diff --git a/Cargo.toml b/Cargo.toml
index 08c5588..5c938e9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,7 +35,7 @@ log = "0.4.28"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.145"
 thiserror = "2.0.17"
-tokio = { version = "1.47.1", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.47.1", features = ["macros", "rt-multi-thread", "process"] }
 toml = "0.9.7"
 
 [dev-dependencies]
@@ -43,6 +43,7 @@ httpmock = "0.8"
 tokio-test = "0.4"
 temp-env = "0.3"
 tempfile = "3.12"
+futures = "0.3"
 
 [lints.clippy]
 uninlined-format-args = "warn"
diff --git a/tests/cli_integration_tests.rs b/tests/cli_integration_tests.rs
new file mode 100644
index 0000000..b896130
--- /dev/null
+++ b/tests/cli_integration_tests.rs
@@ -0,0 +1,719 @@
+//! CLI Integration Tests for cull-gmail
+//!
+//! This module provides comprehensive integration testing for the CLI interface,
+//! validating argument parsing, subcommand execution, configuration handling,
+//! and error scenarios without requiring actual Gmail API connectivity.
+
+use std::collections::HashMap;
+use std::fs;
+use std::path::PathBuf;
+use std::process::{Command, Stdio};
+use tempfile::TempDir;
+use tokio::process::Command as AsyncCommand;
+
+/// Test utilities and common setup for CLI integration tests
+mod test_utils {
+    use super::*;
+
+    /// Test fixture containing temporary directories and mock configurations
+    pub struct CliTestFixture {
+        pub temp_dir: TempDir,
+        pub config_dir: PathBuf,
+        pub binary_path: PathBuf,
+    }
+
+    impl CliTestFixture {
+        /// Create a new test fixture with temporary directory structure
+        pub fn new() -> std::io::Result<Self> {
+            let temp_dir = TempDir::new()?;
+            let config_dir = temp_dir.path().join(".config").join("cull-gmail");
+            fs::create_dir_all(&config_dir)?;
+
+            // Get the path to the compiled binary
+            let binary_path = if std::env::var("CARGO_MANIFEST_DIR").is_ok() {
+                // Running under cargo test - use target directory
+                PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap())
+                    .join("target")
+                    .join("release")
+                    .join("cull-gmail")
+            } else {
+                // Fallback for other scenarios
+                std::env::current_exe()
+                    .unwrap()
+                    .parent()
+                    .unwrap()
+                    .parent()
+                    .unwrap()
+                    .join("cull-gmail")
+            };
+
+            Ok(Self {
+                temp_dir,
+                config_dir,
+                binary_path,
+            })
+        }
+
+        /// Create a mock configuration file
+        pub fn create_config_file(&self, content: &str) -> std::io::Result<PathBuf> {
+            let config_file = self.config_dir.join("config.toml");
+            fs::write(&config_file, content)?;
+            Ok(config_file)
+        }
+
+        /// Create a mock client credentials file
+        pub fn create_credentials_file(&self, content: &str) -> std::io::Result<PathBuf> {
+            let creds_file = self.config_dir.join("client_secret.json");
+            fs::write(&creds_file, content)?;
+            Ok(creds_file)
+        }
+
+        /// Execute CLI command with arguments and environment variables
+        pub fn execute_cli(
+            &self,
+            args: &[&str],
+            env_vars: Option<HashMap<&str, &str>>,
+        ) -> std::io::Result<std::process::Output> {
+            let mut cmd = Command::new(&self.binary_path);
+            cmd.args(args);
+            cmd.env("HOME", self.temp_dir.path());
+            cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
+
+            if let Some(env) = env_vars {
+                for (key, value) in env {
+                    cmd.env(key, value);
+                }
+            }
+
+            cmd.output()
+        }
+
+        /// Execute async CLI command for testing interactive scenarios
+        pub async fn execute_cli_async(
+            &self,
+            args: &[&str],
+            env_vars: Option<HashMap<&str, &str>>,
+        ) -> std::io::Result<std::process::Output> {
+            let mut cmd = AsyncCommand::new(&self.binary_path);
+            cmd.args(args);
+            cmd.env("HOME", self.temp_dir.path());
+            cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
+
+            if let Some(env) = env_vars {
+                for (key, value) in env {
+                    cmd.env(key, value);
+                }
+            }
+
+            cmd.output().await
+        }
+    }
+
+    /// Mock Gmail API responses for testing
+    pub fn mock_credentials_json() -> &'static str {
+        r#"{
+            "installed": {
+                "client_id": "test-client-id.googleusercontent.com",
+                "project_id": "test-project",
+                "auth_uri": "https://accounts.google.com/o/oauth2/auth",
+                "token_uri": "https://oauth2.googleapis.com/token",
+                "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
+                "client_secret": "test-client-secret",
+                "redirect_uris": ["http://localhost"]
+            }
+        }"#
+    }
+
+    /// Mock configuration TOML content
+    pub fn mock_config_toml() -> &'static str {
+        r#"
+[client]
+client_id = "test-client-id"
+client_secret = "test-client-secret"
+max_results = "100"
+
+[[rules]]
+name = "old_promotions"
+query = "category:promotions older_than:30d"
+action = "delete"
+enabled = true
+
+[[rules]]
+name = "old_social" 
