diff --git a/Cargo.toml b/Cargo.toml
index 62709453b..60c9b2143 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -165,6 +165,7 @@ unimplemented = "deny"
 
 [dev-dependencies]
 tokio-test = "0.4"
+parking_lot = "0.12"
 
 # OS keystore (macOS Keychain for master key storage)
 [target.'cfg(target_os = "macos")'.dependencies]
diff --git a/src/config.rs b/src/config.rs
index c3a9ec8ac..e523af69c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -6677,11 +6677,10 @@ pub fn run_onboarding() -> anyhow::Result<Option<PathBuf>> {
 mod tests {
     use super::*;
     use std::result::Result as StdResult;
-    use std::sync::{Mutex, OnceLock};
 
-    fn env_test_lock() -> &'static Mutex<()> {
-        static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
-        LOCK.get_or_init(|| Mutex::new(()))
+    fn env_test_lock() -> &'static parking_lot::Mutex<()> {
+        static LOCK: std::sync::OnceLock<parking_lot::Mutex<()>> = std::sync::OnceLock::new();
+        LOCK.get_or_init(|| parking_lot::Mutex::new(()))
     }
 
     struct EnvGuard {
@@ -6691,12 +6690,14 @@ mod tests {
 
     impl EnvGuard {
         fn new() -> Self {
-            const KEYS: [&str; 26] = [
+            // NOTE: Keep in sync with provider env vars that affect test behavior
+            const KEYS: [&str; 27] = [
                 "SPACEBOT_DIR",
                 "SPACEBOT_DEPLOYMENT",
                 "SPACEBOT_CRON_TIMEZONE",
                 "SPACEBOT_USER_TIMEZONE",
                 "ANTHROPIC_API_KEY",
+                "ANTHROPIC_BASE_URL",
                 "ANTHROPIC_OAUTH_TOKEN",
                 "OPENAI_API_KEY",
                 "OPENROUTER_API_KEY",
@@ -6859,7 +6860,7 @@ api_key = "sk-proj-xyz789"
 
     #[test]
     fn test_llm_provider_tables_parse_with_env_and_lowercase_keys() {
-        let _lock = env_test_lock().lock().unwrap_or_else(|e| e.into_inner());
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         let toml = r#"
@@ -6905,6 +6906,9 @@ api_key = "static-provider-key"
 
     #[test]
     fn test_legacy_llm_keys_auto_migrate_to_providers() {
+        let _lock = env_test_lock().lock();
+        let _env = EnvGuard::new();
+
         let toml = r#"
 [llm]
 anthropic_key = "legacy-anthropic-key"
@@ -7035,9 +7039,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_needs_onboarding_without_config_or_env() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         assert!(Config::needs_onboarding());
@@ -7045,9 +7047,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_needs_onboarding_with_anthropic_env_key() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7059,9 +7059,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_needs_onboarding_false_with_oauth_credentials() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         // Create an OAuth credentials file in the EnvGuard's temp dir
@@ -7078,9 +7076,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_needs_onboarding_false_with_openai_oauth_credentials() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         let instance_dir = Config::default_instance_dir();
@@ -7098,9 +7094,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_load_from_env_populates_legacy_key_and_provider() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7122,9 +7116,7 @@ name = "My OpenRouter"
 
     #[test]
     fn test_hosted_deployment_forces_api_bind_from_toml() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7144,9 +7136,7 @@ bind = "127.0.0.1"
 
     #[test]
     fn test_hosted_deployment_forces_api_bind_from_env_defaults() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7262,9 +7252,7 @@ bind = "127.0.0.1"
 
     #[test]
     fn test_cron_timezone_resolution_precedence() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7321,9 +7309,7 @@ id = "main"
 
     #[test]
     fn test_cron_timezone_invalid_falls_back_to_system() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7343,9 +7329,7 @@ id = "main"
 
     #[test]
     fn test_cron_timezone_invalid_default_uses_env_fallback() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7368,9 +7352,7 @@ id = "main"
 
     #[test]
     fn test_user_timezone_resolution_precedence() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7417,9 +7399,7 @@ id = "main"
 
     #[test]
     fn test_user_timezone_falls_back_to_cron_timezone() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         let toml = r#"
@@ -7445,9 +7425,7 @@ id = "main"
 
     #[test]
     fn test_user_timezone_invalid_falls_back_to_cron_timezone() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         let toml = r#"
@@ -7470,9 +7448,7 @@ id = "main"
 
     #[test]
     fn test_user_timezone_invalid_config_uses_env_fallback() {
-        let _lock = env_test_lock()
-            .lock()
-            .expect("failed to lock env test mutex");
+        let _lock = env_test_lock().lock();
         let _env = EnvGuard::new();
 
         unsafe {
@@ -7760,6 +7736,9 @@ startup_delay_secs = 2
     /// `LlmConfig` without wiring it up in `load_from_env` / `from_toml`, this test fails.
     #[test]
     fn all_shorthand_keys_register_providers_via_toml() {
+        let _lock = env_test_lock().lock();
+        let _env = EnvGuard::new();
+
         // (toml_key, toml_value, provider_name, expected_base_url_substring)
         let cases: &[(&str, &str, &str, &str)] = &[
             ("anthropic_key", "test-key", "anthropic", "anthropic.com"),
@@ -7824,7 +7803,7 @@ startup_delay_secs = 2
 
     #[test]
     fn all_shorthand_keys_register_providers_via_env() {
-        let _lock = env_test_lock().lock().unwrap();
+        let _lock = env_test_lock().lock();
 
         // (env_var, env_value, provider_name, expected_base_url_substring)
         let cases: &[(&str, &str, &str, &str)] = &[
@@ -8248,7 +8227,7 @@ startup_delay_secs = 2
 
     #[test]
     fn toml_round_trip_with_named_instances() {
-        let _guard = env_test_lock().lock().unwrap();
+        let _guard = env_test_lock().lock();
         let guard = EnvGuard::new();
 
         let toml_content = r#"
@@ -8289,7 +8268,7 @@ chat_id = "-100111"
 
     #[test]
     fn toml_backward_compat_no_adapter_field() {
-        let _guard = env_test_lock().lock().unwrap();
+        let _guard = env_test_lock().lock();
         let guard = EnvGuard::new();
 
         let toml_content = r#"