fix(tracing): skip NoOpTrace context reset on GeneratorExit

src/agents/tracing/traces.py

@@ -399,6 +399,10 @@ def __enter__(self) -> Trace:
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
+        # Same-task generator close should still reset the context var so the
+        # NoOpTrace doesn't linger as the current trace. Cross-context closes
+        # (different task / event loop) raise ValueError from contextvars,
+        # which the finish() helper swallows below.
         self.finish(reset_current=True)
 
     def start(self, mark_as_current: bool = False):
@@ -407,7 +411,14 @@ def start(self, mark_as_current: bool = False):
 
     def finish(self, reset_current: bool = False):
         if reset_current and self._prev_context_token is not None:
-            Scope.reset_current_trace(self._prev_context_token)
+            try:
+                Scope.reset_current_trace(self._prev_context_token)
+            except ValueError:
+                # The context token was created in a different Context (e.g.
+                # the trace was entered in another task and the generator is
+                # closing from the parent's context). Skipping reset here is
+                # safe: that other Context owns its own contextvar copy.
+                pass
             self._prev_context_token = None
 
     @property

tests/tracing/test_traces_impl.py

@@ -1,3 +1,4 @@
+import contextvars
 import logging
 from typing import Any, cast
 
@@ -42,6 +43,41 @@ def test_no_op_trace_double_enter_logs_error(caplog) -> None:
     trace.__exit__(None, None, None)
 
 
+def test_no_op_trace_resets_context_on_same_task_generator_exit() -> None:
+    """NoOpTrace must reset the current trace on a same-task GeneratorExit.
+
+    A previous version skipped reset unconditionally on GeneratorExit, which
+    handles the cross-task GC case but leaves NoOpTrace as the current trace
+    after a normal same-context generator close, suppressing later tracing.
+    Now the reset is attempted and any ValueError (from a token created in a
+    different Context) is swallowed.
+    """
+    Scope.set_current_trace(None)
+    trace = NoOpTrace()
+    trace.__enter__()
+    assert trace._prev_context_token is not None
+    trace.__exit__(GeneratorExit, GeneratorExit(), None)
+    # Same-task close: reset succeeded, token consumed, current trace cleared.
+    assert trace._prev_context_token is None
+    assert Scope.get_current_trace() is None
+
+
+def test_no_op_trace_swallows_cross_context_reset_error() -> None:
+    """A token created in a different Context raises ValueError on reset; swallow it."""
+    Scope.set_current_trace(None)
+    trace = NoOpTrace()
+
+    other_context = contextvars.copy_context()
+    other_context.run(trace.__enter__)
+    token = trace._prev_context_token
+    assert token is not None
+
+    # Resetting from our context (not the one that set it) raises ValueError;
+    # the helper must swallow that and clear the stored token.
+    trace.__exit__(GeneratorExit, GeneratorExit(), None)
+    assert trace._prev_context_token is None
+
+
 def test_trace_impl_lifecycle_sets_scope() -> None:
     Scope.set_current_trace(None)
     processor = DummyProcessor()