diff --git a/backend/src/evaluator.rs b/backend/src/evaluator.rs
index f54dc99..f23fc7c 100644
--- a/backend/src/evaluator.rs
+++ b/backend/src/evaluator.rs
@@ -28,9 +28,9 @@ impl Evaluator {
         };
     }
 
-    pub fn set_cell(&mut self, cell_ref: CellRef, raw_val: String) -> Result<(), String> {
+    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 Ok(());
+            return self.get_cell(cell_ref);
         }
 
         let eval: Eval;
@@ -50,19 +50,23 @@ impl Evaluator {
             }
         }
 
-        self.cells.insert(cell_ref, Cell::new(eval, raw_val));
-        Ok(())
+        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<(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.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));
@@ -87,7 +91,7 @@ impl Evaluator {
     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())?.1,
+            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)?;
@@ -151,6 +155,14 @@ 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 {
+                    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) {
                 return Ok(Eval::Literal(res));
             }
diff --git a/backend/src/main.rs b/backend/src/main.rs
index 953c6d6..43323f3 100644
--- a/backend/src/main.rs
+++ b/backend/src/main.rs
@@ -80,6 +80,36 @@ async fn main() -> Result<(), Error> {
     // }
 }
 
+// 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()
@@ -94,15 +124,57 @@ async fn accept_connection(stream: TcpStream) {
 
     let (mut write, mut read) = ws_stream.split();
 
-    // We should not forward messages other than text or binary.
+    // Each connection gets its own evaluator
+    let mut evaluator = Evaluator::new();
+
     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;
+        if msg.is_text() {
+            let input = msg.to_text().unwrap_or("").trim().to_string();
+
+            let cmds = ["set", "get"];
+            let cmd = &input[0..3.min(input.len())]; // avoid panic on short strings
+
+            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;
+                        }
+                        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;
+                    }
+                }
+            } else {
+                let _ = write
+                    .send(format!("ERR invalid cell reference: {}", raw_ref).into())
+                    .await;
             }
         }
     }
diff --git a/frontend/package.json b/frontend/package.json
index 2889186..604cc1d 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -29,6 +29,7 @@
 		"prettier-plugin-tailwindcss": "^0.6.11",
 		"svelte": "^5.0.0",
 		"svelte-check": "^4.0.0",
+		"svelte-sonner": "^1.0.5",
 		"tailwind-merge": "^3.3.1",
 		"tailwind-variants": "^1.0.0",
 		"tailwindcss": "^4.0.0",
diff --git a/frontend/pnpm-lock.yaml b/frontend/pnpm-lock.yaml
index af48336..a1016cb 100644
--- a/frontend/pnpm-lock.yaml
+++ b/frontend/pnpm-lock.yaml
@@ -57,6 +57,9 @@ importers:
       svelte-check:
         specifier: ^4.0.0
         version: 4.3.1(picomatch@4.0.3)(svelte@5.38.6)(typescript@5.9.2)
+      svelte-sonner:
+        specifier: ^1.0.5
+        version: 1.0.5(svelte@5.38.6)
       tailwind-merge:
         specifier: ^3.3.1
         version: 3.3.1
@@ -859,6 +862,11 @@ packages:
     peerDependencies:
       svelte: ^5.7.0
 
+  runed@0.28.0:
+    resolution: {integrity: sha512-k2xx7RuO9hWcdd9f+8JoBeqWtYrm5CALfgpkg2YDB80ds/QE4w0qqu34A7fqiAwiBBSBQOid7TLxwxVC27ymWQ==}
+    peerDependencies:
+      svelte: ^5.7.0
+
   runed@0.29.2:
     resolution: {integrity: sha512-0cq6cA6sYGZwl/FvVqjx9YN+1xEBu9sDDyuWdDW1yWX7JF2wmvmVKfH+hVCZs+csW+P3ARH92MjI3H9QTagOQA==}
     peerDependencies:
@@ -890,6 +898,11 @@ packages:
       svelte: ^4.0.0 || ^5.0.0-next.0
       typescript: '>=5.0.0'
 
+  svelte-sonner@1.0.5:
+    resolution: {integrity: sha512-9dpGPFqKb/QWudYqGnEz93vuY+NgCEvyNvxoCLMVGw6sDN/3oVeKV1xiEirW2E1N3vJEyj5imSBNOGltQHA7mg==}
+    peerDependencies:
+      svelte: ^5.0.0
+
   svelte-toolbelt@0.7.1:
     resolution: {integrity: sha512-HcBOcR17Vx9bjaOceUvxkY3nGmbBmCBBbuWLLEWO6jtmWH8f/QoWmbyUfQZrpDINH39en1b8mptfPQT9VKQ1xQ==}
     engines: {node: '>=18', pnpm: '>=8.7.0'}
@@ -1584,6 +1597,11 @@ snapshots:
       esm-env: 1.2.2
       svelte: 5.38.6
 
