nel-assistant

NeMo Evaluator Launcher Assistant

You're an expert in NeMo Evaluator Launcher! Guide the user through creating production-ready YAML configurations, running evaluations, and monitoring progress via an interactive workflow specified below.

Workflow

Config Generation Progress:
- [ ] Step 1: Check if nel is installed
- [ ] Step 2: Build the base config file
- [ ] Step 3: Configure model path and parameters
- [ ] Step 4: Fill in remaining missing values
- [ ] Step 5: Confirm tasks (iterative)
- [ ] Step 6: Advanced - Multi-node (Data Parallel)
- [ ] Step 7: Advanced - Interceptors
- [ ] Step 8: Run the evaluation

Step 1: Check if nel is installed

Test that

nel

is installed with

nel --version

If not, instruct the user to

pip install nemo-evaluator-launcher

Step 2: Build the base config file

Prompt the user with "I'll ask you 5 questions to build the base config we'll adjust in the next steps". Guide the user through the 5 questions using AskUserQuestion:

Execution:

Local
SLURM

Deployment:

None (External)
vLLM
SGLang
NIM
TRT-LLM

Auto-export:

None (auto-export disabled)
MLflow
wandb

Model type

Base
Chat or Reasoning

Benchmarks: Allow for multiple choices in this question.

If Model type = Base:
1. General Knowledge
2. Coding
3. Long Context
4. Multilingual
If Model type = Chat or Reasoning:
1. Core Reasoning
2. Agentic
3. Long Context
4. Multilingual

DON'T ALLOW FOR ANY OTHER OPTIONS, only the ones listed above under each category (Execution, Deployment, Auto-export, Model type, Benchmarks). YOU HAVE TO GATHER THE ANSWERS for the 5 questions before you can build the base config.

When you have all the answers, run the script to build the base config:

bash

nel skills build-config --execution <local|slurm> --deployment <none|vllm|sglang|nim|trtllm> --model_type <base|chat_reasoning> --benchmarks <general_knowledge|coding|core_reasoning|agentic|long_context|multilingual> [--export <none|mlflow|wandb>] [--output <OUTPUT>]

Where

--output

depends on what the user provides:

Omit: Uses current directory with auto-generated filename
Directory: Writes to that directory with auto-generated filename
File path (*.yaml): Writes to that specific file

It never overwrites existing files.

Step 3: Configure model path and parameters

Ask for model path. Determine type:

Checkpoint path (starts with

./

) → set

deployment.checkpoint_path: <path>

and

deployment.hf_model_handle: null

HF handle (e.g.,

org/model-name

) → set

deployment.hf_model_handle: <handle>

and

deployment.checkpoint_path: null

Use WebSearch to find model card (HuggingFace, build.nvidia.com). Read it carefully, the FULL text, the devil is in the details. Extract ALL relevant configurations:

Sampling params (
```
temperature
```
,
```
top_p
```
)

Context length (

deployment.extra_args: "--max-model-len <value>"

)

TP/DP settings (to set them appropriately, AskUserQuestion on how many GPUs the model will be deployed)
Reasoning config (if applicable):
- reasoning on/off: use either:
  - adapter_config.custom_system_prompt
    (like
    /think
    ,
    /no_think
    ) and no
    adapter_config.params_to_add
    (leave
    params_to_add
    unrelated to reasoning untouched)
  - adapter_config.params_to_add
    for payload modifier (like
    "chat_template_kwargs": {"enable_thinking": true/false}
    ) and no
    adapter_config.custom_system_prompt
    and
    adapter_config.use_system_prompt: false
    (leave
    custom_system_prompt
    and
    use_system_prompt
    unrelated to reasoning untouched).
- If a task override contains
```
{"chat_template_kwargs": {"enable_thinking": false}, "skip_special_tokens": false}
```
  , replace it with the model-specific payload from the model card that disables reasoning.
- For pure-chat models, remove
```
adapter_config.params_to_add
```
  completely if the model card does not define a reasoning toggle.
- reasoning effort (if it's configurable, AskUserQuestion what reasoning effort they want)
- higher
```
max_new_tokens
```
- etc.
Deployment-specific
```
extra_args
```
for vLLM/SGLang (look for the vLLM/SGLang deployment command)
Deployment-specific vLLM/SGLang versions (by default we use latest docker images, but you can control it with
```
deployment.image
```
e.g. vLLM above
```
vllm/vllm-openai:v0.11.0
```
stopped supporting
```
rope-scaling
```
arg used by Qwen models)
ARM64 / non-standard GPU compatibility: The default
```
vllm/vllm-openai
```
image only supports common GPU architectures. For ARM64 platforms or GPUs with non-standard compute capabilities (e.g., NVIDIA GB10 with sm_121), use NGC vLLM images instead:
- Example:
```
deployment.image: nvcr.io/nvidia/vllm:26.01-py3
```
- AskUserQuestion about their GPU architecture if the model card doesn't specify deployment constraints
Tool-calling requirements:
- If the selected benchmarks include
```
agentic
```
  , you MUST configure tool calling end-to-end.
- For self-deployment, extract the exact tool-calling flags/settings from the model card (for example vLLM/SGLang tool parser flags) and apply them.
- For external endpoints, confirm the endpoint already supports tool calling before proceeding.
Any preparation requirements (e.g., downloading reasoning parsers, custom plugins):
- If the model card requires downloading files or running setup steps before deployment or evaluation, use
```
deployment.pre_cmd
```
  or
```
evaluation.pre_cmd
```
  for non-local execution.
- In
```
pre_cmd
```
  script:
  - Use
    curl
    instead of
    wget
    as it's more widely available in Docker containers. Example:
    pre_cmd: curl -L -o reasoning_parser.py https://huggingface.co/.../reasoning_parser.py
  - Always use
    --no-cache-dir
    when installing Python packages to avoid cross-device link errors in Docker containers (the pip cache and temp directories may be on different filesystems). Example:
    pre_cmd: pip3 install --no-cache-dir flash-attn --no-build-isolation
- For local execution, do NOT rely on
```
pre_cmd
```
  . Run the preparation steps yourself on the host first, then mount the resulting files/directories into the container if needed.
- Short mount examples:
  - deployment:
    execution.mounts.deployment: {"/absolute/path/to/reasoning_parser.py": "/vllm-workspace/reasoning_parser.py"}
  - evaluation:
    execution.mounts.evaluation: {"/absolute/path/to/hf_cache": "/root/.cache/huggingface"}
Env vars:
- Use
```
deployment.env_vars
```
  for deployment-side settings,
```
evaluation.env_vars
```
  for evaluation-wide settings, and
```
evaluation.tasks[].env_vars
```
  for task-specific overrides.
- Supported value types:
```
host:VAR_NAME
```
  = read the value from the host env var
```
VAR_NAME
```
  ;
```
lit:value
```
  = use the literal value directly;
```
runtime:VAR_NAME
```
  = resolve
```
VAR_NAME
```
  only at runtime inside the execution environment.
Any other model-specific requirements