+query = "category:social older_than:60d"
+action = "trash"
+enabled = false
+"#
+    }
+}
+
+/// Test CLI argument parsing and help output
+mod argument_parsing_tests {
+    use super::test_utils::*;
+
+    #[test]
+    fn test_cli_help_output() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["--help"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(output.status.success());
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        
+        // Verify help output contains key elements
+        assert!(stdout.contains("cull-gmail"));
+        assert!(stdout.contains("USAGE:") || stdout.contains("Usage:"));
+        assert!(stdout.contains("labels"));
+        assert!(stdout.contains("messages"));
+        assert!(stdout.contains("rules"));
+    }
+
+    #[test]
+    fn test_cli_version_output() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["--version"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(output.status.success());
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        
+        // Should contain version information
+        assert!(stdout.contains("cull-gmail"));
+        assert!(stdout.contains("0.0.10") || stdout.trim().split_whitespace().count() >= 2);
+    }
+
+    #[test]
+    fn test_verbosity_flags() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Test different verbosity levels
+        let verbosity_tests = [
+            (vec!["-v", "labels"], "WARN"),
+            (vec!["-vv", "labels"], "INFO"), 
+            (vec!["-vvv", "labels"], "DEBUG"),
+            (vec!["-vvvv", "labels"], "TRACE"),
+        ];
+
+        for (args, _expected_level) in verbosity_tests {
+            let output = fixture
+                .execute_cli(&args, None)
+                .expect("Failed to execute CLI");
+
+            // Command should parse successfully (may succeed with valid auth or fail gracefully)
+            // The important thing is that verbosity flags are accepted (not argument parsing error)
+            let exit_code = output.status.code().unwrap_or(0);
+            assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+        }
+    }
+
+    #[test]
+    fn test_invalid_subcommand() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["invalid-command"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(!output.status.success());
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        
+        // Should show error message about invalid subcommand
+        assert!(stderr.contains("error:") || stderr.contains("unrecognized"));
+    }
+}
+
+/// Test labels subcommand functionality
+mod labels_tests {
+    use super::test_utils::*;
+
+    #[test]
+    fn test_labels_help() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["labels", "--help"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(output.status.success());
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        
+        assert!(stdout.contains("labels") || stdout.contains("List Gmail labels"));
+    }
+
+    #[test]
+    fn test_labels_without_credentials() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["labels"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(!output.status.success());
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        
+        // Should fail with configuration or authentication error (unless valid credentials exist)
+        if !output.status.success() {
+            assert!(
+                stderr.contains("config") || 
+                stderr.contains("credentials") || 
+                stderr.contains("authentication") ||
+                stderr.contains("client_secret") ||
+                stderr.contains("OAuth") ||
+                stderr.contains("token")
+            );
+        }
+    }
+
+    #[test]
+    fn test_labels_with_mock_config() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Create mock configuration files
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config file");
+        fixture
+            .create_credentials_file(mock_credentials_json())
+            .expect("Failed to create credentials file");
+
+        let output = fixture
+            .execute_cli(&["labels"], None)
+            .expect("Failed to execute CLI");
+
+        // Should proceed further than config validation or succeed entirely
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        // Test passes if:
+        // 1. Command succeeds entirely, or
+        // 2. Fails at OAuth/authentication step (not config parsing)
+        assert!(
+            output.status.success() ||
+            !stderr.contains("config") ||
+            stderr.contains("OAuth") ||
+            stderr.contains("authentication") ||
+            stderr.contains("token")
+        );
+    }
+}
+
+/// Test messages subcommand functionality  
+mod messages_tests {
+    use super::test_utils::*;
+
+    #[test]
+    fn test_messages_help() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "--help"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(output.status.success());
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        
+        assert!(stdout.contains("messages"));
+        assert!(stdout.contains("query") || stdout.contains("QUERY"));
+    }
+
+    #[test]
+    fn test_messages_list_action() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "--query", "in:inbox", "list"], None)
+            .expect("Failed to execute CLI");
+
+        // Should parse arguments correctly (may succeed or fail gracefully, but not with parse error)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+    }
+
+    #[test]
+    fn test_messages_trash_action() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "--query", "in:spam", "trash"], None)
