[state=open]:duration-500",
+		variants: {
+			side: {
+				top: "data-[state=closed]:slide-out-to-top data-[state=open]:slide-in-from-top inset-x-0 top-0 h-auto border-b",
+				bottom: "data-[state=closed]:slide-out-to-bottom data-[state=open]:slide-in-from-bottom inset-x-0 bottom-0 h-auto border-t",
+				left: "data-[state=closed]:slide-out-to-left data-[state=open]:slide-in-from-left inset-y-0 left-0 h-full w-3/4 border-r sm:max-w-sm",
+				right: "data-[state=closed]:slide-out-to-right data-[state=open]:slide-in-from-right inset-y-0 right-0 h-full w-3/4 border-l sm:max-w-sm",
+			},
+		},
+		defaultVariants: {
+			side: "right",
+		},
+	});
+
+	export type Side = VariantProps<typeof sheetVariants>["side"];
+</script>
+
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+	import XIcon from "@lucide/svelte/icons/x";
+	import type { Snippet } from "svelte";
+	import SheetOverlay from "./sheet-overlay.svelte";
+	import { cn, type WithoutChildrenOrChild } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		side = "right",
+		portalProps,
+		children,
+		...restProps
+	}: WithoutChildrenOrChild<SheetPrimitive.ContentProps> & {
+		portalProps?: SheetPrimitive.PortalProps;
+		side?: Side;
+		children: Snippet;
+	} = $props();
+</script>
+
+<SheetPrimitive.Portal {...portalProps}>
+	<SheetOverlay />
+	<SheetPrimitive.Content
+		bind:ref
+		data-slot="sheet-content"
+		class={cn(sheetVariants({ side }), className)}
+		{...restProps}
+	>
+		{@render children?.()}
+		<SheetPrimitive.Close
+			class="ring-offset-background focus-visible:ring-ring rounded-xs focus-visible:outline-hidden absolute right-4 top-4 opacity-70 transition-opacity hover:opacity-100 focus-visible:ring-2 focus-visible:ring-offset-2 disabled:pointer-events-none"
+		>
+			<XIcon class="size-4" />
+			<span class="sr-only">Close</span>
+		</SheetPrimitive.Close>
+	</SheetPrimitive.Content>
+</SheetPrimitive.Portal>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-description.svelte b/frontend/src/lib/components/ui/sheet/sheet-description.svelte
new file mode 100644
index 0000000..333b17a
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-description.svelte
@@ -0,0 +1,17 @@
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: SheetPrimitive.DescriptionProps = $props();
+</script>
+
+<SheetPrimitive.Description
+	bind:ref
+	data-slot="sheet-description"
+	class={cn("text-muted-foreground text-sm", className)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-footer.svelte b/frontend/src/lib/components/ui/sheet/sheet-footer.svelte
new file mode 100644
index 0000000..dd9ed84
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-footer.svelte
@@ -0,0 +1,20 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLDivElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sheet-footer"
+	class={cn("mt-auto flex flex-col gap-2 p-4", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-header.svelte b/frontend/src/lib/components/ui/sheet/sheet-header.svelte
new file mode 100644
index 0000000..757a6a5
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-header.svelte
@@ -0,0 +1,20 @@
+<script lang="ts">
+	import type { HTMLAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLDivElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sheet-header"
+	class={cn("flex flex-col gap-1.5 p-4", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-overlay.svelte b/frontend/src/lib/components/ui/sheet/sheet-overlay.svelte
new file mode 100644
index 0000000..345e197
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-overlay.svelte
@@ -0,0 +1,20 @@
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: SheetPrimitive.OverlayProps = $props();
+</script>
+
+<SheetPrimitive.Overlay
+	bind:ref
+	data-slot="sheet-overlay"
+	class={cn(
+		"data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=open]:fade-in-0 fixed inset-0 z-50 bg-black/50",
+		className
+	)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-title.svelte b/frontend/src/lib/components/ui/sheet/sheet-title.svelte
new file mode 100644
index 0000000..9fda327
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-title.svelte
@@ -0,0 +1,17 @@
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: SheetPrimitive.TitleProps = $props();
+</script>
+
+<SheetPrimitive.Title
+	bind:ref
+	data-slot="sheet-title"
+	class={cn("text-foreground font-semibold", className)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sheet/sheet-trigger.svelte b/frontend/src/lib/components/ui/sheet/sheet-trigger.svelte
new file mode 100644
index 0000000..e266975
--- /dev/null
+++ b/frontend/src/lib/components/ui/sheet/sheet-trigger.svelte
@@ -0,0 +1,7 @@
+<script lang="ts">
+	import { Dialog as SheetPrimitive } from "bits-ui";
+
+	let { ref = $bindable(null), ...restProps }: SheetPrimitive.TriggerProps = $props();
+</script>
+
+<SheetPrimitive.Trigger bind:ref data-slot="sheet-trigger" {...restProps} />
diff --git a/frontend/src/lib/components/ui/sidebar/constants.ts b/frontend/src/lib/components/ui/sidebar/constants.ts
new file mode 100644
index 0000000..4de4435
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/constants.ts
@@ -0,0 +1,6 @@
+export const SIDEBAR_COOKIE_NAME = "sidebar:state";
+export const SIDEBAR_COOKIE_MAX_AGE = 60 * 60 * 24 * 7;
+export const SIDEBAR_WIDTH = "16rem";
+export const SIDEBAR_WIDTH_MOBILE = "18rem";
+export const SIDEBAR_WIDTH_ICON = "3rem";
+export const SIDEBAR_KEYBOARD_SHORTCUT = "b";
diff --git a/frontend/src/lib/components/ui/sidebar/context.svelte.ts b/frontend/src/lib/components/ui/sidebar/context.svelte.ts
new file mode 100644
index 0000000..15248ad
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/context.svelte.ts
@@ -0,0 +1,81 @@
+import { IsMobile } from "$lib/hooks/is-mobile.svelte.js";
+import { getContext, setContext } from "svelte";
+import { SIDEBAR_KEYBOARD_SHORTCUT } from "./constants.js";
+
+type Getter<T> = () => T;
+
+export type SidebarStateProps = {
+	/**
+	 * A getter function that returns the current open state of the sidebar.