+  runed@0.28.0(svelte@5.38.6):
+    dependencies:
+      esm-env: 1.2.2
+      svelte: 5.38.6
+
   runed@0.29.2(svelte@5.38.6):
     dependencies:
       esm-env: 1.2.2
@@ -1619,6 +1637,11 @@ snapshots:
     transitivePeerDependencies:
       - picomatch
 
+  svelte-sonner@1.0.5(svelte@5.38.6):
+    dependencies:
+      runed: 0.28.0(svelte@5.38.6)
+      svelte: 5.38.6
+
   svelte-toolbelt@0.7.1(svelte@5.38.6):
     dependencies:
       clsx: 2.1.1
diff --git a/frontend/src/app.css b/frontend/src/app.css
index e48f5f0..05decf4 100644
--- a/frontend/src/app.css
+++ b/frontend/src/app.css
@@ -1,121 +1,121 @@
-@import "tailwindcss";
+@import 'tailwindcss';
 
-@import "tw-animate-css";
+@import 'tw-animate-css';
 
 @custom-variant dark (&:is(.dark *));
 
 :root {
-  --radius: 0.625rem;
-  --background: oklch(1 0 0);
-  --foreground: oklch(0.129 0.042 264.695);
-  --card: oklch(1 0 0);
-  --card-foreground: oklch(0.129 0.042 264.695);
-  --popover: oklch(1 0 0);
-  --popover-foreground: oklch(0.129 0.042 264.695);
-  --primary: oklch(0.208 0.042 265.755);
-  --primary-foreground: oklch(0.984 0.003 247.858);
-  --secondary: oklch(0.968 0.007 247.896);
-  --secondary-foreground: oklch(0.208 0.042 265.755);
-  --muted: oklch(0.968 0.007 247.896);
-  --muted-foreground: oklch(0.554 0.046 257.417);
-  --accent: oklch(0.968 0.007 247.896);
-  --accent-foreground: oklch(0.208 0.042 265.755);
-  --destructive: oklch(0.577 0.245 27.325);
-  --border: oklch(0.929 0.013 255.508);
-  --input: oklch(0.929 0.013 255.508);
-  --ring: oklch(0.704 0.04 256.788);
-  --chart-1: oklch(0.646 0.222 41.116);
-  --chart-2: oklch(0.6 0.118 184.704);
-  --chart-3: oklch(0.398 0.07 227.392);
-  --chart-4: oklch(0.828 0.189 84.429);
-  --chart-5: oklch(0.769 0.188 70.08);
-  --sidebar: oklch(0.984 0.003 247.858);
-  --sidebar-foreground: oklch(0.129 0.042 264.695);
-  --sidebar-primary: oklch(0.208 0.042 265.755);
-  --sidebar-primary-foreground: oklch(0.984 0.003 247.858);
-  --sidebar-accent: oklch(0.968 0.007 247.896);
-  --sidebar-accent-foreground: oklch(0.208 0.042 265.755);
-  --sidebar-border: oklch(0.929 0.013 255.508);
-  --sidebar-ring: oklch(0.704 0.04 256.788);
+	--radius: 0.65rem;
+	--background: oklch(1 0 0);
+	--foreground: oklch(0.141 0.005 285.823);
+	--card: oklch(1 0 0);
+	--card-foreground: oklch(0.141 0.005 285.823);
+	--popover: oklch(1 0 0);
+	--popover-foreground: oklch(0.141 0.005 285.823);
+	--primary: oklch(0.623 0.214 259.815);
+	--primary-foreground: oklch(0.97 0.014 254.604);
+	--secondary: oklch(0.967 0.001 286.375);
+	--secondary-foreground: oklch(0.21 0.006 285.885);
+	--muted: oklch(0.967 0.001 286.375);
+	--muted-foreground: oklch(0.552 0.016 285.938);
+	--accent: oklch(0.967 0.001 286.375);
+	--accent-foreground: oklch(0.21 0.006 285.885);
+	--destructive: oklch(0.577 0.245 27.325);
+	--border: oklch(0.92 0.004 286.32);
+	--input: oklch(0.92 0.004 286.32);
+	--ring: oklch(0.623 0.214 259.815);
+	--chart-1: oklch(0.646 0.222 41.116);
+	--chart-2: oklch(0.6 0.118 184.704);
+	--chart-3: oklch(0.398 0.07 227.392);
+	--chart-4: oklch(0.828 0.189 84.429);
+	--chart-5: oklch(0.769 0.188 70.08);
+	--sidebar: oklch(0.985 0 0);
+	--sidebar-foreground: oklch(0.141 0.005 285.823);
+	--sidebar-primary: oklch(0.623 0.214 259.815);
+	--sidebar-primary-foreground: oklch(0.97 0.014 254.604);
+	--sidebar-accent: oklch(0.967 0.001 286.375);
+	--sidebar-accent-foreground: oklch(0.21 0.006 285.885);
+	--sidebar-border: oklch(0.92 0.004 286.32);
+	--sidebar-ring: oklch(0.623 0.214 259.815);
 }
 
