diff --git a/Cargo.lock b/Cargo.lock
index c4faaff..2a55a26 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -184,6 +184,7 @@ dependencies = [
  "axum",
  "chrono",
  "colony-types",
+ "futures-util",
  "serde",
  "serde_json",
  "sqlx",
@@ -443,6 +444,17 @@ version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cecba35d7ad927e23624b22ad55235f2239cfa44fd10428eecbeba6d6a717718"
 
+[[package]]
+name = "futures-macro"
+version = "0.3.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e835b70203e41293343137df5c0664546da5745f82ec9b84d40be8336958447b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "futures-sink"
 version = "0.3.32"
@@ -463,6 +475,7 @@ checksum = "389ca41296e6190b48053de0321d02a77f32f8a5d2461dd38762c0593805c6d6"
 dependencies = [
  "futures-core",
  "futures-io",
+ "futures-macro",
  "futures-sink",
  "futures-task",
  "memchr",
diff --git a/Cargo.toml b/Cargo.toml
index 5e295e5..ef4e6cc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,4 +12,5 @@ sqlx = { version = "0.8", features = ["runtime-tokio", "sqlite", "chrono", "uuid
 axum = { version = "0.8", features = ["ws"] }
 tower-http = { version = "0.6", features = ["cors", "fs"] }
 ts-rs = { version = "10", features = ["serde-json-impl", "uuid-impl", "chrono-impl"] }
+futures-util = "0.3"
 thiserror = "2"
diff --git a/crates/colony/Cargo.toml b/crates/colony/Cargo.toml
index ea67d82..ade5973 100644
--- a/crates/colony/Cargo.toml
+++ b/crates/colony/Cargo.toml
@@ -13,4 +13,5 @@ tokio = { workspace = true }
 sqlx = { workspace = true }
 axum = { workspace = true }
 tower-http = { workspace = true }
+futures-util = { workspace = true }
 thiserror = { workspace = true }
diff --git a/crates/colony/src/main.rs b/crates/colony/src/main.rs
index ad34f84..b9c692d 100644
--- a/crates/colony/src/main.rs
+++ b/crates/colony/src/main.rs
@@ -1,8 +1,11 @@
 mod db;
 mod routes;
+mod state;
+mod ws;
 
 use axum::{routing::get, Router};
 use sqlx::sqlite::SqlitePoolOptions;
+use state::AppState;
 use std::env;
 use tower_http::services::{ServeDir, ServeFile};
 
@@ -19,18 +22,18 @@ async fn main() {
 
     eprintln!("colony: connected to {}", db_url);
 
-    // Enable WAL mode
     sqlx::query("PRAGMA journal_mode=WAL")
         .execute(&pool)
         .await
         .unwrap();
 
-    // Run embedded migrations
     sqlx::migrate!("./migrations")
         .run(&pool)
         .await
         .expect("Failed to run migrations");
 
+    let state = AppState::new(pool);
+
     eprintln!("colony: migrations done, starting on port {}", port);
 
     let app = Router::new()
@@ -46,11 +49,11 @@ async fn main() {
             "/api/channels/{channel_id}/messages",
             get(routes::list_messages).post(routes::post_message),
         )
-        // Serve frontend static files, fallback to index.html for SPA routing
+        .route("/ws/{channel_id}", get(ws::ws_handler))
         .fallback_service(
             ServeDir::new("static").fallback(ServeFile::new("static/index.html")),
         )
-        .with_state(pool);
+        .with_state(state);
 
     let listener = tokio::net::TcpListener::bind(format!("0.0.0.0:{}", port))
         .await
diff --git a/crates/colony/src/routes.rs b/crates/colony/src/routes.rs
index a0c6ffb..b034d85 100644
--- a/crates/colony/src/routes.rs
+++ b/crates/colony/src/routes.rs
@@ -9,6 +9,7 @@ use sqlx::SqlitePool;
 use uuid::Uuid;
 
 use crate::db::*;
+use crate::state::AppState;
 
