diff --git a/src/apm_cli/cli.py b/src/apm_cli/cli.py
index 5263aafbd..d276439bb 100644
--- a/src/apm_cli/cli.py
+++ b/src/apm_cli/cli.py
@@ -12,6 +12,7 @@
 from apm_cli.commands._helpers import (
     ERROR,
     RESET,
+    WARNING,
     _check_and_notify_updates,
     print_version,
 )
@@ -74,34 +75,117 @@ def cli(ctx):
 cli.add_command(marketplace_search, name="search")
 
 
+def _get_current_code_page() -> "Optional[int]":
+    """Get current Windows console code page using WinAPI.
+    
+    Returns the code page number (e.g., 65001 for UTF-8, 950 for CP950).
+    Returns None if detection fails or on non-Windows platforms.
+    """
+    if sys.platform != "win32":
+        return None
+    
+    try:
+        kernel32 = ctypes.windll.kernel32  # type: ignore[attr-defined]
+        return kernel32.GetConsoleOutputCP()
+    except Exception:
+        return None
+
+
+def _code_page_to_encoding_name(cp: int) -> str:
+    """Map code page number to readable encoding name.
+    
+    Args:
+        cp: Code page number (e.g., 950, 65001).
+    
+    Returns:
+        Human-readable encoding name or fallback name.
+    """
+    cp_map = {
+        65001: "UTF-8",
+        950: "cp950 (Traditional Chinese)",
+        936: "cp936 (Simplified Chinese)",
+        932: "cp932 (Japanese)",
+        949: "cp949 (Korean)",
+        1252: "cp1252 (Western European)",
+        1251: "cp1251 (Cyrillic)",
+    }
+    return cp_map.get(cp, f"cp{cp}")
+
+
+def _try_switch_to_utf8() -> bool:
+    """Try to switch console to UTF-8 (code page 65001).
+    
+    This function:
+    1. Checks if console is already UTF-8.
+    2. If not, attempts to switch using SetConsoleCP/SetConsoleOutputCP.
+    3. Verifies success by re-checking the code page.
+    
+    Returns:
+        True if already UTF-8 or successfully switched, False otherwise.
+    """
+    if sys.platform != "win32":
+        return True
+    
+    try:
+        kernel32 = ctypes.windll.kernel32  # type: ignore[attr-defined]
+        
+        # Check current console code page
+        current_cp = kernel32.GetConsoleOutputCP()
+        if current_cp == 65001:
+            return True  # Already UTF-8
+        
+        # Attempt to switch to UTF-8
+        kernel32.SetConsoleOutputCP(65001)
+        kernel32.SetConsoleCP(65001)
+        
+        # Verify success
+        new_cp = kernel32.GetConsoleOutputCP()
+        return new_cp == 65001
+    except Exception:
+        return False
+
+
+def _warn_encoding_issue(failed_cp: int) -> None:
+    """Warn user if console UTF-8 switch failed.
+    
+    Args:
+        failed_cp: The code page that failed to switch from.
+    """
+    encoding_name = _code_page_to_encoding_name(failed_cp)
+    click.echo(
+        f"\n{WARNING}Warning: Console is {encoding_name}, UTF-8 switch failed.{RESET}\n",
+        err=True,
+    )
+    click.echo(
+        f"{WARNING}Display issues may occur. Suggestions:{RESET}",
+        err=True,
+    )
+    click.echo("  - Run: chcp 65001  (if available)", err=True)
+    click.echo("  - Or use: Windows Terminal or VS Code terminal\n", err=True)
+
+
 def _configure_encoding() -> None:
     """Configure stdout/stderr for full Unicode on Windows.
 
-    The default Windows console encoding (cp1252) cannot represent many Unicode
-    characters used in APM output (box-drawing, check marks, arrows, etc.).
+    The default Windows console encoding (cp1252 or cp950) cannot represent many
+    Unicode characters used in APM output (box-drawing, check marks, arrows, etc.).
 
