Function TestRunAgentPersistsSubSessionOnError

pkg/runtime/runtime_test.go:4135–4170

TestRunAgentPersistsSubSessionOnError covers the background-agent path (runCollecting) when the sub-agent's model stream fails. Before the fix, runCollecting returned early on ErrorEvent without calling parent.AddSubSession, so the sub-session was silently dropped from the parent's in-memory record

(t *testing.T)

// parent.AddSubSession, so the sub-session was silently dropped from the
// parent's in-memory record — invisible to any code that walks session.Messages.
func TestRunAgentPersistsSubSessionOnError(t *testing.T) {
	t.Parallel()

	parentProv := &mockProvider{id: "test/mock-model", stream: &mockStream{}}
	failingProv := &mockProviderWithError{id: "test/mock-model"}

	worker := agent.New("worker", "Worker agent", agent.WithModel(failingProv))
	root := agent.New("root", "Root agent", agent.WithModel(parentProv))
	agent.WithSubAgents(worker)(root)

	tm := team.New(team.WithAgents(root, worker))
	rt, err := NewLocalRuntime(t.Context(), tm, WithSessionCompaction(false), WithModelStore(mockModelStore{}))
	require.NoError(t, err)

	sess := session.New(session.WithUserMessage("Test"), session.WithToolsApproved(true))

	result := rt.RunAgent(t.Context(), agenttool.RunParams{
		AgentName:     "worker",
		Task:          "do something",
		ParentSession: sess,
	})

	require.NotEmpty(t, result.ErrMsg, "RunAgent should surface the sub-session error")

	// The parent session must hold a sub-session record even though the
	// sub-agent errored — without the fix AddSubSession was skipped and
	// the entire partial transcript was lost.
	var subSessionItems int
	for _, item := range sess.Messages {
		if item.SubSession != nil {
			subSessionItems++
		}
	}
	assert.Equal(t, 1, subSessionItems,
		"parent session must record the sub-session even when the background agent errored")
}

// TestReasoningOnlyTurnEmitsWarning is a regression test for
// https://github.com/docker/docker-agent/issues/3145. A thinking-mode model