+	 * We use a getter function here to support `bind:open` on the `Sidebar.Provider`
+	 * component.
+	 */
+	open: Getter<boolean>;
+
+	/**
+	 * A function that sets the open state of the sidebar. To support `bind:open`, we need
+	 * a source of truth for changing the open state to ensure it will be synced throughout
+	 * the sub-components and any `bind:` references.
+	 */
+	setOpen: (open: boolean) => void;
+};
+
+class SidebarState {
+	readonly props: SidebarStateProps;
+	open = $derived.by(() => this.props.open());
+	openMobile = $state(false);
+	setOpen: SidebarStateProps["setOpen"];
+	#isMobile: IsMobile;
+	state = $derived.by(() => (this.open ? "expanded" : "collapsed"));
+
+	constructor(props: SidebarStateProps) {
+		this.setOpen = props.setOpen;
+		this.#isMobile = new IsMobile();
+		this.props = props;
+	}
+
+	// Convenience getter for checking if the sidebar is mobile
+	// without this, we would need to use `sidebar.isMobile.current` everywhere
+	get isMobile() {
+		return this.#isMobile.current;
+	}
+
+	// Event handler to apply to the `<svelte:window>`
+	handleShortcutKeydown = (e: KeyboardEvent) => {
+		if (e.key === SIDEBAR_KEYBOARD_SHORTCUT && (e.metaKey || e.ctrlKey)) {
+			e.preventDefault();
+			this.toggle();
+		}
+	};
+
+	setOpenMobile = (value: boolean) => {
+		this.openMobile = value;
+	};
+
+	toggle = () => {
+		return this.#isMobile.current
+			? (this.openMobile = !this.openMobile)
+			: this.setOpen(!this.open);
+	};
+}
+
+const SYMBOL_KEY = "scn-sidebar";
+
+/**
+ * Instantiates a new `SidebarState` instance and sets it in the context.
+ *
+ * @param props The constructor props for the `SidebarState` class.
+ * @returns  The `SidebarState` instance.
+ */
+export function setSidebar(props: SidebarStateProps): SidebarState {
+	return setContext(Symbol.for(SYMBOL_KEY), new SidebarState(props));
+}
+
+/**
+ * Retrieves the `SidebarState` instance from the context. This is a class instance,
+ * so you cannot destructure it.
+ * @returns The `SidebarState` instance.
+ */
+export function useSidebar(): SidebarState {
+	return getContext(Symbol.for(SYMBOL_KEY));
+}
diff --git a/frontend/src/lib/components/ui/sidebar/index.ts b/frontend/src/lib/components/ui/sidebar/index.ts
new file mode 100644
index 0000000..318a341
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/index.ts
@@ -0,0 +1,75 @@
+import { useSidebar } from "./context.svelte.js";
+import Content from "./sidebar-content.svelte";
+import Footer from "./sidebar-footer.svelte";
+import GroupAction from "./sidebar-group-action.svelte";
+import GroupContent from "./sidebar-group-content.svelte";
+import GroupLabel from "./sidebar-group-label.svelte";
+import Group from "./sidebar-group.svelte";
+import Header from "./sidebar-header.svelte";
+import Input from "./sidebar-input.svelte";
+import Inset from "./sidebar-inset.svelte";
+import MenuAction from "./sidebar-menu-action.svelte";
+import MenuBadge from "./sidebar-menu-badge.svelte";
+import MenuButton from "./sidebar-menu-button.svelte";
+import MenuItem from "./sidebar-menu-item.svelte";
+import MenuSkeleton from "./sidebar-menu-skeleton.svelte";
+import MenuSubButton from "./sidebar-menu-sub-button.svelte";
+import MenuSubItem from "./sidebar-menu-sub-item.svelte";
+import MenuSub from "./sidebar-menu-sub.svelte";
+import Menu from "./sidebar-menu.svelte";
+import Provider from "./sidebar-provider.svelte";
+import Rail from "./sidebar-rail.svelte";
+import Separator from "./sidebar-separator.svelte";
+import Trigger from "./sidebar-trigger.svelte";
+import Root from "./sidebar.svelte";
+
+export {
+	Content,
+	Footer,
+	Group,
+	GroupAction,
+	GroupContent,
+	GroupLabel,
+	Header,
+	Input,
+	Inset,
+	Menu,
+	MenuAction,
+	MenuBadge,
+	MenuButton,
+	MenuItem,
+	MenuSkeleton,
+	MenuSub,
+	MenuSubButton,
+	MenuSubItem,
+	Provider,
+	Rail,
+	Root,
+	Separator,
+	//
+	Root as Sidebar,
+	Content as SidebarContent,
+	Footer as SidebarFooter,
+	Group as SidebarGroup,
+	GroupAction as SidebarGroupAction,
+	GroupContent as SidebarGroupContent,
+	GroupLabel as SidebarGroupLabel,
+	Header as SidebarHeader,
+	Input as SidebarInput,
+	Inset as SidebarInset,
+	Menu as SidebarMenu,
+	MenuAction as SidebarMenuAction,
+	MenuBadge as SidebarMenuBadge,
+	MenuButton as SidebarMenuButton,
+	MenuItem as SidebarMenuItem,
+	MenuSkeleton as SidebarMenuSkeleton,
+	MenuSub as SidebarMenuSub,
+	MenuSubButton as SidebarMenuSubButton,
+	MenuSubItem as SidebarMenuSubItem,
+	Provider as SidebarProvider,
+	Rail as SidebarRail,
+	Separator as SidebarSeparator,
+	Trigger as SidebarTrigger,
+	Trigger,
+	useSidebar,
+};
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-content.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-content.svelte
new file mode 100644
index 0000000..f121800
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-content.svelte
@@ -0,0 +1,24 @@
+<script lang="ts">
+	import type { HTMLAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-content"
+	data-sidebar="content"
+	class={cn(
+		"flex min-h-0 flex-1 flex-col gap-2 overflow-auto group-data-[collapsible=icon]:overflow-hidden",
+		className
+	)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-footer.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-footer.svelte
new file mode 100644
index 0000000..6259cb9
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-footer.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import type { HTMLAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-footer"
+	data-sidebar="footer"
+	class={cn("flex flex-col gap-2 p-2", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-group-action.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-group-action.svelte
new file mode 100644
index 0000000..fb84e4a
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-group-action.svelte
@@ -0,0 +1,36 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { Snippet } from "svelte";
+	import type { HTMLButtonAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		child,
+		...restProps
+	}: WithElementRef<HTMLButtonAttributes> & {
+		child?: Snippet<[{ props: Record<string, unknown> }]>;
+	} = $props();
+
+	const mergedProps = $derived({
+		class: cn(
+			"text-sidebar-foreground ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground outline-hidden absolute right-3 top-3.5 flex aspect-square w-5 items-center justify-center rounded-md p-0 transition-transform focus-visible:ring-2 [&>svg]:size-4 [&>svg]:shrink-0",
+			// Increases the hit area of the button on mobile.