     This function:
-    1. Sets ``PYTHONIOENCODING`` so child processes and redirected pipes
-       default to UTF-8.
-    2. Switches the console codepage to 65001 (UTF-8) via the Win32 API so
-       the terminal itself renders UTF-8 byte sequences correctly.
-    3. Reconfigures the Python text-mode streams to UTF-8.
+    1. Attempts to switch console to UTF-8 (code page 65001) via WinAPI.
+    2. Sets ``PYTHONIOENCODING`` for child processes.
+    3. Reconfigures Python text-mode streams to UTF-8.
+    4. Only warns if UTF-8 switch fails.
 
     On non-Windows platforms this is a no-op.
     """
     if sys.platform != "win32":
         return
 
-    # 1. Help child processes / pipes default to UTF-8
-    os.environ.setdefault("PYTHONIOENCODING", "utf-8")
+    # 1. Try to switch console to UTF-8
+    utf8_success = _try_switch_to_utf8()
 
-    # 2. Switch the console codepage to UTF-8
-    try:
-        kernel32 = ctypes.windll.kernel32  # type: ignore[attr-defined]
-        kernel32.SetConsoleOutputCP(65001)
-        kernel32.SetConsoleCP(65001)
-    except (OSError, AttributeError):
-        pass  # not a real console or ctypes unavailable
+    # 2. Help child processes / pipes default to UTF-8
+    os.environ.setdefault("PYTHONIOENCODING", "utf-8")
 
     # 3. Reconfigure Python streams to UTF-8
     for name in ("stdout", "stderr"):
@@ -115,6 +199,12 @@ def _configure_encoding() -> None:
                 except Exception:
                     pass
 
+    # 4. Warn only if UTF-8 switch failed
+    if not utf8_success:
+        current_cp = _get_current_code_page()
+        if current_cp and current_cp != 65001:
+            _warn_encoding_issue(current_cp)
+
 
 def main():
     """Main entry point for the CLI."""
diff --git a/src/apm_cli/commands/_helpers.py b/src/apm_cli/commands/_helpers.py
index 3bf0ba9e4..6f220455f 100644
--- a/src/apm_cli/commands/_helpers.py
+++ b/src/apm_cli/commands/_helpers.py
@@ -363,7 +363,7 @@ def _auto_detect_author():
 
