refactor(agent): make resolver sole runtime owner

tests/agent/test_consolidate_offset.py

@@ -518,9 +518,11 @@ class TestNewCommandArchival:
         loop.sessions.save(session)
 
         call_count = 0
+        expected_runtime = loop.llm_runtime()
 
-        async def _failing_summarize(_messages, *, session_key=None) -> bool:
+        async def _failing_summarize(_messages, *, runtime, session_key=None) -> bool:
             nonlocal call_count
+            assert runtime is expected_runtime
             assert session_key == "cli:test"
             call_count += 1
             return False
@@ -528,7 +530,7 @@ class TestNewCommandArchival:
         loop.consolidator.archive = _failing_summarize  # type: ignore[method-assign]
 
         new_msg = InboundMessage(channel="cli", sender_id="user", chat_id="test", content="/new")
-        response = await loop._process_message(new_msg)
+        response = await loop._process_message(new_msg, runtime=expected_runtime)
 
         assert response is not None
         assert "new session started" in response.content.lower()
@@ -553,9 +555,11 @@ class TestNewCommandArchival:
 
         archived_count = -1
         archived_session_key = None
+        expected_runtime = loop.llm_runtime()
 
-        async def _fake_summarize(messages, *, session_key=None) -> bool:
+        async def _fake_summarize(messages, *, runtime, session_key=None) -> bool:
             nonlocal archived_count, archived_session_key
+            assert runtime is expected_runtime
             archived_count = len(messages)
             archived_session_key = session_key
             return True
@@ -563,7 +567,7 @@ class TestNewCommandArchival:
         loop.consolidator.archive = _fake_summarize  # type: ignore[method-assign]
 
         new_msg = InboundMessage(channel="cli", sender_id="user", chat_id="test", content="/new")
-        response = await loop._process_message(new_msg)
+        response = await loop._process_message(new_msg, runtime=expected_runtime)
 
         assert response is not None
         assert "new session started" in response.content.lower()
@@ -582,15 +586,17 @@ class TestNewCommandArchival:
             session.add_message("user", f"msg{i}")
             session.add_message("assistant", f"resp{i}")
         loop.sessions.save(session)
+        expected_runtime = loop.llm_runtime()
 
-        async def _ok_summarize(_messages, *, session_key=None) -> bool:
+        async def _ok_summarize(_messages, *, runtime, session_key=None) -> bool:
+            assert runtime is expected_runtime
             assert session_key == "cli:test"
             return True
 
         loop.consolidator.archive = _ok_summarize  # type: ignore[method-assign]
 
         new_msg = InboundMessage(channel="cli", sender_id="user", chat_id="test", content="/new")
-        response = await loop._process_message(new_msg)
+        response = await loop._process_message(new_msg, runtime=expected_runtime)
 
         assert response is not None
         assert "new session started" in response.content.lower()
@@ -610,8 +616,10 @@ class TestNewCommandArchival:
 
         archived = asyncio.Event()
         release_archive = asyncio.Event()
+        expected_runtime = loop.llm_runtime()
 
-        async def _slow_summarize(_messages, *, session_key=None) -> bool:
+        async def _slow_summarize(_messages, *, runtime, session_key=None) -> bool:
+            assert runtime is expected_runtime
             assert session_key == "cli:test"
             await release_archive.wait()
             archived.set()
@@ -620,7 +628,7 @@ class TestNewCommandArchival:
         loop.consolidator.archive = _slow_summarize  # type: ignore[method-assign]
 
         new_msg = InboundMessage(channel="cli", sender_id="user", chat_id="test", content="/new")
-        await loop._process_message(new_msg)
+        await loop._process_message(new_msg, runtime=expected_runtime)
 
         assert not archived.is_set()
         release_archive.set()

tests/agent/test_loop_consolidation_tokens.py

@@ -6,6 +6,7 @@ import nanobot.agent.memory as memory_module
 from nanobot.agent.loop import AgentLoop
 from nanobot.bus.queue import MessageBus
 from nanobot.providers.base import LLMResponse
+from nanobot.session.manager import replay_max_messages_for_context
 
