feat(tui): add agent interaction workflows

tests/agent/test_loop_save_turn.py

@@ -1819,6 +1819,33 @@ async def test_system_subagent_followup_is_persisted_before_prompt_assembly(tmp_
     ]
 
 
+@pytest.mark.asyncio
+async def test_turn_usage_is_persisted_with_the_saved_session(tmp_path: Path) -> None:
+    loop = _make_full_loop(tmp_path)
+    loop.consolidator.maybe_consolidate_by_tokens = AsyncMock(return_value=False)  # type: ignore[method-assign]
+
+    async def fake_run_agent_loop(initial_messages, **_kwargs):
+        loop._last_usage = {"prompt_tokens": 64, "completion_tokens": 9}
+        return (
+            "done",
+            [],
+            [*initial_messages, {"role": "assistant", "content": "done"}],
+            "stop",
+            False,
+        )
+
+    loop._run_agent_loop = fake_run_agent_loop  # type: ignore[method-assign]
+    await loop._process_message(
+        InboundMessage(channel="cli", sender_id="user", chat_id="usage", content="hello")
+    )
+
+    loop.sessions.invalidate("cli:usage")
+    assert loop.sessions.get_or_create("cli:usage").metadata["_last_usage"] == {
+        "prompt_tokens": 64,
+        "completion_tokens": 9,
+    }
+
+
 @pytest.mark.asyncio
 async def test_system_subagent_followup_does_not_log_content(tmp_path: Path) -> None:
     loop = _make_full_loop(tmp_path)

tests/bus/test_runtime_events.py

@@ -99,6 +99,7 @@ async def test_runtime_event_publisher_consumes_turn_metadata_on_complete() -> N
     bus.subscribe(seen.append)
     publisher.record_turn_runtime("cli:direct", "runtime")
     publisher.record_turn_latency("cli:direct", 123)
+    publisher.record_turn_usage("cli:direct", {"prompt_tokens": 40, "completion_tokens": 2})
 
     await publisher.turn_completed(
         channel="cli",
@@ -119,9 +120,11 @@ async def test_runtime_event_publisher_consumes_turn_metadata_on_complete() -> N
     assert first.context.metadata == {"source": "test"}
     assert first.latency_ms == 123
     assert first.runtime == "runtime"
+    assert first.usage == {"prompt_tokens": 40, "completion_tokens": 2}
     assert isinstance(second, TurnCompleted)
     assert second.latency_ms is None
     assert second.runtime is None
+    assert second.usage == {}
 
 
 @pytest.mark.asyncio

tests/webui/test_session_context.py

@@ -40,6 +40,7 @@ def test_session_context_separates_archive_progress_from_replay() -> None:
         "estimated_session_tokens": replay_tokens + summary_tokens,
         "archived_summary": "The archived conversation settled the old question.",
         "archived_summary_at": "2026-08-13T10:00:00Z",
+        "last_usage": None,
     }
 
 
@@ -54,3 +55,22 @@ def test_session_context_tolerates_untrusted_summary_metadata() -> None:
 
     assert payload["archived_summary"] is None
     assert payload["archived_summary_at"] is None
+
+
+def test_session_context_sanitizes_usage_metadata() -> None:
+    session = Session(
+        key="websocket:context",
+        metadata={
+            "_last_usage": {
+                "prompt_tokens": 120,
+                "completion_tokens": 8,
+                "negative": -1,
+                "boolean": True,
+                "text": "invalid",
+            }
+        },
+    )
+
+    payload = session_context_payload(session)
+
+    assert payload["last_usage"] == {"prompt_tokens": 120, "completion_tokens": 8}