     try:
         result = subprocess.run(
-            ["git", "config", "user.name"], capture_output=True, text=True, timeout=5
+            ["git", "config", "user.name"], capture_output=True, text=True, encoding="utf-8", timeout=5
         )
         if result.returncode == 0 and result.stdout.strip():
             return result.stdout.strip()
@@ -382,6 +382,7 @@ def _auto_detect_description(project_name):
             ["git", "config", "--get", "remote.origin.url"],
             capture_output=True,
             text=True,
+            encoding="utf-8",
             timeout=5,
         )
         if result.returncode == 0 and result.stdout.strip():
diff --git a/src/apm_cli/commands/install.py b/src/apm_cli/commands/install.py
index 10813f347..9e8b0119b 100644
--- a/src/apm_cli/commands/install.py
+++ b/src/apm_cli/commands/install.py
@@ -436,6 +436,7 @@ def _validate_package_exists(package, verbose=False, auth_resolver=None):
                 cmd,
                 capture_output=True,
                 text=True,
+                encoding="utf-8",
                 timeout=30,
                 env=validate_env,
             )
diff --git a/src/apm_cli/core/token_manager.py b/src/apm_cli/core/token_manager.py
index 1bc152acb..93afdd603 100644
--- a/src/apm_cli/core/token_manager.py
+++ b/src/apm_cli/core/token_manager.py
@@ -111,6 +111,7 @@ def resolve_credential_from_git(host: str) -> Optional[str]:
                 input=f"protocol=https\nhost={host}\n\n",
                 capture_output=True,
                 text=True,
+                encoding="utf-8",
                 timeout=GitHubTokenManager._get_credential_timeout(),
                 env={**os.environ, 'GIT_TERMINAL_PROMPT': '0',
                      'GIT_ASKPASS': '' if sys.platform != 'win32' else 'echo'},
diff --git a/src/apm_cli/deps/github_downloader.py b/src/apm_cli/deps/github_downloader.py
index 9776f7efb..0e5a15355 100644
--- a/src/apm_cli/deps/github_downloader.py
+++ b/src/apm_cli/deps/github_downloader.py
@@ -1557,7 +1557,7 @@ def _try_sparse_checkout(self, dep_ref: DependencyReference, temp_clone_path: Pa
             for cmd in cmds:
                 result = subprocess.run(
                     cmd, cwd=str(temp_clone_path), env=env,
-                    capture_output=True, text=True, timeout=120,
+                    capture_output=True, text=True, encoding="utf-8", timeout=120,
                 )
                 if result.returncode != 0:
                     _debug(f"Sparse-checkout step failed ({' '.join(cmd)}): {result.stderr.strip()}")
diff --git a/src/apm_cli/policy/discovery.py b/src/apm_cli/policy/discovery.py
index 437bc1160..d4e13ee9f 100644
--- a/src/apm_cli/policy/discovery.py
+++ b/src/apm_cli/policy/discovery.py
@@ -134,6 +134,7 @@ def _extract_org_from_git_remote(
             ["git", "remote", "get-url", "origin"],
             capture_output=True,
             text=True,
+            encoding="utf-8",
             cwd=project_root,
             timeout=5,
         )
diff --git a/src/apm_cli/runtime/codex_runtime.py b/src/apm_cli/runtime/codex_runtime.py
index 002531b93..9e88e8804 100644
--- a/src/apm_cli/runtime/codex_runtime.py
+++ b/src/apm_cli/runtime/codex_runtime.py
@@ -41,8 +41,8 @@ def execute_prompt(self, prompt_content: str, **kwargs) -> str:
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT,  # Merge stderr into stdout for streaming
                 text=True,
+                encoding="utf-8",
                 bufsize=1,  # Line buffered
-                universal_newlines=True
             )
             
             output_lines = []
@@ -107,6 +107,7 @@ def get_runtime_info(self) -> Dict[str, Any]:
                 ["codex", "--version"],
                 capture_output=True,
                 text=True,
+                encoding="utf-8",
                 timeout=10
             )
             
diff --git a/src/apm_cli/runtime/copilot_runtime.py b/src/apm_cli/runtime/copilot_runtime.py
index 46dd49b90..485057f11 100644
--- a/src/apm_cli/runtime/copilot_runtime.py
+++ b/src/apm_cli/runtime/copilot_runtime.py
@@ -59,8 +59,8 @@ def execute_prompt(self, prompt_content: str, **kwargs) -> str:
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT,  # Merge stderr into stdout for streaming
                 text=True,
+                encoding="utf-8",
                 bufsize=1,  # Line buffered
-                universal_newlines=True
             )
             
             output_lines = []
@@ -125,6 +125,7 @@ def get_runtime_info(self) -> Dict[str, Any]:
                 ["copilot", "--version"],
                 capture_output=True,
                 text=True,
+                encoding="utf-8",
                 timeout=10
             )
             
diff --git a/src/apm_cli/runtime/llm_runtime.py b/src/apm_cli/runtime/llm_runtime.py
index df24869ff..a43e0839d 100644
--- a/src/apm_cli/runtime/llm_runtime.py
+++ b/src/apm_cli/runtime/llm_runtime.py
@@ -20,8 +20,8 @@ def __init__(self, model_name: Optional[str] = None):
         
         # Verify llm CLI is available
         try:
-            result = subprocess.run(['llm', '--version'], 
-                                  capture_output=True, text=True, check=True)
+            result = subprocess.run(['llm', '--version'],
+                                  capture_output=True, text=True, encoding="utf-8", check=True)
         except (subprocess.CalledProcessError, FileNotFoundError):
             raise RuntimeError("llm CLI not found. Please install: pip install llm")
     