+			"after:absolute after:-inset-2 md:after:hidden",
+			"group-data-[collapsible=icon]:hidden",
+			className
+		),
+		"data-slot": "sidebar-group-action",
+		"data-sidebar": "group-action",
+		...restProps,
+	});
+</script>
+
+{#if child}
+	{@render child({ props: mergedProps })}
+{:else}
+	<button bind:this={ref} {...mergedProps}>
+		{@render children?.()}
+	</button>
+{/if}
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-group-content.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-group-content.svelte
new file mode 100644
index 0000000..415255f
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-group-content.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLDivElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-group-content"
+	data-sidebar="group-content"
+	class={cn("w-full text-sm", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-group-label.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-group-label.svelte
new file mode 100644
index 0000000..e292945
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-group-label.svelte
@@ -0,0 +1,34 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { Snippet } from "svelte";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		children,
+		child,
+		class: className,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> & {
+		child?: Snippet<[{ props: Record<string, unknown> }]>;
+	} = $props();
+
+	const mergedProps = $derived({
+		class: cn(
+			"text-sidebar-foreground/70 ring-sidebar-ring outline-hidden flex h-8 shrink-0 items-center rounded-md px-2 text-xs font-medium transition-[margin,opacity] duration-200 ease-linear focus-visible:ring-2 [&>svg]:size-4 [&>svg]:shrink-0",
+			"group-data-[collapsible=icon]:-mt-8 group-data-[collapsible=icon]:opacity-0",
+			className
+		),
+		"data-slot": "sidebar-group-label",
+		"data-sidebar": "group-label",
+		...restProps,
+	});
+</script>
+
+{#if child}
+	{@render child({ props: mergedProps })}
+{:else}
+	<div bind:this={ref} {...mergedProps}>
+		{@render children?.()}
+	</div>
+{/if}
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-group.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-group.svelte
new file mode 100644
index 0000000..ec18a69
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-group.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import type { HTMLAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-group"
+	data-sidebar="group"
+	class={cn("relative flex w-full min-w-0 flex-col p-2", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-header.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-header.svelte
new file mode 100644
index 0000000..a1b2db1
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-header.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import type { HTMLAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-header"
+	data-sidebar="header"
+	class={cn("flex flex-col gap-2 p-2", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-input.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-input.svelte
new file mode 100644
index 0000000..19b3666
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-input.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import type { ComponentProps } from "svelte";
+	import { Input } from "$lib/components/ui/input/index.js";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		value = $bindable(""),
+		class: className,
+		...restProps
+	}: ComponentProps<typeof Input> = $props();
+</script>
+
+<Input
+	bind:ref
+	bind:value
+	data-slot="sidebar-input"
+	data-sidebar="input"
+	class={cn("bg-background h-8 w-full shadow-none", className)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-inset.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-inset.svelte
new file mode 100644
index 0000000..d862761
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-inset.svelte
@@ -0,0 +1,24 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<main
+	bind:this={ref}
+	data-slot="sidebar-inset"
+	class={cn(
+		"bg-background relative flex w-full flex-1 flex-col",
+		"md:peer-data-[variant=inset]:m-2 md:peer-data-[variant=inset]:ml-0 md:peer-data-[variant=inset]:peer-data-[state=collapsed]:ml-2 md:peer-data-[variant=inset]:rounded-xl md:peer-data-[variant=inset]:shadow-sm",
+		className
+	)}
+	{...restProps}
+>
+	{@render children?.()}
+</main>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-action.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-action.svelte
new file mode 100644
index 0000000..fa3fb0c
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-action.svelte
@@ -0,0 +1,43 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { Snippet } from "svelte";
+	import type { HTMLButtonAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		showOnHover = false,
+		children,
+		child,
+		...restProps
+	}: WithElementRef<HTMLButtonAttributes> & {
+		child?: Snippet<[{ props: Record<string, unknown> }]>;
+		showOnHover?: boolean;
+	} = $props();
+
+	const mergedProps = $derived({
+		class: cn(
+			"text-sidebar-foreground ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground peer-hover/menu-button:text-sidebar-accent-foreground outline-hidden absolute right-1 top-1.5 flex aspect-square w-5 items-center justify-center rounded-md p-0 transition-transform focus-visible:ring-2 [&>svg]:size-4 [&>svg]:shrink-0",
+			// Increases the hit area of the button on mobile.