 
 def _make_loop(tmp_path, *, estimated_tokens: int, context_window_tokens: int) -> AgentLoop:
@@ -222,7 +223,7 @@ async def test_preflight_consolidation_receives_pending_summary(tmp_path) -> Non
     loop.consolidator.maybe_consolidate_by_tokens.assert_any_await(
         session,
         runtime=runtime,
-        replay_max_messages=loop._max_messages,
+        replay_max_messages=replay_max_messages_for_context(runtime.context_window_tokens),
     )
     assert len(loop.consolidator.maybe_consolidate_by_tokens.call_args_list) == 2
     assert all(

tests/agent/test_loop_progress.py

@@ -21,6 +21,7 @@ from nanobot.bus.outbound_events import (
 )
 from nanobot.bus.queue import MessageBus
 from nanobot.providers.base import LLMResponse, ToolCallRequest
+from nanobot.providers.factory import ProviderSnapshot
 from nanobot.session.webui_turns import WebuiTurnCoordinator
 from nanobot.utils.progress_events import (
     invoke_file_edit_progress,
@@ -815,8 +816,14 @@ class TestToolEventProgress:
         ))
 
         assert len(scheduled_title) == 1
-        loop.provider = MagicMock()
-        loop.model = "switched-after-turn"
+        next_provider = MagicMock()
+        next_provider.generation = loop.llm_runtime().generation
+        loop.runtime_resolver.adopt_snapshot(ProviderSnapshot(
+            provider=next_provider,
+            model="switched-after-turn",
+            context_window_tokens=loop.context_window_tokens,
+            signature=("switched-after-turn",),
+        ))
 
         await scheduled_title[0]  # type: ignore[misc]
 

tests/agent/test_loop_save_turn.py

@@ -19,6 +19,7 @@ from nanobot.bus.outbound_events import (
 from nanobot.bus.queue import MessageBus
 from nanobot.cron.session_turns import CRON_HISTORY_META, CRON_TRIGGER_META
 from nanobot.providers.base import LLMResponse
+from nanobot.providers.factory import ProviderSnapshot
 from nanobot.session.automation_turns import AUTOMATION_HISTORY_META
 from nanobot.session.goal_state import GOAL_STATE_KEY
 from nanobot.session.manager import Session, SessionManager
@@ -69,8 +70,17 @@ def test_agent_loop_llm_runtime_reflects_current_provider_and_model(tmp_path: Pa
     assert runtime.model == "test-model"
 
     next_provider = MagicMock()
-    loop.provider = next_provider
-    loop.model = "next-model"
+    next_provider.generation = SimpleNamespace(
+        temperature=0.1,
+        max_tokens=4096,
+        reasoning_effort=None,
+    )
+    loop.runtime_resolver.adopt_snapshot(ProviderSnapshot(
+        provider=next_provider,
+        model="next-model",
+        context_window_tokens=runtime.context_window_tokens,
+        signature=("next-model",),
+    ))
     runtime = loop.llm_runtime()
 
     assert runtime.provider is next_provider

tests/agent/test_max_messages_config.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from dataclasses import replace
 from pathlib import Path
 from unittest.mock import AsyncMock, MagicMock, patch
 
@@ -67,11 +68,13 @@ class TestMaxMessagesInit:
 
     def test_default_for_200k_context_reaches_file_cap(self, tmp_path: Path) -> None:
         loop = _make_loop(tmp_path)
-        assert loop._max_messages == FILE_MAX_MESSAGES
+        runtime = loop.runtime_resolver.runtime
+        assert replay_max_messages_for_context(runtime.context_window_tokens) == FILE_MAX_MESSAGES
 
     def test_default_scales_with_context_window(self, tmp_path: Path) -> None:
         loop = _make_loop(tmp_path, context_window_tokens=32_768)
-        assert loop._max_messages == 327
+        runtime = loop.runtime_resolver.runtime
+        assert replay_max_messages_for_context(runtime.context_window_tokens) == 327
 
     def test_provider_refresh_resyncs_context_derived_limit(self, tmp_path: Path) -> None:
         old_provider = MagicMock()
@@ -93,9 +96,10 @@ class TestMaxMessagesInit:
             ),
         )
 
