diff --git a/CHANGELOG.md b/CHANGELOG.md
index ea69d3c..c56e598 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,9 +10,11 @@ The format follows *Keep a Changelog*. Versions use semantic versioning with pre
 - Syntax highlighting for **COBOL**, **Dotenv**, **Proto**, **GraphQL**, **reStructuredText**, and **Nginx**.
 - Language picker/menu entries for the new languages.
 - Sample fixtures for manual verification of detection and highlighting.
+- macOS document-type registration for supported file extensions.
 
 ### Improved
 - Extension and dotfile language detection for `.cob`, `.cbl`, `.cobol`, `.env*`, `.proto`, `.graphql`, `.gql`, `.rst`, and `.conf`.
+- Opening files from Finder/Open With now reuses the active window when available.
 
 ## [v0.4.2-beta] - 2026-02-08
 
diff --git a/Info-macOS.plist b/Info-macOS.plist
new file mode 100644
index 0000000..7fce2e8
--- /dev/null
+++ b/Info-macOS.plist
@@ -0,0 +1,97 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>CFBundleDisplayName</key>
+    <string>Neon Vision Editor</string>
+    <key>CFBundleName</key>
+    <string>Neon Vision Editor</string>
+    <key>CFBundleIdentifier</key>
+    <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+    <key>CFBundleShortVersionString</key>
+    <string>$(MARKETING_VERSION)</string>
+    <key>CFBundleVersion</key>
+    <string>$(CURRENT_PROJECT_VERSION)</string>
+    <key>CFBundlePackageType</key>
+    <string>APPL</string>
+    <key>LSApplicationCategoryType</key>
+    <string>public.app-category.developer-tools</string>
+    <key>ITSAppUsesNonExemptEncryption</key>
+    <false/>
+    <key>NSHighResolutionCapable</key>
+    <true/>
+    <key>CFBundleDocumentTypes</key>
+    <array>
+        <dict>
+            <key>CFBundleTypeName</key>
+            <string>Neon Vision Editor Document</string>
+            <key>CFBundleTypeRole</key>
+            <string>Editor</string>
+            <key>LSHandlerRank</key>
+            <string>Default</string>
+            <key>CFBundleTypeExtensions</key>
+            <array>
+                <string>swift</string>
+                <string>py</string>
+                <string>pyi</string>
+                <string>js</string>
+                <string>mjs</string>
+                <string>cjs</string>
+                <string>ts</string>
+                <string>tsx</string>
+                <string>php</string>
+                <string>phtml</string>
+                <string>csv</string>
+                <string>tsv</string>
+                <string>toml</string>
+                <string>ini</string>
+                <string>yaml</string>
+                <string>yml</string>
+                <string>xml</string>
+                <string>sql</string>
+                <string>log</string>
+                <string>vim</string>
+                <string>ipynb</string>
+                <string>java</string>
+                <string>kt</string>
+                <string>kts</string>
+                <string>go</string>
+                <string>rb</string>
+                <string>rs</string>
+                <string>ps1</string>
+                <string>psm1</string>
+                <string>html</string>
+                <string>htm</string>
+                <string>css</string>
+                <string>c</string>
+                <string>cpp</string>
+                <string>cc</string>
+                <string>hpp</string>
+                <string>hh</string>
+                <string>h</string>
+                <string>m</string>
+                <string>mm</string>
+                <string>cs</string>
+                <string>json</string>
+                <string>jsonc</string>
+                <string>json5</string>
+                <string>md</string>
+                <string>markdown</string>
+                <string>sh</string>
+                <string>bash</string>
+                <string>zsh</string>
+                <string>cob</string>
+                <string>cbl</string>
+                <string>cobol</string>
+                <string>env</string>
+                <string>proto</string>
+                <string>graphql</string>
+                <string>gql</string>
+                <string>rst</string>
+                <string>conf</string>
+                <string>nginx</string>
+            </array>
+        </dict>
+    </array>
+</dict>
+</plist>
diff --git a/Neon Vision Editor.xcodeproj/project.pbxproj b/Neon Vision Editor.xcodeproj/project.pbxproj
index aaa2dd4..1854a1d 100644
--- a/Neon Vision Editor.xcodeproj/project.pbxproj	
+++ b/Neon Vision Editor.xcodeproj/project.pbxproj	
@@ -285,6 +285,8 @@
 				ENABLE_RESOURCE_ACCESS_USB = NO;
 				ENABLE_USER_SELECTED_FILES = readwrite;
 				GENERATE_INFOPLIST_FILE = YES;
+				"GENERATE_INFOPLIST_FILE[sdk=macosx*]" = NO;
+				"INFOPLIST_FILE[sdk=macosx*]" = "Info-macOS.plist";
 				INFOPLIST_KEY_CFBundleDisplayName = "Neon Vision Editor";
 				INFOPLIST_KEY_ITSAppUsesNonExemptEncryption = NO;
 				INFOPLIST_KEY_LSApplicationCategoryType = "public.app-category.developer-tools";
@@ -358,6 +360,8 @@
 				ENABLE_RESOURCE_ACCESS_USB = NO;
 				ENABLE_USER_SELECTED_FILES = readwrite;
 				GENERATE_INFOPLIST_FILE = YES;
+				"GENERATE_INFOPLIST_FILE[sdk=macosx*]" = NO;
+				"INFOPLIST_FILE[sdk=macosx*]" = "Info-macOS.plist";
 				INFOPLIST_KEY_CFBundleDisplayName = "Neon Vision Editor";
 				INFOPLIST_KEY_ITSAppUsesNonExemptEncryption = NO;
 				INFOPLIST_KEY_LSApplicationCategoryType = "public.app-category.developer-tools";
diff --git a/Neon Vision Editor/App/NeonVisionEditorApp.swift b/Neon Vision Editor/App/NeonVisionEditorApp.swift
index f64cc0e..4eb4a1f 100644
--- a/Neon Vision Editor/App/NeonVisionEditorApp.swift	
+++ b/Neon Vision Editor/App/NeonVisionEditorApp.swift	
@@ -8,15 +8,34 @@ import AppKit
 