 // ── Error handling ──
 
@@ -75,30 +76,30 @@ pub async fn health() -> &'static str {
 
 // ── Channels ──
 
-pub async fn list_channels(State(db): State<SqlitePool>) -> Result<Json<Vec<Channel>>> {
+pub async fn list_channels(State(state): State<AppState>) -> Result<Json<Vec<Channel>>> {
     let rows = sqlx::query_as::<_, ChannelRow>("SELECT * FROM channels ORDER BY created_at")
-        .fetch_all(&db)
+        .fetch_all(&state.db)
         .await?;
 
     let channels: Vec<Channel> = rows.iter().map(|r| r.to_api()).collect();
     Ok(Json(channels))
 }
 
-pub async fn list_users(State(db): State<SqlitePool>) -> Result<Json<Vec<User>>> {
+pub async fn list_users(State(state): State<AppState>) -> Result<Json<Vec<User>>> {
     let rows = sqlx::query_as::<_, UserRow>("SELECT * FROM users ORDER BY created_at")
-        .fetch_all(&db)
+        .fetch_all(&state.db)
         .await?;
     Ok(Json(rows.iter().map(|r| r.to_api()).collect()))
 }
 
 pub async fn get_me(
-    State(db): State<SqlitePool>,
+    State(state): State<AppState>,
     Query(user_param): Query<UserParam>,
 ) -> Result<Json<User>> {
     let username = user_param.user.as_deref().unwrap_or("benji");
     let row = sqlx::query_as::<_, UserRow>("SELECT * FROM users WHERE username = ?")
         .bind(username)
-        .fetch_optional(&db)
+        .fetch_optional(&state.db)
         .await?;
     match row {
         Some(r) => Ok(Json(r.to_api())),
@@ -107,36 +108,36 @@ pub async fn get_me(
 }
 
 pub async fn create_channel(
-    State(db): State<SqlitePool>,
+    State(state): State<AppState>,
     Query(user_param): Query<UserParam>,
     Json(body): Json<CreateChannel>,
 ) -> Result<impl IntoResponse> {
     let id = Uuid::new_v4().to_string();
-    let created_by = resolve_user(&db, &user_param).await?;
+    let created_by = resolve_user(&state.db, &user_param).await?;
 
     sqlx::query("INSERT INTO channels (id, name, description, created_by) VALUES (?, ?, ?, ?)")
         .bind(&id)
         .bind(&body.name)
         .bind(&body.description)
         .bind(created_by)
-        .execute(&db)
+        .execute(&state.db)
         .await?;
 
     let row = sqlx::query_as::<_, ChannelRow>("SELECT * FROM channels WHERE id = ?")
         .bind(&id)
-        .fetch_one(&db)
+        .fetch_one(&state.db)
         .await?;
 
     Ok((StatusCode::CREATED, Json(row.to_api())))
 }
 
 pub async fn get_channel(
-    State(db): State<SqlitePool>,
+    State(state): State<AppState>,
     Path(id): Path<String>,
 ) -> Result<Json<Channel>> {
     let row = sqlx::query_as::<_, ChannelRow>("SELECT * FROM channels WHERE id = ?")
         .bind(&id)
-        .fetch_optional(&db)
+        .fetch_optional(&state.db)
         .await?;
 
     match row {
@@ -148,7 +149,7 @@ pub async fn get_channel(
 // ── Messages ──
 
 pub async fn list_messages(
-    State(db): State<SqlitePool>,
+    State(state): State<AppState>,
     Path(channel_id): Path<String>,
     Query(query): Query<MessageQuery>,
 ) -> Result<Json<Vec<Message>>> {
@@ -186,13 +187,13 @@ pub async fn list_messages(
         q = q.bind(b);
     }
 