+			"after:absolute after:-inset-2 md:after:hidden",
+			"peer-data-[size=sm]/menu-button:top-1",
+			"peer-data-[size=default]/menu-button:top-1.5",
+			"peer-data-[size=lg]/menu-button:top-2.5",
+			"group-data-[collapsible=icon]:hidden",
+			showOnHover &&
+				"peer-data-[active=true]/menu-button:text-sidebar-accent-foreground group-focus-within/menu-item:opacity-100 group-hover/menu-item:opacity-100 data-[state=open]:opacity-100 md:opacity-0",
+			className
+		),
+		"data-slot": "sidebar-menu-action",
+		"data-sidebar": "menu-action",
+		...restProps,
+	});
+</script>
+
+{#if child}
+	{@render child({ props: mergedProps })}
+{:else}
+	<button bind:this={ref} {...mergedProps}>
+		{@render children?.()}
+	</button>
+{/if}
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-badge.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-badge.svelte
new file mode 100644
index 0000000..69e5a3c
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-badge.svelte
@@ -0,0 +1,29 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-menu-badge"
+	data-sidebar="menu-badge"
+	class={cn(
+		"text-sidebar-foreground pointer-events-none absolute right-1 flex h-5 min-w-5 select-none items-center justify-center rounded-md px-1 text-xs font-medium tabular-nums",
+		"peer-hover/menu-button:text-sidebar-accent-foreground peer-data-[active=true]/menu-button:text-sidebar-accent-foreground",
+		"peer-data-[size=sm]/menu-button:top-1",
+		"peer-data-[size=default]/menu-button:top-1.5",
+		"peer-data-[size=lg]/menu-button:top-2.5",
+		"group-data-[collapsible=icon]:hidden",
+		className
+	)}
+	{...restProps}
+>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-button.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-button.svelte
new file mode 100644
index 0000000..4bef683
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-button.svelte
@@ -0,0 +1,103 @@
+<script lang="ts" module>
+	import { tv, type VariantProps } from "tailwind-variants";
+
+	export const sidebarMenuButtonVariants = tv({
+		base: "peer/menu-button outline-hidden ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground group-has-data-[sidebar=menu-action]/menu-item:pr-8 data-[active=true]:bg-sidebar-accent data-[active=true]:text-sidebar-accent-foreground data-[state=open]:hover:bg-sidebar-accent data-[state=open]:hover:text-sidebar-accent-foreground group-data-[collapsible=icon]:size-8! group-data-[collapsible=icon]:p-2! flex w-full items-center gap-2 overflow-hidden rounded-md p-2 text-left text-sm transition-[width,height,padding] focus-visible:ring-2 disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 data-[active=true]:font-medium [&>span:last-child]:truncate [&>svg]:size-4 [&>svg]:shrink-0",
+		variants: {
+			variant: {
+				default: "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
+				outline:
+					"bg-background hover:bg-sidebar-accent hover:text-sidebar-accent-foreground shadow-[0_0_0_1px_var(--sidebar-border)] hover:shadow-[0_0_0_1px_var(--sidebar-accent)]",
+			},
+			size: {
+				default: "h-8 text-sm",
+				sm: "h-7 text-xs",
+				lg: "group-data-[collapsible=icon]:p-0! h-12 text-sm",
+			},
+		},
+		defaultVariants: {
+			variant: "default",
+			size: "default",
+		},
+	});
+
+	export type SidebarMenuButtonVariant = VariantProps<
+		typeof sidebarMenuButtonVariants
+	>["variant"];
+	export type SidebarMenuButtonSize = VariantProps<typeof sidebarMenuButtonVariants>["size"];
+</script>
+
+<script lang="ts">
+	import * as Tooltip from "$lib/components/ui/tooltip/index.js";
+	import { cn, type WithElementRef, type WithoutChildrenOrChild } from "$lib/utils.js";
+	import { mergeProps } from "bits-ui";
+	import type { ComponentProps, Snippet } from "svelte";
+	import type { HTMLAttributes } from "svelte/elements";
+	import { useSidebar } from "./context.svelte.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		child,
+		variant = "default",
+		size = "default",
+		isActive = false,
+		tooltipContent,
+		tooltipContentProps,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLButtonElement>, HTMLButtonElement> & {
+		isActive?: boolean;
+		variant?: SidebarMenuButtonVariant;
+		size?: SidebarMenuButtonSize;
+		tooltipContent?: Snippet | string;
+		tooltipContentProps?: WithoutChildrenOrChild<ComponentProps<typeof Tooltip.Content>>;
+		child?: Snippet<[{ props: Record<string, unknown> }]>;
+	} = $props();
+
+	const sidebar = useSidebar();
+
+	const buttonProps = $derived({
+		class: cn(sidebarMenuButtonVariants({ variant, size }), className),
+		"data-slot": "sidebar-menu-button",
+		"data-sidebar": "menu-button",
+		"data-size": size,
+		"data-active": isActive,
+		...restProps,
+	});
+</script>
+
+{#snippet Button({ props }: { props?: Record<string, unknown> })}
+	{@const mergedProps = mergeProps(buttonProps, props)}
+	{#if child}
+		{@render child({ props: mergedProps })}
+	{:else}
+		<button bind:this={ref} {...mergedProps}>
+			{@render children?.()}
+		</button>
+	{/if}
+{/snippet}
+
+{#if !tooltipContent}
+	{@render Button({})}
+{:else}
+	<Tooltip.Root>
+		<Tooltip.Trigger>
+			{#snippet child({ props })}
+				{@render Button({ props })}
+			{/snippet}
+		</Tooltip.Trigger>
+		<Tooltip.Content
+			side="right"
+			align="center"
+			hidden={sidebar.state !== "collapsed" || sidebar.isMobile}
+			{...tooltipContentProps}
+		>
+			{#if typeof tooltipContent === "string"}
+				{tooltipContent}
+			{:else if tooltipContent}
+				{@render tooltipContent()}
+			{/if}
+		</Tooltip.Content>
+	</Tooltip.Root>
+{/if}
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-item.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-item.svelte
new file mode 100644
index 0000000..4db4453
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-item.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLLIElement>, HTMLLIElement> = $props();