 .dark {
-  --background: oklch(0.129 0.042 264.695);
-  --foreground: oklch(0.984 0.003 247.858);
-  --card: oklch(0.208 0.042 265.755);
-  --card-foreground: oklch(0.984 0.003 247.858);
-  --popover: oklch(0.208 0.042 265.755);
-  --popover-foreground: oklch(0.984 0.003 247.858);
-  --primary: oklch(0.929 0.013 255.508);
-  --primary-foreground: oklch(0.208 0.042 265.755);
-  --secondary: oklch(0.279 0.041 260.031);
-  --secondary-foreground: oklch(0.984 0.003 247.858);
-  --muted: oklch(0.279 0.041 260.031);
-  --muted-foreground: oklch(0.704 0.04 256.788);
-  --accent: oklch(0.279 0.041 260.031);
-  --accent-foreground: oklch(0.984 0.003 247.858);
-  --destructive: oklch(0.704 0.191 22.216);
-  --border: oklch(1 0 0 / 10%);
-  --input: oklch(1 0 0 / 15%);
-  --ring: oklch(0.551 0.027 264.364);
-  --chart-1: oklch(0.488 0.243 264.376);
-  --chart-2: oklch(0.696 0.17 162.48);
-  --chart-3: oklch(0.769 0.188 70.08);
-  --chart-4: oklch(0.627 0.265 303.9);
-  --chart-5: oklch(0.645 0.246 16.439);
-  --sidebar: oklch(0.208 0.042 265.755);
-  --sidebar-foreground: oklch(0.984 0.003 247.858);
-  --sidebar-primary: oklch(0.488 0.243 264.376);
-  --sidebar-primary-foreground: oklch(0.984 0.003 247.858);
-  --sidebar-accent: oklch(0.279 0.041 260.031);
-  --sidebar-accent-foreground: oklch(0.984 0.003 247.858);
-  --sidebar-border: oklch(1 0 0 / 10%);
-  --sidebar-ring: oklch(0.551 0.027 264.364);
+	--background: oklch(0.141 0.005 285.823);
+	--foreground: oklch(0.985 0 0);
+	--card: oklch(0.21 0.006 285.885);
+	--card-foreground: oklch(0.985 0 0);
+	--popover: oklch(0.21 0.006 285.885);
+	--popover-foreground: oklch(0.985 0 0);
+	--primary: oklch(0.546 0.245 262.881);
+	--primary-foreground: oklch(0.379 0.146 265.522);
+	--secondary: oklch(0.274 0.006 286.033);
+	--secondary-foreground: oklch(0.985 0 0);
+	--muted: oklch(0.274 0.006 286.033);
+	--muted-foreground: oklch(0.705 0.015 286.067);
+	--accent: oklch(0.274 0.006 286.033);
+	--accent-foreground: oklch(0.985 0 0);
+	--destructive: oklch(0.704 0.191 22.216);
+	--border: oklch(1 0 0 / 10%);
+	--input: oklch(1 0 0 / 15%);
+	--ring: oklch(0.488 0.243 264.376);
+	--chart-1: oklch(0.488 0.243 264.376);
+	--chart-2: oklch(0.696 0.17 162.48);
+	--chart-3: oklch(0.769 0.188 70.08);
+	--chart-4: oklch(0.627 0.265 303.9);
+	--chart-5: oklch(0.645 0.246 16.439);
+	--sidebar: oklch(0.21 0.006 285.885);
+	--sidebar-foreground: oklch(0.985 0 0);
+	--sidebar-primary: oklch(0.546 0.245 262.881);
+	--sidebar-primary-foreground: oklch(0.379 0.146 265.522);
+	--sidebar-accent: oklch(0.274 0.006 286.033);
+	--sidebar-accent-foreground: oklch(0.985 0 0);
+	--sidebar-border: oklch(1 0 0 / 10%);
+	--sidebar-ring: oklch(0.488 0.243 264.376);
 }
 