@@ -52,8 +52,8 @@ def execute_prompt(self, prompt_content: str, **kwargs) -> str:
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT,  # Merge stderr into stdout for streaming
                 text=True,
+                encoding="utf-8",
                 bufsize=1,  # Line buffered
-                universal_newlines=True
             )
             
             output_lines = []
@@ -86,8 +86,8 @@ def list_available_models(self) -> Dict[str, Any]:
             Dict[str, Any]: Dictionary of available models and their info
         """
         try:
-            result = subprocess.run(['llm', 'models', 'list'], 
-                                  capture_output=True, text=True, check=True)
+            result = subprocess.run(['llm', 'models', 'list'],
+                                  capture_output=True, text=True, encoding="utf-8", check=True)
             models = {}
             for line in result.stdout.strip().split('\n'):
                 if line.strip():
@@ -136,8 +136,8 @@ def is_available() -> bool:
             bool: True if runtime is available, False otherwise
         """
         try:
-            subprocess.run(['llm', '--version'], 
-                          capture_output=True, text=True, check=True)
+            subprocess.run(['llm', '--version'],
+                          capture_output=True, text=True, encoding="utf-8", check=True)
             return True
         except (subprocess.CalledProcessError, FileNotFoundError):
             return False
diff --git a/src/apm_cli/runtime/manager.py b/src/apm_cli/runtime/manager.py
index c3ebc3946..bc78b79dd 100644
--- a/src/apm_cli/runtime/manager.py
+++ b/src/apm_cli/runtime/manager.py
@@ -53,7 +53,7 @@ def get_embedded_script(self, script_name: str) -> str:
                 bundle_dir = Path(sys._MEIPASS)
                 script_path = bundle_dir / "scripts" / "runtime" / script_name
                 if script_path.exists():
-                    return script_path.read_text()
+                    return script_path.read_text(encoding="utf-8")
             
             # Fall back to direct file access for development
             # Look for scripts relative to the repo structure
@@ -61,7 +61,7 @@ def get_embedded_script(self, script_name: str) -> str:
             repo_root = current_file.parent.parent.parent.parent  # Go up to repo root
             script_path = repo_root / "scripts" / "runtime" / script_name
             if script_path.exists():
-                return script_path.read_text()
+                return script_path.read_text(encoding="utf-8")
             
             raise FileNotFoundError(f"Script not found: {script_name}")
         except Exception as e:
@@ -85,15 +85,15 @@ def get_token_helper_script(self) -> str:
                 bundle_dir = Path(sys._MEIPASS)
                 script_path = bundle_dir / "scripts" / "github-token-helper.sh"
                 if script_path.exists():
-                    return script_path.read_text()
-            
+                    return script_path.read_text(encoding="utf-8")
+
             # Fall back to direct file access for development
             # Look for scripts relative to the repo structure
             current_file = Path(__file__)
             repo_root = current_file.parent.parent.parent.parent  # Go up to repo root
             script_path = repo_root / "scripts" / "github-token-helper.sh"
             if script_path.exists():
-                return script_path.read_text()
+                return script_path.read_text(encoding="utf-8")
             
             raise FileNotFoundError("github-token-helper.sh not found")
         except Exception as e:
@@ -111,35 +111,35 @@ def run_embedded_script(self, script_content: str, common_content: str,
             if self._is_windows:
                 # Write common utilities as PowerShell
                 common_script = temp_path / "setup-common.ps1"
-                common_script.write_text(common_content)
+                common_script.write_text(common_content, encoding="utf-8")
                 
                 # Write GitHub token helper (empty on Windows)
                 token_helper_content = self.get_token_helper_script()
                 if token_helper_content:
                     token_helper_script = temp_path / "github-token-helper.ps1"
-                    token_helper_script.write_text(token_helper_content)
+                    token_helper_script.write_text(token_helper_content, encoding="utf-8")
                 