 #if os(macOS)
 final class AppDelegate: NSObject, NSApplicationDelegate {
-    weak var viewModel: EditorViewModel?
+    weak var viewModel: EditorViewModel? {
+        didSet {
+            guard let viewModel else { return }
+            Task { @MainActor in
+                self.flushPendingURLs(into: viewModel)
+            }
+        }
+    }
+    private var pendingOpenURLs: [URL] = []
 
     func application(_ application: NSApplication, open urls: [URL]) {
         Task { @MainActor in
-            for url in urls {
-                self.viewModel?.openFile(url: url)
+            let target = WindowViewModelRegistry.shared.activeViewModel() ?? self.viewModel
+            if let target {
+                urls.forEach { target.openFile(url: $0) }
+            } else {
+                self.pendingOpenURLs.append(contentsOf: urls)
             }
         }
     }
+
+    @MainActor
+    private func flushPendingURLs(into viewModel: EditorViewModel) {
+        guard !pendingOpenURLs.isEmpty else { return }
+        let urls = pendingOpenURLs
+        pendingOpenURLs.removeAll()
+        urls.forEach { viewModel.openFile(url: $0) }
+    }
 }
 
 private struct DetachedWindowContentView: View {
diff --git a/README.md b/README.md
index 6bbfed5..812b3ad 100644
--- a/README.md
+++ b/README.md
@@ -118,6 +118,8 @@ If macOS blocks first launch:
 - Added extension and dotfile mapping for `.cob`, `.cbl`, `.cobol`, `.env*`, `.proto`, `.graphql`, `.gql`, `.rst`, and `.conf`.
 - Added language picker entries for the new languages across toolbar and command menus.
 - Added sample fixtures for manual verification of new language detection and highlighting.
+- Finder/Open With now opens files in the active window when available.
+- Added macOS document-type registration for supported extensions.
 
 ### v0.4.2-beta (summary)
 
diff --git a/homebrew-tap/Casks/neon-vision-editor.rb b/homebrew-tap/Casks/neon-vision-editor.rb
index 02b8438..383cf97 100644
--- a/homebrew-tap/Casks/neon-vision-editor.rb
+++ b/homebrew-tap/Casks/neon-vision-editor.rb
@@ -1,6 +1,6 @@
 cask "neon-vision-editor" do
-  version "0.4.2-beta"
-  sha256 "aa832ffecd207ebd869ac16d61e3cd3d741eda051f2456ee5a7215e46fed8431"
+  version "0.4.3-beta"
+sha256 "d615e4302aa5137e084ff2835badd3280cad8bfba9bb410d80b2bac99f092737"
 
   url "https://github.com/h3pdesign/Neon-Vision-Editor/releases/download/v#{version}/Neon.Vision.Editor.app.zip"
   name "Neon Vision Editor"