NeMo Guardrails vs LLM Guard

Which platform fits which scenario

This table matches common team situations to the platform that fits them better, and names the condition under which the other option wins. Read each row as a starting point, then check it against your own traffic, team skills and existing deployments.

How NeMo Guardrails and LLM Guard sit in the request path

The two tools differ in where they run and who writes the rules. NeMo Guardrails wraps a model call in configured rails, while LLM Guard applies scanners to prompts and responses that your application calls directly. The cards below cover what each one means for the people who operate it.

Capability and requirements, side by side

This table sets license, maintenance, detection scope, Python support, configuration and deployment for NeMo Guardrails and LLM Guard side by side. Read the maintenance and license rows first, since they decide whether a new rollout is worth considering at all. Where a capability is not covered by a researched source, the cell says what to confirm with the vendor or in your own environment.

What the licenses and editions mean for your team

What drives running cost for each guardrail

Moving from LLM Guard to NeMo Guardrails

This sequence turns an existing LLM Guard deployment into a NeMo Guardrails configuration you can test side by side with production traffic before cutting over. It keeps the scanner settings you have already tuned and rebuilds only the policy logic that NeMo expresses differently.

1. Inventory every enabled LLM Guard scanner

   The platform or security engineer who owns the current deployment lists each input and output scanner that runs in production, along with its threshold, its configuration values and the endpoint or application it protects. Include scanners called from application code as well as those in a gateway or API server, because these are easy to miss. Done means you have a single table with one row per scanner and the traffic path it sits on. Confirm the exact scanner names and versions against the LLM Guard documentation, since LLM Guard documents 15 input scanners and 20 output scanners and your deployment may use a subset.

2. Map each scanner to a rail or a retained check

   For each row in the inventory, decide whether NeMo Guardrails covers the same risk with a built-in rail, a self-check or model-based check, or a custom action, or whether the check should stay outside NeMo as a retained scanner. Input and output scanners usually map to input and output rails, while behaviors such as topic restrictions map to dialog rails. The security architect signs off on the map, and the output is a document that marks each scanner as replaced, partly replaced or retained. Verify each NeMo capability against the current NeMo Guardrails documentation before you commit to it, because feature coverage differs between releases.

3. Rebuild policies in config.yml and Colang

   The engineer who writes guardrail policy creates a NeMo configuration folder with a config.yml file, any Python actions, and Colang files that encode the mapped rules. Scanner thresholds and example prompts carry over as values in this step, but the policy logic (what triggers a block, what message the user sees, and how a refusal is phrased) is written again in NeMo's model. The output is a configuration that loads without errors in the Python API or the guardrails server. Choose a Colang version deliberately: Colang 1.0 is the default, and 2.0 is supported as well.

4. Convert Colang 1.0 files only where 2.x is needed

   If the team chooses Colang 2.x for any rails, the engineer runs the nemoguardrails convert tool on the Colang 1.0 files and reviews the results against NVIDIA's Colang 1.0 to 2.x migration guide. The tool output is a starting point, not a finished migration, and NVIDIA states that converted configurations still need manual review. Plan that review as a named task with an owner, not as a side effect of testing. Done means every converted file has been read by someone who knows the original policy and the converted rails match the intended behavior.

5. Review converted policies manually

   A second engineer who did not write the conversion reads each converted Colang file and compares it to the original policy and the scanner inventory from the first step. They check that blocked categories, refusal messages, and fallback paths behave as intended, including edge cases such as multilingual input and long outputs. The reviewer records every change in a short log that the security team can read. The step closes when the reviewer approves the configuration and the log lists no unresolved differences from the original policy.

6. Run parallel traffic tests against both stacks

   The platform team routes a copy of production or representative traffic through both the existing LLM Guard path and the new NeMo Guardrails configuration, with the LLM Guard result used for live decisions. Responses from both stacks are logged side by side, and the team tracks disagreements in blocks, false positives, false negatives, and added latency. Use the test prompts you already maintain for LLM Guard as the first regression set, because they carry the history of what your application had to block. Done means disagreements are explained, each one is classified as an intended change or a defect, and the defects are fixed and retested.

7. Cut over and retire the old scanners

   After the parallel results meet the acceptance criteria agreed in the previous step, the team switches live traffic to NeMo Guardrails, keeps LLM Guard available for a rollback window defined in the change plan, and then removes it from the request path. Confirm that any model dependencies NeMo needs are documented and available in the production environment before the switch. Because the LLM Guard repository is archived and receives no security fixes, the team should not keep it running in production longer than the rollback plan requires. The step closes with a change record that names the new configuration version, the approver, and the retired components.

Where guardrail projects usually run long

Questions buyers ask before hiring help with NeMo Guardrails