diff --git a/.github/workflows/ci-nix.yml b/.github/workflows/ci-nix.yml
new file mode 100644
index 0000000..8e92045
--- /dev/null
+++ b/.github/workflows/ci-nix.yml
@@ -0,0 +1,38 @@
+name: Nix CI
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+jobs:
+  nix-tests:
+    name: Nix Build & Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v27
+        with:
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+
+      - name: Build ARC with Nix
+        run: nix build .#arc
+
+      - name: Run flake checks
+        run: nix flake check --show-trace
+
+      - name: Run Makefile tests inside Nix environment
+        run: |
+          nix develop -c bash -c "make test"
+
+      # Changed step:
+      - name: Run arc --help via Nix app
+        run: |
+          nix run .#arc -- --help
diff --git a/.github/workflows/ci-python.yml b/.github/workflows/ci-python.yml
new file mode 100644
index 0000000..076fdf4
--- /dev/null
+++ b/.github/workflows/ci-python.yml
@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+jobs:
+  python-tests:
+    name: Run make test (Python)
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.11", "3.12"]
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Upgrade pip
+        run: python -m pip install --upgrade pip
+
+      - name: Install project (normal install)
+        run: |
+          python -m pip install .
+
+      - name: Run tests via Makefile
+        run: make test
+
+      - name: Run arc --help
+        run: arc --help
diff --git a/.gitignore b/.gitignore
index abd32e8..340da67 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
-*__pycache__*
\ No newline at end of file
+*__pycache__*
+build/
+src/analysis_ready_code.egg-info/
diff --git a/Makefile b/Makefile
index 3e781dd..e2f06a2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,17 +1,128 @@
 # Makefile for ARC
-.PHONY: test install help
+SHELL := /usr/bin/env bash
+
+APP_NAME := arc
+BIN_DIR ?= $(HOME)/.local/bin
+# Flake attribute for the ARC app
+NIX_ATTR := .#arc
+
+.PHONY: help test install uninstall detect-nix \
+        install-with-nix install-with-python install-nix install-python \
+        uninstall-nix-wrapper uninstall-python
 
 help:
 	@echo "Targets:"
-	@echo "  make test     - Run unit tests"
-	@echo "  make install  - Show how to install via Kevin's Package Manager"
+	@echo "  make test               - Run unit tests"
+	@echo "  make install            - Install ARC using Nix if available (and usable),"
+	@echo "                            otherwise fall back to Python."
+	@echo "  make uninstall          - Uninstall ARC (Nix wrapper + Python package)"
+	@echo "  make install-nix        - Force Nix installation (no fallback)"
+	@echo "  make install-python     - Force Python installation"
+	@echo "  make uninstall-nix-wrapper - Remove only the arc binary/symlink from BIN_DIR"
+	@echo "  make uninstall-python   - Remove the Python package 'arc'"
 
 test:
 	@python -m unittest discover -s tests -p "test_*.py" -t .
 
