Casper Devnet Launcher
Casper Devnet Launcher is a Rust local development Casper network, based on and heavily inspired
by the NCTL workflow, to make local devnets quick and easy for smart contract developers.
It embeds the essential node-launcher behavior in-process, so you only need the casper-node
and (optionally) casper-sidecar binaries.
Why this exists
NCTL is fantastic for core protocol development and for building assets from source trees, but it comes with a large shell script surface, external process supervision, and multi-step UX. This tool targets application and contract developers who want a repeatable, portable devnet for development, CI, and tests.
Comparison with NCTL
| Area | NCTL | Casper Devnet Launcher (this repo) |
|---|---|---|
| Primary audience | Core protocol development | Smart contract/app developers, CI/tests |
| Process control | External supervisor (supervisord) | In-process process control |
| Setup workflow | Multiple commands | Single command: casper-devnet start |
| Implementation | Large shell script | Rust binary (portable) |
| Node launcher | External casper-node-launcher |
Embedded launcher logic |
| Requirements | Node + launcher + sidecar + scripts | Assets bundle (node + sidecar + templates) |
| Keys/accounts | Random keys, friction to name/locate | Deterministic keys from a seed (BIP32 paths) |
| macOS devnet start | Often requires extra local compilation | Planned: download pre-built bundles |
| Network feedback | Extra commands to watch blocks/txs | Persistent SSE connection with live output |
Installation
Usage
Add a local assets bundle:
Download assets from the latest release:
Force re-download:
Override the target triple:
Security note
casper-devnet assets pull downloads pre-built binaries from
https://github.com/veles-labs/devnet-launcher-assets/releases.
If you are not comfortable running pre-built binaries, download the assets repo and rebuild the
binaries locally using the provided scripts before installing them with assets add.
List available protocol versions:
Start a devnet:
Create assets without starting processes:
Use --setup-only when you want to tweak chainspecs or node configs before launching.
Rebuild assets:
Common flags
--protocol-version <version>: Protocol version to use from the assets store (defaults to newest bundle)--network-name <name>: Network name for configs/paths (default:casper-dev)--net-path <path>: Override the network runtime root (default: platform data dir.../networks)--node-count <n>: Number of nodes (aliases:--nodes,--validators; default: 4)--users <n>: Number of user accounts (default: node count)--delay <seconds>: Genesis activation delay (default: 3). Keep it short for local devnets; increase if you need more time to attach tooling before genesis.--log-level <level>: Child process log level (default:info)--node-log-format <format>: Node logging format in config (default:json)--setup-only: Build assets and exit--force-setup: Rebuild assets even if they exist--seed <string>: Seed for deterministic devnet keys (default:default)
Assets bundle layout
The bundle is extracted into the platform data directory and should include a versioned root with the following shape:
v2.1.1/bin/casper-node
v2.1.1/bin/casper-sidecar
v2.1.1/chainspec.toml
v2.1.1/sidecar-config.toml
v2.1.1/node-config.toml
For manual rebuilds and bundle scripts, see https://github.com/veles-labs/devnet-launcher-assets/`.
Notes
- The launcher runs the node directly and manages processes internally; no external supervisor is required.
- The embedded launcher state is handled within the process; only the node/sidecar binaries are required.
- Assets are stored under the platform data directory (e.g.,
~/.local/share/xyz.veleslabs.casper-devneton Linux or~/Library/Application Support/xyz.veleslabs.casper-devneton macOS), withassets/for bundles andnetworks/for runtime assets.