# Supervision chooses what restarts

> For agents: start with the [agent guide](https://ratstack.sh/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

Free workshop: [Build Agent Loops That Never Stop Shipping](/tokenmaxx#interested).

OTP restart strategies distinguish independent children from dependent siblings. A persistently broken child also needs a limit on repeated restarts.

> The point of letting an entire subsystem terminate and be restarted is that it brings you back to a state known to function properly.

Source: [Q01](/lore/durability-bibliography#q01); [B1](/lore/durability-bibliography#b1-erlang-and-otp-in-action), [B2](/lore/durability-bibliography#b2-elixir-in-action), [B3](/lore/durability-bibliography#b3-designing-elixir-systems-with-otp).

## Failure it prevents

Healthy siblings restart unnecessarily, or dependent siblings continue with stale state.

## Our Effect 4.0.0 reading

No OTP restart supervisor was found in the checked source. [Scope](/lore/scopes-own-resources) and `FiberSet` handle lifetime. Use XState for explicit restart modes and a host for runtime restart.

Source: `packages/effect/src/Effect.ts`, `packages/effect/src/Scope.ts`, `packages/effect/src/FiberSet.ts`.

## How to check

Generate child failures and repeated restart attempts. Check affected dependents, escalation, and reconstructed state. This check is our proposal. The books do not prescribe it.

Continue with [Restart must reconstruct known state](/lore/restart-from-known-state), [Circuit breakers have state](/lore/circuit-breakers-have-state).

Connect this to [the existing rat-stack guidance](/lore/lifecycles-are-machines).

Use [the durability skill](/skills/durability) for the full review. Return to [the durability index](/lore/durability).

## Sources

1. [Logan, Martin; Merritt, Eric; Carlsson, Richard. Erlang and OTP in Action.](https://www.manning.com/books/erlang-and-otp-in-action)
   Manning. The Erlang/OTP Platform: Let It Crash; process isolation; §4.2.2 supervisor restart strategy. Accessed 2026-10-23.

2. [Jurić, Saša. Elixir in Action, Third Edition. Manning, 2024.](https://www.manning.com/books/elixir-in-action-third-edition)
   Manning. §5.4.3 Shared-Nothing Concurrency; Chapters 8–9, fault tolerance and supervision; Other Use Cases for ETS. Accessed 2026-10-23.

3. [Gray II, James Edward; Tate, Bruce A. Designing Elixir Systems with OTP. Pragmatic Bookshelf, 2019.](https://pragprog.com/titles/jgotp/designing-elixir-systems-with-otp/)
   Pragmatic Bookshelf. Build a Functional Core; Isolate Process Machinery in a Boundary; Customize Your Lifecycle; Big, Loud Worker-Bees; Add Persistence as a Boundary Service; Test the Boundary. Accessed 2026-10-23.

4. [Effect contributors. Effect 4.0.0. Effect.ts](https://github.com/Effect-TS/effect/blob/67ba4e46a11ccda0b6761578bfd22c04ae00167d/packages/effect/src/Effect.ts)
   Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.

5. [Effect contributors. Effect 4.0.0. Scope.ts](https://github.com/Effect-TS/effect/blob/67ba4e46a11ccda0b6761578bfd22c04ae00167d/packages/effect/src/Scope.ts)
   Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.

6. [Effect contributors. Effect 4.0.0. FiberSet.ts](https://github.com/Effect-TS/effect/blob/67ba4e46a11ccda0b6761578bfd22c04ae00167d/packages/effect/src/FiberSet.ts)
   Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.

## Linked from

- Agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms.txt)

- Change log → What changed in the files served here, newest first. → [Read page](https://ratstack.sh/log)

- Circuit breakers have state → A breaker stops doomed calls and controls probes before restoring traffic. → [Read page](https://ratstack.sh/lore/circuit-breakers-have-state)

- Durability bibliography → Books, checked short quotations, source limits, and Effect mapping provenance. → [Read page](https://ratstack.sh/lore/durability-bibliography)

- Durability starts with a recovery record → A reading order for storage, replay, worker ownership, overload, and recovery tests. → [Read page](https://ratstack.sh/lore/durability)

- Effect is not BEAM → Fibers share a runtime; scope ownership does not supply isolated heaps or OTP restart strategies. → [Read page](https://ratstack.sh/lore/effect-is-not-beam)

- Every task needs an owner → Give child work a lifetime, a failure observer, and a recovery decision. → [Read page](https://ratstack.sh/lore/every-task-needs-an-owner)

- Full agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms-full.txt)

- Lifecycles are machines → XState owns finite lifecycle states while declared Effect actors own side effects. → [Read page](https://ratstack.sh/lore/lifecycles-are-machines)

- Rat Stack lore | rat-stack → Short, source-grounded notes on the ideas and decisions behind rat-stack. → [Read page](https://ratstack.sh/lore)

- Source change history (log.md) → The generated change log as Markdown. → [Read page](https://ratstack.sh/log.md)