[tgasser-nv]

Description

This PR is the first in a stack-of-5 to adds a Rust native plugin for NeMo Relay which calls the Guardrails hooks server /v1/hooks/nemo-relay endpoint. The line-count in the PR is inflated by the Cargo.lock file which is 3,459 lines long. Actual code is ~470 lines, tests ~680 lines, misc files ~210.

The functionality builds up in the stack as below:

• feat(relay): NeMo Relay Rust plugin scaffold #2489 (this PR): Rust scaffolding including cargo workspace, plugin crate, manifest, config schema, packaging script, and host lifecycle tests.
• feat(relay): NeMo Relay PreToolUse Rust client #2493: Hooks server client issuing tool call check
• TODO: End-to-end tests against a real hooks server
• TODO: User docs
• TODO: CI for the plugin

Related Issue(s)

• feat(hooks): Add Hooks Server PreToolUse schema #2472
• feat(hooks): Add Hooks Server #2473
• NGR-901

Verification

Pre-commit

$ uv run pre-commit run --all-files
check yaml...............................................................Passed
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
ruff (legacy alias)......................................................Passed
ruff format..............................................................Passed
Insert license in comments...............................................Passed
zizmor...................................................................Passed
ty.......................................................................Passed

Unit-tests

$ cargo test -p nemo-guardrails-relay-plugin
    Finished `test` profile [unoptimized + debuginfo] target(s) in 9.36s
     Running unittests src/lib.rs (target/debug/deps/nemo_guardrails_relay_plugin-9341a014c3c8bb84)

running 12 tests
.....
test result: ok. 12 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

     Running tests/lifecycle.rs (target/debug/deps/lifecycle-c7975f94b358de3d)

running 8 tests
.....
test result: ok. 8 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 5.34s

   Doc-tests nemo_guardrails_relay_plugin

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s```

AI Assistance

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Checklist

• I've read the CONTRIBUTING guidelines.
• This PR links to a triaged issue assigned to me.
• My PR title follows the project commit convention.
• I've updated the documentation if applicable.
• I've added tests if applicable.
• I've noted any verification beyond CI and any checks I couldn't run.
• I did not update generated changelog files manually.
• I addressed all CodeRabbit, Greptile, and other review comments, or replied with why no change is needed.
• @mentions of the person or team responsible for reviewing proposed changes.

Summary by CodeRabbit

• New Features
  • Added an early-stage NeMo Guardrails checks plugin for Relay, with configuration for an endpoint, request headers, timeout, and priority. Invalid settings are reported during validation; checks are not yet registered.
  • Added tools to package the plugin as a directory or .tar.gz/.zip archive, with integrity information included in the bundle.
• Documentation
  • Added setup, configuration, compatibility, build, and packaging guidance.
• Chores
  • Added Rust build and formatting support.

[greptile-apps]

Confidence Score: 5/5

[Low impact] The PR appears safe to merge as a scaffold.

Summary

Adds the Rust plugin scaffold, configuration checks, bundle packaging, and Relay host tests. The plugin does not call the Guardrails service yet.

• Relay can load and validate the Guardrails plugin.
• The packaging script creates repeatable Relay plugin bundles.
• The repository now builds the Relay plugin in a Rust workspace.

_{Reviews (6) · Last reviewed commit: "Remove endpoint validation from schema a..." · Reviewed by Greptile}

[coderabbitai]

No actionable comments were generated in the recent review.

ℹ️ Recent review info

⚙️ Run configuration

• Source mode: Auto
• Repository: NVIDIA-NeMo/Guardrails
• Branch: feat/relay-rust-client
• File: .coderabbit.yaml
• Commit: eeaa5c8
• Layers: Repository YAML
• Review profile: CHILL
• Plan: Enterprise
• Run ID: 5e0d0b22-b227-4aae-bb89-5e8a22f2917a

📥 Commits

Reviewing files that changed from the base of the PR and between 61f1013 and eeaa5c8.

⛔ Files ignored due to path filters: 1

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing: 16

• .cargo/config.toml
• .dockerignore
• .gitattributes
• .gitignore
• .pre-commit-config.yaml
• Cargo.toml
• crates/nemo-guardrails-relay-plugin/Cargo.toml
• crates/nemo-guardrails-relay-plugin/README.md
• crates/nemo-guardrails-relay-plugin/config.schema.json
• crates/nemo-guardrails-relay-plugin/relay-plugin.toml
• crates/nemo-guardrails-relay-plugin/scripts/package_bundle.py
• crates/nemo-guardrails-relay-plugin/scripts/test_package_bundle.py
• crates/nemo-guardrails-relay-plugin/src/config.rs
• crates/nemo-guardrails-relay-plugin/src/lib.rs
• crates/nemo-guardrails-relay-plugin/tests/lifecycle.rs
• rust-toolchain.toml

Included review availability: This review used your included allowance. Your plan provides up to 12 included reviews per hour; 11 remain after this review.

Walkthrough

This change adds a Rust workspace and a NeMo Guardrails Relay plugin scaffold. It defines plugin configuration and validation, integrates the plugin with Relay, adds lifecycle and packaging tests, and provides a script to create plugin bundles.

Changes: NeMo Guardrails Relay plugin

Layer / File(s)	Summary
Workspace and crate setup Cargo.toml, crates/nemo-guardrails-relay-plugin/Cargo.toml, rust-toolchain.toml, .cargo/config.toml, .dockerignore, .gitattributes, .gitignore, .pre-commit-config.yaml	Adds the Rust workspace and plugin crate, sets build dependencies and toolchain, and updates repository settings for Rust builds and files.
Configuration schema and validation crates/nemo-guardrails-relay-plugin/config.schema.json, crates/nemo-guardrails-relay-plugin/src/config.rs, crates/nemo-guardrails-relay-plugin/README.md	Defines the configuration fields and defaults. Parses and validates endpoints, headers, timeout, and priority, with tests for valid and invalid values.
Relay registration and lifecycle crates/nemo-guardrails-relay-plugin/relay-plugin.toml, crates/nemo-guardrails-relay-plugin/src/lib.rs, crates/nemo-guardrails-relay-plugin/tests/lifecycle.rs, crates/nemo-guardrails-relay-plugin/README.md	Adds the plugin manifest and registration entry point. Reports configuration diagnostics and tests Relay compatibility, configuration rejection, activation, and unloading.
Bundle creation and archive tests crates/nemo-guardrails-relay-plugin/scripts/*, crates/nemo-guardrails-relay-plugin/README.md	Packages the compiled library, schema, and license files. Supports tar.gz and ZIP archives with normalized metadata; tests validation and repeatable archive output.

Priority: Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Merge Risk: Minimal · up to eeaa5

The scaffold is mergeable after normal checks; it does not register checks yet, as intended for this stage.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly identifies the main change: an initial Rust plugin scaffold for NeMo Relay. It matches the workspace, plugin crate, manifest, configuration, packaging, and lifecycle test additions.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Test Results For Major Changes		The PR introduces a new Rust plugin and packaging flow, so it is a major change. The description documents testing information, including successful pre-commit checks and `cargo test -p nemo-guardrail…

Full details: Test Results For Major Changes

Explanation

The PR introduces a new Rust plugin and packaging flow, so it is a major change. The description documents testing information, including successful pre-commit checks and cargo test -p nemo-guardrails-relay-plugin results with 12 unit tests and 7 lifecycle tests passing. Numeric or convergence changes are not applicable, and no performance-impact requirement is indicated.

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[willkill07]

The scaffolding overall looks great