+</script>
+
+<li
+	bind:this={ref}
+	data-slot="sidebar-menu-item"
+	data-sidebar="menu-item"
+	class={cn("group/menu-item relative", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</li>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-skeleton.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-skeleton.svelte
new file mode 100644
index 0000000..cc63b04
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-skeleton.svelte
@@ -0,0 +1,36 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import { Skeleton } from "$lib/components/ui/skeleton/index.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		showIcon = false,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLElement>> & {
+		showIcon?: boolean;
+	} = $props();
+
+	// Random width between 50% and 90%
+	const width = `${Math.floor(Math.random() * 40) + 50}%`;
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="sidebar-menu-skeleton"
+	data-sidebar="menu-skeleton"
+	class={cn("flex h-8 items-center gap-2 rounded-md px-2", className)}
+	{...restProps}
+>
+	{#if showIcon}
+		<Skeleton class="size-4 rounded-md" data-sidebar="menu-skeleton-icon" />
+	{/if}
+	<Skeleton
+		class="max-w-(--skeleton-width) h-4 flex-1"
+		data-sidebar="menu-skeleton-text"
+		style="--skeleton-width: {width};"
+	/>
+	{@render children?.()}
+</div>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte
new file mode 100644
index 0000000..987f104
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte
@@ -0,0 +1,43 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { Snippet } from "svelte";
+	import type { HTMLAnchorAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		children,
+		child,
+		class: className,
+		size = "md",
+		isActive = false,
+		...restProps
+	}: WithElementRef<HTMLAnchorAttributes> & {
+		child?: Snippet<[{ props: Record<string, unknown> }]>;
+		size?: "sm" | "md";
+		isActive?: boolean;
+	} = $props();
+
+	const mergedProps = $derived({
+		class: cn(
+			"text-sidebar-foreground ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground [&>svg]:text-sidebar-accent-foreground outline-hidden flex h-7 min-w-0 -translate-x-px items-center gap-2 overflow-hidden rounded-md px-2 focus-visible:ring-2 disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 [&>span:last-child]:truncate [&>svg]:size-4 [&>svg]:shrink-0",
+			"data-[active=true]:bg-sidebar-accent data-[active=true]:text-sidebar-accent-foreground",
+			size === "sm" && "text-xs",
+			size === "md" && "text-sm",
+			"group-data-[collapsible=icon]:hidden",
+			className
+		),
+		"data-slot": "sidebar-menu-sub-button",
+		"data-sidebar": "menu-sub-button",
+		"data-size": size,
+		"data-active": isActive,
+		...restProps,
+	});
+</script>
+
+{#if child}
+	{@render child({ props: mergedProps })}
+{:else}
+	<a bind:this={ref} {...mergedProps}>
+		{@render children?.()}
+	</a>
+{/if}
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-item.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-item.svelte
new file mode 100644
index 0000000..681d0f1
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub-item.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		children,
+		class: className,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLLIElement>> = $props();
+</script>
+
+<li
+	bind:this={ref}
+	data-slot="sidebar-menu-sub-item"
+	data-sidebar="menu-sub-item"
+	class={cn("group/menu-sub-item relative", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</li>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub.svelte
new file mode 100644
index 0000000..8ab1111
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu-sub.svelte
@@ -0,0 +1,25 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLUListElement>> = $props();
+</script>
+
+<ul
+	bind:this={ref}
+	data-slot="sidebar-menu-sub"
+	data-sidebar="menu-sub"
+	class={cn(
+		"border-sidebar-border mx-3.5 flex min-w-0 translate-x-px flex-col gap-1 border-l px-2.5 py-0.5",
+		"group-data-[collapsible=icon]:hidden",
+		className
+	)}
+	{...restProps}
+>
+	{@render children?.()}
+</ul>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-menu.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-menu.svelte
new file mode 100644
index 0000000..946ccce
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-menu.svelte
@@ -0,0 +1,21 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLUListElement>, HTMLUListElement> = $props();
+</script>
+
+<ul
+	bind:this={ref}
+	data-slot="sidebar-menu"
+	data-sidebar="menu"
+	class={cn("flex w-full min-w-0 flex-col gap-1", className)}
+	{...restProps}
+>
+	{@render children?.()}
+</ul>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-provider.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-provider.svelte
new file mode 100644
index 0000000..2c13b5d
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-provider.svelte
@@ -0,0 +1,53 @@
+<script lang="ts">
+	import * as Tooltip from '$lib/components/ui/tooltip/index.js';
+	import { cn, type WithElementRef } from '$lib/utils.js';
+	import type { HTMLAttributes } from 'svelte/elements';
+	import {
+		SIDEBAR_COOKIE_MAX_AGE,
+		SIDEBAR_COOKIE_NAME,
+		SIDEBAR_WIDTH,
+		SIDEBAR_WIDTH_ICON
+	} from './constants.js';
+	import { setSidebar } from './context.svelte.js';
+
+	let {
+		ref = $bindable(null),
+		open = $bindable(false),
+		onOpenChange = () => {},
+		class: className,
+		style,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLDivElement>> & {
+		open?: boolean;
+		onOpenChange?: (open: boolean) => void;
+	} = $props();
+
+	const sidebar = setSidebar({
+		open: () => open,
+		setOpen: (value: boolean) => {
+			open = value;
+			onOpenChange(value);
+
+			// This sets the cookie to keep the sidebar state.