                 # Write main script as PowerShell
                 main_script = temp_path / "setup-script.ps1"
-                main_script.write_text(script_content)
+                main_script.write_text(script_content, encoding="utf-8")
             else:
                 # Write common utilities as bash
                 common_script = temp_path / "setup-common.sh"
-                common_script.write_text(common_content)
+                common_script.write_text(common_content, encoding="utf-8")
                 common_script.chmod(0o755)
                 
                 # Write GitHub token helper
                 try:
                     token_helper_content = self.get_token_helper_script()
                     token_helper_script = temp_path / "github-token-helper.sh"
-                    token_helper_script.write_text(token_helper_content)
+                    token_helper_script.write_text(token_helper_content, encoding="utf-8")
                     token_helper_script.chmod(0o755)
                 except Exception as e:
                     click.echo(f"{Fore.YELLOW}[!]  Token helper not available, scripts may use fallback authentication: {e}{Style.RESET_ALL}")
                 
                 # Write main script as bash
                 main_script = temp_path / "setup-script.sh"
-                main_script.write_text(script_content)
+                main_script.write_text(script_content, encoding="utf-8")
                 main_script.chmod(0o755)
             
             # Execute script with environment that includes npm authentication
@@ -166,6 +166,7 @@ def run_embedded_script(self, script_content: str, common_content: str,
                     cwd=temp_dir,
                     capture_output=False,  # Show output to user
                     text=True,
+                    encoding="utf-8",
                     env=env
                 )
                 return result.returncode == 0
@@ -255,6 +256,7 @@ def list_runtimes(self) -> Dict[str, Dict[str, str]]:
                         version_cmd,
                         capture_output=True,
                         text=True,
+                        encoding="utf-8",
                         timeout=5
                     )
                     if result.returncode == 0:
@@ -293,7 +295,8 @@ def remove_runtime(self, runtime_name: str) -> bool:
                 result = subprocess.run(
                     ["npm", "uninstall", "-g", "@github/copilot"],
                     capture_output=True,
-                    text=True
+                    text=True,
+                    encoding="utf-8",
                 )
                 if result.returncode == 0:
                     click.echo(f"{Fore.GREEN}[+] Successfully removed {runtime_name} runtime{Style.RESET_ALL}")
diff --git a/src/apm_cli/version.py b/src/apm_cli/version.py
index cd68a8144..20adddfe1 100644
--- a/src/apm_cli/version.py
+++ b/src/apm_cli/version.py
@@ -85,6 +85,7 @@ def get_build_sha() -> str:
                 cwd=repo_root,
                 capture_output=True,
                 text=True,
+                encoding="utf-8",
                 timeout=5,
             )
             if result.returncode == 0:
diff --git a/tests/unit/policy/test_discovery.py b/tests/unit/policy/test_discovery.py
index 250599001..98ff2c7f6 100644
--- a/tests/unit/policy/test_discovery.py
+++ b/tests/unit/policy/test_discovery.py
@@ -106,6 +106,7 @@ def test_successful_remote(self, mock_run):
             ["git", "remote", "get-url", "origin"],
             capture_output=True,
             text=True,
+            encoding="utf-8",
             cwd=Path("/fake"),
             timeout=5,
         )
diff --git a/tests/unit/test_init_command.py b/tests/unit/test_init_command.py
index af21b9e79..6da5accb6 100644
--- a/tests/unit/test_init_command.py
+++ b/tests/unit/test_init_command.py
@@ -123,7 +123,7 @@ def test_init_existing_project_with_force(self):
                 assert result.exit_code == 0
                 assert "APM project initialized successfully!" in result.output
                 # Should overwrite the file with minimal structure
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                     # Minimal structure
                     assert "dependencies" in config
@@ -146,7 +146,7 @@ def test_init_preserves_existing_config(self):
                     "description": "Custom description",
                     "author": "Custom Author",
                 }
-                with open("apm.yml", "w") as f:
+                with open("apm.yml", "w", encoding="utf-8") as f:
                     yaml.dump(existing_config, f)
 
                 result = self.runner.invoke(cli, ["init", "--yes"])
@@ -176,7 +176,7 @@ def test_init_interactive_mode(self):
                 assert "Author" in result.output
 
