runtime: extract a generic launcher and split the bare and cow binaries

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
     "crates/cow-venue",
     "crates/nexum-cli",
+    "crates/nexum-launch",
     "crates/nexum-macros",
     "crates/nexum-runtime",
     "crates/nexum-sdk",
@@ -11,6 +12,7 @@ members = [
     "crates/nexum-venue-sdk",
     "crates/nexum-venue-test",
     "crates/nexum-world",
+    "crates/shepherd",
     "crates/shepherd-backtest",
     "crates/shepherd-cow-host",
     "crates/shepherd-sdk",

Dockerfile

@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1.6
 #
-# Multi-stage build for `nexum` (Shepherd) - the engine binary
-# plus the five production WASM modules baked into a single image.
+# Multi-stage build for `shepherd` - the cow composition-root engine
+# binary plus the five production WASM modules baked into a single image.
 #
 # Stage 1 (`build`): full Rust toolchain + wasm32-wasip2 target, builds
 # the engine in release mode + each module to a Component Model wasm
@@ -65,7 +65,7 @@ FROM chef AS build
 # changed workspace crate. `--locked` stays on the real builds below, which
 # validate the committed Cargo.lock verbatim.
 COPY --from=planner /src/recipe.json recipe.json
-RUN cargo chef cook --release -p nexum-cli --recipe-path recipe.json \
+RUN cargo chef cook --release -p shepherd --recipe-path recipe.json \
  && cargo chef cook --release --target wasm32-wasip2 \
       -p twap-monitor -p ethflow-watcher -p price-alert \
       -p balance-tracker -p stop-loss --recipe-path recipe.json
@@ -77,7 +77,7 @@ COPY . .
 
 # Engine binary in release. --locked ensures the committed Cargo.lock
 # is used verbatim so builds are reproducible.
-RUN cargo build -p nexum-cli --release --locked
+RUN cargo build -p shepherd --release --locked
 
 # Five production modules. The wasm artefacts land under
 # `target/wasm32-wasip2/release/<name_with_underscores>.wasm`.
@@ -108,7 +108,7 @@ RUN apt-get update \
     && install -d -o root     -g root     -m 0755 /etc/shepherd
 
 # Engine binary.
-COPY --from=build /src/target/release/nexum /usr/local/bin/nexum
+COPY --from=build /src/target/release/shepherd /usr/local/bin/shepherd
 
 # Module .wasm artefacts. The Component Model wasm files are loaded
 # by the engine at boot via the `[[modules]]` entries in engine.toml.
@@ -138,5 +138,5 @@ EXPOSE 9100
 # `--engine-config /etc/shepherd/engine.toml` matches the production
 # guide's expected mount point. Operators override via
 # `docker run ... -v /path/to/engine.toml:/etc/shepherd/engine.toml:ro`.
-ENTRYPOINT ["/usr/bin/tini", "--", "nexum"]
+ENTRYPOINT ["/usr/bin/tini", "--", "shepherd"]
 CMD ["--engine-config", "/etc/shepherd/engine.toml"]

README.md

@@ -33,7 +33,9 @@ Looking for the org? See **[github.com/nullislabs](https://github.com/nullislabs
 | Path | Purpose |
 | --- | --- |
 | `crates/nexum-runtime/` | The **engine** - the Nexum Runtime's reference host: a wasmtime implementation of the `nexum:host` contract. |
-| `crates/nexum-cli/` | The `nexum` binary - a thin CLI over the runtime library. |
+| `crates/nexum-launch/` | The generic launcher library - shared CLI, config load, tracing, and the preset-driven launch. |
+| `crates/nexum-cli/` | The bare `nexum` binary - the core lattice with no extension payload. |
+| `crates/shepherd/` | The `shepherd` binary - the cow composition root wiring the cow-api extension. |
 | `crates/nexum-sdk/` | Generic guest SDK - the host trait seam, bind macro, chain/config/address helpers, wasi:http `fetch`, and tracing facade for any module. |
 | `crates/shepherd-sdk/` | CoW-domain guest SDK - the cow-api trait and CoW Protocol helpers on top of `nexum-sdk`. |
 | `wit/nexum-host/` | The **`nexum:host`** WIT package - the host/guest contract every engine implements and every module imports. |

crates/nexum-cli/Cargo.toml

@@ -13,13 +13,8 @@ name = "nexum"
 path = "src/main.rs"
 
 [dependencies]
+nexum-launch = { path = "../nexum-launch" }
 nexum-runtime = { path = "../nexum-runtime" }
-# Composition root wires the cow-api host extension into the reference
-# lattice; the runtime itself carries no cow dependency.
-shepherd-cow-host = { path = "../shepherd-cow-host" }
 
 anyhow.workspace = true
-clap.workspace = true
 tokio.workspace = true
-tracing.workspace = true
-tracing-subscriber.workspace = true

crates/nexum-cli/src/main.rs

@@ -1,48 +1,11 @@
-#![cfg_attr(not(test), warn(unused_crate_dependencies))]
-
-mod cli;
-mod launch;
+//! The bare `nexum` engine binary: the core lattice with no extension
+//! payload, composed over the generic launcher.
 
-use clap::Parser;
-use tracing::info;
-use tracing_subscriber::EnvFilter;
+#![cfg_attr(not(test), warn(unused_crate_dependencies))]
 
-use crate::cli::Cli;
-use nexum_runtime::engine_config;
+use nexum_runtime::preset::CoreRuntime;
 
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
-    let cli = Cli::parse();
-
-    let mut engine_cfg = engine_config::load_or_default(cli.engine_config.as_deref())?;
-    if let Some(n) = cli.log_backfill_concurrency {
-        engine_cfg.engine.log_backfill_concurrency = n;
-    }
-
-    let env_filter = EnvFilter::try_from_default_env()
-        .or_else(|_| EnvFilter::try_new(&engine_cfg.engine.log_level))
-        .unwrap_or_else(|_| EnvFilter::new("info"));
-    // Structured logging: JSON by default (machine-readable
-    // for production; one `jq` query reconstructs any dispatch
-    // timeline); `--pretty-logs` opts back into the 0.1 human-readable
-    // formatter for local dev. The same `EnvFilter` applies to both
-    // so `RUST_LOG=debug` works identically.
-    if cli.pretty_logs {
-        tracing_subscriber::fmt()
-            .with_env_filter(env_filter)
-            .with_target(true)
-            .init();
-    } else {
-        tracing_subscriber::fmt()
-            .with_env_filter(env_filter)
-            .with_target(true)
-            .json()
-            .flatten_event(true)
-            .with_current_span(false)
-            .init();
-    }
-
-    info!("nexum starting");
-
-    launch::run_from_config(&engine_cfg, cli.wasm.as_deref(), cli.manifest.as_deref()).await
+    nexum_launch::run("nexum", CoreRuntime).await
 }

crates/nexum-launch/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "nexum-launch"
+version = "0.2.0"
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+
+[lints]
+workspace = true
+
+[dependencies]
+nexum-runtime = { path = "../nexum-runtime" }
+
+anyhow.workspace = true
+clap.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true