hermes-agent/tests/agent/test_turn_context.py
alt-glitch 3713483874 fix(mcp): refresh agent tool snapshot between turns (cache-safe late-binding)
A slow MCP server (HTTP/OAuth, 2-6s cold connect) that finishes connecting
after the agent's one-time tool snapshot was uncallable for the rest of the
session. The merged pre-first-turn late-refresh only helps during the dead air
before the user's first keystroke; once a turn starts it bails to protect the
prompt cache, so a user who types before the server connects never gets the
tools without a manual /reload-mcp.

Refresh the snapshot in the per-turn prologue (build_turn_context), before this
turn's first API call assembles tools=. This is cache-safe by construction: the
refresh only ever extends a fresh request prefix at a turn boundary, never
mutates the cached prefix of an in-flight turn. So late tools become callable on
the user's NEXT turn automatically, with no /reload-mcp and no cache cost.

- tools/mcp_tool.py: has_registered_mcp_tools() — cheap guard so sessions with
  no MCP servers (the common case) skip the rebuild entirely.
- agent/turn_context.py: call the shared refresh_agent_mcp_tools() helper at the
  top of the prologue when MCP servers are registered.
- tests: 3 contract tests through the real build_turn_context (adds late tool;
  skipped when no servers; no snapshot churn when unchanged).

.hermes/plans/: SPEC + PLAN documenting the root cause, the cache-safety
constraint, and why the existing fixes (#48403/#41630/#42802) don't close it.
2026-06-19 11:57:43 -07:00

