Adversarial BEAM Gate

A BEAM runtime-architecture review gate for Elixir systems — pass/fail: a single blind reviewer subagent judges the work against this gate's rules with an adversarial mandate, and the work passes only when every rule is PASS or N/A. This skill renders verdicts; it never fixes the work.

The rules target one failure mode: code that assumes guarantees the runtime never made — that restarts restore data, that mailboxes push back, that broadcasts arrive, that delivery happens exactly once and in order, that a lookup is still true at the following insert, that node-local uniqueness holds cluster-wide, that the wall clock only moves forward. These bugs compile cleanly, pass unit tests, and surface as production incidents. Each rule carries an Evidence of violation paragraph so a reviewer can decide PASS/FAIL/N/A from artifact evidence alone. The sibling gate adversarial-elixir judges paradigm fit (OO habits ported onto the BEAM); this gate judges runtime semantics — run both for full coverage.

When to Apply

• An Elixir feature that supervises processes, consumes events/jobs/streams, broadcasts over PubSub, or shares state via ETS/Registry is about to merge and needs an objective PASS/FAIL on its runtime assumptions.
• An agent (Claude, Codex) authored OTP-shaped code and you want an independent check that it did not assume durable broadcasts, exactly-once delivery, ordered cross-process messages, or restart-survivable in-memory state.
• A system is being prepared for clustering or higher load, and the single-node/low-traffic assumptions baked into it need to be surfaced as verdicts.
• An incident postmortem fixed one instance of a delivery/overload bug and you want the same class hunted across the affected area.

Do not apply to non-Elixir codebases (the reviewer prompt's precondition aborts with "GATE NOT APPLICABLE"), or when the user wants explanations and refactors rather than a verdict. The dist-* category goes N/A when the application demonstrably never clusters; Oban/Broadway appear in rules as canonical remedies but any mechanism with the same property passes — the reviewer prompt carries the applicability axes.

Review Protocol

Follow these steps exactly — the gate's value is that every review runs the same way.