+            .expect("Failed to execute CLI");
+
+        // Trash command should be accepted (not argument parsing error)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+    }
+
+    #[test]
+    fn test_messages_pagination_options() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&[
+                "messages", 
+                "--query", "in:inbox",
+                "--max-results", "50",
+                "--pages", "2",
+                "list"
+            ], None)
+            .expect("Failed to execute CLI");
+
+        // Pagination arguments should be accepted (not argument parsing error)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+    }
+
+    #[test]
+    fn test_messages_invalid_action() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "--query", "test", "invalid-action"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(!output.status.success());
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(stderr.contains("error:") || stderr.contains("invalid"));
+    }
+
+    #[test]
+    fn test_messages_without_query() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "list"], None)
+            .expect("Failed to execute CLI");
+
+        // Messages list should work with or without explicit query (may use defaults)
+        // The test validates that the command is well-formed, not the query requirement
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+    }
+}
+
+/// Test rules subcommand functionality
+mod rules_tests {
+    use super::test_utils::*;
+
+    #[test]
+    fn test_rules_help() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["rules", "--help"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(output.status.success());
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        
+        assert!(stdout.contains("rules"));
+        assert!(stdout.contains("config") || stdout.contains("run"));
+    }
+
+    #[test]
+    fn test_rules_config_subcommand() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["rules", "config"], None)
+            .expect("Failed to execute CLI");
+
+        // Should attempt to create/display config
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        
+        // Should either succeed or show meaningful output about config
+        assert!(
+            output.status.success() ||
+            stdout.contains("config") ||
+            stderr.contains("config") ||
+            stdout.contains("toml") ||
+            stderr.contains("toml")
+        );
+    }
+
+    #[test]
+    fn test_rules_run_without_config() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["rules", "run"], None)
+            .expect("Failed to execute CLI");
+
+        // Should fail gracefully when no config is found
+        assert!(!output.status.success());
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(
+            stderr.contains("config") || 
+            stderr.contains("file") || 
+            stderr.contains("not found")
+        );
+    }
+
+    #[test]
+    fn test_rules_run_with_config() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config file");
+
+        let output = fixture
+            .execute_cli(&["rules", "run"], None)
+            .expect("Failed to execute CLI");
+
+        // Should proceed past config parsing (may fail at auth)
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(
+            !stderr.contains("config") || 
+            stderr.contains("credentials") ||
+            stderr.contains("authentication")
+        );
+    }
+
+    #[test]
+    fn test_rules_run_execution() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config file");
+
+        let output = fixture
+            .execute_cli(&["rules", "run"], None)
+            .expect("Failed to execute CLI");
+
+        // Rules run command should be accepted (not argument parsing error)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 2, "Exit code 2 indicates argument parsing error, got: {}", exit_code);
+    }
+}
+
+/// Test configuration and environment handling
+mod configuration_tests {
+    use super::test_utils::*;
+    use std::collections::HashMap;
+
+    #[test]
+    fn test_config_file_hierarchy() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Create config in expected location
+        let config_content = r#"
+[client]
+client_id = "test-from-config"
+client_secret = "secret-from-config"
+"#;
+        fixture
+            .create_config_file(config_content)
+            .expect("Failed to create config");
+
+        // Any command should now find the config
+        let output = fixture
+            .execute_cli(&["labels"], None)
+            .expect("Failed to execute CLI");
+
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        
+        // Should not complain about missing config anymore
+        assert!(!stderr.contains("config file not found"));
+    }
+
+    #[test]
+    fn test_environment_variable_precedence() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let mut env_vars = HashMap::new();
+        env_vars.insert("CULL_GMAIL_CLIENT_ID", "env-client-id");
+        env_vars.insert("CULL_GMAIL_CLIENT_SECRET", "env-secret");
+
+        let output = fixture
+            .execute_cli(&["labels"], Some(env_vars))
+            .expect("Failed to execute CLI");
+
+        // Environment variables should be recognized
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(!stderr.contains("client_id"));
+    }
+
+    #[test]
+    fn test_invalid_config_format() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Create malformed config
+        fixture
+            .create_config_file("invalid toml content [[[")
+            .expect("Failed to create config");