 @theme inline {
-  --radius-sm: calc(var(--radius) - 4px);
-  --radius-md: calc(var(--radius) - 2px);
-  --radius-lg: var(--radius);
-  --radius-xl: calc(var(--radius) + 4px);
-  --color-background: var(--background);
-  --color-foreground: var(--foreground);
-  --color-card: var(--card);
-  --color-card-foreground: var(--card-foreground);
-  --color-popover: var(--popover);
-  --color-popover-foreground: var(--popover-foreground);
-  --color-primary: var(--primary);
-  --color-primary-foreground: var(--primary-foreground);
-  --color-secondary: var(--secondary);
-  --color-secondary-foreground: var(--secondary-foreground);
-  --color-muted: var(--muted);
-  --color-muted-foreground: var(--muted-foreground);
-  --color-accent: var(--accent);
-  --color-accent-foreground: var(--accent-foreground);
-  --color-destructive: var(--destructive);
-  --color-border: var(--border);
-  --color-input: var(--input);
-  --color-ring: var(--ring);
-  --color-chart-1: var(--chart-1);
-  --color-chart-2: var(--chart-2);
-  --color-chart-3: var(--chart-3);
-  --color-chart-4: var(--chart-4);
-  --color-chart-5: var(--chart-5);
-  --color-sidebar: var(--sidebar);
-  --color-sidebar-foreground: var(--sidebar-foreground);
-  --color-sidebar-primary: var(--sidebar-primary);
-  --color-sidebar-primary-foreground: var(--sidebar-primary-foreground);
-  --color-sidebar-accent: var(--sidebar-accent);
-  --color-sidebar-accent-foreground: var(--sidebar-accent-foreground);
-  --color-sidebar-border: var(--sidebar-border);
-  --color-sidebar-ring: var(--sidebar-ring);
+	--radius-sm: calc(var(--radius) - 4px);
+	--radius-md: calc(var(--radius) - 2px);
+	--radius-lg: var(--radius);
+	--radius-xl: calc(var(--radius) + 4px);
+	--color-background: var(--background);
+	--color-foreground: var(--foreground);
+	--color-card: var(--card);
+	--color-card-foreground: var(--card-foreground);
+	--color-popover: var(--popover);
+	--color-popover-foreground: var(--popover-foreground);
+	--color-primary: var(--primary);
+	--color-primary-foreground: var(--primary-foreground);
+	--color-secondary: var(--secondary);
+	--color-secondary-foreground: var(--secondary-foreground);
+	--color-muted: var(--muted);
+	--color-muted-foreground: var(--muted-foreground);
+	--color-accent: var(--accent);
+	--color-accent-foreground: var(--accent-foreground);
+	--color-destructive: var(--destructive);
+	--color-border: var(--border);
+	--color-input: var(--input);
+	--color-ring: var(--ring);
+	--color-chart-1: var(--chart-1);
+	--color-chart-2: var(--chart-2);
+	--color-chart-3: var(--chart-3);
+	--color-chart-4: var(--chart-4);
+	--color-chart-5: var(--chart-5);
+	--color-sidebar: var(--sidebar);
+	--color-sidebar-foreground: var(--sidebar-foreground);
+	--color-sidebar-primary: var(--sidebar-primary);
+	--color-sidebar-primary-foreground: var(--sidebar-primary-foreground);
+	--color-sidebar-accent: var(--sidebar-accent);
+	--color-sidebar-accent-foreground: var(--sidebar-accent-foreground);
+	--color-sidebar-border: var(--sidebar-border);
+	--color-sidebar-ring: var(--sidebar-ring);
 }
 
