diff --git a/refresh_coordinator.go b/refresh_coordinator.go
index 236d96b..254e690 100644
--- a/refresh_coordinator.go
+++ b/refresh_coordinator.go
@@ -498,7 +498,7 @@ func (t *refreshAttemptTracker) mutateState(mutate func(cur *attemptState) *atte
 		if next == nil {
 			return cur
 		}
-		if t.state.CompareAndSwap(t.state.Load(), next) {
+		if t.state.CompareAndSwap(cur, next) {
 			return next
 		}
 	}
diff --git a/universal_cache.go b/universal_cache.go
index aa4adad..827aaf8 100644
--- a/universal_cache.go
+++ b/universal_cache.go
@@ -396,8 +396,16 @@ func (c *UniversalCache) getLocal(key string) (interface{}, bool) {
 			return value, true
 		}
 		c.mu.RUnlock()
-		// Expired — fall through to the write-locked slow path below to
-		// remove the entry under exclusive access.
+		// Expired — return miss immediately. The periodic cleanup goroutine
+		// will evict the stale entry. NEVER fall through to the write-locked
+		// slow path for Token/JWK/Session caches: under Yaegi the write Lock
+		// at line 403 costs 10-100ms per acquisition, and Go's RWMutex
+		// writer-priority semantics block ALL new RLock callers while a Lock
+		// is pending. A single expired-token event turns every concurrent
+		// request from read-parallel into write-serialized — the exact
+		// convoy that produced the 737-goroutine pileup at 0x400275a608.
+		atomic.AddInt64(&c.misses, 1)
+		return nil, false
 	}
 
 	c.mu.Lock()