Nemo Relay Plugin Build Agent Skill

Build a Plugin

Use this skill when a user wants to package reusable NeMo Relay runtime behavior

behind plugin configuration.

Keep reusable plugin behavior separate from one-off application startup code.

Use This When

Use this skill when the behavior should be activated by shared config and reused

across applications, teams, or process startup paths.

Common cases:

• Register subscribers, guardrails, intercepts, or a small bundle of related

runtime behavior.

• Validate operator-supplied config before changing runtime behavior.
• Give reusable behavior a stable plugin kind and activation lifecycle.
• Package behavior that should be enabled, disabled, or rolled out through

plugin config rather than repeated application startup code.

Do Not Use This When

Do not build a plugin when a narrower NeMo Relay surface is enough:

• One request or tenant needs temporary behavior -> use scope-local middleware.
• The user only needs first-time scopes, tool calls, or LLM calls ->

nemo-relay-instrument-calls.

• The user only needs to choose an exporter path ->

nemo-relay-plugin-observability.

• The behavior depends on live callables, provider clients, file handles,

credentials, or framework objects inside config.

Embedded Plugin Model

• Plugins package reusable process-level behavior.
• A plugin exposes a stable kind string and receives component-local config

from a shared plugin document.

• Plugin config must be JSON-compatible across Rust, Python, Node.js, files,

tests, and deployment systems.

• Validation is deterministic and side-effect free. It inspects config and

returns structured diagnostics before runtime behavior changes.

• Registration runs after validation and installs real behavior through

PluginContext, such as subscribers, guardrails, request intercepts,

execution intercepts, or stream execution intercepts.

• PluginContext gives the plugin system enough ownership to qualify runtime

names and roll back partial setup when activation fails.

• Disabled components should still validate when possible so operators can find

config problems before rollout.

Default Path

• Decide whether a plugin is actually needed. Prefer direct instrumentation or

scope-local behavior when the use case is not reusable process-level

behavior.

• Pick one first runtime surface: subscriber-oriented export, sanitize

guardrail, conditional guardrail, request intercept, execution intercept, or

stream execution intercept.

• Choose a stable plugin kind and the smallest JSON-compatible config shape.
• Define diagnostics for missing fields, unsupported values, unknown fields,

unsafe config, and invalid field combinations.

• Validate config before initialization. Validation must not open network

connections, create clients, register middleware, or mutate process state.

• If validation returns error diagnostics, return them and stop without

initialization or registration.

• Register runtime behavior through PluginContext, not by hand-registering

global behavior inside application startup.

• Test activation, disabled components, validation failures, and registration

failure rollback.

• Document how to enable the plugin, what config fields are supported, and how

to roll back the component.

10. For a dynamic plugin that should provide structured fields in

nemo-relay plugins edit, declare the config_schema capability and

reference a local Draft 7 or Draft 2020-12 JSON Schema file from

[config_schema].path in relay-plugin.toml. Schema-less plugins remain

editable as raw JSON objects.

Config Shape

The top-level plugin document contains version, components, and policy.

Each component supplies the plugin kind, enabled, and component-local

config:

{
  "version": 1,
  "components": [
    {
      "kind": "redaction-policy",
      "enabled": true,
      "config": {
        "preset": "strict"
      }
    }
  ],
  "policy": {
    "unknown_component": "warn",
    "unknown_field": "warn",
    "unsupported_value": "error"
  }
}

Keep business logic in plugin code, not in config. Use references to secrets or

endpoints rather than embedding sensitive values.

Binding Pointers

• Python: nemo_relay.plugin
• Node.js: nemo-relay-node/plugin
• Rust: nemo_relay::plugin
• Go and raw FFI are source-first or advanced surfaces.

Use the same canonical snake_case config keys across bindings and files. Node

helper functions can be camelCase, but plugin config objects remain

snake_case.

Failure Modes To Avoid

• Do not put callables, clients, credentials, framework objects, file handles,

or caches in plugin config.

• Do not perform runtime registration during validation.
• Do not skip validation for disabled components.
• Do not register directly through global startup code when PluginContext

should own the runtime behavior.

• Do not combine unrelated subscribers, request transforms, and policy checks

in the first plugin unless one config document clearly owns the bundle.

• Do not export raw production payloads or secrets. Add telemetry sanitization

before data leaves the process.

• Do not ignore partial activation failures. Roll back or surface a clear

diagnostic.

Validation Checklist

• [ ] Stable plugin kind chosen.
• [ ] Config shape is JSON-compatible and uses snake_case.
• [ ] Required fields and unsupported values produce stable diagnostics.
• [ ] Unknown fields follow the configured policy.
• [ ] Disabled components still report config problems where possible.
• [ ] Initialization installs behavior through PluginContext.
• [ ] A forced registration failure does not leave partial runtime behavior

active.

• [ ] Docs or examples show how to enable and roll back the plugin.
• [ ] Dynamic plugins that need structured CLI editing package a valid local

JSON Schema and declare config_schema in relay-plugin.toml.

Use Another Skill When

• You only need to wrap direct tool or LLM calls ->

nemo-relay-instrument-calls

• You need to set up traces or exporters without packaging a plugin ->

nemo-relay-plugin-observability

• You need to debug plugin activation, missing events, or load failures ->

nemo-relay-debug-runtime-integration