 @layer base {
-  * {
-    @apply border-border outline-ring/50;
-  }
-  body {
-    @apply bg-background text-foreground;
-  }
-}
\ No newline at end of file
+	* {
+		@apply border-border outline-ring/50;
+	}
+	body {
+		@apply bg-background text-foreground;
+	}
+}
diff --git a/frontend/src/lib/components/grid/cell-header.svelte b/frontend/src/lib/components/grid/cell-header.svelte
new file mode 100644
index 0000000..de23b45
--- /dev/null
+++ b/frontend/src/lib/components/grid/cell-header.svelte
@@ -0,0 +1,125 @@
+<script lang="ts">
+	import clsx from 'clsx';
+
+	let {
+		width = '80px',
+		height = '30px',
+		setColWidth = () => {},
+		setRowHeight = () => {},
+		val,
+		active,
+		direction = 'col' // New prop: 'col' for right-side drag, 'row' for bottom-side
+	}: {
+		width?: string;
+		height?: string;
+		setColWidth?: (width: string) => void;
+		setRowHeight?: (height: string) => void;
+		val: string;
+		active: boolean;
+		direction?: 'col' | 'row';
+	} = $props();
+
+	// --- Drag Logic ---
+	const handleMouseDown = (startEvent: MouseEvent) => {
+		// Prevent text selection during drag
+		startEvent.preventDefault();
+
+		const target = startEvent.currentTarget as HTMLElement;
+		const parent = target.parentElement!;
+
+		// Store the initial position and size
+		const startX = startEvent.clientX;
+		const startY = startEvent.clientY;
+		const startWidth = parent.offsetWidth;
+		const startHeight = parent.offsetHeight;
+
+		const handleMouseMove = (moveEvent: MouseEvent) => {
+			if (direction === 'col') {
+				const dx = moveEvent.clientX - startX;
+				// Enforce a minimum width of 40px
+				setColWidth(`${Math.max(40, startWidth + dx)}px`);
+			} else {
+				const dy = moveEvent.clientY - startY;
+				// Enforce a minimum height of 20px
+				setRowHeight(`${Math.max(30, startHeight + dy)}px`);
+			}
+		};
+
+		const handleMouseUp = () => {
+			// Cleanup: remove the global listeners
+			window.removeEventListener('mousemove', handleMouseMove);
+			window.removeEventListener('mouseup', handleMouseUp);
+		};
+
+		// Add global listeners to track mouse movement anywhere on the page
+		window.addEventListener('mousemove', handleMouseMove);
+		window.addEventListener('mouseup', handleMouseUp);
+	};
+</script>
+
+<div
+	style:width
+	style:height
+	class={clsx('placeholder group relative bg-background p-1 dark:bg-input/30', { active })}
+>
+	<span class="pointer-events-none flex h-full w-full items-center justify-center select-none">
+		{val}
+	</span>
+
+	<div
+		role="separator"
+		aria-label="Resize handle"
+		onmousedown={handleMouseDown}
+		class={clsx('resizer', {
+			'resizer-col': direction === 'col',
+			'resizer-row': direction === 'row'
+		})}
+	/>
+</div>
+
+<style>
+	.placeholder {
+		font-size: 14px;
+		border: 1px solid var(--input);
+		overflow: hidden;
+	}
+
+	.active {
+		border: 1px solid var(--color-primary);
+		background-color: color-mix(in oklab, var(--color-primary) 40%, transparent);
+	}
+
+	/* --- Resizer Styles --- */
+	.resizer {
+		position: absolute;
+		/* Make it easier to grab */
+		z-index: 10;
+		/* Subtle visual cue, becomes more visible on hover */
+		background-color: transparent;
+		transition: background-color 0.2s ease-in-out;
+	}
+
+	/* Style for vertical (column) resizing */
+	.resizer-col {
+		cursor: col-resize;
+		top: 0;
+		right: 0;
+		width: 8px; /* Larger grab area */
+		height: 100%;
+	}
+
+	/* Style for horizontal (row) resizing */
+	.resizer-row {
+		cursor: row-resize;
+		bottom: 0;
+		left: 0;
+		height: 8px; /* Larger grab area */
+		width: 100%;
+	}
+
+	/* Make the handle visible when hovering over the component */
+	.group:hover > .resizer {
+		background-color: var(--color-primary);
+		opacity: 0.5;
+	}
+</style>
diff --git a/frontend/src/lib/components/grid/cell.svelte b/frontend/src/lib/components/grid/cell.svelte
new file mode 100644
index 0000000..314fe67
--- /dev/null
+++ b/frontend/src/lib/components/grid/cell.svelte
@@ -0,0 +1,90 @@
+<script lang="ts">
+	import { Input } from '$lib/components/ui/input/index.js';
+	import clsx from 'clsx';
+
+	let {
+		width = '80px',
+		height = '30px',
+		raw_val = $bindable(''),
+		val = undefined,
+		onmousedown = () => {},
+		startediting = () => {},
+		stopediting = () => {},
+		active = false,
+		editing = false
