When delegate_task spawns a child agent with a different model/provider, the
child's init_agent loaded the plugin context-engine GLOBAL singleton by
reference (`_selected_engine = _candidate`) and then called update_model() on
it with the child's (smaller) context_length. Because parent and child shared
the same object, this mutated the PARENT's compressor: e.g. DeepSeek 1M ctx
silently dropped to 204800 and the compression threshold from 200K to 40K
after any delegate_task with a different model.
Deepcopy the singleton before assigning/mutating it (agent_init.py) so the
child gets its own instance and the parent's compressor is untouched.
Salvaged from #42452 by @liuhao1024 (authorship preserved). Added a
source-pin regression test that fails if the production line reverts to the
bare alias, plus an end-to-end test driving get_plugin_context_engine() and a
StubEngine.update_model() — the original PR's tests exercised copy.deepcopy in
isolation but did not guard the actual agent_init code path.
Closes#42449. Supersedes #42469, #42474 (same one-line fix, no test).
Remove unused imports (F401) and duplicate/shadowed import
redefinitions (F811) across the codebase using ruff's safe
autofixes. No behavioral changes -- imports only.
- ~1400 safe autofixes applied across 644 files (net -1072 lines)
- __init__.py re-exports preserved (excluded from F401 removal so
public re-export surfaces stay intact)
- Re-exports that are imported or monkeypatched by tests but look
unused in their defining module are kept with explicit # noqa:
F401 (gateway/run.py load_dotenv; run_agent re-exports from
agent.message_sanitization, agent.context_compressor,
agent.retry_utils, agent.prompt_builder, agent.process_bootstrap,
agent.codex_responses_adapter)
- Unsafe F841 (unused-variable) fixes deliberately skipped -- those
can change behavior when the RHS has side effects
- ruff lints remain disabled in pyproject.toml (only PLW1514 is
selected); this is a one-time cleanup, not a config change
Verification:
- python -m compileall: clean
- pytest --collect-only: all 27161 tests collect (zero import errors)
- core entry points import clean (run_agent, model_tools, cli,
toolsets, hermes_state, batch_runner, gateway)
- static scan: every name any test imports directly from an edited
module still resolves
- PluginContext.register_context_engine() lets plugins replace the
built-in ContextCompressor with a custom ContextEngine implementation
- PluginManager stores the registered engine; only one allowed
- run_agent.py checks for a plugin engine at init before falling back
to the default ContextCompressor
- reset_session_state() now calls engine.on_session_reset() instead of
poking internal attributes directly
- ContextCompressor.on_session_reset() handles its own internals
(_context_probed, _previous_summary, etc.)
- 19 new tests covering ABC contract, defaults, plugin slot registration,
rejection of duplicates/non-engines, and compressor reset behavior
- All 34 existing compressor tests pass unchanged