-install:
-	@echo "ARC is distributed via Kevin's Package Manager."
-	@echo "Install it with:"
-	@echo "    package-manager install arc"
-	@echo ""
-	@echo "(This 'make install' does not perform any other actions.)"
+# -------------------------------------------------------------------
+# Smart installation selector
+# -------------------------------------------------------------------
+install: detect-nix
+
+detect-nix:
+	@if command -v nix >/dev/null 2>&1; then \
+		echo "Nix detected → trying Nix-based installation…"; \
+		if $(MAKE) install-with-nix; then \
+			echo "Nix installation succeeded."; \
+		else \
+			echo "Nix installation failed → falling back to Python…"; \
+			$(MAKE) install-with-python; \
+		fi; \
+	else \
+		echo "Nix NOT found → installing via Python…"; \
+		$(MAKE) install-with-python; \
+	fi
+
+# Convenience aliases, if you want to force one path:
+install-nix:
+	$(MAKE) install-with-nix
+
+install-python:
+	$(MAKE) install-with-python
+
+# -------------------------------------------------------------------
+# Nix installation (flakes + nix-command enabled via flags)
+# -------------------------------------------------------------------
+install-with-nix:
+	@echo "Building ARC using Nix ($(NIX_ATTR))..."
+	nix --extra-experimental-features 'nix-command flakes' build $(NIX_ATTR)
+	@echo "Installing into $(BIN_DIR)..."
+	mkdir -p "$(BIN_DIR)"
+	ln -sf "$(PWD)/result/bin/$(APP_NAME)" "$(BIN_DIR)/$(APP_NAME)"
+	@echo "Done (Nix). Run: $(APP_NAME) --help"
+
+# -------------------------------------------------------------------
+# Python installation (fallback if Nix is unavailable or unusable)
+# - In a virtualenv: install into the venv (no --user).
+# - Outside a virtualenv: install with --user.
+# -------------------------------------------------------------------
+install-with-python:
+	@echo "Installing ARC via Python…"
+	@if [ -n "$$VIRTUAL_ENV" ]; then \
+		echo "Virtualenv detected at $$VIRTUAL_ENV → installing into venv (no --user)…"; \
+		python -m pip install --upgrade .; \
+	else \
+		echo "No virtualenv detected → installing with --user…"; \
+		python -m pip install --user --upgrade .; \
+	fi
+	@echo "Ensuring $(BIN_DIR) exists..."
+	mkdir -p "$(BIN_DIR)"
+	@echo "Checking for arc binary in $(BIN_DIR)…"
+	@if [ ! -f "$(BIN_DIR)/$(APP_NAME)" ] && [ ! -L "$(BIN_DIR)/$(APP_NAME)" ]; then \
+		echo "arc executable not found in $(BIN_DIR), creating wrapper…"; \
+		echo '#!/usr/bin/env bash' > "$(BIN_DIR)/$(APP_NAME)"; \
+		echo 'python -m arc "$$@"' >> "$(BIN_DIR)/$(APP_NAME)"; \
+		chmod +x "$(BIN_DIR)/$(APP_NAME)"; \
+	else \
+		echo "arc already present in $(BIN_DIR), not touching it."; \
+	fi
+	@echo "Done (Python). Make sure $(BIN_DIR) is in your PATH."
+
+# -------------------------------------------------------------------
+# High-level uninstall target (calls Nix + Python uninstall helpers)
+# -------------------------------------------------------------------
+uninstall: uninstall-nix-wrapper uninstall-python
+	@echo "=== Uninstall finished ==="
+
+# -------------------------------------------------------------------
+# Nix side: remove wrapper/binary from BIN_DIR
+# -------------------------------------------------------------------
+uninstall-nix-wrapper:
+	@echo "Removing '$(APP_NAME)' from $(BIN_DIR)..."
+	@if [ -L "$(BIN_DIR)/$(APP_NAME)" ] || [ -f "$(BIN_DIR)/$(APP_NAME)" ]; then \
+		rm -f "$(BIN_DIR)/$(APP_NAME)"; \
+		echo "✔ Removed $(BIN_DIR)/$(APP_NAME)"; \
+	else \
+		echo "⚠ No '$(APP_NAME)' binary found in $(BIN_DIR)."; \
+	fi
+
+# -------------------------------------------------------------------
+# Python side: uninstall the arc package
+# - In a virtualenv: uninstall from venv.
+# - Outside a virtualenv: uninstall from user/system environment.
+# -------------------------------------------------------------------
+uninstall-python:
+	@echo "Checking for Python installation of 'arc'…"
+	@if python -c "import arc" >/dev/null 2>&1; then \
+		echo "Python package 'arc' detected → uninstalling…"; \
+		if [ -n "$$VIRTUAL_ENV" ]; then \
+			echo "Virtualenv detected ($$VIRTUAL_ENV) → uninstalling inside venv…"; \
+			python -m pip uninstall -y arc; \
+		else \
+			echo "No virtualenv detected → uninstalling from user/system environment…"; \
+			python -m pip uninstall -y arc; \
+		fi; \
+		echo "✔ Python uninstall complete."; \
+	else \
+		echo "⚠ Python module 'arc' not installed. Skipping Python uninstall."; \
+	fi
diff --git a/cli.py b/cli.py
deleted file mode 100644
index f6eaf03..0000000
--- a/cli.py
+++ /dev/null
@@ -1,71 +0,0 @@
-import argparse
-
-def parse_arguments():
-    parser = argparse.ArgumentParser(
-        description="Scan directories and print/compile file contents."
-    )
-    parser.add_argument(
-        "paths",
-        nargs='+',
-        help="List of files or directories to scan."
-    )
-    parser.add_argument(
-        "-t", "--file-types",
-        nargs='+',
-        default=[],
-        help="Filter by file types (e.g., .txt, .log)."
-    )
-    parser.add_argument(
-        "-x", "--ignore-file-strings",
-        nargs='+',
-        default=[],
-        help="Ignore files and folders containing these strings."
-    )
-    parser.add_argument(
-        "-S", "--show-hidden",
-        action='store_true',
-        dest='show_hidden',
-        default=False,
-        help="Include hidden directories and files in the scan."
-    )
-    parser.add_argument(
-        "-v", "--verbose",
-        action='store_true',
-        help="Enable verbose mode."
-    )
-    parser.add_argument(
-        "-N", "--no-comments",
-        action='store_true',
-        help="Remove comments from the displayed content based on file type."
-    )
-    parser.add_argument(
-        "-z", "--compress",
-        action='store_true',
-        help="Compress code (for supported file types)."
-    )
-    parser.add_argument(
-        "-p", "--path-contains",
-        nargs='+',
-        default=[],
-        help="Display files whose paths contain one of these strings."
-    )
-    parser.add_argument(
-        "-C", "--content-contains",
-        nargs='+',
-        default=[],
-        help="Display files containing one of these strings in their content."
-    )
-    parser.add_argument(
-        "-G", "--no-gitignore",
-        action='store_true',
-        help="Do not respect .gitignore files during scan."
-    )
-    parser.add_argument(
-        "-b", "--scan-binary-files",
-        action='store_true',
-        help="Scan binary files as well (by default these are ignored)."
-    )
-    # Convert show_hidden to ignore_hidden for downstream use
-    args = parser.parse_args()
-    args.ignore_hidden = not args.show_hidden
-    return args
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..f10181d
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,81 @@
+{