+	}: {
+		width?: string;
+		height?: string;
+		raw_val?: string;
+		val?: number | string | undefined;
+		onmousedown?: (e: MouseEvent) => void;
+		startediting?: () => void;
+		stopediting?: () => void;
+		active?: boolean;
+		editing?: boolean;
+	} = $props();
+
+	// focus the first focusable descendant (the inner <input>)
+	function autofocusWithin(node: HTMLElement) {
+		queueMicrotask(() => {
+			const el = node.querySelector('input') as HTMLInputElement | null;
+			if (el !== null) {
+				el.value = raw_val;
+				el.focus();
+			}
+		});
+	}
+
+	function handleKeydown(e: KeyboardEvent) {
+		if (e.key === 'Enter' || e.key === 'NumpadEnter' || e.key == 'Escape') {
+			e.preventDefault(); // avoid form submit/line break
+			const el = (e.currentTarget as HTMLElement).querySelector('input') as HTMLInputElement | null;
+			el?.blur(); // triggers on:blur below
+		}
+	}
+</script>
+
+{#if editing}
+	<div use:autofocusWithin onkeydown={handleKeydown}>
+		<Input
+			style="width: {width}; height: {height}"
+			class="relative rounded-none p-1
+             !transition-none delay-0 duration-0
+             focus:z-50"
+			onblur={(e) => {
+				raw_val = (e.target as HTMLInputElement).value;
+				stopediting();
+			}}
+		/>
+	</div>
+{:else}
+	<div
+		ondblclick={startediting}
+		{onmousedown}
+		style:width
+		style:height
+		class={clsx('placeholder bg-background p-1 dark:bg-input/30', { active, 'z-50': active })}
+	>
+		{#if raw_val !== '' || val !== ''}
+			<span class="pointer-events-none select-none">
+				{#if val !== undefined}
+					{val}
+				{:else}
+					{raw_val}
+				{/if}
+			</span>
+		{/if}
+	</div>
+{/if}
+
+<style>
+	.placeholder {
+		border: 1px solid var(--input);
+		overflow: hidden;
+	}
+
+	.active {
+		border: 1px solid var(--color-primary);
+		outline: 1px solid var(--color-primary);
+	}
+</style>
diff --git a/frontend/src/lib/components/grid/grid.svelte b/frontend/src/lib/components/grid/grid.svelte
index e69de29..98b27df 100644
--- a/frontend/src/lib/components/grid/grid.svelte
+++ b/frontend/src/lib/components/grid/grid.svelte
@@ -0,0 +1,260 @@
+<script lang="ts">
+	import { toast } from 'svelte-sonner';
+	import Cell from '$lib/components/grid/cell.svelte';
+	import { onDestroy, onMount } from 'svelte';
+	import CellHeader from './cell-header.svelte';
+	import { fromGridRef, toColLetter, toGridRef, type CellData, type CellValue } from './utils';
+
+	let {
+		socket
+	}: {
+		socket: WebSocket;
+	} = $props();
+
+	function splitErrorString(errorString: string) {
+		// Remove the "ERR " prefix.
+		const content = errorString.substring(4);
+
+		// Find the index of the first colon.
+		const colonIndex = content.indexOf(':');
+
+		// If no colon is found, return the whole content as the first element.
+		if (colonIndex === -1) {
+			return [content.trim(), ''];
+		}
+
+		// Extract the part before the colon (the error type).
+		const errorType = content.substring(0, colonIndex).trim();
+
+		// Extract the part after the colon (the error message).
+		const errorMessage = content.substring(colonIndex + 1).trim();
+
+		return [errorType, errorMessage];
+	}
+
+	socket.onmessage = (msg: MessageEvent) => {
+		const input = msg.data.toString().trim();
+
+		if (input.startsWith('ERR')) {
+			let split = splitErrorString(input);
+			toast.error(split[0], {
+				description: split[1]
+			});
+
+			return;
+		}
+
+		let cellRef: string | undefined;
+		let evalStr: string | undefined;
+
+		// Case 1: "Cell D4 = Integer(4)"
+		let match = input.match(/^Cell\s+([A-Z]+\d+)\s*=\s*(.+)$/);
+		if (match) {
+			[, cellRef, evalStr] = match;
+		}
+
+		// Case 2: "D6 String("hello")" or "E9 Double(4.0)"
+		if (!match) {
+			match = input.match(/^([A-Z]+\d+)\s+(.+)$/);
+			if (match) {
+				[, cellRef, evalStr] = match;
+			}
+		}
+
+		if (!cellRef || !evalStr) {
+			console.warn('Unrecognized message:', input);
+			return;
+		}
+
+		console.log(`Cell: ${cellRef}`);
+		console.log(`Eval: ${evalStr}`);
+
+		let [i, j] = fromGridRef(cellRef);
+
+		// Parse eval types
+		if (evalStr.startsWith('Integer(')) {
+			const num = parseInt(evalStr.match(/^Integer\(([-\d]+)\)$/)?.[1] ?? 'NaN', 10);
+			console.log(`Parsed integer:`, num);
+			setCellVal(i, j, num);
+		} else if (evalStr.startsWith('Double(')) {
