test(render_detail): cover untested _build_event_details branches (#860)

tests/copilot_usage/test_render_detail.py

@@ -608,3 +608,27 @@ def test_multi_model_shutdown_via_full_render(self) -> None:
         row = next(line for line in output.splitlines() if "2025-01-01 01:00" in line)
         assert re.search(r"\b7\b", row)  # total model calls = 3 + 4
         assert re.search(r"\b800\b", row)  # total output tokens = 500 + 300
+
+
+# ---------------------------------------------------------------------------
+# Issue #860 — untested branch in _build_event_details
+# ---------------------------------------------------------------------------
+
+
+class TestBuildEventDetailsUntestedBranches:
+    """Cover the remaining _build_event_details branch unique to this module."""
+
+    def test_tool_execution_complete_with_model(self) -> None:
+        """TOOL_EXECUTION_COMPLETE with model set must include 'model=...'."""
+        from copilot_usage.render_detail import _build_event_details
+
+        ev = SessionEvent(
+            type=EventType.TOOL_EXECUTION_COMPLETE,
+            data={
+                "toolCallId": "tc1",
+                "model": "claude-sonnet-4",
+                "success": True,
+            },
+        )
+        detail = _build_event_details(ev)
+        assert "model=claude-sonnet-4" in detail