diff --git a/Sources/carton/Combine/Builder.swift b/Sources/carton/Combine/Builder.swift
index 83bc885..426ab0d 100644
--- a/Sources/carton/Combine/Builder.swift
+++ b/Sources/carton/Combine/Builder.swift
@@ -21,30 +21,63 @@ struct BuilderError: Error, CustomStringConvertible {
   let description: String
 }
 
-struct Builder {
+final class Builder {
   let publisher: AnyPublisher<String, Error>
 
-  private let process: TSCBasic.Process
-
-  init(_ arguments: [String]) {
+  init(_ arguments: [String], _ terminal: TerminalController) {
     let subject = PassthroughSubject<String, Error>()
-    publisher = subject.eraseToAnyPublisher()
+    publisher = subject
+      .handleEvents(receiveOutput: {
+        terminal.write($0)
+      }, receiveCompletion: {
+        switch $0 {
+        case .finished:
+          terminal.write("Build completed successfully\n\n", inColor: .green, bold: false)
+        case let .failure(error):
+          let errorString = String(describing: error)
+          if errorString.isEmpty {
+            terminal.write("Build failed, check the build process output above.\n", inColor: .red)
+          } else {
+            terminal.write("Build failed and produced following output: \n", inColor: .red)
+            print(error)
+          }
+        }
+      })
+      .eraseToAnyPublisher()
 