+			document.cookie = `${SIDEBAR_COOKIE_NAME}=${open}; path=/; max-age=${SIDEBAR_COOKIE_MAX_AGE}`;
+		}
+	});
+</script>
+
+<svelte:window onkeydown={sidebar.handleShortcutKeydown} />
+
+<Tooltip.Provider delayDuration={0}>
+	<div
+		data-slot="sidebar-wrapper"
+		style="--sidebar-width: {SIDEBAR_WIDTH}; --sidebar-width-icon: {SIDEBAR_WIDTH_ICON}; {style}"
+		class={cn(
+			'group/sidebar-wrapper flex min-h-svh w-full has-data-[variant=inset]:bg-sidebar',
+			className
+		)}
+		bind:this={ref}
+		{...restProps}
+	>
+		{@render children?.()}
+	</div>
+</Tooltip.Provider>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-rail.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-rail.svelte
new file mode 100644
index 0000000..5df80f7
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-rail.svelte
@@ -0,0 +1,36 @@
+<script lang="ts">
+	import { cn, type WithElementRef } from '$lib/utils.js';
+	import type { HTMLAttributes } from 'svelte/elements';
+	import { useSidebar } from './context.svelte.js';
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLButtonElement>, HTMLButtonElement> = $props();
+
+	const sidebar = useSidebar();
+</script>
+
+<button
+	bind:this={ref}
+	data-sidebar="rail"
+	data-slot="sidebar-rail"
+	aria-label="Toggle Sidebar"
+	tabIndex={-1}
+	onclick={sidebar.toggle}
+	title="Toggle Sidebar"
+	class={cn(
+		'absolute inset-y-0 z-[2000] hidden w-4 -translate-x-1/2 transition-all ease-linear group-data-[side=left]:-right-4 group-data-[side=right]:left-0 after:absolute after:inset-y-0 after:left-[calc(1/2*100%-1px)] after:w-[2px] hover:after:bg-sidebar-border sm:flex',
+		'in-data-[side=left]:cursor-w-resize in-data-[side=right]:cursor-e-resize',
+		'[[data-side=left][data-state=collapsed]_&]:cursor-e-resize [[data-side=right][data-state=collapsed]_&]:cursor-w-resize',
+		'group-data-[collapsible=offcanvas]:translate-x-0 group-data-[collapsible=offcanvas]:after:left-full hover:group-data-[collapsible=offcanvas]:bg-sidebar',
+		'[[data-side=left][data-collapsible=offcanvas]_&]:-right-2',
+		'[[data-side=right][data-collapsible=offcanvas]_&]:-left-2',
+		className
+	)}
+	{...restProps}
+>
+	{@render children?.()}
+</button>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-separator.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-separator.svelte
new file mode 100644
index 0000000..5a7deda
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-separator.svelte
@@ -0,0 +1,19 @@
+<script lang="ts">
+	import { Separator } from "$lib/components/ui/separator/index.js";
+	import { cn } from "$lib/utils.js";
+	import type { ComponentProps } from "svelte";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: ComponentProps<typeof Separator> = $props();
+</script>
+
+<Separator
+	bind:ref
+	data-slot="sidebar-separator"
+	data-sidebar="separator"
+	class={cn("bg-sidebar-border", className)}
+	{...restProps}
+/>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar-trigger.svelte b/frontend/src/lib/components/ui/sidebar/sidebar-trigger.svelte
new file mode 100644
index 0000000..1825182
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar-trigger.svelte
@@ -0,0 +1,35 @@
+<script lang="ts">
+	import { Button } from "$lib/components/ui/button/index.js";
+	import { cn } from "$lib/utils.js";
+	import PanelLeftIcon from "@lucide/svelte/icons/panel-left";
+	import type { ComponentProps } from "svelte";
+	import { useSidebar } from "./context.svelte.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		onclick,
+		...restProps
+	}: ComponentProps<typeof Button> & {
+		onclick?: (e: MouseEvent) => void;
+	} = $props();
+
+	const sidebar = useSidebar();
+</script>
+
+<Button
+	data-sidebar="trigger"
+	data-slot="sidebar-trigger"
+	variant="ghost"
+	size="icon"
+	class={cn("size-7", className)}
+	type="button"
+	onclick={(e) => {
+		onclick?.(e);
+		sidebar.toggle();
+	}}
+	{...restProps}
+>
+	<PanelLeftIcon />
+	<span class="sr-only">Toggle Sidebar</span>
+</Button>
diff --git a/frontend/src/lib/components/ui/sidebar/sidebar.svelte b/frontend/src/lib/components/ui/sidebar/sidebar.svelte
new file mode 100644
index 0000000..f825157
--- /dev/null
+++ b/frontend/src/lib/components/ui/sidebar/sidebar.svelte
@@ -0,0 +1,101 @@
+<script lang="ts">
+	import * as Sheet from '$lib/components/ui/sheet/index.js';
+	import { cn, type WithElementRef } from '$lib/utils.js';
+	import type { HTMLAttributes } from 'svelte/elements';
+	import { SIDEBAR_WIDTH_MOBILE } from './constants.js';
+	import { useSidebar } from './context.svelte.js';
+
+	let {
+		ref = $bindable(null),
+		side = 'left',
+		variant = 'sidebar',
+		collapsible = 'offcanvas',
+		class: className,
+		children,
+		...restProps
+	}: WithElementRef<HTMLAttributes<HTMLDivElement>> & {
+		side?: 'left' | 'right';
+		variant?: 'sidebar' | 'floating' | 'inset';
+		collapsible?: 'offcanvas' | 'icon' | 'none';
+	} = $props();
+
+	const sidebar = useSidebar();
+</script>
+
+{#if collapsible === 'none'}
+	<div
+		class={cn(
+			'flex h-full w-(--sidebar-width) flex-col bg-sidebar text-sidebar-foreground',
+			className
+		)}
+		bind:this={ref}
+		{...restProps}
+	>
+		{@render children?.()}
+	</div>
+{:else if sidebar.isMobile}
+	<Sheet.Root bind:open={() => sidebar.openMobile, (v) => sidebar.setOpenMobile(v)} {...restProps}>
+		<Sheet.Content
+			data-sidebar="sidebar"
+			data-slot="sidebar"
+			data-mobile="true"
+			class="w-(--sidebar-width) bg-sidebar p-0 text-sidebar-foreground [&>button]:hidden"
+			style="--sidebar-width: {SIDEBAR_WIDTH_MOBILE};"
+			{side}
+		>
+			<Sheet.Header class="sr-only">
+				<Sheet.Title>Sidebar</Sheet.Title>
+				<Sheet.Description>Displays the mobile sidebar.</Sheet.Description>
+			</Sheet.Header>
+			<div class="flex h-full w-full flex-col">
+				{@render children?.()}
+			</div>
+		</Sheet.Content>
+	</Sheet.Root>
+{:else}
+	<div
+		bind:this={ref}
+		class="group peer hidden text-sidebar-foreground md:block"
+		data-state={sidebar.state}
+		data-collapsible={sidebar.state === 'collapsed' ? collapsible : ''}
+		data-variant={variant}
+		data-side={side}
+		data-slot="sidebar"
+	>
+		<!-- This is what handles the sidebar gap on desktop -->
+		<div
+			data-slot="sidebar-gap"
+			class={cn(
+				'relative w-(--sidebar-width) bg-transparent transition-[width] duration-100 ease-linear',
+				'group-data-[collapsible=offcanvas]:w-0',
+				'group-data-[side=right]:rotate-180',
+				variant === 'floating' || variant === 'inset'
+					? 'group-data-[collapsible=icon]:w-[calc(var(--sidebar-width-icon)+(--spacing(4))+2px)]'
+					: 'group-data-[collapsible=icon]:w-(--sidebar-width-icon)'
+			)}
+		></div>
+		<div
+			data-slot="sidebar-container"
+			class={cn(
+				'fixed inset-y-0 z-[1000] hidden h-svh w-(--sidebar-width) transition-[left,right,width] duration-100 ease-linear md:flex',
+				side === 'left'
+					? 'left-0 group-data-[collapsible=offcanvas]:left-[calc(var(--sidebar-width)*-1)]'
+					: 'right-0 group-data-[collapsible=offcanvas]:right-[calc(var(--sidebar-width)*-1)]',
+				// Adjust the padding for floating and inset variants.