-    let rows = q.fetch_all(&db).await?;
+    let rows = q.fetch_all(&state.db).await?;
     let messages: Vec<Message> = rows.iter().map(|r| r.to_api_message()).collect();
     Ok(Json(messages))
 }
 
 pub async fn post_message(
-    State(db): State<SqlitePool>,
+    State(state): State<AppState>,
     Path(channel_id): Path<String>,
     Query(user_param): Query<UserParam>,
     Json(body): Json<PostMessage>,
@@ -202,7 +203,7 @@ pub async fn post_message(
         "SELECT COUNT(*) FROM channels WHERE id = ?",
     )
     .bind(&channel_id)
-    .fetch_one(&db)
+    .fetch_one(&state.db)
     .await?;
 
     if channel_exists == 0 {
@@ -215,7 +216,7 @@ pub async fn post_message(
             "SELECT channel_id FROM messages WHERE id = ?",
         )
         .bind(reply_id.to_string())
-        .fetch_optional(&db)
+        .fetch_optional(&state.db)
         .await?;
 
         match reply_channel {
@@ -228,7 +229,7 @@ pub async fn post_message(
     }
 
     let id = Uuid::new_v4().to_string();
-    let user_id = resolve_user(&db, &user_param).await?;
+    let user_id = resolve_user(&state.db, &user_param).await?;
 
     let msg_type = match body.r#type {
         MessageType::Text => "text",
@@ -256,7 +257,7 @@ pub async fn post_message(
     .bind(&body.content)
     .bind(&metadata_json)
     .bind(&reply_to)
-    .execute(&db)
+    .execute(&state.db)
     .await?;
 
     // Fetch the full message with user
@@ -265,10 +266,16 @@ pub async fn post_message(
          FROM messages m JOIN users u ON m.user_id = u.id WHERE m.id = ?",
     )
     .bind(&id)
-    .fetch_one(&db)
+    .fetch_one(&state.db)
     .await?;
 
-    Ok((StatusCode::CREATED, Json(row.to_api_message())))
+    let message = row.to_api_message();
+
+    // Broadcast to WebSocket subscribers
+    let tx = state.get_sender(&channel_id).await;
+    let _ = tx.send(WsEvent::Message(message.clone()));
+
+    Ok((StatusCode::CREATED, Json(message)))
 }
 
