Effect is not BEAM

BEAM processes isolate their state. Supervision11 observes worker failure and applies restart policy. Restart still loses volatile state.Ā¶

Shared-nothing concurrency ensures complete isolation between processes: one process canā€™t compromise the internal state of another.Ā¶

Source: Q0333; B133, B233, B333.Ā¶

Failure it prevents

A failed computation has already changed shared state, while the caller assumes process isolation.Ā¶

Our Effect 4.0.0 reading

Scope34 and FiberSet own local lifetimes. They do not supply separate heaps or OTP restart strategies. Use a host boundary for hard isolation.Ā¶

Source: packages/effect/src/Scope.ts, packages/effect/src/FiberSet.ts, packages/effect/src/Fiber.ts.Ā¶

How to check

State which failure the boundary contains. Test a worker defect29 and a hard runtime exit separately. This check is our proposal. The books do not prescribe it.Ā¶

Continue with Supervision chooses what restarts11, Durable work needs storage14.Ā¶

Connect this to the existing rat-stack guidance23.Ā¶

Use the durability skill for the full review. Return to the durability index34.Ā¶

Sources

  1. Logan, Martin; Merritt, Eric; Carlsson, Richard. Erlang and OTP in Action.. Manning. The Erlang/OTP Platform: Let It Crash; process isolation; Ā§4.2.2 supervisor restart strategy. Accessed 2026-10-23.
  2. Jurić, SaÅ”a. Elixir in Action, Third Edition. Manning, 2024.. Manning. Ā§5.4.3 Shared-Nothing Concurrency; Chapters 8ā€“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.. 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. Scope.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. FiberSet.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. Fiber.ts. Effect-TS. Pinned source for our Effect mapping, not a claim from the book. Accessed 2026-10-23.

Last changed 2026-10-23 in 58dc623. Source on GitHub. Change log.

Linked from

  1. Agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.

    Effect is not BEAM ā€” Fibers share a runtime; scope ownership does not supply isolated heaps or OTP restart strategies.

  2. Bulkheads isolate scarce capacity. Reserve independent capacity for workloads that must not starve each other.

    Continue with Backpressure reaches the producer, Effect is not BEAM.Ā¶

  3. Change log. What changed in the files served here, newest first.

    Effect is not BEAM ā€” new page: docs(lore): land the durability wiki pages and bibliography

  4. durability. Keep a rat-stack app standing when a provider, pool, or dependency slows down or a worker dies. Use at any I/O boundary, connection pool, provider call, shared waiter, fan-out, flag, gate, or work that can outlive a request, or when asked "what happens when this is slow", "add a timeout", "make this durable", or "what survives a crash".

    Effect is not BEAM: fibers share one runtime and lose state with it.Ā¶

  5. Durability bibliography. Books, checked short quotations, source limits, and Effect mapping provenance.

    process isolationĀ¶

  6. Durability starts with a recovery record. A reading order for storage, replay, worker ownership, overload, and recovery tests.

    Effect is not BEAM: Fibers share a runtime; scope ownership does not supply isolated heaps or OTP restart strategies.Ā¶

  7. Full agent guide. An Effect stack so pure (aspirational) Kit Langton will blush.
  8. Rat Stack lore | rat-stack. Short, source-grounded notes on the ideas and decisions behind rat-stack.

    Effect is not BEAM ā€” Fibers share a runtime; scope ownership does not supply isolated heaps or OTP restart strategies.

  9. Source change history (log.md). The generated change log as Markdown.

    Effect is not BEAM ā€” new page: docs(lore): land the durability wiki pages and bibliography