+  description = "Analysis-Ready Code (ARC) - recursively scan directories and prepare code for automated analysis.";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+
+        python = pkgs.python3;
+
+        # Main ARC package built from pyproject.toml
+        arcPkg = pkgs.python3Packages.buildPythonApplication {
+          pname = "analysis-ready-code";
+          version = "0.1.0";
+
+          src = ./.;
+
+          # We are using pyproject.toml with a PEP 517 backend.
+          format = "pyproject";
+
+          nativeBuildInputs = with pkgs.python3Packages; [
+            setuptools
+            wheel
+          ];
+
+          # xclip is not a Python lib, but we can still add it as a runtime
+          # dependency so that `xclip` is available in PATH when running ARC
+          # inside a Nix environment.
+          propagatedBuildInputs = with pkgs; [
+            xclip
+          ];
+
+          meta = {
+            description = "Utility that scans directories and prepares code for AI/computer analysis by stripping comments, filtering files, and optionally compressing content.";
+            homepage = "https://github.com/kevinveenbirkenbach/analysis-ready-code";
+            license = pkgs.lib.licenses.agpl3Plus;
+            platforms = pkgs.lib.platforms.unix;
+          };
+        };
+      in {
+        # Default package for `nix build .` and `nix build .#arc`
+        packages.arc = arcPkg;
+        packages.default = arcPkg;
+
+        # App for `nix run .#arc`
+        apps.arc = {
+          type = "app";
+          program = "${arcPkg}/bin/arc";
+        };
+
+        # Default app for `nix run .`
+        apps.default = self.apps.${system}.arc;
+
+        # Dev shell for local development
+        devShells.default = pkgs.mkShell {
+          name = "arc-dev-shell";
+
+          buildInputs = with pkgs; [
+            python3
+            python3Packages.pip
+            python3Packages.setuptools
+            python3Packages.wheel
+            xclip
+          ];
+
+          shellHook = ''
+            echo "ARC dev shell ready. Typical usage:"
+            echo "  make test"
+            echo "  arc . -x"
+          '';
+        };
+      }
+    );
+}
diff --git a/main.py b/main.py
deleted file mode 100755
index 5852dd6..0000000
--- a/main.py
+++ /dev/null
@@ -1,49 +0,0 @@
-#!/usr/bin/env python3
-import os
-import sys
-from cli import parse_arguments
-from directory_handler import DirectoryHandler
-
-def main():
-    args = parse_arguments()
-    
-    for path in args.paths:
-        if os.path.isdir(path):
-            DirectoryHandler.handle_directory(
-                path,
-                file_types=args.file_types,
-                ignore_file_strings=args.ignore_file_strings,
-                ignore_hidden=args.ignore_hidden,
-                verbose=args.verbose,
-                no_comments=args.no_comments,
-                compress=args.compress,
-                path_contains=args.path_contains,
-                content_contains=args.content_contains,
-                no_gitignore=args.no_gitignore,
-                scan_binary_files=args.scan_binary_files
-            )
-        elif os.path.isfile(path):
-            if DirectoryHandler.should_print_file(
-                path,
-                file_types=args.file_types,
-                ignore_file_strings=args.ignore_file_strings,
-                ignore_hidden=args.ignore_hidden,
-                path_contains=args.path_contains,
-                content_contains=args.content_contains,
-                scan_binary_files=args.scan_binary_files
-            ):
-                DirectoryHandler.handle_file(
-                    path,
-                    file_types=args.file_types,
-                    ignore_file_strings=args.ignore_file_strings,
-                    ignore_hidden=args.ignore_hidden,
-                    no_comments=args.no_comments,
-                    compress=args.compress,
-                    scan_binary_files=args.scan_binary_files
-                )
-        else:
-            print(f"Error: {path} is neither a valid file nor a directory.")
-            sys.exit(1)
-
-if __name__ == "__main__":
-    main()
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..0d080fa
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,52 @@
+[build-system]
+requires = ["setuptools>=61", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "analysis-ready-code"
+version = "0.1.0"
+description = "A utility that recursively scans directories and transforms source code into an analysis-ready format, removing comments and optionally compressing content."
+readme = "README.md"
+license = { text = "AGPL-3.0" }
+authors = [
+    { name = "Kevin Veen-Birkenbach", email = "kevin@veen.world" }
+]
+
+requires-python = ">=3.8"
+
+dependencies = [
+    # No dependencies needed for ARC
+]
+
+# Optional: define console script (if you ever want pip-installable CLI)
+# ARC normally uses a symlink, but this keeps it compatible with pip.
+[project.scripts]
+arc = "arc.__main__:main"
+
+[project.urls]
+Homepage = "https://github.com/kevinveenbirkenbach/analysis-ready-code"
+Source = "https://github.com/kevinveenbirkenbach/analysis-ready-code"
+Issues = "https://github.com/kevinveenbirkenbach/analysis-ready-code/issues"
+
+[tool.setuptools]
+package-dir = {"" = "src"}
+
+[tool.setuptools.packages.find]
+where = ["src"]
+include = ["arc*"]
+
+[tool.setuptools.package-data]
+# if you need non-Python files inside packages
+arc = ["py.typed"]
+
+[tool.coverage.run]
+branch = true
+source = ["src/arc"]
+
+[tool.coverage.report]
+show_missing = true
+
+[tool.mypy]
+python_version = "3.10"
+warn_unused_configs = true
+ignore_missing_imports = true
diff --git a/src/__init__.py b/src/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/arc/__init__.py b/src/arc/__init__.py
new file mode 100644
index 0000000..9e0e0c4
--- /dev/null
+++ b/src/arc/__init__.py
@@ -0,0 +1,111 @@
+import io
+import os
+import subprocess
+import sys
+
+from .cli import parse_arguments
+from .directory_handler import DirectoryHandler
+from .tee import Tee
+
+import shutil
+import subprocess
+
+def copy_to_clipboard(text: str, quiet: bool = False):
+    if shutil.which("xclip"):
+        subprocess.run(["xclip", "-selection", "clipboard"], input=text, text=True)
+        return
+
+    if shutil.which("wl-copy"):
+        subprocess.run(["wl-copy"], input=text, text=True)
+        return
+
+    if shutil.which("pbcopy"):
+        subprocess.run(["pbcopy"], input=text, text=True)
+        return
+
+    if not quiet:
+        print("Warning: No clipboard tool found (xclip, wl-copy, pbcopy)", file=sys.stderr)
+
+def main() -> None:
+    args = parse_arguments()
+
+    # QUIET MODE:
+    # - no terminal output
+    # - but clipboard buffer still active
+    #
+    # Normal:
+    # - output goes to stdout