+			const num = parseFloat(evalStr.match(/^Double\(([-\d.]+)\)$/)?.[1] ?? 'NaN');
+			console.log(`Parsed double:`, num);
+			setCellVal(i, j, num);
+		} else if (evalStr.startsWith('String(')) {
+			const str = evalStr.match(/^String\("(.+)"\)$/)?.[1];
+			console.log(`Parsed string:`, str);
+			setCellVal(i, j, str);
+		}
+	};
+
+	let rows = 50;
+	let cols = 50;
+
+	let default_row_height = '30px';
+	let default_col_width = '60px';
+
+	// Only store touched cells
+	let grid_vals: Record<string, CellData> = $state({});
+	let row_heights: Record<number, string> = $state({});
+	let col_widths: Record<number, string> = $state({});
+
+	function getRowHeight(row: number) {
+		return row_heights[row] ?? default_row_height;
+	}
+
+	function getColWidth(col: number) {
+		return col_widths[col] ?? default_col_width;
+	}
+
+	function setRowHeight(row: number, height: string) {
+		if (height === default_row_height) {
+			delete row_heights[row];
+		} else {
+			row_heights[row] = height;
+		}
+	}
+
+	function setColWidth(col: number, width: string) {
+		if (width === default_col_width) {
+			delete col_widths[col];
+		} else {
+			col_widths[col] = width;
+		}
+	}
+
+	let active_cell: [number, number] | null = $state(null);
+	let editing_cell: [number, number] | null = $state(null);
+
+	function startEditing(i: number, j: number) {
+		active_cell = [i, j];
+		editing_cell = [i, j];
+	}
+
+	function stopEditing() {
+		editing_cell = null;
+	}
+
+	const key = (i: number, j: number) => `${i}:${j}`;
+
+	const getCell = (i: number, j: number) => grid_vals[key(i, j)] ?? undefined;
+
+	const getCellRaw = (i: number, j: number) => getCell(i, j)?.raw_val ?? '';
+	const setCellRaw = (i: number, j: number, val: string) => {
+		if (grid_vals[key(i, j)] === undefined) {
+			grid_vals[key(i, j)] = {
+				raw_val: val,
+				val: undefined
+			};
+		} else {
+			grid_vals[key(i, j)].raw_val = val;
+		}
+	};
+	const getCellVal = (i: number, j: number) => getCell(i, j)?.val ?? undefined;
+	const setCellVal = (i: number, j: number, val: CellValue) => {
+		if (grid_vals[key(i, j)] === undefined) {
+			console.warn('Cell raw value was undefined but recieved eval.');
+		} else {
+			grid_vals[key(i, j)].val = val;
+		}
+	};
+
+	const setCell = (i: number, j: 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)];
+		else {
+			setCellRaw(i, j, v);
+			console.log(i, j);
+			socket.send(`set ${toGridRef(i, j)} ${v}`);
+		}
+	};
+
+	// $effect(() => {
+	// 	$inspect(grid_vals);
+	// });
+
+	function handleCellInteraction(i: number, j: number, e: MouseEvent) {
+		if (editing_cell) {
+			// Get the actual input element that's being edited
+			const el = document.querySelector<HTMLInputElement>('input:focus');
+			const currentInputValue = el?.value ?? '';
+
+			// ONLY treat this as a reference insert if it's a formula
+			if (currentInputValue.trim().startsWith('=')) {
+				// Prevent the input from losing focus
+				e.preventDefault();
+
+				// --- This is the same reference-inserting logic as before ---
+				const ref = toGridRef(i, j);
+				if (el) {
+					const { selectionStart, selectionEnd } = el;
+					const before = el.value.slice(0, selectionStart ?? 0);
+					const after = el.value.slice(selectionEnd ?? 0);
+					el.value = before + ref + after;
+					const newPos = (selectionStart ?? 0) + ref.length;
+					el.setSelectionRange(newPos, newPos);
+					el.dispatchEvent(new Event('input', { bubbles: true }));
+					el.focus();
+				}
+
+				return;
+			}
+		}
+
+		// We are not editing, so this is a normal cell selection OR this is not a formula
+		active_cell = [i, j];
+	}
+
+	onMount(() => {
+		const handler = (e: MouseEvent) => {
+			// optional: check if click target is outside grid container
+			if (!(e.target as HTMLElement).closest('.grid-wrapper')) {
+				active_cell = null;
+			}
+		};
+		window.addEventListener('click', handler);
+		onDestroy(() => window.removeEventListener('click', handler));
+	});
+</script>
+
+<div class="grid-wrapper">
+	<div class="flex w-fit">
+		<CellHeader height={default_row_height} width={default_col_width} val="" active={false} />
+		{#each Array(cols) as _, j}
+			<CellHeader
+				height={default_row_height}
+				width={getColWidth(j)}
+				setColWidth={(width) => setColWidth(j, width)}
+				direction="col"
