ACT — sandboxed, signed tools for AI agents

Every agent tool you install today runs with your permissions: your files, your keys, the whole network. ACT packages a tool as one WebAssembly component that declares what it needs — this directory, these hosts — and the host enforces it: anything undeclared is denied, anything declared still waits for your grant, and every decision lands in an audit trail. The same .wasm is an MCP server, a CLI tool, and it runs in a browser tab.

Try it in your browser → real pandas on your CSV, sandboxed to the one file you hand it. Nothing to install.

mkdir -p /tmp/demo
npx @actcore/act call actpkg.dev/library/sqlite query \
  --args '{"sql":"SELECT sqlite_version()"}' \
  --session-args '{"database_path":"/tmp/demo/app.db"}' \
  --allow 'fs=/tmp/demo/**'

Docs · Components · Website

• act — run, call, inspect, and serve ACT components from local files, HTTP URLs, or OCI registries. Components built for wasm32-wasip2 (with async) and wasm32-wasip3 run the same way, under the same capability grants
• act-build — post-process compiled WASM components: embed metadata, skills, and custom sections

# act (CLI host)
npm i -g @actcore/act
pip install act-cli
cargo install act-cli

# act-build (build tool)
npm i -g @actcore/act-build
pip install act-build
cargo install act-build

Pre-built binaries available on GitHub Releases and Docker (ghcr.io/actcore/act).

# Discover tools in a component
act info --tools actpkg.dev/library/sqlite

# Call a tool. sqlite is session-based: --session-args opens a session for
# this one call. --allow lets it touch /data and nothing else.
act call actpkg.dev/library/sqlite query \
  --args '{"sql":"SELECT sqlite_version()"}' \
  --session-args '{"database_path":"/data/app.db"}' \
  --allow 'fs=/data/**'

# Serve over MCP stdio
act run --mcp actpkg.dev/library/sqlite --allow 'fs=/data/**'

# Serve over MCP Streamable HTTP, at http://[::1]:3000/mcp
act run --mcp --http -l '[::1]:3000' actpkg.dev/library/sqlite --allow 'fs=/data/**'

Components can be referenced as:

• OCI refs: actpkg.dev/library/sqlite (a tag or @sha256: digest is optional)
• HTTP URLs: https://example.com/component.wasm
• Local paths: ./component.wasm

Remote components are cached in ~/.cache/act/components/.

The default mode is ask: an interactive run prompts, a headless one denies. Grants come from flags, or per profile in ~/.config/act/config.toml.

Aliases: fs = wasi:filesystem, http = wasi:http, sockets = wasi:sockets, creds = act:credentials; output always shows the full id. IPv6 goes in brackets (http=[::1]:8080). A rule never exceeds what the component declared. act run --help lists every class and its shorthand.

run and call write a structured audit trail to stderr: what component is running and under what capability modes, every capability decision as it resolves, and a per-call summary. It is on by default and independent of RUST_LOG — only --no-audit (or [audit] enabled = false in the config file) turns it off.

audit: act-cli/tests/fixtures/fs-canary.wasm sha256:f17cda │ act:credentials=deny wasi:filesystem=ask wasi:http=deny wasi:sockets=deny
audit: ⚠ declared ask, no prompt channel — every access will be denied: wasi:filesystem
audit: ? ask-deny  wasi:filesystem  /tmp/probe.txt   no prompt channel  mode:ask
audit: ● read  tool-error 1ms  args:43ebc7  req:0005a4

That's a real, captured transcript of one headless call with no --grant: the first line is the instantiation header (component, digest, resolved mode per capability class); the second warns that a declared ask capability has no prompt channel to answer it, so every access degrades to deny; the third is the immediate denial (denials and asks print the moment they resolve, never batched); the fourth is the per-call rollup — outcome, duration, an args: digest of the tool arguments (or the full values with --audit-args), and a req: id for joining this line back to a client log. Allowed operations coalesce into that rollup line instead of one line each, e.g. filesystem: 12 read under /data/**.

act run --mcp --http -l <addr> serves the same MCP server as stdio over Streamable HTTP, at one endpoint: /mcp. --http requires --mcp. The earlier REST binding (/info, /tools, …) was removed in 0.12.0.

# Embed act:component metadata, act:skill, and WASM custom sections
act-build pack target/wasm32-wasip2/release/my_component.wasm

# Validate without modifying
act-build validate target/wasm32-wasip2/release/my_component.wasm

# Publish as a CNCF Wasm OCI Artifact
act-build push my_component.wasm ghcr.io/you/my-component:0.1.0 \
  --also-tag latest \
  --source https://github.com/actpkg/my-component \
  --skip-if-identical

Metadata is resolved via merge-patch from project manifests:

1. Base from Cargo.toml, pyproject.toml, or package.json (name, version, description)
2. Inline patch from the same manifest ([package.metadata.act], [tool.act], or "act" in package.json)
3. act.toml — highest priority, applied last

act-build push produces artifacts conformant with the CNCF TAG-Runtime Wasm OCI Artifact spec: manifest config has media type application/vnd.wasm.config.v0+json (with architecture, os, layerDigests, and component.{exports,imports} derived from the component's exports and imports), and the layer is application/wasm.

Authentication is resolved in order: OCI_USERNAME/OCI_PASSWORD env, then GITHUB_TOKEN for ghcr.io, then ~/.docker/config.json (or $DOCKER_CONFIG/config.json), then anonymous.

RISC-V (riscv64) is a first-class target. Regressions on RISC-V are release-blocking.

A glibc build of act or act-build requires glibc 2.34 or newer — Debian 12, Ubuntu 22.04, RHEL 9 and later. This is a supported-platform commitment, not an incidental build setting: it is asserted in CI, and lowering it is a breaking change.

Which channels it applies to:

The floor is one symbol. DNS SVCB/HTTPS lookups call res_query(3), which glibc did not export under that name before 2.34 — earlier releases had only __res_query, and a modern glibc keeps that as a compat symbol new code cannot link against, so there is no spelling that satisfies both. Nothing else in the binary requires past glibc 2.33.

On an older distribution, use a musl build: musl exports the symbol outright and carries no floor. Building from source does not lift the requirement — it is the same call — so musl is the answer there, not cargo build.

cargo build --release        # both tools
cargo build -p act-cli       # act only
cargo build -p act-build     # act-build only

Set RUST_LOG=act=debug for verbose output.

MIT OR Apache-2.0