diff --git a/surfsense_backend/tests/unit/tasks/chat/streaming/test_tool_activity_metadata.py b/surfsense_backend/tests/unit/tasks/chat/streaming/test_tool_activity_metadata.py
new file mode 100644
index 000000000..c2e68dacd
--- /dev/null
+++ b/surfsense_backend/tests/unit/tasks/chat/streaming/test_tool_activity_metadata.py
@@ -0,0 +1,42 @@
+"""Unit tests for ``AgentEventRelayState.tool_activity_metadata``."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.tasks.chat.streaming.relay.state import AgentEventRelayState
+from app.tasks.chat.streaming.relay.task_span import open_task_span
+
+pytestmark = pytest.mark.unit
+
+
+def test_returns_none_when_no_span_and_no_thinking_step() -> None:
+    state = AgentEventRelayState.for_invocation()
+    assert state.tool_activity_metadata(thinking_step_id=None) is None
+    assert state.tool_activity_metadata(thinking_step_id="") is None
+    assert state.tool_activity_metadata(thinking_step_id="   ") is None
+
+
+def test_thinking_step_id_only() -> None:
+    state = AgentEventRelayState.for_invocation()
+    assert state.tool_activity_metadata(thinking_step_id="thinking-3") == {
+        "thinkingStepId": "thinking-3",
+    }
+
+
+def test_span_only_when_active() -> None:
+    state = AgentEventRelayState.for_invocation()
+    open_task_span(state, run_id="run-x")
+    assert state.tool_activity_metadata(thinking_step_id=None) == {
+        "spanId": state.active_span_id,
+    }
+
+
+def test_merges_span_and_thinking_step_when_both_set() -> None:
+    state = AgentEventRelayState.for_invocation()
+    open_task_span(state, run_id="run-x")
+    md = state.tool_activity_metadata(thinking_step_id="thinking-7")
+    assert md == {
+        "spanId": state.active_span_id,
+        "thinkingStepId": "thinking-7",
+    }