-        assert loop._max_messages == 327
-        loop._refresh_provider_snapshot()
-        assert loop._max_messages == FILE_MAX_MESSAGES
+        initial = loop.runtime_resolver.runtime
+        assert replay_max_messages_for_context(initial.context_window_tokens) == 327
+        refreshed = loop.llm_runtime()
+        assert replay_max_messages_for_context(refreshed.context_window_tokens) == FILE_MAX_MESSAGES
 
 
 class TestGetHistoryWithMaxMessages:
@@ -136,7 +140,7 @@ class TestMaxMessagesIntegration:
     async def test_process_message_passes_limit_to_history_call(self, tmp_path: Path) -> None:
         """The real message path should pass max_messages into session history replay."""
         loop = _make_loop(tmp_path)
-        loop._max_messages = 25
+        runtime = replace(loop.llm_runtime(), context_window_tokens=32_768)
         loop.provider.chat_with_retry = AsyncMock(
             return_value=LLMResponse(content="ok", tool_calls=[], usage={})
         )
@@ -146,12 +150,13 @@ class TestMaxMessagesIntegration:
         session = loop.sessions.get_or_create("cli:test")
         with patch.object(session, "get_history", wraps=session.get_history) as mock_hist:
             result = await loop._process_message(
-                InboundMessage(channel="cli", sender_id="user", chat_id="test", content="hello")
+                InboundMessage(channel="cli", sender_id="user", chat_id="test", content="hello"),
+                runtime=runtime,
             )
 
         assert result is not None
         assert mock_hist.call_count == 1
-        assert mock_hist.call_args.kwargs["max_messages"] == 25
+        assert mock_hist.call_args.kwargs["max_messages"] == 327
         assert mock_hist.call_args.kwargs["extend_to_user"] is False
 
     @pytest.mark.asyncio
@@ -182,8 +187,7 @@ class TestMaxMessagesIntegration:
         tmp_path: Path,
     ) -> None:
         """A live user turn should not extend history to an older long tool turn."""
-        loop = _make_loop(tmp_path)
-        loop._max_messages = 6
+        loop = _make_loop(tmp_path, context_window_tokens=8_000)
         loop.provider.chat_with_retry = AsyncMock(
             return_value=LLMResponse(content="ok", tool_calls=[], usage={})
         )
@@ -194,7 +198,7 @@ class TestMaxMessagesIntegration:
         session.add_message("user", "old")
         session.add_message("assistant", "old answer")
         session.add_message("user", "long older turn")
-        for i in range(8):
+        for i in range(70):
             session.messages.extend(_tool_round(f"older-{i}"))
         session.add_message("assistant", "older final")
 

tests/agent/test_runtime_refresh.py

@@ -18,7 +18,7 @@ def _provider(default_model: str, max_tokens: int = 123) -> MagicMock:
     return provider
 
 
-def test_provider_refresh_updates_all_model_dependents(tmp_path: Path) -> None:
+def test_provider_refresh_updates_only_runtime_resolver(tmp_path: Path) -> None:
     old_provider = _provider("old-model")
     new_provider = _provider("new-model", max_tokens=456)
     loop = AgentLoop(
@@ -35,8 +35,9 @@ def test_provider_refresh_updates_all_model_dependents(tmp_path: Path) -> None:
         ),
     )
 
-    loop._refresh_provider_snapshot()
+    runtime = loop.llm_runtime()
 
+    assert runtime is loop.runtime_resolver.runtime
     assert loop.provider is new_provider
     assert loop.model == "new-model"
     assert loop.context_window_tokens == 2000
@@ -50,6 +51,29 @@ def test_provider_refresh_updates_all_model_dependents(tmp_path: Path) -> None:
     assert not hasattr(loop.consolidator, "max_completion_tokens")
 
 
+def test_loop_has_no_mutable_runtime_mirrors_or_legacy_snapshot_api(tmp_path: Path) -> None:
+    loop = AgentLoop(
+        bus=MessageBus(),
+        provider=_provider("test-model"),
+        workspace=tmp_path,
+        model="test-model",
+        context_window_tokens=1000,
+    )
+
+    assert {
+        "provider",
+        "model",
+        "context_window_tokens",
+        "model_presets",
+        "_active_preset",
+        "_provider_signature",
+        "_max_messages",
+    }.isdisjoint(loop.__dict__)
+    assert not hasattr(loop, "_apply_provider_snapshot")
+    assert not hasattr(loop, "_build_model_preset_snapshot")
+    assert not hasattr(loop, "_sync_replay_max_messages")
+
+
 def test_llm_runtime_refreshes_provider_snapshot(tmp_path: Path) -> None:
     old_provider = _provider("old-model")
     new_provider = _provider("new-model", max_tokens=456)
@@ -118,7 +142,7 @@ def test_settings_context_window_refreshes_runtime_state(
     loop = AgentLoop.from_config(config, provider_snapshot_loader=loader)
 
