Since #35491, every Router joins the module-global _live_routers weak set at
construction, and every model cost map swap replays the deployments of every
member on top of the freshly adopted map. #36039 isolated the register_model
ledger half of that replay but not this half: under pytest-xdist, a Router
created by an earlier test in the same worker that was still referenced (or
simply not yet garbage collected) re-registered its deployments during
TestPriceDataReloadIntegration::test_distributed_reload_check_function, and
register_model hydrated the sparse mocked gpt-3.5-turbo entry into a full
ModelInfo dict, failing the exact-equality assert (reruns cannot help since
the polluting router survives in the worker process)
The autouse isolate_litellm_state fixture now snapshots _live_routers before
each test and restores its membership on teardown, so a test's routers stop
contributing to cost map rebuilds once the test ends. A canary pair in
test_conftest_isolation.py asserts the rollback
Since #35491, register_model records every registration in the process-global
_runtime_registered_model_cost ledger, and every cost map swap replays that
ledger on top of the freshly adopted map. Under pytest-xdist, any earlier test
in the same worker that registered gpt-3.5-turbo leaked into
TestPriceDataReloadIntegration::test_distributed_reload_check_function: the
replay ballooned its sparse mocked entry into a full ModelInfo dict and failed
the exact-equality assert, breaking the proxy-infra shard whenever loadscope
happened to co-schedule such a test first (reruns cannot help since the
pollution is process-wide)
The autouse isolate_litellm_state fixture now snapshots the ledger before each
test and restores it in place on teardown, so no test's registrations outlive
it. A regression pair in test_conftest_isolation.py asserts the rollback