-    let stdout: TSCBasic.Process.OutputClosure = {
-      guard let string = String(data: Data($0), encoding: .utf8) else { return }
-      subject.send(string)
+    DispatchQueue.global().async {
+      let stdout: TSCBasic.Process.OutputClosure = {
+        guard let string = String(data: Data($0), encoding: .utf8) else { return }
+        subject.send(string)
+      }
+
+      var stderrBuffer = [UInt8]()
+
+      let stderr: TSCBasic.Process.OutputClosure = {
+        stderrBuffer.append(contentsOf: $0)
+      }
+
+      let process = Process(
+        arguments: arguments,
+        outputRedirection: .stream(stdout: stdout, stderr: stderr),
+        verbose: true,
+        startNewProcessGroup: true
+      )
+
+      let result = Result<ProcessResult, Error> {
+        try process.launch()
+        return try process.waitUntilExit()
+      }
+
+      switch result.map(\.exitStatus) {
+      case .success(.terminated(code: 0)):
+        subject.send(completion: .finished)
+      case let .failure(error):
+        subject.send(completion: .failure(error))
+      default:
+        let errorDescription = String(data: Data(stderrBuffer), encoding: .utf8) ?? ""
+        return subject.send(completion: .failure(BuilderError(description: errorDescription)))
+      }
     }
-
-    let stderr: TSCBasic.Process.OutputClosure = {
-      guard let string = String(data: Data($0), encoding: .utf8) else { return }
-      subject.send(completion: .failure(BuilderError(description: string)))
-    }
-
-    process = Process(
-      arguments: arguments,
-      outputRedirection: .stream(stdout: stdout, stderr: stderr),
-      verbose: true,
-      startNewProcessGroup: true
-    )
   }
 }
diff --git a/Sources/carton/Combine/Catch.swift b/Sources/carton/Combine/Catch.swift
new file mode 100644
index 0000000..82b806f
--- /dev/null
+++ b/Sources/carton/Combine/Catch.swift
@@ -0,0 +1,332 @@
+// MIT License
+
+// Copyright (c) 2019 Sergej Jaskiewicz
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+// ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+// ┃                                                                                     ┃
+// ┃                   Auto-generated from GYB template. DO NOT EDIT!                    ┃
+// ┃                                                                                     ┃
+// ┃                                                                                     ┃
+// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+//
+//  Publishers.Catch.swift
+//
+//
+//  Created by Sergej Jaskiewicz on 25.12.2019.
+//
+
+import COpenCombineHelpers
+import OpenCombine
+
+extension Publisher {
+  /// Handles errors from an upstream publisher by replacing it with another publisher.
+  ///
+  /// The following example replaces any error from the upstream publisher and replaces
+  /// the upstream with a `Just` publisher. This continues the stream by publishing
+  /// a single value and completing normally.
+  /// ```
+  /// enum SimpleError: Error { case error }
+  /// let errorPublisher = (0..<10).publisher.tryMap { v -> Int in
+  ///     if v < 5 {
+  ///         return v
+  ///     } else {
+  ///         throw SimpleError.error
+  ///     }
+  /// }
+  ///
+  /// let noErrorPublisher = errorPublisher.catch { _ in
+  ///     return Just(100)
+  /// }
+  /// ```
+  /// Backpressure note: This publisher passes through `request` and `cancel` to
+  /// the upstream. After receiving an error, the publisher sends sends any unfulfilled
+  /// demand to the new `Publisher`.
+  ///
+  /// - Parameter handler: A closure that accepts the upstream failure as input and
+  ///   returns a publisher to replace the upstream publisher.
+  /// - Returns: A publisher that handles errors from an upstream publisher by replacing
+  ///   the failed publisher with another publisher.
+  public func `catch`<NewPublisher: Publisher>(
+    _ handler: @escaping (Failure) -> NewPublisher
+  ) -> Publishers.Catch<Self, NewPublisher>
+    where NewPublisher.Output == Output {
+    return .init(upstream: self, handler: handler)
+  }
+}
+
+extension Publishers {
+  /// A publisher that handles errors from an upstream publisher by replacing the failed
+  /// publisher with another publisher.
+  public struct Catch<Upstream: Publisher, NewPublisher: Publisher>: Publisher
+    where Upstream.Output == NewPublisher.Output {
+    public typealias Output = Upstream.Output
+
+    public typealias Failure = NewPublisher.Failure
+
+    /// The publisher that this publisher receives elements from.
+    public let upstream: Upstream
+
+    /// A closure that accepts the upstream failure as input and returns a publisher
+    /// to replace the upstream publisher.
+    public let handler: (Upstream.Failure) -> NewPublisher
+
+    /// Creates a publisher that handles errors from an upstream publisher by
+    /// replacing the failed publisher with another publisher.
+    ///
+    /// - Parameters:
+    ///   - upstream: The publisher that this publisher receives elements from.
+    ///   - handler: A closure that accepts the upstream failure as input and returns
+    ///     a publisher to replace the upstream publisher.
+    public init(upstream: Upstream,
+                handler: @escaping (Upstream.Failure) -> NewPublisher) {
+      self.upstream = upstream
+      self.handler = handler
+    }
+
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+      where Downstream.Input == Output, Downstream.Failure == Failure {
+      let inner = Inner(downstream: subscriber, handler: handler)
+      let uncaughtS = Inner.UncaughtS(inner: inner)
+      upstream.subscribe(uncaughtS)
+    }
+  }
+}
+
+extension Publishers.Catch {
+  private final class Inner<Downstream: Subscriber>:
+    Subscription,
+    CustomStringConvertible,
+    CustomReflectable,
+    CustomPlaygroundDisplayConvertible
+    where Downstream.Input == Upstream.Output,
+    Downstream.Failure == NewPublisher.Failure {
+    struct UncaughtS: Subscriber,
+      CustomStringConvertible,
+      CustomReflectable,
+      CustomPlaygroundDisplayConvertible {
+      typealias Input = Upstream.Output
+
+      typealias Failure = Upstream.Failure
+
+      let inner: Inner