245 lines
8.1 KiB
Python

"""Unit tests for the extracted turn prologue (``agent/turn_context.py``).
These exercise ``build_turn_context`` against a lightweight fake agent to
confirm the prologue produces the right ``TurnContext`` and applies the
``agent`` side effects the loop relies on — without spinning up a real
``AIAgent`` or hitting any provider.
"""
from __future__ import annotations
import types
from unittest.mock import patch
import pytest
from agent.turn_context import TurnContext, build_turn_context
class _FakeTodoStore:
def has_items(self):
return True
def _hydrate(self, *_a, **_k):
pass
class _FakeGuardrails:
def __init__(self):
self.reset_called = False
def reset_for_turn(self):
self.reset_called = True
class _FakeAgent:
"""Minimal stand-in covering only what the prologue touches."""
def __init__(self):
self.session_id = "sess-1"
self.model = "test/model"
self.provider = "openrouter"
self.base_url = "https://openrouter.ai/api/v1"
self.api_key = "sk-x"
self.api_mode = "chat_completions"
self.platform = "cli"
self.quiet_mode = True
self.max_iterations = 90
self.tools = []
self.valid_tool_names = set()
self.enabled_toolsets = None
self.disabled_toolsets = None
self.compression_enabled = False
self.context_compressor = types.SimpleNamespace(
protect_first_n=2, protect_last_n=2
)
self._cached_system_prompt = "SYSTEM"
self._memory_store = None
self._memory_manager = None
self._memory_nudge_interval = 0
self._turns_since_memory = 0
self._user_turn_count = 0
self._todo_store = _FakeTodoStore()
self._tool_guardrails = _FakeGuardrails()
self._compression_warning = None
self._interrupt_requested = False
self._memory_write_origin = "assistant_tool"
self._stream_context_scrubber = None
self._stream_think_scrubber = None
# Attributes the prologue assigns; recorded for assertions.
self._invalid_tool_retries = -1
self._vision_supported = None
self._persist_calls = 0
# --- methods the prologue calls ---
def _ensure_db_session(self):
pass
def _restore_primary_runtime(self):
pass
def _cleanup_dead_connections(self):
return False
def _emit_status(self, _msg):
pass
def _replay_compression_warning(self):
pass
def _hydrate_todo_store(self, *_a, **_k):
pass
def _safe_print(self, *_a, **_k):
pass
def _persist_session(self, *_a, **_k):
self._persist_calls += 1
@pytest.fixture(autouse=True)
def _stub_runtime_main():
"""``build_turn_context`` calls ``auxiliary_client.set_runtime_main`` as a
production side effect (telling aux tools the live main provider/model).
That writes a module-level global these unit tests don't care about and
which would otherwise leak into sibling tests (e.g. provider-parity
resolution) when the per-test process isolation plugin is disabled. Stub
it out so the prologue tests stay hermetic.
"""
with patch("agent.auxiliary_client.set_runtime_main", lambda *a, **k: None):
yield
def _build(agent, **overrides):
kwargs = dict(
agent=agent,
user_message="hello",
system_message=None,
conversation_history=None,
task_id=None,
stream_callback=None,
persist_user_message=None,
restore_or_build_system_prompt=lambda *a, **k: None,
install_safe_stdio=lambda: None,
sanitize_surrogates=lambda s: s,
summarize_user_message_for_log=lambda s: s,
set_session_context=lambda _sid: None,
set_current_write_origin=lambda _o: None,
ra=lambda: types.SimpleNamespace(_set_interrupt=lambda *a, **k: None),
)
kwargs.update(overrides)
return build_turn_context(**kwargs)
def test_returns_turn_context_with_user_message_appended():
agent = _FakeAgent()
ctx = _build(agent)
assert isinstance(ctx, TurnContext)
assert ctx.user_message == "hello"
# The user turn was appended and indexed.
assert ctx.messages[-1] == {"role": "user", "content": "hello"}
assert ctx.current_turn_user_idx == len(ctx.messages) - 1
assert ctx.active_system_prompt == "SYSTEM"
def test_applies_agent_side_effects():
agent = _FakeAgent()
_build(agent)
# Retry counters reset, guardrails reset, vision re-armed, turn counted.
assert agent._invalid_tool_retries == 0
assert agent._tool_guardrails.reset_called is True
assert agent._vision_supported is True
assert agent._user_turn_count == 1
# Crash-resilience persistence fired once.
assert agent._persist_calls == 1
# task/turn ids assigned on the agent.
assert agent._current_task_id
assert agent._current_turn_id
def test_task_id_passthrough():
agent = _FakeAgent()
ctx = _build(agent, task_id="fixed-task")
assert ctx.effective_task_id == "fixed-task"
assert agent._current_task_id == "fixed-task"
def test_persist_user_message_becomes_original():
agent = _FakeAgent()
ctx = _build(agent, user_message="api-prefixed", persist_user_message="clean")
# original_user_message tracks the clean persist override.
assert ctx.original_user_message == "clean"
# but the appended user turn carries the full (sanitized) message.
assert ctx.messages[-1]["content"] == "api-prefixed"
def test_memory_nudge_fires_at_interval():
agent = _FakeAgent()
agent._memory_nudge_interval = 1
agent.valid_tool_names = {"memory"}
agent._memory_store = object()
ctx = _build(agent)
assert ctx.should_review_memory is True
assert agent._turns_since_memory == 0 # reset after firing
def test_no_review_when_memory_disabled():
agent = _FakeAgent()
ctx = _build(agent)
assert ctx.should_review_memory is False
# ── Between-turns MCP refresh (cache-safe late-binding) ──────────────────────
#
# A slow MCP server that connects after the agent's build-time tool snapshot
# must become callable by the user's NEXT turn — without mutating an in-flight
# turn's cached request prefix. The prologue is exactly that boundary, so the
# refresh hook lives here. These assert the contract (R1/R2/R6 in the spec),
# not timing permutations.
def test_between_turns_refresh_adds_late_tool_when_servers_registered():
"""R1: a tool that registered since build lands in this turn's snapshot."""
agent = _FakeAgent()
new_def = {"type": "function", "function": {"name": "mcp_x_tool", "description": "", "parameters": {}}}
import model_tools
with patch("tools.mcp_tool.has_registered_mcp_tools", return_value=True), \
patch.object(model_tools, "get_tool_definitions", return_value=[new_def]):
_build(agent)
assert "mcp_x_tool" in agent.valid_tool_names
assert any(t["function"]["name"] == "mcp_x_tool" for t in agent.tools)
def test_between_turns_refresh_skipped_when_no_servers():
"""R6: the common case (no MCP servers) never walks the registry."""
agent = _FakeAgent()
import model_tools
with patch("tools.mcp_tool.has_registered_mcp_tools", return_value=False), \
patch.object(model_tools, "get_tool_definitions") as gtd:
_build(agent)
gtd.assert_not_called()
def test_between_turns_refresh_no_churn_when_unchanged():
"""R2: an unchanged tool set leaves the snapshot object identity intact
(no needless swap → nothing for the next request prefix to diff against)."""
agent = _FakeAgent()
same = [{"type": "function", "function": {"name": "a", "description": "", "parameters": {}}}]
agent.tools = same
agent.valid_tool_names = {"a"}
import model_tools
with patch("tools.mcp_tool.has_registered_mcp_tools", return_value=True), \
patch.object(
model_tools, "get_tool_definitions",
return_value=[{"type": "function", "function": {"name": "a", "description": "", "parameters": {}}}],
):
_build(agent)
assert agent.tools is same # not replaced → no churn