subagent: fix a real test race on the process-wide OTEL_RESOURCE_ATTRIBUTES env var

hive-subagent-mcp/src/session.rs

@@ -443,10 +443,21 @@ mod tests {
         );
     }
 
+    // One test, not two: `subagent_otel_attrs` reads the real process-wide
+    // `OTEL_RESOURCE_ATTRIBUTES` env var, and cargo runs tests in parallel
+    // threads by default — two separate tests each mutating that global
+    // raced each other (and, in this container, lost to the agent's own
+    // real ambient value). Sequencing both assertions in one test removes
+    // the race instead of papering over it with a mutex.
     #[test]
-    fn otel_attrs_appends_when_ambient_var_is_set() {
+    fn otel_attrs_append_ambient_value_or_stand_alone() {
-        // SAFETY: test-only env mutation, single-threaded within this fn's
+        // SAFETY: test-only env mutation; sequenced within this one test so
-        // scope (no other test in this crate touches this var — checked).
+        // no other test's concurrent read/write of the same var can race it.
+        unsafe {
+            std::env::remove_var("OTEL_RESOURCE_ATTRIBUTES");
+        }
+        assert_eq!(subagent_otel_attrs("batch-1"), "subagent=batch-1");
+
         unsafe {
             std::env::set_var("OTEL_RESOURCE_ATTRIBUTES", "agent=damocles");
         }
@@ -459,14 +470,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn otel_attrs_stands_alone_when_ambient_var_is_unset() {
-        unsafe {
-            std::env::remove_var("OTEL_RESOURCE_ATTRIBUTES");
-        }
-        assert_eq!(subagent_otel_attrs("batch-1"), "subagent=batch-1");
-    }
-
     #[test]
     fn build_config_only_appends_system_prompt_when_given() {
         let with = build_config("n", None, Some("/tmp/p.md"));