     payload = update_agent_settings({"context_window_tokens": ["262144"]})
-    loop._refresh_provider_snapshot()
+    loop.llm_runtime()
 
     assert payload["requires_restart"] is False
     assert loop.context_window_tokens == 262_144

tests/agent/test_self_model_preset.py

@@ -54,9 +54,10 @@ def test_model_preset_setter_updates_state(tmp_path) -> None:
     assert loop.model_preset == "fast"
     assert loop.model == "openai/gpt-4.1"
     assert loop.context_window_tokens == 32_768
-    assert loop.provider.generation.temperature == 0.5
-    assert loop.provider.generation.max_tokens == 4096
-    assert loop.provider.generation.reasoning_effort == "low"
+    runtime = loop.llm_runtime()
+    assert runtime.generation.temperature == 0.5
+    assert runtime.generation.max_tokens == 4096
+    assert runtime.generation.reasoning_effort == "low"
     assert not hasattr(loop.subagents, "model")
     assert not hasattr(loop.consolidator, "model")
     assert not hasattr(loop.consolidator, "context_window_tokens")
@@ -174,7 +175,7 @@ def test_active_model_preset_survives_unchanged_config_refresh(tmp_path) -> None
     )
 
     loop.set_model_preset("fast")
-    loop._refresh_provider_snapshot()
+    loop.llm_runtime()
 
     assert loop.model_preset == "fast"
     assert loop.provider is fast_provider
@@ -210,7 +211,7 @@ def test_config_model_refresh_clears_active_model_preset(tmp_path) -> None:
     )
 
     loop.set_model_preset("fast")
-    loop._refresh_provider_snapshot()
+    loop.llm_runtime()
 
     assert loop.model_preset is None
     assert loop.provider is webui_provider
@@ -292,7 +293,7 @@ def test_self_tool_set_model_clears_active_preset(tmp_path) -> None:
     tool = MyTool(runtime_state=loop, modify_allowed=True)
     result = tool._modify("model", "anthropic/claude-opus-4-5")
     assert "Error" not in result
-    assert loop._active_preset is None
+    assert loop.model_preset is None
     assert loop.model == "anthropic/claude-opus-4-5"
 
 
@@ -323,5 +324,7 @@ def test_from_config_static_preset_loader_does_not_enable_hot_reload(tmp_path) -
     fake_provider = _provider("openai/gpt-4.1")
     with patch("nanobot.providers.factory.make_provider", return_value=fake_provider):
         loop = AgentLoop.from_config(config)
-    assert loop._provider_snapshot_loader is None
-    assert loop._preset_snapshot_loader is not None
+        default_runtime = loop.runtime_resolver.runtime
+        resolved = loop.runtime_resolver.resolve_preset("fast")
+    assert resolved.model == "openai/gpt-4.1-mini"
+    assert loop.runtime_resolver.runtime is default_runtime

tests/agent/tools/test_self_tool.py

@@ -35,6 +35,12 @@ def _make_mock_loop(**overrides):
     loop._concurrency_gate = None
     loop._unified_session = False
     loop._extra_hooks = []
+    loop.set_runtime_model.side_effect = lambda value: setattr(loop, "model", value)
+    loop.set_runtime_context_window.side_effect = lambda value: setattr(
+        loop,
+        "context_window_tokens",
+        value,
+    )
 
     # web_config mock — needed for check tests
     loop.web_config = MagicMock()
@@ -237,12 +243,12 @@ class TestModifyRestricted:
 
     @pytest.mark.asyncio
     async def test_modify_context_window_valid(self):
-        loop = _make_mock_loop(_sync_replay_max_messages=MagicMock())
+        loop = _make_mock_loop()
         tool = _make_tool(runtime_state=loop)
         result = await tool.execute(action="set", key="context_window_tokens", value=131072)
         assert "Set context_window_tokens" in result
         assert loop.context_window_tokens == 131072
-        loop._sync_replay_max_messages.assert_called_once_with()
+        loop.set_runtime_context_window.assert_called_once_with(131072)
 
     @pytest.mark.asyncio
     async def test_modify_none_value_for_restricted_int(self):