Idempotency keys for LLM agent retries. Deterministic content-derived keys (UUIDv5 or sha256-hex) so retries dedupe at the provider.
Stable canonical hash of LLM request/message structures. Recursive key-sorting JSON canonicalization + sha256, with per-provider ignore-lists so semantically-equal Anthropic/OpenAI/Bedrock requests produce the same hash. Useful for cache keys and idempotency.