# ctx.invariants `InvariantService` — provided by `@deepseek-ai/dsh-invariants`. Package-owned invariant registry with global and regex-based selection. [Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/support/invariants/src/index.ts#L94) ### ctx.invariants.register(packageName, installer) ```ts website-api /** * Register one package's invariant installer. The package name is reserved * even when filtering disables its checks. Enabled installers run in a child * fiber; failure disposes that fiber and releases the reservation. * @param packageName - full npm package name that owns the contribution. * @param installer - synchronous listener installer for the child context. * @returns an effect-scoped disposer for the registration. */ register(packageName: string, installer: InvariantInstaller): () => void ``` Register one package's invariant installer. The package name is reserved even when filtering disables its checks. Enabled installers run in a child fiber; failure disposes that fiber and releases the reservation. - `packageName` — full npm package name that owns the contribution. - `installer` — synchronous listener installer for the child context. **Returns** an effect-scoped disposer for the registration. [Source](https://github.com/deepseek-harness/deepseek-harness/blob/master/packages/support/invariants/src/index.ts#L136)