 // ── Joined row type for message + user ──
diff --git a/crates/colony/src/state.rs b/crates/colony/src/state.rs
new file mode 100644
index 0000000..0dab77d
--- /dev/null
+++ b/crates/colony/src/state.rs
@@ -0,0 +1,43 @@
+use colony_types::WsEvent;
+use sqlx::SqlitePool;
+use std::collections::HashMap;
+use std::sync::Arc;
+use tokio::sync::{broadcast, RwLock};
+
+const BROADCAST_CAPACITY: usize = 256;
+
+#[derive(Clone)]
+pub struct AppState {
+    pub db: SqlitePool,
+    channels: Arc<RwLock<HashMap<String, broadcast::Sender<WsEvent>>>>,
+}
+
+impl AppState {
+    pub fn new(db: SqlitePool) -> Self {
+        Self {
+            db,
+            channels: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    pub async fn get_sender(&self, channel_id: &str) -> broadcast::Sender<WsEvent> {
+        let read = self.channels.read().await;
+        if let Some(tx) = read.get(channel_id) {
+            return tx.clone();
+        }
+        drop(read);
+
+        let mut write = self.channels.write().await;
+        // Double-check after acquiring write lock
+        if let Some(tx) = write.get(channel_id) {
+            return tx.clone();
+        }
+        let (tx, _) = broadcast::channel(BROADCAST_CAPACITY);
+        write.insert(channel_id.to_string(), tx.clone());
+        tx
+    }
+
+    pub async fn subscribe(&self, channel_id: &str) -> broadcast::Receiver<WsEvent> {
+        self.get_sender(channel_id).await.subscribe()
+    }
+}
diff --git a/crates/colony/src/ws.rs b/crates/colony/src/ws.rs
new file mode 100644
index 0000000..8ccac3e
--- /dev/null
+++ b/crates/colony/src/ws.rs
@@ -0,0 +1,102 @@
+use axum::{
+    extract::{ws::WebSocket, Path, State, WebSocketUpgrade},
+    response::IntoResponse,
+};
+use futures_util::{SinkExt, StreamExt};
+use serde::Deserialize;
+use std::time::Duration;
+use tokio::time::interval;
+
+use crate::state::AppState;
+
+#[derive(Deserialize)]
+struct AuthMessage {
+    #[serde(rename = "type")]
+    msg_type: String,
+    #[allow(dead_code)]
+    token: Option<String>,
+    user: Option<String>,
+}
+
+pub async fn ws_handler(
+    ws: WebSocketUpgrade,
+    Path(channel_id): Path<String>,
+    State(state): State<AppState>,
+) -> impl IntoResponse {
+    ws.on_upgrade(move |socket| handle_socket(socket, channel_id, state))
+}
+
+async fn handle_socket(socket: WebSocket, channel_id: String, state: AppState) {
+    let (mut sender, mut receiver) = socket.split();
+
+    // Wait for auth message (first message must be {"type":"auth", "user":"..."})
+    let _user = match tokio::time::timeout(Duration::from_secs(10), receiver.next()).await {
+        Ok(Some(Ok(msg))) => {
+            if let axum::extract::ws::Message::Text(text) = msg {
+                match serde_json::from_str::<AuthMessage>(&text) {
+                    Ok(auth) if auth.msg_type == "auth" => {
+                        auth.user.unwrap_or_else(|| "anonymous".to_string())
+                    }
+                    _ => {
+                        let _ = sender
+                            .send(axum::extract::ws::Message::Text(
+                                r#"{"error":"first message must be {\"type\":\"auth\",\"user\":\"...\"}}"#.into(),
+                            ))
+                            .await;
+                        return;
+                    }
+                }
+            } else {
+                return;
+            }
+        }
+        _ => return, // Timeout or disconnect
+    };
+
+    // Subscribe to channel broadcast
+    let mut rx = state.subscribe(&channel_id).await;
+
+    // Send confirmation
+    let _ = sender
+        .send(axum::extract::ws::Message::Text(
+            r#"{"event":"connected"}"#.into(),
+        ))
+        .await;
+
+    // Ping interval for keepalive
+    let mut ping_interval = interval(Duration::from_secs(30));
+
+    loop {
+        tokio::select! {
+            // Broadcast message received → forward to client
+            msg = rx.recv() => {
+                match msg {
+                    Ok(event) => {
+                        let json = serde_json::to_string(&event).unwrap();
+                        if sender.send(axum::extract::ws::Message::Text(json.into())).await.is_err() {
+                            break; // Client disconnected
+                        }
+                    }
+                    Err(tokio::sync::broadcast::error::RecvError::Lagged(n)) => {
+                        eprintln!("colony: ws client lagged by {} messages", n);
+                    }
+                    Err(_) => break, // Channel closed
+                }
+            }
+            // Client message (we don't expect any after auth, but drain to detect disconnect)
+            msg = receiver.next() => {
+                match msg {
+                    Some(Ok(axum::extract::ws::Message::Close(_))) | None => break,
+                    Some(Err(_)) => break,
+                    _ => {} // Ignore other messages
+                }
+            }
+            // Keepalive ping
+            _ = ping_interval.tick() => {
+                if sender.send(axum::extract::ws::Message::Ping(vec![].into())).await.is_err() {
+                    break;
+                }
+            }
+        }
+    }
+}
diff --git a/ui/colony/src/App.tsx b/ui/colony/src/App.tsx
index 0b79506..79a3302 100644
--- a/ui/colony/src/App.tsx
+++ b/ui/colony/src/App.tsx
@@ -6,6 +6,7 @@ import { ChannelSidebar } from "@/components/ChannelSidebar";
 import { MessageItem } from "@/components/MessageItem";
 import { ComposeBox } from "@/components/ComposeBox";
 import { Sheet, SheetContent, SheetTrigger } from "@/components/ui/sheet";
+import { useChannelSocket } from "@/hooks/useChannelSocket";
 
 export default function App() {
   const [channels, setChannels] = useState<Channel[]>([]);
@@ -34,10 +35,21 @@ export default function App() {
         setMessages(msgs);
       }
     } catch {
-      // Silently ignore fetch errors during polling
+      // Silently ignore fetch errors
     }
   }, []);
 