+    # - optionally tee into buffer
+
+    buffer = None
+
+    if args.clipboard:
+        buffer = io.StringIO()
+
+        if args.quiet:
+            # quiet + clipboard → only buffer, no stdout
+            output_stream = buffer
+        else:
+            # normal + clipboard → stdout + buffer
+            output_stream = Tee(sys.stdout, buffer)
+    else:
+        # no clipboard
+        if args.quiet:
+            # quiet without clipboard → suppress ALL output
+            class NullWriter:
+                def write(self, *_): pass
+                def flush(self): pass
+            output_stream = NullWriter()
+        else:
+            output_stream = sys.stdout
+
+    # Process all paths
+    for path in args.paths:
+        if os.path.isdir(path):
+            DirectoryHandler.handle_directory(
+                path,
+                file_types=args.file_types,
+                ignore_file_strings=args.ignore_file_strings,
+                ignore_hidden=args.ignore_hidden,
+                verbose=args.verbose and not args.quiet,
+                no_comments=args.no_comments,
+                compress=args.compress,
+                path_contains=args.path_contains,
+                content_contains=args.content_contains,
+                no_gitignore=args.no_gitignore,
+                scan_binary_files=args.scan_binary_files,
+                output_stream=output_stream,
+            )
+        elif os.path.isfile(path):
+            if DirectoryHandler.should_print_file(
+                path,
+                file_types=args.file_types,
+                ignore_file_strings=args.ignore_file_strings,
+                ignore_hidden=args.ignore_hidden,
+                path_contains=args.path_contains,
+                content_contains=args.content_contains,
+                scan_binary_files=args.scan_binary_files,
+            ):
+                DirectoryHandler.handle_file(
+                    path,
+                    file_types=args.file_types,
+                    ignore_file_strings=args.ignore_file_strings,
+                    ignore_hidden=args.ignore_hidden,
+                    no_comments=args.no_comments,
+                    compress=args.compress,
+                    scan_binary_files=args.scan_binary_files,
+                    output_stream=output_stream,
+                )
+        else:
+            if not args.quiet:
+                print(f"Error: {path} is neither file nor directory.", file=sys.stderr)
+            sys.exit(1)
+
+    # Copy to clipboard if enabled
+    if buffer is not None:
+        text = buffer.getvalue()
+        try:
+            subprocess.run(["xclip", "-selection", "clipboard"], input=text, text=True, check=False)
+        except FileNotFoundError:
+            if not args.quiet:
+                print("Warning: xclip not found.", file=sys.stderr)
diff --git a/src/arc/__main__.py b/src/arc/__main__.py
new file mode 100644
index 0000000..a032a20
--- /dev/null
+++ b/src/arc/__main__.py
@@ -0,0 +1,18 @@
+# src/arc/__main__.py
+
+from . import main as _arc_main
+
+
+def main() -> None:
+    """
+    Entry point for the `arc` console script and `python -m arc`.
+
+    This keeps all CLI logic in `arc.__init__.py` (main()) and simply
+    delegates to it, so both setuptools/entry_points and Nix wrappers
+    can reliably import `arc.__main__:main`.
+    """
+    _arc_main()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/arc/cli.py b/src/arc/cli.py
new file mode 100644
index 0000000..1ca9033
--- /dev/null
+++ b/src/arc/cli.py
@@ -0,0 +1,120 @@
+import argparse
+
+
+def parse_arguments():
+    parser = argparse.ArgumentParser(
+        description="Scan directories and print/compile file contents."
+    )
+
+    # Positional: paths
+    parser.add_argument(
+        "paths",
+        nargs="+",
+        help="List of files or directories to scan.",
+    )
+
+    # File type filter
+    parser.add_argument(
+        "-t",
+        "--file-types",
+        nargs="+",
+        default=[],
+        help="Filter by file types (e.g., .py, .js, .c).",
+    )
+
+    # Ignore file/path strings (was previously -x, jetzt -I)
+    parser.add_argument(
+        "-I",
+        "--ignore-file-strings",
+        nargs="+",
+        default=[],
+        help="Ignore files and folders containing these strings.",
+    )
+
+    # Clipboard: alias -x
+    parser.add_argument(
+        "-x",
+        "--clipboard",
+        action="store_true",
+        help="Copy the output to the X clipboard via xclip (alias: -x).",
+    )
+
+    # Quiet mode
+    parser.add_argument(
+        "-q",
+        "--quiet",
+        action="store_true",
+        help="Suppress terminal output (useful with --clipboard).",
+    )
+
+    # Show hidden files
+    parser.add_argument(
+        "-S",
+        "--show-hidden",
+        action="store_true",
+        dest="show_hidden",
+        default=False,
+        help="Include hidden directories and files.",
+    )
+
+    # Verbose
+    parser.add_argument(
+        "-v",
+        "--verbose",
+        action="store_true",
+        help="Enable verbose mode.",
+    )
+
+    # Strip comments
+    parser.add_argument(
+        "-N",
+        "--no-comments",
+        action="store_true",
+        help="Remove comments from files before printing.",
+    )
+
+    # Compress
+    parser.add_argument(
+        "-z",
+        "--compress",
+        action="store_true",
+        help="Compress content instead of printing plain text.",
+    )
+
+    # Path filter
+    parser.add_argument(
+        "-p",
+        "--path-contains",
+        nargs="+",
+        default=[],
+        help="Only include files whose *path* contains one of these strings.",
+    )
+
+    # Content filter
+    parser.add_argument(
+        "-C",
+        "--content-contains",
+        nargs="+",
+        default=[],
+        help="Only include files whose *content* contains one of these strings.",
+    )
+
+    # Ignore .gitignore
+    parser.add_argument(
+        "-G",
+        "--no-gitignore",
+        action="store_true",
+        help="Do not respect .gitignore files during scan.",
+    )
+
+    # Scan binary files
+    parser.add_argument(
+        "-b",
+        "--scan-binary-files",
+        action="store_true",
+        help="Also scan binary files (ignored by default).",
+    )
+
+    args = parser.parse_args()
+    args.ignore_hidden = not args.show_hidden
+    return args
diff --git a/code_processor.py b/src/arc/code_processor.py
similarity index 100%
rename from code_processor.py
rename to src/arc/code_processor.py
index 7a89e24..1d0fa2f 100644
--- a/code_processor.py
+++ b/src/arc/code_processor.py
@@ -1,9 +1,9 @@
+import io
 import re
+import tokenize
 import zlib
 from dataclasses import dataclass
 from typing import Dict, Tuple, Pattern, Optional
-import io
-import tokenize
 