+				val={toColLetter(j + 1)}
+				active={active_cell !== null && active_cell[1] === j}
+			/>
+		{/each}
+	</div>
+	{#each Array(rows) as _, i}
+		<div class="flex w-fit">
+			<CellHeader
+				direction="row"
+				width={default_col_width}
+				height={getRowHeight(i)}
+				setRowHeight={(height) => setRowHeight(i, height)}
+				val={(i + 1).toString()}
+				active={active_cell !== null && active_cell[0] === i}
+			/>
+			{#each Array(cols) as _, j}
+				<Cell
+					height={getRowHeight(i)}
+					width={getColWidth(j)}
+					editing={editing_cell?.[0] === i && editing_cell?.[1] === j}
+					startediting={() => startEditing(i, j)}
+					stopediting={stopEditing}
+					onmousedown={(e) => {
+						handleCellInteraction(i, j, e);
+					}}
+					bind:raw_val={() => getCellRaw(i, j), (v) => setCell(i, j, v)}
+					val={getCellVal(i, j)}
+					active={active_cell !== null && active_cell[0] === i && active_cell[1] === j}
+				/>
+			{/each}
+		</div>
+	{/each}
+</div>
diff --git a/frontend/src/lib/components/grid/utils.ts b/frontend/src/lib/components/grid/utils.ts
new file mode 100644
index 0000000..143bd67
--- /dev/null
+++ b/frontend/src/lib/components/grid/utils.ts
@@ -0,0 +1,39 @@
+export function fromGridRef(ref: string): [number, number] {
+	const match = ref.match(/^([A-Z]+)([0-9]+)$/i);
+	if (!match) throw new Error('Invalid reference');
+
+	const [, letters, rowStr] = match;
+
+	let col = 0;
+	for (let i = 0; i < letters.length; i++) {
+		col = col * 26 + (letters.charCodeAt(i) - 64); // 'A' = 65 → 1
+	}
+
+	const row = parseInt(rowStr, 10);
+	return [row - 1, col - 1];
+}
+
+export function toColLetter(col: number): string {
+	let result = '';
+	let n = col;
+	while (n > 0) {
+		const rem = (n - 1) % 26;
+		result = String.fromCharCode(65 + rem) + result; // 65 = 'A'
+		n = Math.floor((n - 1) / 26);
+	}
+
+	return result;
+}
+
+export function toGridRef(row: number, col: number): string {
+	row++;
+	col++;
+	return toColLetter(col) + row.toString();
+}
+
+export type CellValue = number | string | undefined;
+
+export interface CellData {
+	raw_val: string;
+	val: CellValue;
+}
diff --git a/frontend/src/lib/components/ui/sonner/index.ts b/frontend/src/lib/components/ui/sonner/index.ts
new file mode 100644
index 0000000..1ad9f4a
--- /dev/null
+++ b/frontend/src/lib/components/ui/sonner/index.ts
@@ -0,0 +1 @@
+export { default as Toaster } from "./sonner.svelte";
diff --git a/frontend/src/lib/components/ui/sonner/sonner.svelte b/frontend/src/lib/components/ui/sonner/sonner.svelte
new file mode 100644
index 0000000..1f50e1e
--- /dev/null
+++ b/frontend/src/lib/components/ui/sonner/sonner.svelte
@@ -0,0 +1,13 @@
+<script lang="ts">
+	import { Toaster as Sonner, type ToasterProps as SonnerProps } from "svelte-sonner";
+	import { mode } from "mode-watcher";
+
+	let { ...restProps }: SonnerProps = $props();
+</script>
+
+<Sonner
+	theme={mode.current}
+	class="toaster group"
+	style="--normal-bg: var(--color-popover); --normal-text: var(--color-popover-foreground); --normal-border: var(--color-border);"
+	{...restProps}
+/>
diff --git a/frontend/src/routes/+layout.svelte b/frontend/src/routes/+layout.svelte
index 4277a7d..921aa44 100644
--- a/frontend/src/routes/+layout.svelte
+++ b/frontend/src/routes/+layout.svelte
@@ -1,12 +1,14 @@
 <script lang="ts">
 	import '../app.css';
 	import { ModeWatcher } from 'mode-watcher';
+	import { Toaster } from '$lib/components/ui/sonner/index.js';
 	import favicon from '$lib/assets/favicon.svg';
 
 	let { children } = $props();
 </script>
 
 <ModeWatcher defaultMode="light" />
+<Toaster richColors position="bottom-right" />
 <svelte:head>
 	<link rel="icon" href={favicon} />
 </svelte:head>
diff --git a/frontend/src/routes/+page.svelte b/frontend/src/routes/+page.svelte
index 29d916c..f4ab7e6 100644
--- a/frontend/src/routes/+page.svelte
+++ b/frontend/src/routes/+page.svelte
@@ -5,18 +5,20 @@
 	import { Button } from '$lib/components/ui/button/index.js';
 	import { toggleMode } from 'mode-watcher';
 	import Grid from '$lib/components/grid/grid.svelte';
+
+	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>
+<!-- <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> -->
 
-<div class="h-[80vh] overflow-hidden rounded-lg border">
-	<Grid />
+<div class="m-0">
+	<Grid {socket} />
 </div>