# Configure hooks and isolated attempts

Hooks prepare fixtures around execution. Browser isolation prevents one attempt's cookies/storage from contaminating another; hooks restore application/backend state that browser isolation cannot reset.

## Choose the correct lifecycle

| Hook phase                   | Scope                       | Suitable use                                     |
| ---------------------------- | --------------------------- | ------------------------------------------------ |
| beforeRun / afterRun         | Root section only           | Start/stop a shared disposable environment       |
| beforeSection / afterSection | Selected section entry/exit | Allocate/remove section fixtures                 |
| beforeEach / afterEach       | Each attempt                | Authenticate its own context and reset test data |

Setup proceeds root-to-leaf; cleanup reverses order and is attempted after setup/test errors. Context creation precedes per-test hooks; supported video starts before those hooks. Cleanup must tolerate partial initialization and a null browser when creation failed.

## Declare trusted work

Each hook has a unique ID and exactly one `function` registry name or `instruction`. Function names are references, not inline executable YAML. For example:

```yaml
hooks:
  beforeEach:
    - { id: authenticate, function: authenticateUser }
  afterEach:
    - { id: cleanup, function: removeFixture }
```

Resolve those names in a trusted project module. It receives run/test/section/session context, shared fixture state, and browser actions when available. Credentials stay in the executing environment. [Canonical hook guidance](../../../integration/agent-testing.md#lifecycle-hooks) includes bindings, overrides and review-policy configuration.

## Verify isolation

The runtime must create a unique isolated browser context per attempt and target every action/capture to it. New tabs in one profile share cookies/local storage and are insufficient. Probe with disposable same-origin markers and clean them up before claiming support.

A section login does not carry into new per-attempt contexts. Re-authenticate each attempt or install project-owned state through an explicit hook. Release owned pages/contexts honestly; page closure is not always full context disposal.

Current T3 preview tabs share storage. Use them to observe repository implementation, not to assert product-runtime isolation. [Runtime mappings](../../../integration/testing-runtimes.md) explains supported adapter responsibilities and live-tool verification.

See [configuration reference](../reference/configuration.md) for the division between catalog settings, runtime capabilities and report-review policy.