 
 @dataclass(frozen=True)
diff --git a/directory_handler.py b/src/arc/directory_handler.py
similarity index 65%
rename from directory_handler.py
rename to src/arc/directory_handler.py
index a661622..ef5a427 100644
--- a/directory_handler.py
+++ b/src/arc/directory_handler.py
@@ -1,6 +1,9 @@
-import os
 import fnmatch
-from code_processor import CodeProcessor
+import os
+import sys
+
+from .code_processor import CodeProcessor
+
 
 class DirectoryHandler:
     @staticmethod
@@ -13,19 +16,23 @@ class DirectoryHandler:
         """
         gitignore_data = []
         for dirpath, _, filenames in os.walk(root_path):
-            if '.gitignore' in filenames:
-                gitignore_path = os.path.join(dirpath, '.gitignore')
+            if ".gitignore" in filenames:
+                gitignore_path = os.path.join(dirpath, ".gitignore")
                 try:
-                    with open(gitignore_path, 'r') as f:
+                    with open(gitignore_path, "r") as f:
                         lines = f.readlines()
                     # Filter out empty lines and comments.
-                    patterns = [line.strip() for line in lines if line.strip() and not line.strip().startswith('#')]
+                    patterns = [
+                        line.strip()
+                        for line in lines
+                        if line.strip() and not line.strip().startswith("#")
+                    ]
                     # Save the base directory and its patterns.
                     gitignore_data.append((dirpath, patterns))
-                except Exception as e:
-                    print(f"Error reading {gitignore_path}: {e}")
+                except Exception as e:  # pragma: no cover - defensive
+                    print(f"Error reading {gitignore_path}: {e}", file=sys.stderr)
         return gitignore_data
-    
+
     @staticmethod
     def is_binary_file(file_path):
         """
@@ -34,19 +41,19 @@ class DirectoryHandler:
         is found or if more than 30% of the bytes in the sample are non-text.
         """
         try:
-            with open(file_path, 'rb') as f:
+            with open(file_path, "rb") as f:
                 chunk = f.read(1024)
             # If there's a null byte, it's almost certainly binary.
-            if b'\x00' in chunk:
+            if b"\x00" in chunk:
                 return True
-            
+
             # Define a set of text characters (ASCII printable + common control characters)
             text_chars = bytearray({7, 8, 9, 10, 12, 13, 27} | set(range(0x20, 0x7F)))
             # Count non-text characters in the chunk.
             non_text = sum(byte not in text_chars for byte in chunk)
             if len(chunk) > 0 and (non_text / len(chunk)) > 0.30:
                 return True
-        except Exception:
+        except Exception:  # pragma: no cover - defensive
             # If the file cannot be read in binary mode, assume it's not binary.
             return False
         return False
@@ -65,15 +72,15 @@ class DirectoryHandler:
                 # file_path and base_dir are on different drives.
                 continue
             # If the file is not under the current .gitignore base_dir, skip it.
-            if rel_path.startswith('..'):
+            if rel_path.startswith(".."):
                 continue
             # Check all patterns.
             for pattern in patterns:
-                if pattern.endswith('/'):
+                if pattern.endswith("/"):
                     # Directory pattern: check if any folder in the relative path matches.
                     parts = rel_path.split(os.sep)
                     for part in parts[:-1]:
-                        if fnmatch.fnmatch(part + '/', pattern):
+                        if fnmatch.fnmatch(part + "/", pattern):
                             return True
                 else:
                     # Check if the relative path matches the pattern.
@@ -87,7 +94,7 @@ class DirectoryHandler:
         Filter out directories based on ignore_file_strings and hidden status.
         """
         if ignore_hidden:
-            dirs[:] = [d for d in dirs if not d.startswith('.')]
+            dirs[:] = [d for d in dirs if not d.startswith(".")]
         dirs[:] = [d for d in dirs if not any(ig in d for ig in ignore_file_strings)]
 
