Build a Rust Native Plugin | NVIDIA NeMo Relay

Use the nemo-relay-plugin crate to create an in-process native plugin without writing the C ABI by hand. The SDK exports the stable ABI entry point and provides typed helpers for the supported registration surfaces.

This example builds a native plugin that registers an event subscriber. The repository also includes an extended example in examples/rust-native-plugin with validation, middleware, marks, scopes, and a configuration schema.

Create the Project

Create a Rust library project with this Cargo.toml file:

1 [package]
2 name = "acme-native-policy"
3 version = "0.1.0"
4 edition = "2024"
5 
6 [lib]
7 crate-type = ["cdylib"]
8 
9 [dependencies]
10 nemo-relay-plugin = "0.5.0"
11 serde_json = "1"

Add the following implementation to src/lib.rs:

1 use nemo_relay_plugin::{Json, NativePlugin, PluginContext, Result};
2 use serde_json::Map;
3 
4 struct NativePolicy;
5 
6 impl NativePlugin for NativePolicy {
7     fn plugin_kind(&self) -> &str {
8         "acme.native_policy"
9     }
10 
11     fn register(
12         &mut self,
13         _config: &Map<String, Json>,
14         context: &mut PluginContext<'_>,
15     ) -> Result<()> {
16         context.register_subscriber("audit", |_| {})
17     }
18 }
19 
20 nemo_relay_plugin::nemo_relay_plugin!(nemo_relay_register_plugin, || NativePolicy);

Create the Manifest

Create relay-plugin.toml with the following content:

1 manifest_version = 1
2 
3 [plugin]
4 id = "acme.native_policy"
5 kind = "rust_dynamic"
6 
7 [compat]
8 relay = ">=0.5,<1.0"
9 native_api = "1"
10 
11 [defaults]
12 enabled = false
13 
14 [capabilities]
15 items = ["plugin_native"]
16 
17 [source]
18 artifact = "target/release/<platform-library-file>"
19 
20 [integrity]
21 sha256 = "sha256:<artifact-sha256>"
22 
23 [load]
24 library = "target/release/<platform-library-file>"
25 symbol = "nemo_relay_register_plugin"

Update the library filename for your platform: use .dylib on macOS, .so on Linux, or .dll on Windows. Replace <platform-library-file> in both manifest fields with that filename.

Build, Register, and Validate

Build the library, calculate its digest, and register the plugin with the following commands. The digest command requires Python 3.

$ cargo build --release
$ python - <<'PY'
$ from hashlib import sha256
$ from pathlib import Path
$ 
$ artifact = Path("target/release/<platform-library-file>")
$ print(f"sha256:{sha256(artifact.read_bytes()).hexdigest()}")
$ PY
$ nemo-relay plugins add ./relay-plugin.toml
$ nemo-relay plugins enable acme.native_policy
$ nemo-relay plugins validate acme.native_policy

Use the following PowerShell command on Windows:

1 $artifact = ".\\target\\release\\<platform-library-file>"
2 $hash = (Get-FileHash -Algorithm SHA256 $artifact).Hash.ToLower()
3 "sha256:$hash"

Replace <platform-library-file> in the digest command, then replace sha256:<artifact-sha256> with its output before you run plugins add. The command writes a [[plugins.dynamic]] manifest reference. Use nemo-relay plugins edit or edit that record to add component fields when the plugin accepts configuration.

Keep tests outside src, use the shared DTOs re-exported by nemo-relay-plugin, and do not retain host-owned ABI handles after a callback returns. Refer to Configure Discoverable Plugins for trust-policy configuration.