# INVARIANT

URL: https://tailrace.dev/docs/reference/errors/INVARIANT

> An internal contract was breached - for example restore outside egress.



## What it means [#what-it-means]

`InvariantViolationError` (`code: INVARIANT`). A hard product invariant was violated regardless of policy.

## Message shape [#message-shape]

```text
<reason> → https://tailrace.dev/docs/reference/errors/INVARIANT
```

## Common causes [#common-causes]

1. Calling `tailrace.restore` at a `model`, `tool`, `mcp`, or `telemetry` boundary.
2. Asking the vault/actions layer to do something only egress may do.

## Fixes [#fixes]

1. Restore only at `{ kind: "egress", sink: "…" }`.
2. Keep model/tool paths on `check` (tokenize/mask/block), not `restore`.

## Safe to catch? [#safe-to-catch]

Treat as a programmer error. Fix the call site; do not swallow and continue.