     @staticmethod
@@ -100,7 +107,7 @@ class DirectoryHandler:
 
         if content_contains:
             try:
-                with open(file_path, 'r') as f:
+                with open(file_path, "r") as f:
                     content = f.read()
                 if any(whitelist_str in content for whitelist_str in content_contains):
                     return True
@@ -109,7 +116,15 @@ class DirectoryHandler:
         return False
 
     @staticmethod
-    def should_print_file(file_path, file_types, ignore_file_strings, ignore_hidden, path_contains, content_contains, scan_binary_files=False):
+    def should_print_file(
+        file_path,
+        file_types,
+        ignore_file_strings,
+        ignore_hidden,
+        path_contains,
+        content_contains,
+        scan_binary_files=False,
+    ):
         """
         Determines if a file should be printed based on various criteria.
         By default, binary files are skipped unless scan_binary_files is True.
@@ -118,7 +133,7 @@ class DirectoryHandler:
         if not scan_binary_files and DirectoryHandler.is_binary_file(file_path):
             return False
 
-        if ignore_hidden and os.path.basename(file_path).startswith('.'):
+        if ignore_hidden and os.path.basename(file_path).startswith("."):
             return False
 
         if file_types and not any(file_path.endswith(ft) for ft in file_types):
@@ -128,31 +143,36 @@ class DirectoryHandler:
             return False
 
         if path_contains or content_contains:
-            return DirectoryHandler.path_or_content_contains(file_path, path_contains, content_contains)
+            return DirectoryHandler.path_or_content_contains(
+                file_path, path_contains, content_contains
+            )
         return True
 
     @staticmethod
-    def print_file_content(file_path, no_comments, compress):
+    def print_file_content(file_path, no_comments, compress, output_stream):
         """
         Prints the content of a file, optionally removing comments or compressing the output.
         """
         try:
-            with open(file_path, 'r') as f:
+            with open(file_path, "r") as f:
                 content = f.read()
             if no_comments:
                 file_type = os.path.splitext(file_path)[1]
                 content = CodeProcessor.remove_comments(content, file_type)
-            print(f"<< START: {file_path} >>")
+            print(f"<< START: {file_path} >>", file=output_stream)
             if compress:
                 compressed_content = CodeProcessor.compress(content)
-                print("COMPRESSED CODE:")
-                print(compressed_content)
+                print("COMPRESSED CODE:", file=output_stream)
+                print(compressed_content, file=output_stream)
             else:
-                print(content)
-            print("<< END >>\n")
+                print(content, file=output_stream)
+            print("<< END >>\n", file=output_stream)
         except UnicodeDecodeError:
-            print(f"Warning: Could not read file due to encoding issues: {file_path}")
-            exit(1)
+            print(
+                f"Warning: Could not read file due to encoding issues: {file_path}",
+                file=sys.stderr,
+            )
+            sys.exit(1)
 
     @staticmethod
     def handle_directory(directory, **kwargs):
@@ -160,34 +180,49 @@ class DirectoryHandler:
         Scans the directory and processes each file while respecting .gitignore rules.
         """
         gitignore_data = []
-        if not kwargs.get('no_gitignore'):
+        if not kwargs.get("no_gitignore"):
             gitignore_data = DirectoryHandler.load_gitignore_patterns(directory)
 
+        output_stream = kwargs.get("output_stream", sys.stdout)
+
         for root, dirs, files in os.walk(directory):
-            DirectoryHandler.filter_directories(dirs, kwargs['ignore_file_strings'], kwargs['ignore_hidden'])
+            DirectoryHandler.filter_directories(
+                dirs, kwargs["ignore_file_strings"], kwargs["ignore_hidden"]
+            )
             for file in files:
                 file_path = os.path.join(root, file)
                 if gitignore_data and DirectoryHandler.is_gitignored(file_path, gitignore_data):
-                    if kwargs.get('verbose'):
-                        print(f"Skipped (gitignored): {file_path}")
+                    if kwargs.get("verbose"):
+                        print(f"Skipped (gitignored): {file_path}", file=output_stream)
                     continue
 
                 if DirectoryHandler.should_print_file(
                     file_path,
-                    kwargs['file_types'],
-                    kwargs['ignore_file_strings'],
-                    kwargs['ignore_hidden'],
-                    kwargs['path_contains'],
-                    kwargs['content_contains'],
-                    scan_binary_files=kwargs.get('scan_binary_files', False)
+                    kwargs["file_types"],
+                    kwargs["ignore_file_strings"],
+                    kwargs["ignore_hidden"],
+                    kwargs["path_contains"],
+                    kwargs["content_contains"],
+                    scan_binary_files=kwargs.get("scan_binary_files", False),
                 ):
-                    DirectoryHandler.print_file_content(file_path, kwargs['no_comments'], kwargs['compress'])
-                elif kwargs.get('verbose'):
-                    print(f"Skipped file: {file_path}")
+                    DirectoryHandler.print_file_content(
+                        file_path,
+                        kwargs["no_comments"],
+                        kwargs["compress"],
+                        output_stream=output_stream,
+                    )
+                elif kwargs.get("verbose"):
+                    print(f"Skipped file: {file_path}", file=output_stream)
 
     @staticmethod
     def handle_file(file_path, **kwargs):
         """
         Processes an individual file.
         """
-        DirectoryHandler.print_file_content(file_path, kwargs['no_comments'], kwargs['compress'])
+        output_stream = kwargs.get("output_stream", sys.stdout)
+        DirectoryHandler.print_file_content(
+            file_path,
+            kwargs["no_comments"],
+            kwargs["compress"],
+            output_stream=output_stream,
+        )
diff --git a/src/arc/tee.py b/src/arc/tee.py
new file mode 100644
index 0000000..6bd8545
--- /dev/null
+++ b/src/arc/tee.py
@@ -0,0 +1,23 @@
+from typing import TextIO
+
+
+class Tee:
+    """
+    Simple tee-like stream that writes everything to multiple underlying streams.
+
+    Typical usage:
+        tee = Tee(sys.stdout, buffer)
+        print("hello", file=tee)
+    """
+
+    def __init__(self, *streams: TextIO) -> None:
+        self.streams = streams
+
+    def write(self, data: str) -> None:
+        for stream in self.streams:
+            stream.write(data)
+
+    def flush(self) -> None:
+        for stream in self.streams:
+            if hasattr(stream, "flush"):
+                stream.flush()
diff --git a/tests/unit/test_arc.py b/tests/unit/test_arc.py
index db25775..7e3c9ce 100644
--- a/tests/unit/test_arc.py
+++ b/tests/unit/test_arc.py
@@ -6,13 +6,14 @@ import tempfile
 import unittest
 from contextlib import redirect_stdout
 