+				variant === 'floating' || variant === 'inset'
+					? 'p-2 group-data-[collapsible=icon]:w-[calc(var(--sidebar-width-icon)+(--spacing(4))+2px)]'
+					: 'group-data-[collapsible=icon]:w-(--sidebar-width-icon) group-data-[side=left]:border-r group-data-[side=right]:border-l',
+				className
+			)}
+			{...restProps}
+		>
+			<div
+				data-sidebar="sidebar"
+				data-slot="sidebar-inner"
+				class="flex h-full w-full flex-col bg-sidebar group-data-[variant=floating]:rounded-lg group-data-[variant=floating]:border group-data-[variant=floating]:border-sidebar-border group-data-[variant=floating]:shadow-sm"
+			>
+				{@render children?.()}
+			</div>
+		</div>
+	</div>
+{/if}
diff --git a/frontend/src/lib/components/ui/skeleton/index.ts b/frontend/src/lib/components/ui/skeleton/index.ts
new file mode 100644
index 0000000..186db21
--- /dev/null
+++ b/frontend/src/lib/components/ui/skeleton/index.ts
@@ -0,0 +1,7 @@
+import Root from "./skeleton.svelte";
+
+export {
+	Root,
+	//
+	Root as Skeleton,
+};
diff --git a/frontend/src/lib/components/ui/skeleton/skeleton.svelte b/frontend/src/lib/components/ui/skeleton/skeleton.svelte
new file mode 100644
index 0000000..c7e3d26
--- /dev/null
+++ b/frontend/src/lib/components/ui/skeleton/skeleton.svelte
@@ -0,0 +1,17 @@
+<script lang="ts">
+	import { cn, type WithElementRef, type WithoutChildren } from "$lib/utils.js";
+	import type { HTMLAttributes } from "svelte/elements";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		...restProps
+	}: WithoutChildren<WithElementRef<HTMLAttributes<HTMLDivElement>>> = $props();
+</script>
+
+<div
+	bind:this={ref}
+	data-slot="skeleton"
+	class={cn("bg-accent animate-pulse rounded-md", className)}
+	{...restProps}
+></div>
diff --git a/frontend/src/lib/components/ui/tooltip/index.ts b/frontend/src/lib/components/ui/tooltip/index.ts
new file mode 100644
index 0000000..313a7f0
--- /dev/null
+++ b/frontend/src/lib/components/ui/tooltip/index.ts
@@ -0,0 +1,21 @@
+import { Tooltip as TooltipPrimitive } from "bits-ui";
+import Trigger from "./tooltip-trigger.svelte";
+import Content from "./tooltip-content.svelte";
+
+const Root = TooltipPrimitive.Root;
+const Provider = TooltipPrimitive.Provider;
+const Portal = TooltipPrimitive.Portal;
+
+export {
+	Root,
+	Trigger,
+	Content,
+	Provider,
+	Portal,
+	//
+	Root as Tooltip,
+	Content as TooltipContent,
+	Trigger as TooltipTrigger,
+	Provider as TooltipProvider,
+	Portal as TooltipPortal,
+};
diff --git a/frontend/src/lib/components/ui/tooltip/tooltip-content.svelte b/frontend/src/lib/components/ui/tooltip/tooltip-content.svelte
new file mode 100644
index 0000000..e495efe
--- /dev/null
+++ b/frontend/src/lib/components/ui/tooltip/tooltip-content.svelte
@@ -0,0 +1,47 @@
+<script lang="ts">
+	import { Tooltip as TooltipPrimitive } from "bits-ui";
+	import { cn } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		sideOffset = 0,
+		side = "top",
+		children,
+		arrowClasses,
+		...restProps
+	}: TooltipPrimitive.ContentProps & {
+		arrowClasses?: string;
+	} = $props();
+</script>
+
+<TooltipPrimitive.Portal>
+	<TooltipPrimitive.Content
+		bind:ref
+		data-slot="tooltip-content"
+		{sideOffset}
+		{side}
+		class={cn(
+			"bg-primary text-primary-foreground animate-in fade-in-0 zoom-in-95 data-[state=closed]:animate-out data-[state=closed]:fade-out-0 data-[state=closed]:zoom-out-95 data-[side=bottom]:slide-in-from-top-2 data-[side=left]:slide-in-from-right-2 data-[side=right]:slide-in-from-left-2 data-[side=top]:slide-in-from-bottom-2 origin-(--bits-tooltip-content-transform-origin) z-50 w-fit text-balance rounded-md px-3 py-1.5 text-xs",
+			className
+		)}
+		{...restProps}
+	>
+		{@render children?.()}
+		<TooltipPrimitive.Arrow>
+			{#snippet child({ props })}
+				<div
+					class={cn(
+						"bg-primary z-50 size-2.5 rotate-45 rounded-[2px]",
+						"data-[side=top]:translate-x-1/2 data-[side=top]:translate-y-[calc(-50%_+_2px)]",
+						"data-[side=bottom]:-translate-x-1/2 data-[side=bottom]:-translate-y-[calc(-50%_+_1px)]",
+						"data-[side=right]:translate-x-[calc(50%_+_2px)] data-[side=right]:translate-y-1/2",
