Over a weekend, Henry Garner CTO of Allium, built a Byzantine fault-tolerant distributed system with strong consistency and crash recovery under arbitrary failures using Claude and the behavioral specification language Allium. Garner described system behavior conversationally in Allium, avoiding any implementation code. The prompt for the first 4,749 lines of Kotlin and 103 passing unit tests took just 50 minutes. This feat was enabled by 3,000 lines of underlying Allium specs developed with distributed systems experts András Gerlits, Martin Kleppmann and Mark Burgess.

Allium operates between TLA+ and prose, using rules like the EntryExpires idempotency specification. Guidance blocks steer Claude towards specific choices, such as using a ConcurrentHashMap for idempotency checks at 10,000 events/sec. Resolved questions preempt design debates, like the expected copies threshold for Byzantine fault detection. These constructs allowed Garner to decompose the monolithic spec into 10 files over several hours of iterative conversation.

The resulting system processes inventory movements at scale with sub-100ms tail latency and zero dropped requests. It sustained thousands of RPS against its strongly consistent datastore, with crash-recovery scenarios exposing and fixing subtle distributed systems bugs through the specs. Garner's approach demonstrates a novel method for rapidly generating complex distributed systems code via LLM-guided specification.