-# Ensure project root is on sys.path when running via discover
+# Ensure src/ is on sys.path when running via discover
 PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
-if PROJECT_ROOT not in sys.path:
-    sys.path.insert(0, PROJECT_ROOT)
+SRC_ROOT = os.path.join(PROJECT_ROOT, "src")
+if SRC_ROOT not in sys.path:
+    sys.path.insert(0, SRC_ROOT)
 
-from code_processor import CodeProcessor
-from directory_handler import DirectoryHandler
+from arc.code_processor import CodeProcessor
+from arc.directory_handler import DirectoryHandler
 
 
 class TestCodeProcessor(unittest.TestCase):
@@ -35,7 +36,7 @@ def f():
         self.assertNotIn("# a comment", out)
         # tolerate whitespace normalization from tokenize.untokenize
         self.assertRegex(out, r'y\s*=\s*"string with # not a comment"')
-        self.assertIn('triple quoted but not a docstring', out)
+        self.assertIn("triple quoted but not a docstring", out)
 
     def test_cstyle_comment_stripping(self):
         src = '''\
@@ -170,8 +171,12 @@ class TestDirectoryHandler(unittest.TestCase):
             with open(p, "w") as f:
                 f.write("# comment only\nx=1\n")
             buf = io.StringIO()
-            with redirect_stdout(buf):
-                DirectoryHandler.print_file_content(p, no_comments=True, compress=False)
+            DirectoryHandler.print_file_content(
+                p,
+                no_comments=True,
+                compress=False,
+                output_stream=buf,
+            )
             out = buf.getvalue()
             self.assertIn("<< START:", out)
             # be whitespace-tolerant (tokenize may insert spaces)
@@ -179,8 +184,12 @@ class TestDirectoryHandler(unittest.TestCase):
             self.assertNotIn("# comment only", out)
 
