A reducer/effect state machine for multi-step transaction approval (prepare, authenticate, preflight, complete). Operations are injected as closures (TransactionApprovalOperations), effects run through a coordinator, and stale requests are cancelled via request/alert tokens. The pattern is generic enough to extract for any multi-step async workflow needing stale-response suppression, reentrancy guards, and testable operation injection; tests use an ApprovalOperationsStub.

Self-contained arbitrary-precision unsigned integer used for Ethereum value and gas arithmetic. Implements checked add/multiply, range validation, and hex conversion without importing internal modules — extractable as a standalone utility for any Web3/blockchain codebase.

Ethereum fee estimation with EIP-1559 capability detection per chain/endpoint, fee-history percentile analysis, fallback to legacy gas pricing, and a OneShotGate ensuring a single completion for concurrent callers. Cleanly separates market detection, caching, and fallback; the fee model and slider-speed logic are portable.

A production JWT acquisition/refresh subsystem for keyless Alchemy RPC: protocol-based authorization via AlchemyAuthorizationProviding, single-flight broker requests through an actor, rejected-token tombstoning, exponential backoff, versioned persisted token state with cross-process file locking, and cooldown-based persistence repair. The store/broker/clock protocol seams make the refresh pattern extractable to any token-auth infrastructure.

A generic JSON-RPC client with typed request wrapping, request cancellation tokens, exponential-backoff retry, and authorization refresh on 401/403 via Alchemy JWTs. The request, cancellation, and retry scaffolding is framework-agnostic and reusable for any remote JSON-RPC API.

Deterministic identicon generation from Ethereum/Solana addresses, producing stable HSL-based block grids. A small, dependency-free utility that can be dropped into any app needing human-recognizable address fingerprints.