+						"data-[side=left]:-translate-y-[calc(50%_-_3px)]",
+						arrowClasses
+					)}
+					{...props}
+				></div>
+			{/snippet}
+		</TooltipPrimitive.Arrow>
+	</TooltipPrimitive.Content>
+</TooltipPrimitive.Portal>
diff --git a/frontend/src/lib/components/ui/tooltip/tooltip-trigger.svelte b/frontend/src/lib/components/ui/tooltip/tooltip-trigger.svelte
new file mode 100644
index 0000000..1acdaa4
--- /dev/null
+++ b/frontend/src/lib/components/ui/tooltip/tooltip-trigger.svelte
@@ -0,0 +1,7 @@
+<script lang="ts">
+	import { Tooltip as TooltipPrimitive } from "bits-ui";
+
+	let { ref = $bindable(null), ...restProps }: TooltipPrimitive.TriggerProps = $props();
+</script>
+
+<TooltipPrimitive.Trigger bind:ref data-slot="tooltip-trigger" {...restProps} />
diff --git a/frontend/src/lib/hooks/is-mobile.svelte.ts b/frontend/src/lib/hooks/is-mobile.svelte.ts
new file mode 100644
index 0000000..4829c00
--- /dev/null
+++ b/frontend/src/lib/hooks/is-mobile.svelte.ts
@@ -0,0 +1,9 @@
+import { MediaQuery } from "svelte/reactivity";
+
+const DEFAULT_MOBILE_BREAKPOINT = 768;
+
+export class IsMobile extends MediaQuery {
+	constructor(breakpoint: number = DEFAULT_MOBILE_BREAKPOINT) {
+		super(`max-width: ${breakpoint - 1}px`);
+	}
+}
diff --git a/frontend/src/routes/+layout.svelte b/frontend/src/routes/+layout.svelte
index 921aa44..f4e4afd 100644
--- a/frontend/src/routes/+layout.svelte
+++ b/frontend/src/routes/+layout.svelte
@@ -3,6 +3,8 @@
 	import { ModeWatcher } from 'mode-watcher';
 	import { Toaster } from '$lib/components/ui/sonner/index.js';
 	import favicon from '$lib/assets/favicon.svg';
+	import * as Sidebar from '$lib/components/ui/sidebar/index.js';
+	import LeadSidebar from '$lib/components/ui/lead-sidebar/lead-sidebar.svelte';
 
 	let { children } = $props();
 </script>
@@ -13,4 +15,10 @@
 	<link rel="icon" href={favicon} />
 </svelte:head>
 
-{@render children?.()}
+<Sidebar.Provider>
+	<LeadSidebar />
+
+	<main>
+		{@render children?.()}
+	</main>
+</Sidebar.Provider>
diff --git a/frontend/src/routes/+layout.ts b/frontend/src/routes/+layout.ts
new file mode 100644
index 0000000..189f71e
--- /dev/null
+++ b/frontend/src/routes/+layout.ts
@@ -0,0 +1 @@
+export const prerender = true;
diff --git a/frontend/src/routes/+page.svelte b/frontend/src/routes/+page.svelte
index f4ab7e6..e412480 100644
--- a/frontend/src/routes/+page.svelte
+++ b/frontend/src/routes/+page.svelte
@@ -1,24 +1,37 @@
 <script lang="ts">
-	import SunIcon from '@lucide/svelte/icons/sun';
-	import MoonIcon from '@lucide/svelte/icons/moon';
-
-	import { Button } from '$lib/components/ui/button/index.js';
-	import { toggleMode } from 'mode-watcher';
 	import Grid from '$lib/components/grid/grid.svelte';
+	import * as Sidebar from '$lib/components/ui/sidebar/index.js';
+	import { fade } from 'svelte/transition';
+
+	import { useSidebar } from '$lib/components/ui/sidebar/index.js';
+	const sidebar = useSidebar();
 
 	let socket = new WebSocket('ws://localhost:7050');
 </script>
 
-<!-- <Button onclick={toggleMode} variant="outline" size="icon"> -->
-<!-- 	<SunIcon -->
-<!-- 		class="h-[1.2rem] w-[1.2rem] scale-100 rotate-0 !transition-all dark:scale-0 dark:-rotate-90" -->
-<!-- 	/> -->
-<!-- 	<MoonIcon -->
-<!-- 		class="absolute h-[1.2rem] w-[1.2rem] scale-0 rotate-90 !transition-all dark:scale-100 dark:rotate-0" -->
-<!-- 	/> -->
-<!-- 	<span class="sr-only">Toggle theme</span> -->
-<!-- </Button> -->
+{#if sidebar?.openMobile || sidebar?.open}
+	<button
+		class="fixed inset-0 z-[700] bg-black/40"
+		aria-label="Close sidebar"
+		onclick={() => (sidebar.isMobile ? sidebar.setOpenMobile(false) : sidebar.setOpen(false))}
+		transition:fade={{ duration: 100 }}
+	></button>
+{/if}
 
-<div class="m-0">
-	<Grid {socket} />
+<div class="absolute left-0 min-h-0 w-full">
+	<div class="flex h-[100vh] flex-col">
+		<div class="h-[60px] w-full p-3">
+			<Sidebar.Trigger />
+		</div>
+
+		<div class="grid-wrapper min-h-0 w-full flex-1">
+			<Grid class="h-full min-w-0" {socket} />
+		</div>
+	</div>
 </div>
+
+<style>
+	.grid-wrapper {
+		border-top: 2px solid var(--color-input);
+	}
+</style>