                 # Verify the interactive values were applied to apm.yml
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                     assert config["name"] == "my-test-project"
                     assert config["version"] == "1.5.0"
@@ -234,7 +234,7 @@ def test_init_validates_project_structure(self):
                 project_path = Path(tmp_dir) / "test-project"
 
                 # Verify apm.yml minimal structure
-                with open(project_path / "apm.yml") as f:
+                with open(project_path / "apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                     assert config["name"] == "test-project"
                     assert "version" in config
@@ -273,7 +273,7 @@ def test_init_auto_detection(self):
 
                 assert result.exit_code == 0
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                     # Should auto-detect author from git
                     assert config["author"] == "Test User"
diff --git a/tests/unit/test_init_plugin.py b/tests/unit/test_init_plugin.py
index 1b27237e0..60faf4704 100644
--- a/tests/unit/test_init_plugin.py
+++ b/tests/unit/test_init_plugin.py
@@ -68,7 +68,7 @@ def test_plugin_json_structure(self):
                 result = self.runner.invoke(cli, ["init", "--plugin", "--yes"])
                 assert result.exit_code == 0, result.output
 
-                with open("plugin.json") as f:
+                with open("plugin.json", encoding="utf-8") as f:
                     data = json.load(f)
 
                 assert data["name"] == "my-plugin"
@@ -90,7 +90,7 @@ def test_apm_yml_has_dev_dependencies(self):
                 result = self.runner.invoke(cli, ["init", "--plugin", "--yes"])
                 assert result.exit_code == 0, result.output
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
 
                 assert "devDependencies" in config
@@ -179,7 +179,7 @@ def test_yes_mode_works_with_plugin(self):
                 assert Path("apm.yml").exists()
                 assert Path("plugin.json").exists()
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                 # --yes + --plugin uses 0.1.0 version
                 assert config["version"] == "0.1.0"
@@ -197,7 +197,7 @@ def test_plugin_flag_without_plugin(self):
                 assert Path("apm.yml").exists()
                 assert not Path("plugin.json").exists()
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                 assert "devDependencies" not in config
             finally:
@@ -212,11 +212,11 @@ def test_plugin_version_defaults_to_0_1_0(self):
             try:
                 self.runner.invoke(cli, ["init", "--plugin", "--yes"])
 
-                with open("plugin.json") as f:
+                with open("plugin.json", encoding="utf-8") as f:
                     data = json.load(f)
                 assert data["version"] == "0.1.0"
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                 assert config["version"] == "0.1.0"
             finally:
@@ -231,7 +231,7 @@ def test_plugin_author_is_object(self):
             try:
                 self.runner.invoke(cli, ["init", "--plugin", "--yes"])
 
-                with open("plugin.json") as f:
+                with open("plugin.json", encoding="utf-8") as f:
                     data = json.load(f)
                 assert isinstance(data["author"], dict)
                 assert "name" in data["author"]
@@ -265,7 +265,7 @@ def test_plugin_with_project_name_argument(self):
                 assert (project_path / "apm.yml").exists()
                 assert (project_path / "plugin.json").exists()
 
-                with open(project_path / "plugin.json") as f:
+                with open(project_path / "plugin.json", encoding="utf-8") as f:
                     data = json.load(f)
                 assert data["name"] == "cool-plugin"
             finally:
@@ -293,7 +293,7 @@ def test_plugin_apm_yml_has_dependencies(self):
             try:
                 self.runner.invoke(cli, ["init", "--plugin", "--yes"])
 
