# 13.4. Runtime and Dev Builds

Morloc Manual > Build Architecture | https://morloc-project.github.io/docs/internals/runtime-and-dev-builds.html | prev: https://morloc-project.github.io/docs/internals/protocols.md | next: https://morloc-project.github.io/docs/future/index.md

The Morloc runtime — the shared library (`libmorloc.so`) and the nexus binary (`morloc-nexus`) — is written in Rust. Language-specific pools and extensions still use their own compilers (g++ for C++, etc.), but they link against the Rust-built `libmorloc.so` through a stable C ABI defined in a single header (`morloc.h`).

## 13.4.1. Build modes

`morloc init -f` installs the runtime by building it from source. It reads one environment variable:

| Variable | Purpose |
| --- | --- |
| `MORLOC_RUST_DIR` | Path to the `data/rust/` Cargo workspace. `morloc init` runs `cargo build --release` there and copies the artifacts into place. Requires a working Rust toolchain (`cargo`). |

`libmorloc.so` and `morloc-nexus` are deliberately **not** shipped as prebuilt binaries. A Morloc release publishes the compiler per platform plus the platform-independent Rust workspace as `morloc-rust-src.tar.gz`; the runtime is then built from that source with the environment’s own toolchain, so the library every pool links is ABI-coherent with the compilers that built those pools.

Under `mim` this is automatic: `mim` unpacks the release’s Rust source into its runtime store, points `MORLOC_RUST_DIR` at it, and provisions `cargo` through the environment’s conda toolchain. You only set the variable by hand when building from a source checkout:

```console
export MORLOC_RUST_DIR=/path/to/compiler/data/rust
morloc init -f
```

## 13.4.2. What the runtime provides

The Rust workspace produces two artifacts:

**`libmorloc.so`**

Shared library linked by every pool. Provides the IPC layer (Unix domain sockets), shared-memory allocator, packet codec, JSON/MessagePack serialization, and worker-pool concurrency primitives.

**`morloc-nexus`**

Pre-compiled CLI entry point. Reads a program’s `manifest.json` file, parses command-line arguments, starts pool daemons, dispatches calls, and prints results.

## 13.4.3. Build dependencies

| Tool | When needed |
| --- | --- |
| `cargo` | Always — `morloc init` builds the runtime from source. Provisioned by `mim` through the environment’s conda toolchain; install via [rustup](https://rustup.rs) only for an unmanaged build. |
| `gcc` / `g++` | Still required for C++ pool compilation and Python/R language extensions. No longer needed for the runtime itself. |

## 13.4.4. Container images

An environment’s container image is generated by `mim` from the same requirements the native backend solves; there is no hand-authored base image to pull. The generated image stages the release’s Rust source and sets `MORLOC_RUST_DIR` itself, so users of `mim` never set it manually on either backend.