             buf = io.StringIO()
-            with redirect_stdout(buf):
-                DirectoryHandler.print_file_content(p, no_comments=True, compress=True)
+            DirectoryHandler.print_file_content(
+                p,
+                no_comments=True,
+                compress=True,
+                output_stream=buf,
+            )
             out = buf.getvalue()
             self.assertIn("COMPRESSED CODE:", out)
             self.assertIn("<< END >>", out)
diff --git a/tests/unit/test_cli.py b/tests/unit/test_cli.py
new file mode 100644
index 0000000..1015858
--- /dev/null
+++ b/tests/unit/test_cli.py
@@ -0,0 +1,60 @@
+# tests/unit/test_cli.py
+import os
+import sys
+import unittest
+from unittest.mock import patch
+
+# Ensure src/ is on sys.path when running via discover
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+SRC_ROOT = os.path.join(PROJECT_ROOT, "src")
+if SRC_ROOT not in sys.path:
+    sys.path.insert(0, SRC_ROOT)
+
+from arc.cli import parse_arguments  # noqa: E402
+
+
+class TestCliParseArguments(unittest.TestCase):
+    def test_basic_paths_and_defaults(self):
+        with patch.object(sys, "argv", ["arc", "foo", "bar"]):
+            args = parse_arguments()
+
+        self.assertEqual(args.paths, ["foo", "bar"])
+        self.assertEqual(args.file_types, [])
+        self.assertEqual(args.ignore_file_strings, [])
+        self.assertFalse(args.clipboard)
+        self.assertFalse(args.quiet)
+        # show_hidden default is False → ignore_hidden should be True
+        self.assertFalse(args.show_hidden)
+        self.assertTrue(args.ignore_hidden)
+
+    def test_clipboard_and_quiet_short_flags(self):
+        with patch.object(sys, "argv", ["arc", ".", "-x", "-q"]):
+            args = parse_arguments()
+
+        self.assertTrue(args.clipboard)
+        self.assertTrue(args.quiet)
+
+    def test_ignore_file_strings_short_and_long(self):
+        # Test only the short form -I collecting multiple values
+        with patch.object(
+            sys,
+            "argv",
+            ["arc", ".", "-I", "build", "dist", "node_modules"],
+        ):
+            args = parse_arguments()
+
+        self.assertEqual(
+            args.ignore_file_strings,
+            ["build", "dist", "node_modules"],
+        )
+
+    def test_show_hidden_switches_ignore_hidden_off(self):
+        with patch.object(sys, "argv", ["arc", ".", "--show-hidden"]):
+            args = parse_arguments()
+
+        self.assertTrue(args.show_hidden)
+        self.assertFalse(args.ignore_hidden)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/unit/test_main.py b/tests/unit/test_main.py
new file mode 100644
index 0000000..58f6546
--- /dev/null
+++ b/tests/unit/test_main.py
@@ -0,0 +1,145 @@
+# tests/unit/test_main.py
+import io
+import os
+import sys
+import tempfile
+import types
+import unittest
+from contextlib import redirect_stdout
+from unittest.mock import patch
+
+# Ensure src/ is on sys.path when running via discover
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+SRC_ROOT = os.path.join(PROJECT_ROOT, "src")
+if SRC_ROOT not in sys.path:
+    sys.path.insert(0, SRC_ROOT)
+
+import arc  # noqa: E402
+
+
+class TestArcMain(unittest.TestCase):
+    def _make_args(
+        self,
+        path,
+        clipboard=False,
+        quiet=False,
+        file_types=None,
+        ignore_file_strings=None,
+        ignore_hidden=True,
+        verbose=False,
+        no_comments=False,
+        compress=False,
+        path_contains=None,
+        content_contains=None,
+        no_gitignore=False,
+        scan_binary_files=False,
+    ):
+        return types.SimpleNamespace(
+            paths=[path],
+            clipboard=clipboard,
+            quiet=quiet,
+            file_types=file_types or [],
+            ignore_file_strings=ignore_file_strings or [],
+            ignore_hidden=ignore_hidden,
+            show_hidden=not ignore_hidden,
+            verbose=verbose,
+            no_comments=no_comments,
+            compress=compress,
+            path_contains=path_contains or [],
+            content_contains=content_contains or [],
+            no_gitignore=no_gitignore,
+            scan_binary_files=scan_binary_files,
+        )
+
+    @patch("arc.subprocess.run")
+    @patch("arc.DirectoryHandler.handle_directory")
+    @patch("arc.parse_arguments")
+    def test_main_clipboard_calls_xclip_and_uses_tee(
+        self, mock_parse_arguments, mock_handle_directory, mock_run
+    ):
+        # create a temporary directory as scan target
+        with tempfile.TemporaryDirectory() as tmpdir:
+            args = self._make_args(path=tmpdir, clipboard=True, quiet=False)
+            mock_parse_arguments.return_value = args
+
+            def fake_handle_directory(path, **kwargs):
+                out = kwargs["output_stream"]
+                # should be a Tee instance
+                self.assertEqual(out.__class__.__name__, "Tee")
+                out.write("FROM ARC\n")
+
+            mock_handle_directory.side_effect = fake_handle_directory
+
+            buf = io.StringIO()
+            with redirect_stdout(buf):
+                arc.main()
+
+        # stdout should contain the text once (via Tee -> sys.stdout)
+        stdout_value = buf.getvalue()
+        self.assertIn("FROM ARC", stdout_value)
+
+        # xclip should have been called with the same text in input
+        mock_run.assert_called_once()
+        called_args, called_kwargs = mock_run.call_args
+        self.assertEqual(called_args[0], ["xclip", "-selection", "clipboard"])
+        self.assertIn("FROM ARC", called_kwargs.get("input", ""))
+
+    @patch("arc.subprocess.run")
+    @patch("arc.DirectoryHandler.handle_directory")
+    @patch("arc.parse_arguments")
+    def test_main_clipboard_quiet_only_clipboard_no_stdout(
+        self, mock_parse_arguments, mock_handle_directory, mock_run
+    ):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            args = self._make_args(path=tmpdir, clipboard=True, quiet=True)
+            mock_parse_arguments.return_value = args
+
+            def fake_handle_directory(path, **kwargs):
+                out = kwargs["output_stream"]
+                # quiet + clipboard → output_stream is a buffer (StringIO)
+                self.assertIsInstance(out, io.StringIO)
+                out.write("SILENT CONTENT\n")
+
+            mock_handle_directory.side_effect = fake_handle_directory
+
+            buf = io.StringIO()
+            # stdout should stay empty
+            with redirect_stdout(buf):
+                arc.main()
+
+        stdout_value = buf.getvalue()
+        self.assertEqual(stdout_value, "")
+
+        mock_run.assert_called_once()
+        called_args, called_kwargs = mock_run.call_args
+        self.assertEqual(called_args[0], ["xclip", "-selection", "clipboard"])
+        self.assertIn("SILENT CONTENT", called_kwargs.get("input", ""))
+
+    @patch("arc.DirectoryHandler.handle_directory")
+    @patch("arc.parse_arguments")
+    def test_main_quiet_without_clipboard_uses_nullwriter(
+        self, mock_parse_arguments, mock_handle_directory
+    ):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            args = self._make_args(path=tmpdir, clipboard=False, quiet=True)
+            mock_parse_arguments.return_value = args
+
+            def fake_handle_directory(path, **kwargs):
+                out = kwargs["output_stream"]
+                # quiet without clipboard → internal NullWriter class
+                self.assertEqual(out.__class__.__name__, "NullWriter")
+                # writing should not raise
+                out.write("SHOULD NOT APPEAR ANYWHERE\n")
+
+            mock_handle_directory.side_effect = fake_handle_directory
+
+            buf = io.StringIO()
+            with redirect_stdout(buf):
+                arc.main()
+
+        # Nothing should be printed to stdout
+        self.assertEqual(buf.getvalue(), "")
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/unit/test_tee.py b/tests/unit/test_tee.py
new file mode 100644
index 0000000..e61a11a
--- /dev/null
+++ b/tests/unit/test_tee.py
@@ -0,0 +1,54 @@
+# tests/unit/test_tee.py
+import io
+import os
+import sys
+import unittest
+
+# Ensure src/ is on sys.path when running via discover
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+SRC_ROOT = os.path.join(PROJECT_ROOT, "src")
+if SRC_ROOT not in sys.path:
+    sys.path.insert(0, SRC_ROOT)
+
+from arc.tee import Tee  # noqa: E402
+
+
+class TestTee(unittest.TestCase):
+    def test_write_writes_to_all_streams(self):
+        buf1 = io.StringIO()
+        buf2 = io.StringIO()
+
+        tee = Tee(buf1, buf2)
+        tee.write("hello")
+        tee.write(" world")
+
+        self.assertEqual(buf1.getvalue(), "hello world")
+        self.assertEqual(buf2.getvalue(), "hello world")
+
+    def test_flush_flushes_all_streams(self):
+        class DummyStream:
+            def __init__(self):
+                self.flushed = False
+                self.data = ""
+
+            def write(self, s):
+                self.data += s
+
+            def flush(self):
+                self.flushed = True
+
+        s1 = DummyStream()
+        s2 = DummyStream()
+
+        tee = Tee(s1, s2)
+        tee.write("x")
+        tee.flush()
+
+        self.assertTrue(s1.flushed)
+        self.assertTrue(s2.flushed)
+        self.assertEqual(s1.data, "x")
+        self.assertEqual(s2.data, "x")
+
+
+if __name__ == "__main__":
+    unittest.main()