# Leani

> Leani is a self-hosted Ethereum indexing node. It answers questions about Ethereum data with processors: built-in ones cover common data, and for anything else you write your own processor. Writing one is the normal path, not an edge case.

Agents, start here:

1. Install the Leani agent skill: `npx skills add smart-byte/leani -g` (Codex, Claude Code, Cursor, and other agents), or see https://leani.dev/docs/guides/ai-agents/. With the binary installed, `leani guide` prints the same guide for that release.
2. Use a built-in processor if one fits: `block-summary` (gas, base fee, blobs per block), `evm-events` (decode chosen events of chosen contracts, no code), `erc20-balances`, `transaction-stats`, `uniswap-observations`, `uniswap-latest`, `blobs-money`, `rollup-txs`.
3. Otherwise write a custom processor in Rust: `map` turns a block into a compact delta, `reduce` folds deltas into state, and Leani supplies sources, backfill, finality, reorgs, storage, and the HTTP API. Write one for aggregates (distinct counts, sums, top-N), transaction values rather than logs, state across contracts, or value filters. Guide: https://leani.dev/docs/guides/custom-processor/
4. Backfill the block range, run `leani serve`, check coverage, then query the HTTP API.

Leani keeps no EVM state: it cannot answer `eth_call`, account balances, or traces.

Command-line rules:

The `leani` CLI is the primary interface. Install with `brew install smart-byte/tap/leani` or build from source.

- `leani subscribe blocks` follows Ethereum Mainnet blocks over P2P with no API key and runs until interrupted. Add `--json` for NDJSON on stdout (progress goes to stderr), `--once` to exit after the first verified result, and `--timeout 5m` to bound the run; an unsatisfied `--once` exits 124 on timeout.
- First use asks the user to accept a checkpoint, the trust anchor for verification. Without a terminal the command fails unless `--yes` is passed. Agents should pass `--yes` only after the user has approved the checkpoint.
- Rows are labelled `unattested` (peers agree and it passes Leani's header rules; it can be undone), `attested` (signed by the sync committee; can still be reorged), or `finalized`. `--once` returns the first row that meets `--finality` (default `unattested`). JSON output mixes row schemas, so dispatch on each row's `schema` field.
- `leani init blocks` then `leani serve` runs a reusable node: HTTP API at http://127.0.0.1:18080, JSON-RPC subset at http://127.0.0.1:18545.

## Documentation Sets

- [Abridged documentation](https://leani.dev/llms-small.txt): a compact version of the documentation for Leani, with non-essential content removed
- [Complete documentation](https://leani.dev/llms-full.txt): the full documentation for Leani
- [Getting started](https://leani.dev/_llms-txt/getting-started.txt)
- [Concepts](https://leani.dev/_llms-txt/concepts.txt)
- [Guides](https://leani.dev/_llms-txt/guides.txt)
- [Operations](https://leani.dev/_llms-txt/operations.txt)
- [Reference](https://leani.dev/_llms-txt/reference.txt)

## Notes

- The complete documentation includes all content from the official documentation
- The content is automatically generated from the same source as the official documentation