Avail

Skill based on Avail Node (availproject/avail), generated from sources/avail. Doc path: sources/avail/README.md, sources/avail/client/basic-authorship/README.md, sources/avail/e2e/README.md, and node/rpc/runtime source (cli, command, kate-rpc, apis).

Avail is a data-availability layer. The Avail Node is the official Substrate-based client. It supports multiple chains (dev, turing, mainnet), Kate RPC for DA queries (rows, proofs, block length, per-tx data proof), and optional custom block authoring via the basic-authorship client. Use this skill to run nodes, script Kate RPC, integrate with light clients or explorers, and reason about runtime APIs.

Core References

Features

Block authoring and runtime

Best Practices

Generation Info

• Source: sources/avail
• Git SHA: 1afb08de9e57101d2e7d6f13e5a7ab99fad09f72
• Generated: 2026-02-24
• Doc path used: sources/avail/README.md, sources/avail/client/basic-authorship/README.md, sources/avail/e2e/README.md, sources/avail/node/src/cli.rs, sources/avail/node/src/command.rs, sources/avail/rpc/kate-rpc/src/lib.rs, sources/avail/runtime/src/apis.rs. Additional docs: Avail wiki.

Kate RPC

Kate RPC exposes data-availability queries (rows, proofs, block length, per-tx data proof). Use it when building light clients, explorers, or tooling that verify or fetch DA data.

Enabling Kate RPC

• CLI: --enable-kate-rpc (default: false). --dev implies --enable-kate-rpc.
• Cell limit: --kate-max-cells-size <N> (default 64, max 10_000). Caps how many cells can be requested in one kate_queryProof / kate_queryMultiProof call.
• Metrics: --enable-kate-rpc-metrics for Kate RPC metrics (optional).

./avail-node --chain mainnet --enable-kate-rpc
./avail-node --enable-kate-rpc --kate-max-cells-size 256

RPC methods

All methods accept an optional block hash at; if omitted, the node uses the best block. Only finalized blocks are queried; requesting a non-finalized block returns an error.

Example (conceptual) for proof queries:

• Cells: list of { row, col }; length must be ≤ kate-max-cells-size (or you get a clear error suggesting to increase the flag or request fewer cells).
• Rows: up to 64 row indices for kate_queryRows.

If the requested block has empty commitments (e.g. pre-DA block), the RPC returns an error.

Key points

• Queries are only valid for finalized blocks.
• Increase --kate-max-cells-size (max 10_000) if you need larger batch proof requests.
• Empty commitments on the requested block cause kate_queryRows / kate_queryProof / kate_queryMultiProof to fail.

<!-- Source references:

• https://github.com/availproject/avail (README.md, RPCs and Custom Flags)
• sources/avail/rpc/kate-rpc/src/lib.rs
• sources/avail/node/src/cli.rs

-->

Avail Node and Chains

How to run the Avail Node binary and which chains are supported. Use this when scripting node startup, CI, or deployment.

Chains

Specify chain with --chain <id>. If omitted or empty, the node errors and asks you to specify (e.g. --chain mainnet).

# Development (single authority, no relay)
cargo run --locked --release -- --dev

# Testnet Turing
cargo run --locked --release -- --chain turing

# Mainnet (with data directory)
mkdir -p output
cargo run --locked --release -- --chain mainnet -d ./output

# Custom chain spec from file
./avail-node --chain /path/to/chain-spec.json

--dev implies --enable-kate-rpc. For other chains you must pass --enable-kate-rpc explicitly if you need Kate RPC.

Optional: network name

For dev and dev.tri you can override the network name/id:

./avail-node --chain dev --network-name my-dev-chain

Docker / Podman

Build and run with a single data volume; expose p2p (30333) and RPC (9944).

docker build -t availnode -f ./dockerfiles/avail-node.Dockerfile .
mkdir output
docker run --rm -p 30333:30333 -p 9944:9944 -v ./output:/output availnode --chain mainnet

For a dev chain with unsafe RPC (e.g. for local tooling):

docker run --rm -p 30333:30333 -p 9944:9944 -v ./output:/output availnode --dev --rpc-methods=unsafe --unsafe-rpc-external --rpc-cors=all

On SELinux use :z on the volume: -v ./output:/output:z.

Key points

• Always set --chain (or use a custom JSON path); the binary does not default to a chain.
• Default RPC: 127.0.0.1:9944. Use --rpc-methods=unsafe and --unsafe-rpc-external only for local dev.
• SDKs for application layer: avail-js, avail-rust, avail-go (separate repos).

<!-- Source references:

• https://github.com/availproject/avail (README.md)
• sources/avail/node/src/command.rs (load_spec)
• sources/avail/README.md

-->

Runtime APIs (Data Availability)

The Avail runtime exposes runtime APIs used by the node and Kate RPC for block length, Kate proofs/rows, and header extension building. Use this when reasoning about off-chain tooling, RPC behavior, or runtime upgrades.

DataAvailApi

• block_length() — returns BlockLength for the current block (used by Kate RPC and sync).

KateApi

All methods take block context (number, extrinsics, block_len) and operate on the application data grid:

• rows(block_number, extrinsics, block_len, rows) — returns Vec<GRow> for the given row indices.
• proof(block_number, extrinsics, block_len, cells) — returns Vec<GDataProof> for the given (row, col) cells.
• multiproof(block_number, extrinsics, block_len, cells) — returns Vec<(GMultiProof, GCellBlock)> for the given cells.
• data_proof(block_number, extrinsics, tx_idx) — returns Option<ProofResponse> for a single transaction at index tx_idx.

These are the backend for the Kate RPC methods; the RPC layer enforces finalized blocks and kate-max-cells-size.

ExtensionBuilder

• build_extension(extrinsics, data_root, block_length, block_number) — builds the HeaderExtension (e.g. V3 with Kate commitment).
• build_data_root(block, extrinsics) — computes the data root for the block.
• check_if_extrinsic_is_post_inherent(uxt) — returns whether the extrinsic is a post-inherent (used during block building).

Key points

• Kate APIs require valid extrinsics and block length from the same block; the node supplies these from the finalized block.
• Header extension (V3) carries the Kate commitment; empty commitment causes Kate RPC to error for that block.

<!-- Source references:

• sources/avail/runtime/src/apis.rs (decl_runtime_apis, impl_runtime_apis)
• sources/avail/runtime/src/kate/

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