-                with open("apm.yml") as f:
+                with open("apm.yml", encoding="utf-8") as f:
                     config = yaml.safe_load(f)
                 assert "dependencies" in config
                 assert config["dependencies"] == {"apm": [], "mcp": []}
diff --git a/tests/unit/test_install_command.py b/tests/unit/test_install_command.py
index 282b6e0b9..e9bbe47a6 100644
--- a/tests/unit/test_install_command.py
+++ b/tests/unit/test_install_command.py
@@ -88,7 +88,7 @@ def test_install_no_apm_yml_with_packages_creates_minimal_apm_yml(
             assert Path("apm.yml").exists()
 
             # Verify apm.yml structure
-            with open("apm.yml") as f:
+            with open("apm.yml", encoding="utf-8") as f:
                 config = yaml.safe_load(f)
                 assert "dependencies" in config
                 assert "apm" in config["dependencies"]
@@ -125,7 +125,7 @@ def test_install_no_apm_yml_with_multiple_packages(
             assert Path("apm.yml").exists()
 
             # Verify both packages are in apm.yml
-            with open("apm.yml") as f:
+            with open("apm.yml", encoding="utf-8") as f:
                 config = yaml.safe_load(f)
                 assert "org1/pkg1" in config["dependencies"]["apm"]
                 assert "org2/pkg2" in config["dependencies"]["apm"]
@@ -147,7 +147,7 @@ def test_install_existing_apm_yml_preserves_behavior(
                 "dependencies": {"apm": [], "mcp": []},
                 "scripts": {},
             }
-            with open("apm.yml", "w") as f:
+            with open("apm.yml", "w", encoding="utf-8") as f:
                 yaml.dump(existing_config, f)
 
             # Mock APMPackage
@@ -165,7 +165,7 @@ def test_install_existing_apm_yml_preserves_behavior(
             assert "Created apm.yml" not in result.output
 
             # Verify original config is preserved
-            with open("apm.yml") as f:
+            with open("apm.yml", encoding="utf-8") as f:
                 config = yaml.safe_load(f)
                 assert config["name"] == "test-project"
                 assert config["author"] == "Test Author"
@@ -202,7 +202,7 @@ def test_install_auto_created_apm_yml_has_correct_metadata(
             assert Path("apm.yml").exists()
 
             # Verify auto-detected project name
-            with open("apm.yml") as f:
+            with open("apm.yml", encoding="utf-8") as f:
                 config = yaml.safe_load(f)
                 assert config["name"] == "my-awesome-project"
                 assert "version" in config
diff --git a/tests/unit/test_llm_runtime.py b/tests/unit/test_llm_runtime.py
index 46c0209ce..5c0b517f8 100644
--- a/tests/unit/test_llm_runtime.py
+++ b/tests/unit/test_llm_runtime.py
@@ -17,8 +17,8 @@ def test_init_success(self, mock_run):
         runtime = LLMRuntime("gpt-4o-mini")
         
         assert runtime.model_name == "gpt-4o-mini"
-        mock_run.assert_called_once_with(['llm', '--version'], 
-                                        capture_output=True, text=True, check=True)
+        mock_run.assert_called_once_with(['llm', '--version'],
+                                        capture_output=True, text=True, encoding="utf-8", check=True)
     
     @patch('apm_cli.runtime.llm_runtime.subprocess.run')
     def test_init_fallback(self, mock_run):
diff --git a/tests/unit/test_runtime_manager.py b/tests/unit/test_runtime_manager.py
index 25578c589..8fb21e46b 100644
--- a/tests/unit/test_runtime_manager.py
+++ b/tests/unit/test_runtime_manager.py
@@ -236,6 +236,7 @@ def test_copilot_npm_success(self):
             ["npm", "uninstall", "-g", "@github/copilot"],
             capture_output=True,
             text=True,
+            encoding="utf-8",
         )
 
     def test_copilot_npm_failure(self):