9cbc221dcb
A general-plugin context engine is one shared instance; agent init copied it per agent with copy.deepcopy() only. Engines that hold a SQLite connection or lock (hermes-lcm) already expose clone_for_agent() for exactly this, but it was never called, so every init logged "could not be safely copied … falling back to built-in compressor" and the engine was unusable through the plugin system. ContextEngine grows clone_for_agent() (default: deepcopy, the previous behaviour) and _select_context_engine calls it; the failure message now names the hook to override. Docs: context-engine-plugin.md documents the per-agent clone contract. Test change (existing on main): tests/agent/test_context_engine.py:: test_agent_init_source_deepcopies_singleton_not_aliases was a source-reading pin on the literal `copy.deepcopy(_candidate)` line, which this fix intentionally replaces. It is superseded by tests/agent/test_plugin_context_engine_clone.py, which drives the real _select_context_engine seam and asserts the invariant it guarded (child update_model() never mutates the shared singleton) plus the new clone_for_agent() path. Fixes #99640 credit: @stephenschoettler #62374 credit: @686f6c61 #99677
63 lines
2.0 KiB
Python
63 lines
2.0 KiB
Python
"""A plugin-registered context engine is one shared instance; agent init hands each agent its own
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copy through ``clone_for_agent()`` (default deepcopy), so engines with uncopyable state (locks,
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SQLite connections — hermes-lcm) stay selectable and a child's model never leaks into the parent
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(#99640, #42449)."""
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import threading
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from unittest.mock import patch
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from agent.agent_init import _select_context_engine
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from agent.context_engine import ContextEngine
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class _Engine(ContextEngine):
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engine_name = "lcm"
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@property
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def name(self):
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return self.engine_name
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def update_from_response(self, usage):
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pass
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def should_compress(self, prompt_tokens=None):
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return False
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def compress(self, messages, current_tokens=None):
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return messages
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class _LockedEngine(_Engine):
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"""Holds a lock (deepcopy raises) and hands out per-agent clones like hermes-lcm does."""
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def __init__(self):
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super().__init__()
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self._lock = threading.Lock()
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self.clones = 0
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def clone_for_agent(self):
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self.clones += 1
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return _LockedEngine()
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def _select(engine):
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with (patch("plugins.context_engine.load_context_engine", return_value=None),
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patch("hermes_cli.plugins.get_plugin_context_engine", return_value=engine)):
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return _select_context_engine({"context": {"engine": engine.name}})
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def test_engine_with_uncopyable_state_is_selected_via_clone_for_agent():
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singleton = _LockedEngine()
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selected = _select(singleton)
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assert isinstance(selected, _LockedEngine) and selected is not singleton
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assert singleton.clones == 1
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def test_default_clone_isolates_parent_from_child_update_model():
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singleton = _Engine()
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singleton.update_model(model="big", context_length=1_000_000)
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child = _select(singleton)
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child.update_model(model="small", context_length=204_800)
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assert child is not singleton
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assert (singleton.context_length, child.context_length) == (1_000_000, 204_800)
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