Three root causes addressed:
1. AIAgent no longer defaults base_url to OpenRouter (9 tests)
Tests that assert OpenRouter-specific behavior (prompt caching,
reasoning extra_body, provider preferences) need explicit base_url
and model set on the agent. Updated test_run_agent.py and
test_provider_parity.py.
2. Credential pool auto-seeding from host env (2 tests)
test_auxiliary_client.py tests for Anthropic OAuth and custom
endpoint fallback were not mocking _select_pool_entry, so the
host's credential pool interfered. Added pool + codex mocks.
3. sys.modules corruption cascade (major - ~250 tests)
test_managed_modal_environment.py replaced sys.modules entries
(tools, hermes_cli, agent packages) with SimpleNamespace stubs
but had NO cleanup fixture. Every subsequent test in the process
saw corrupted imports: 'cannot import get_config_path from
<unknown module name>' and 'module tools has no attribute
environments'. Added _restore_tool_and_agent_modules autouse
fixture matching the pattern in test_managed_browserbase_and_modal.py.
This was also the root cause of CI failures (104 failed on main).
acea9ee20b