+
+        let output = fixture
+            .execute_cli(&["labels"], None)
+            .expect("Failed to execute CLI");
+
+        assert!(!output.status.success());
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(stderr.contains("config") || stderr.contains("parse") || stderr.contains("toml"));
+    }
+}
+
+/// Test error handling and edge cases
+mod error_handling_tests {
+    use super::test_utils::*;
+    use std::collections::HashMap;
+    use std::fs;
+
+    #[test]
+    fn test_graceful_keyboard_interrupt() {
+        // This test would require more complex setup with signal handling
+        // For now, we ensure the CLI handles missing dependencies gracefully
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        let output = fixture
+            .execute_cli(&["messages", "--query", "test", "list"], None)
+            .expect("Failed to execute CLI");
+
+        // Should not crash (no segfault)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 139, "Segmentation fault detected, got exit code: {}", exit_code);
+    }
+
+    #[test]
+    fn test_invalid_query_syntax() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config");
+        fixture
+            .create_credentials_file(mock_credentials_json())
+            .expect("Failed to create credentials");
+
+        let output = fixture
+            .execute_cli(&["messages", "--query", "invalid:query:syntax:::", "list"], None)
+            .expect("Failed to execute CLI");
+
+        // Should handle invalid queries gracefully (no segfault)
+        let exit_code = output.status.code().unwrap_or(0);
+        assert!(exit_code != 139, "Segmentation fault detected, got exit code: {}", exit_code);
+    }
+
+    #[test]
+    fn test_network_timeout_simulation() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Set very short timeout to trigger timeout behavior
+        let mut env_vars = HashMap::new();
+        env_vars.insert("HTTP_TIMEOUT", "1");
+
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config");
+        fixture
+            .create_credentials_file(mock_credentials_json())
+            .expect("Failed to create credentials");
+
+        let output = fixture
+            .execute_cli(&["labels"], Some(env_vars))
+            .expect("Failed to execute CLI");
+
+        // Should handle timeouts gracefully
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(
+            output.status.success() ||
+            stderr.contains("timeout") ||
+            stderr.contains("network") ||
+            stderr.contains("connection")
+        );
+    }
+
+    #[test]
+    fn test_permission_denied_scenarios() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        // Create a config file with restricted permissions
+        let config_path = fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config");
+
+        // Remove read permissions (this might not work on all systems)
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            let mut perms = fs::metadata(&config_path).unwrap().permissions();
+            perms.set_mode(0o000);
+            let _ = fs::set_permissions(&config_path, perms);
+        }
+
+        let output = fixture
+            .execute_cli(&["labels"], None)
+            .expect("Failed to execute CLI");
+
+        // Should handle permission errors gracefully
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        assert!(
+            output.status.success() ||
+            stderr.contains("permission") ||
+            stderr.contains("access") ||
+            stderr.contains("denied")
+        );
+    }
+}
+
+/// Async integration tests for concurrent operations
+mod async_integration_tests {
+    use super::test_utils::*;
+
+    #[tokio::test]
+    async fn test_concurrent_cli_executions() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config");
+
+        // Execute multiple CLI commands concurrently
+        let tasks = vec![
+            fixture.execute_cli_async(&["labels", "--help"], None),
+            fixture.execute_cli_async(&["messages", "--help"], None),
+            fixture.execute_cli_async(&["rules", "--help"], None),
+        ];
+
+        let results = futures::future::join_all(tasks).await;
+        
+        // All help commands should succeed
+        for result in results {
+            let output = result.expect("Failed to execute CLI");
+            assert!(output.status.success());
+        }
+    }
+
+    #[tokio::test]
+    async fn test_async_command_timeout() {
+        let fixture = CliTestFixture::new().expect("Failed to create test fixture");
+        
+        fixture
+            .create_config_file(mock_config_toml())
+            .expect("Failed to create config");
+        fixture
+            .create_credentials_file(mock_credentials_json())
+            .expect("Failed to create credentials");
+
+        // Test with timeout
+        let result = tokio::time::timeout(
+            std::time::Duration::from_secs(30),
+            fixture.execute_cli_async(&["labels"], None)
+        ).await;
+
+        match result {
+            Ok(output) => {
+                let output = output.expect("Failed to execute CLI");
+                // Command completed within timeout (no segfault)
+                let exit_code = output.status.code().unwrap_or(0);
+                assert!(exit_code != 139, "Segmentation fault detected, got exit code: {}", exit_code);
+            }
+            Err(_) => {
+                // Timeout occurred - this is acceptable for integration tests
+                // as we may not have real credentials
+            }
+        }
+    }
+}
\ No newline at end of file