Pinned by hash
A program is one WebAssembly module. berm compiles it once and instantiates it per invocation — arguments go in through syscalls, the result comes back out of guest memory, and the instance is gone.
The OS for agent harnesses. One WebAssembly module, pinned by hash, compiled once, and instantiated per invocation.
cargo add berm Apache-2.0 licensed Compiled by Cranelift Served over MCP
The outer result is the host's — a missing tool, a trap. The inner one is the program reporting failure, which is a result the model should see.
let berm = Berm::load(&engine, &wasm, &[])?;
match berm.call("echo", br#"{"query":"hello"}"#.to_vec())? {
Ok(result) => println!("{result}"),
Err(failure) => eprintln!("{failure}"),
}$ crab ls
NAME DIGEST TOOLS
fixture 222890c498ed echo
$ shasum -a256 ./fixture.wasm
222890c498ed28f4bf60670a223141489d9879020bd1890111b8c11ac79fa31d ./fixture.wasmA program travels as one OCI layer with no tarball around it, so the digest a registry
addresses it by is shasum of the file on your disk.
A program is one WebAssembly module. berm compiles it once and instantiates it per invocation — arguments go in through syscalls, the result comes back out of guest memory, and the instance is gone.
A program reaches the world only through the syscalls it was given, and that list is the Linker it was instantiated with. A call to anything else traps because nothing is registered for it, not because a check said no.
berm ships no syscalls at all. What a filesystem is bounded by, and where bytes persist, are decisions about a host — so they belong to whoever is building one.
Manifest::from_image reads what an image claims to be — its tools, their schemas, when to reach for them — without compiling it and without running it.
bermd serves every deployed program on one MCP endpoint, with tools named {program}.{tool}.
$ bermd &
$ crab deploy
$ crab lsA program is one file, so it travels as one OCI layer: deploy pushes it to
the image its berm.toml names when the host pulls from a registry.
$ cat berm.toml
name = "example"
image = "ghcr.io/org/example"
$ crab deploy --context cloud