+
+      var combineIdentifier: CombineIdentifier { inner.combineIdentifier }
+
+      func receive(subscription: Subscription) {
+        inner.receivePre(subscription: subscription)
+      }
+
+      func receive(_ input: Input) -> Subscribers.Demand {
+        inner.receivePre(input)
+      }
+
+      func receive(completion: Subscribers.Completion<Failure>) {
+        inner.receivePre(completion: completion)
+      }
+
+      var description: String { inner.description }
+
+      var customMirror: Mirror { inner.customMirror }
+
+      var playgroundDescription: Any { description }
+    }
+
+    struct CaughtS: Subscriber,
+      CustomStringConvertible,
+      CustomReflectable,
+      CustomPlaygroundDisplayConvertible {
+      typealias Input = NewPublisher.Output
+
+      typealias Failure = NewPublisher.Failure
+
+      let inner: Inner
+
+      var combineIdentifier: CombineIdentifier { inner.combineIdentifier }
+
+      func receive(subscription: Subscription) {
+        inner.receivePost(subscription: subscription)
+      }
+
+      func receive(_ input: Input) -> Subscribers.Demand {
+        inner.receivePost(input)
+      }
+
+      func receive(completion: Subscribers.Completion<Failure>) {
+        inner.receivePost(completion: completion)
+      }
+
+      var description: String { inner.description }
+
+      var customMirror: Mirror { inner.customMirror }
+
+      var playgroundDescription: Any { description }
+    }
+
+    private enum State {
+      case pendingPre
+      case pre(Subscription)
+      case pendingPost
+      case post(Subscription)
+      case cancelled
+    }
+
+    private let lock = __UnfairLock.allocate() // 0x10
+    private var demand = Subscribers.Demand.none // 0x18
+    private var state = State.pendingPre // 0x20
+    private let downstream: Downstream
+
+    private let handler: (Upstream.Failure) -> NewPublisher
+
+    init(downstream: Downstream,
+         handler: @escaping (Upstream.Failure) -> NewPublisher) {
+      self.downstream = downstream
+      self.handler = handler
+    }
+
+    deinit {
+      lock.deallocate()
+    }
+
+    func receivePre(subscription: Subscription) {
+      lock.lock()
+      guard case .pendingPre = state else {
+        lock.unlock()
+        subscription.cancel()
+        return
+      }
+      state = .pre(subscription)
+      lock.unlock()
+      downstream.receive(subscription: self)
+    }
+
+    func receivePre(_ input: Upstream.Output) -> Subscribers.Demand {
+      lock.lock()
+      demand -= 1
+      lock.unlock()
+      let newDemand = downstream.receive(input)
+      lock.lock()
+      demand += newDemand
+      lock.unlock()
+      return newDemand
+    }
+
+    func receivePre(completion: Subscribers.Completion<Upstream.Failure>) {
+      switch completion {
+      case .finished:
+        lock.lock()
+        if case .pre = state {
+          state = .cancelled
+          lock.unlock()
+          downstream.receive(completion: .finished)
+        } else {
+          lock.unlock()
+        }
+      case let .failure(error):
+        lock.lock()
+        if case .pre = state {
+          state = .pendingPost
+          lock.unlock()
+          handler(error).subscribe(CaughtS(inner: self))
+        } else {
+          lock.unlock()
+        }
+      }
+    }
+
+    func receivePost(subscription: Subscription) {
+      lock.lock()
+      guard case .pendingPost = state else {
+        lock.unlock()
+        subscription.cancel()
+        return
+      }
+      state = .post(subscription)
+      let demand = self.demand
+      lock.unlock()
+      if demand > 0 {
+        subscription.request(demand)
+      }
+    }
+
+    func receivePost(_ input: NewPublisher.Output) -> Subscribers.Demand {
+      downstream.receive(input)
+    }
+
+    func receivePost(completion: Subscribers.Completion<NewPublisher.Failure>) {
+      lock.lock()
+      guard case .post = state else {
+        lock.unlock()
+        return
+      }
+      state = .cancelled
+      lock.unlock()
+      downstream.receive(completion: completion)
+    }
+
+    func request(_ demand: Subscribers.Demand) {
+      if demand == .none {
+        fatalError("API Violation: demand must not be zero")
+      }
+      lock.lock()
+      switch state {
+      case .pendingPre:
+        lock.unlock()
+      case let .pre(subscription):
+        self.demand += demand
+        lock.unlock()
+        subscription.request(demand)
+      case .pendingPost:
+        self.demand += demand
+        lock.unlock()
+      case let .post(subscription):
+        lock.unlock()
+        subscription.request(demand)
+      case .cancelled:
+        lock.unlock()
+      }
+    }
+
+    func cancel() {
+      lock.lock()
+      switch state {
+      case let .pre(subscription), let .post(subscription):
+        state = .cancelled
+        lock.unlock()
+        subscription.cancel()
+      default:
+        state = .cancelled
+        lock.unlock()
+      }
+    }
+
+    var description: String { "Catch" }
+
+    var customMirror: Mirror {
+      let children: [Mirror.Child] = [
+        ("downstream", downstream),
+        ("demand", demand),
+      ]
+      return Mirror(self, children: children)
+    }
+
+    var playgroundDescription: Any { description }
+  }
+}
diff --git a/Sources/carton/Combine/ProgressAnimation.swift b/Sources/carton/Combine/ProgressAnimation.swift
index 3c1fc1a..fb6857a 100644
--- a/Sources/carton/Combine/ProgressAnimation.swift
+++ b/Sources/carton/Combine/ProgressAnimation.swift
@@ -31,7 +31,7 @@ extension Publisher where Output == Progress, Failure: CustomStringConvertible {
       switch $0 {
       case .finished:
         progressAnimation.complete(success: true)
-        terminal.write("Build finished succesfully\n", inColor: .green, bold: false)
+        terminal.write("Build finished succesfully\n", inColor: .green)
       case let .failure(error):
         progressAnimation.complete(success: false)
         terminal.write(error.description, inColor: .red, bold: false)
diff --git a/Sources/carton/Dev.swift b/Sources/carton/Dev.swift
index fd93e09..f06b701 100644
--- a/Sources/carton/Dev.swift
+++ b/Sources/carton/Dev.swift
@@ -14,6 +14,7 @@
 
