test: serialize CONFIRM/HANDOFF env mutations across crates

Avoid parallel cargo test flakes when multiple tests set process env.

crates/grokboy-core/src/browser.rs

@@ -743,6 +743,7 @@ mod tests {
 
     #[test]
     fn handoff_auto_resume_and_abort() {
+        let _env_lock = crate::test_env::lock();
         // SAFETY: tests run serially for this env in practice; restore after.
         let prev = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
         unsafe { std::env::set_var("GROKBOY_HANDOFF_AUTO", "1") };

crates/grokboy-core/src/confirm.rs

@@ -267,6 +267,7 @@ mod tests {
 
     #[test]
     fn confirm_auto_approve_via_confirm_env() {
+        let _env_lock = crate::test_env::lock();
         let prev_c = std::env::var("GROKBOY_CONFIRM_AUTO").ok();
         let prev_h = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
         unsafe {
@@ -288,6 +289,7 @@ mod tests {
 
     #[test]
     fn confirm_auto_falls_back_to_handoff_env() {
+        let _env_lock = crate::test_env::lock();
         let prev_c = std::env::var("GROKBOY_CONFIRM_AUTO").ok();
         let prev_h = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
         unsafe {
@@ -308,6 +310,7 @@ mod tests {
 
     #[test]
     fn execute_approve_and_deny_offline() {
+        let _env_lock = crate::test_env::lock();
         let prev_c = std::env::var("GROKBOY_CONFIRM_AUTO").ok();
         let prev_h = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
         unsafe {

crates/grokboy-core/src/lib.rs

@@ -19,3 +19,17 @@ pub use config::Config;
 pub use model::{ChatMessage, FunctionCall, Role, ToolCall, chat_completion, stream_chat};
 pub use session::{Session, load_or_create, load_session, save_session, sessions_dir};
 pub use tools::{ToolContext, execute_tool, is_completion_tool, tool_definitions};
+
+/// Serialize tests that mutate process env (CONFIRM_AUTO / HANDOFF_AUTO).
+#[cfg(test)]
+pub(crate) mod test_env {
+    use std::sync::{Mutex, MutexGuard, OnceLock};
+
+    pub(crate) fn lock() -> MutexGuard<'static, ()> {
+        static M: OnceLock<Mutex<()>> = OnceLock::new();
+        M.get_or_init(|| Mutex::new(()))
+            .lock()
+            .unwrap_or_else(|e| e.into_inner())
+    }
+}
+

crates/grokboy-core/src/tools.rs

@@ -522,6 +522,7 @@ mod tests {
 
     #[tokio::test]
     async fn browser_handoff_auto_resume_protocol() {
+        let _env_lock = crate::test_env::lock();
         // Offline: with GROKBOY_HANDOFF_AUTO=1, missing Chromium still fail-closes
         // OR (if Chromium present) resumes and returns snapshot/error JSON — never hangs.
         let prev = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
@@ -553,6 +554,7 @@ mod tests {
 
     #[tokio::test]
     async fn request_user_confirm_auto_approve_and_deny() {
+        let _env_lock = crate::test_env::lock();
         let prev_c = std::env::var("GROKBOY_CONFIRM_AUTO").ok();
         let prev_h = std::env::var("GROKBOY_HANDOFF_AUTO").ok();
         unsafe {