+  // WebSocket: append new messages in real-time
+  const handleWsMessage = useCallback((msg: Message) => {
+    setMessages((prev) => {
+      // Deduplicate — the sender also fetches after posting
+      if (prev.some((m) => m.id === msg.id)) return prev;
+      return [...prev, msg];
+    });
+  }, []);
+
+  useChannelSocket(activeChannelId, handleWsMessage);
+
   useEffect(() => { loadChannels(); }, [loadChannels]);
 
   useEffect(() => {
@@ -47,6 +59,7 @@ export default function App() {
     loadMessages();
   }, [activeChannelId, loadMessages]);
 
+  // Auto-scroll only on new messages
   useEffect(() => {
     if (messages.length > prevMsgCountRef.current && scrollRef.current) {
       scrollRef.current.scrollTop = scrollRef.current.scrollHeight;
@@ -54,11 +67,6 @@ export default function App() {
     prevMsgCountRef.current = messages.length;
   }, [messages]);
 
-  useEffect(() => {
-    const interval = setInterval(loadMessages, 3000);
-    return () => clearInterval(interval);
-  }, [loadMessages]);
-
   const messagesById = new Map(messages.map((m) => [m.id, m]));
   const activeChannel = channels.find((c) => c.id === activeChannelId);
 
@@ -76,15 +84,12 @@ export default function App() {
 
   return (
     <div className="flex h-full">
-      {/* Desktop sidebar */}
       <div className="hidden md:block">
         {sidebar}
       </div>
 
       <div className="flex-1 flex flex-col min-w-0">
-        {/* Channel header */}
         <div className="px-3 py-2 md:px-4 border-b border-border flex items-center gap-2">
-          {/* Mobile: Sheet trigger */}
           <Sheet open={sheetOpen} onOpenChange={setSheetOpen}>
             <SheetTrigger className="md:hidden p-1 h-8 w-8 text-muted-foreground hover:text-foreground rounded-sm">
               =
@@ -112,7 +117,6 @@ export default function App() {
           )}
         </div>
 
-        {/* Messages */}
         <div ref={scrollRef} className="flex-1 overflow-y-auto">
           {messages.length === 0 && activeChannelId && (
             <div className="flex items-center justify-center h-full text-muted-foreground text-xs">
diff --git a/ui/colony/src/hooks/useChannelSocket.ts b/ui/colony/src/hooks/useChannelSocket.ts
new file mode 100644
index 0000000..6846f02
--- /dev/null
+++ b/ui/colony/src/hooks/useChannelSocket.ts
@@ -0,0 +1,61 @@
+import { useEffect, useRef, useCallback } from "react";
+import type { Message } from "@/types/Message";
+import { getCurrentUsername } from "@/api";
+
+interface WsMessageEvent {
+  event: "message";
+  data: Message;
+}
+
+interface WsConnectedEvent {
+  event: "connected";
+}
+
+type WsEvent = WsMessageEvent | WsConnectedEvent;
+
+export function useChannelSocket(
+  channelId: string | null,
+  onMessage: (msg: Message) => void,
+) {
+  const wsRef = useRef<WebSocket | null>(null);
+  const reconnectTimer = useRef<ReturnType<typeof setTimeout>>();
+
+  const connect = useCallback(() => {
+    if (!channelId) return;
+
+    const protocol = window.location.protocol === "https:" ? "wss:" : "ws:";
+    const host = window.location.host;
+    const ws = new WebSocket(`${protocol}//${host}/ws/${channelId}`);
+
+    ws.onopen = () => {
+      // Send auth message
+      ws.send(JSON.stringify({
+        type: "auth",
+        user: getCurrentUsername(),
+      }));
+    };
+
+    ws.onmessage = (e) => {
+      const event: WsEvent = JSON.parse(e.data);
+      if (event.event === "message") {
+        onMessage(event.data);
+      }
+    };
+
+    ws.onclose = () => {
+      // Reconnect after 3s
+      reconnectTimer.current = setTimeout(connect, 3000);
+    };
+
+    wsRef.current = ws;
+  }, [channelId, onMessage]);
+
+  useEffect(() => {
+    connect();
+    return () => {
+      clearTimeout(reconnectTimer.current);
+      wsRef.current?.close();
+      wsRef.current = null;
+    };
+  }, [connect]);
+}