 import ArgumentParser
 import Foundation
+import OpenCombine
 import TSCBasic
 
 func processDataOutput(_ arguments: [String]) throws -> Data {
@@ -41,15 +42,17 @@ struct Dev: ParsableCommand {
     else { fatalError("failed to create an instance of `TerminalController`") }
     // try checkDevDependencies(on: localFileSystem, terminal)
 
+    let fm = FileManager.default
+
     terminal.write("Inferring basic settings...\n", inColor: .yellow)
     let swiftPath: String
     if
-      let data = FileManager.default.contents(atPath: ".swift-version"),
+      let data = fm.contents(atPath: ".swift-version"),
       // get the first line of the file
       let swiftVersion = String(data: data, encoding: .utf8)?.components(
         separatedBy: CharacterSet.newlines
       ).first {
-      swiftPath = FileManager.default.homeDirectoryForCurrentUser
+      swiftPath = fm.homeDirectoryForCurrentUser
         .appending(".swiftenv", "versions", swiftVersion, "usr", "bin", "swift")
         .path
     } else {
@@ -89,13 +92,33 @@ struct Dev: ParsableCommand {
     guard let sources = localFileSystem.currentWorkingDirectory?.appending(component: "Sources")
     else { fatalError("failed to infer the sources directory") }
 
-    terminal.write("\nWatching this directory for changes: ", inColor: .green, bold: false)
+    terminal.write("\nBuilding the project before spinning up a server...\n", inColor: .yellow)
+
+    let builderArguments = [swiftPath, "build", "--triple", "wasm32-unknown-wasi"]
+    var subscription: AnyCancellable?
+    try await { completion in
+      subscription = Builder(builderArguments, terminal).publisher
+        .sink(
+          receiveCompletion: { _ in completion(Result<(), Never>.success(())) },
+          receiveValue: { _ in }
+        )
+    }
+
+    guard fm.fileExists(atPath: mainWasmURL.path) else {
+      return terminal.write(
+        "Failed to build the main executable binary, fix the build errors and restart\n"
+      )
+    }
+
+    terminal.write("\nWatching this directory for changes: ", inColor: .green)
     terminal.logLookup("", sources)
     terminal.write("\n")
 
     try Server(
+      builderArguments: builderArguments,
       pathsToWatch: localFileSystem.traverseRecursively(sources),
-      mainWasmPath: mainWasmURL.path
+      mainWasmPath: mainWasmURL.path,
+      terminal
     ).run()
   }
 }
diff --git a/Sources/carton/Server/Server.swift b/Sources/carton/Server/Server.swift
index f68a466..666b677 100644
--- a/Sources/carton/Server/Server.swift
+++ b/Sources/carton/Server/Server.swift
@@ -22,9 +22,15 @@ final class Server {
   private var wsConnection: WebSocket?
   private var subscriptions = [AnyCancellable]()
   private let watcher: Watcher
+  private var builder: Builder?
   private let app: Application
 
-  init(pathsToWatch: [AbsolutePath], mainWasmPath: String) throws {
+  init(
+    builderArguments: [String],
+    pathsToWatch: [AbsolutePath],
+    mainWasmPath: String,
+    _ terminal: TerminalController
+  ) throws {
     watcher = try Watcher(pathsToWatch)
 
     var env = Environment.development
@@ -35,9 +41,24 @@ final class Server {
     }
 
     watcher.publisher
-      .sink { [weak self] _ in
-        self?.wsConnection?.send("reload")
+      .flatMap(maxPublishers: .max(1)) { changes -> AnyPublisher<String, Never> in
+        terminal.write("\nThese paths have changed, rebuilding...\n", inColor: .yellow)
+        for change in changes.map(\.pathString) {
+          terminal.write("- \(change)\n", inColor: .cyan)
+        }
+        terminal.write("\n")
+        return Builder(builderArguments, terminal)
+          .publisher
+          .handleEvents(receiveCompletion: { [weak self] in
+            guard case .finished = $0 else { return }
+            self?.wsConnection?.send("reload")
+          })
+          .catch { _ in Empty().eraseToAnyPublisher() }
+          .eraseToAnyPublisher()
       }
+      .sink(
+        receiveValue: { _ in }
+      )
       .store(in: &subscriptions)
   }
 
diff --git a/TestApp/Sources/TestApp/main.swift b/TestApp/Sources/TestApp/main.swift
index 44913c0..3210dd9 100644
--- a/TestApp/Sources/TestApp/main.swift
+++ b/TestApp/Sources/TestApp/main.swift
@@ -22,4 +22,4 @@ divElement.innerText = "Hello, world"
 let body = document.body.object!
 _ = body.appendChild!(divElement)
 
-print("hello, world")
+print("Hello, world!")
diff --git a/entrypoint/dev.js b/entrypoint/dev.js
index 227b573..4674aca 100644
--- a/entrypoint/dev.js
+++ b/entrypoint/dev.js
@@ -16,7 +16,11 @@ const wasi = new WASI({
 
 const socket = new WebSocket("ws://127.0.0.1:8080/watcher");
 
-socket.onmessage = (message) => console.log(message.data);
+socket.onmessage = (message) => {
+  if (message.data === "reload") {
+    location.reload();
+  }
+};
 
 const startWasiTask = async () => {
   // Fetch our Wasm File