In this investigation, we discovered that the connCache is stale. More precisely, when running the add/remove shard hook in the background, the shard list is not updated properly. This issue could affect tests that depend on this specific field. We should analyze the tests using the connCache, reported in the following, and determine whether they rely on the shard list. If so, we should add the "assumes_stable_shard_list" tag to prevent potential test failures.

Suite concurrency_sharded_replication_with_balancer_and_config_transitions:

• jstests/concurrency/fsm_workloads/crud/move_primary_with_crud.js
• jstests/concurrency/fsm_workloads/ddl/random_ddl/random_ddl_check_metadata_consistency_killop.js
• jstests/concurrency/fsm_workloads/ddl/random_ddl/random_ddl_operations.js
• jstests/concurrency/fsm_workloads/ddl/rename_collection/rename_sharded_collection.js

Suite concurrency_sharded_multi_stmt_txn_with_balancer_and_config_transitions_and_add_remove_shard:

• jstests/concurrency/fsm_workloads/crud/move_primary_with_crud.js
• jstests/concurrency/fsm_workloads/ddl/random_ddl/random_ddl_check_metadata_consistency_killop.js
• jstests/concurrency/fsm_workloads/ddl/random_ddl/random_ddl_operations.js

Suite concurrency_sharded_stepdown_terminate_kill_primary_with_balancer_and_config_transitions_and_add_remove_shard:

• jstests/concurrency/fsm_workloads/crud/move_primary_with_crud.js
• jstests/concurrency/fsm_workloads/ddl/random_ddl/random_ddl_operations.js
• jstests/concurrency/fsm_workloads/ddl/rename_collection/rename_sharded_collection.js

Suite concurrency_sharded_replication_with_balancer_and_config_transitions_and_add_remove_shard:

• jstests/concurrency/fsm_workloads/crud/move_primary_with_crud.js