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6.0.2 Mar 3, 2022

#620 in Asynchronous


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Built-in Filecoin actors

This repo contains the code for the on-chain built-in actors that power the Filecoin network starting from network version 16, epoch 1960320 on 2022-07-06.

These actors are written in Rust and are designed to operate inside the Filecoin Virtual Machine. A reference implementation of the latter exists at filecoin-project/ref-fvm.

The build process of this repo compiles every actor into Wasm bytecode and generates an aggregate bundle to be imported by all clients. The structure of this bundle is standardized. Read below for details.

This codebase was canonicalized in FIP-0031. As a result, this actor implementation is the only one recognized by the network from network version 16 onwards.

Pre-FVM actors

Actors for the following network versions prior to nv16 are implemented here as well:

  • nv14 actors to facilitate testing.
  • nv15 actors to enable the nv15=>nv16 upgrade.

Importable bundle

The main output of this repo is a CARv1 archive bundling all Wasm bytecode for all actors into a single file, with the following characteristics:

  • The CARv1 header points to a single root CID.
  • The root CID resolves to a DAG-CBOR encoded block defining a Manifest type (defined below) containing a version number for the bundle format (currently always 1) and a CID for a ManifestPayload.
  • The ManifestPayload (defined below) is contained within a DAG-CBOR encoded block and defines a type that associates actor type names with their corresponding CIDs.
  • The CIDs for all actors are contained within the same CARv1 archive as compiled Wasm bytecode contained within RAW blocks.

Manifest schema

# Manifest is encoded as: [version, CID]
type Manifest struct {
  version Int
  payload &ManifestPayload
} representation tuple

# ManifestPayload is encoded as: [ ["actorkey", CID], ["actorkey", CID], ... ]
# It alternatively may be interpreted as:
#   type ManifestPayload {String : &ActorBytecode} representation listpairs
# Or simply as a list of tuples.
type ManifestPayload struct {
  system &ActorBytecode
  init &ActorBytecode
  cron &ActorBytecode
  account &ActorBytecode
  storagepower &ActorBytecode
  storageminer &ActorBytecode
  storagemarket &ActorBytecode
  paymentchannel &ActorBytecode
  multisig &ActorBytecode
  reward &ActorBytecode
  verifiedregistry &ActorBytecode
  datacap &ActorBytecode
  placeholder &ActorBytecode
  evm &ActorBytecode
  eam &ActorBytecode
  ethaccount &ActorBytecode
} representation listpairs

# RAW block
type ActorBytecode bytes

Precompiled actor bundles are provided as release binaries in this repo. The fil_builtin_actors_bundle crate on crates.io will not be updated.


We release all actors, the runtime, and the state abstraction at the same time by:

  1. Changing the workspace.package.version in the top-level Cargo.toml file.
  2. Creating a release in GitHub.

This will trigger an automatic bundle-build by GitHub CI, and the generated bundles will be attached to the GitHub release.

Instructions for client implementations

Obtaining an actors bundle

There are two options:

  1. Building from source.
  2. Downloading the precompiled release bundle from GitHub.

Instructions to build from source (option 1):

  1. Clone the repo.
  2. Check out the relevant branch or tag (see Versioning section below).
  3. make bundle from the workspace root.

The bundle be written to output/builtin-actors.car.

Both options are compatible with automation via scripts or CI pipelines.

Integrating an actors bundle

This part is implementation-specific. Options include:

  1. Embedding the bundle's CARv1 bytes into the distribution's binary.
  2. Downloading CARv1 files on start (with some form of checksumming for added security).

Loading and using the actors bundle with ref-fvm

Once the implementation has validated the authenticity of the bundle, it is expected to do the following:

  1. Import the CARv1 into the blockstore.
  2. Retain the root CID in memory, indexed by network version.
  3. Feed the root CID to ref-fvm's Machine constructor, to tell ref-fvm which CodeCID maps to which built-in actor.

Multiple network version support

Because every network version may be backed by different actor code, implementations should be ready to load multiple actor bundles and index them by network version.

When instantiating the ref-fvm Machine, both the network version and the corresponding Manifest root CID must be passed.


A fair question is how crate versioning relates to the protocol concept of ActorVersion. We adopt a policy similar to specs-actors:

  • Major number in crate version correlates with ActorVersion.
  • We generally don't use minor versions; these are always set to 0.
  • We strive for round major crate versions to denote the definitive release for a given network upgrade. However, due to the inability to predict certain aspects of software engineering, this is not a hard rule and further releases may be made by bumping the patch number.

Development versions will use qualifiers such as -rc (release candidate).

As an example of application of this policy to a v10 actor version lineage:

  • Unstable development versions are referenced by commit hash.
  • Stable development versions are tagged as release candidates: 10.0.0-rc1, 10.0.0-rc2, etc.
  • Definitive release: 10.0.0.
  • Patched definitive release: 10.0.1.
  • Patched definitive release: 10.0.2.
  • Network upgrade goes live with 10.0.2.

About this codebase

Relation to specs-actors

This repo supersedes specs-actors, and fulfils two roles:

  • executable specification of built-in actors.
  • canonical, portable implementation of built-in actors.


This codebase was originally forked from the actors v6 implementation of the Forest client, and was adapted to the FVM environment.


Because this codebase is a common good across all Filecoin client implementations, it serves as a convergence area for all Core Devs regardless of the implementation or project they identify with.


Dual-licensed: MIT, Apache Software License v2, by way of the Permissive License Stack.

Except the EVM precompile test data, which is licensed under the LGPL v3 and not included in crates or build artifacts.