When a test uses process-global/irreversible module mocking, prevent cross-test contamination by isolating the affected test files into separate `bun test` runs (batch isolation). Keep mocks narrowly scoped so tests don’t need to mock large dependency graphs, and avoid importing “config/provider” chains in units where tests shouldn’t require them. Practical checklist: - Prefer narrow `mock.module()` for the exact dependency that causes nondeterminism (e.g., config derived from developer machine). - If the runtime mocking mechanism is process-global, run the mocked test(s) in their own `bun test ` (or separate script/job) rather than grouping. - If mocking a dependency would require mocking an entire provider registry, refactor the unit to reduce import chain coupling (e.g., read minimal config directly or inject a loader so the unit under test can be exercised without pulling in the full provider stack). Example (pattern): ```ts // conversations.test.ts mock.module('../config/config-loader', () => ({ loadConfig: mock(async () => ({ assistant: 'claude' })), })); ``` Then run it as an isolated invocation: ```bash cd packages/core && bun test packages/core/src/db/conversations.test.ts ``` This ensures your tests remain deterministic and don’t break due to local `.archon/config.yaml` contents or prior mocked state from other test files.