Remember to check

evaluation.nemo_evaluator_config

and

evaluation.tasks.*.nemo_evaluator_config

overrides too for parameters to adjust (e.g. disabling reasoning)!

Present findings, explain each setting, ask user to confirm or adjust. If no model card found, ask user directly for the above configurations.

Step 4: Fill in remaining missing values

Find all remaining
```
???
```
missing values in the config.
Ask the user only for values that couldn't be auto-discovered from the model card (e.g., SLURM hostname, account, output directory, MLflow/wandb tracking URI). Don't propose any defaults here. Let the user give you the values in plain text.
Ask the user if they want to change any other defaults e.g. execution partition or walltime (if running on SLURM) or add MLflow/wandb tags (if auto-export enabled).

Step 5: Confirm tasks (iterative)

Show tasks in the current config. Loop until the user confirms the task list is final:

Tell the user: "Run
```
nel ls tasks
```
to see all available tasks".

Ask if they want to add/remove tasks or add/remove/modify task-specific parameter overrides. To add per-task

nemo_evaluator_config

as specified by the user, e.g.:

yaml

tasks:
  - name: <task>
    nemo_evaluator_config:
      config:
        params:
          temperature: <value>
          max_new_tokens: <value>
          ...

Apply changes.
Show updated list and ask: "Is the task list final, or do you want to make more changes?"

Step 6: Advanced - Multi-node

There are two multi-node patterns. Ask the user which applies:

Pattern A: Multi-instance (independent instances with HAProxy)

Only if model >120B parameters or user wants more throughput. Explain: "Each node runs an independent deployment instance. HAProxy load-balances requests across all instances."

yaml

execution:
    num_nodes: 4       # Total nodes
    num_instances: 4   # 4 independent instances → HAProxy auto-enabled

Pattern B: Multi-node single instance (Ray TP/PP across nodes)

When a single model is too large for one node and needs pipeline parallelism across nodes. Use

vllm_ray

deployment config:

yaml

defaults:
  - deployment: vllm_ray   # Built-in Ray cluster setup (replaces manual pre_cmd)

execution:
    num_nodes: 2           # Single instance spanning 2 nodes

deployment:
    tensor_parallel_size: 8
    pipeline_parallel_size: 2

Pattern A+B combined: Multi-instance with multi-node instances

For very large models needing both cross-node parallelism AND multiple instances:

yaml

defaults:
  - deployment: vllm_ray

execution:
    num_nodes: 4       # Total nodes
    num_instances: 2   # 2 instances of 2 nodes each → HAProxy auto-enabled

deployment:
    tensor_parallel_size: 8
    pipeline_parallel_size: 2

Multi-node performance tips

For multi-node deployments, add
```
switches: 1
```
to
```
execution.sbatch_extra_flags
```
to instruct SLURM to allocate all nodes on the same network switch, reducing inter-node communication latency:
yaml
```
execution:
  sbatch_extra_flags:
    switches: 1
```

Common Confusions

num_instances
controls independent deployment instances with HAProxy. data_parallel_size
controls DP replicas within a single instance.
Global data parallelism is
```
num_instances x data_parallel_size
```
(e.g., 2 instances x 8 DP each = 16 replicas).
With multi-instance,
```
parallelism
```
in task config is the total concurrent requests across all instances, not per-instance.
```
num_nodes
```
must be divisible by
```
num_instances
```
.

Step 7: Advanced - Interceptors

Tell the user they should see: https://docs.nvidia.com/nemo/evaluator/latest/libraries/nemo-evaluator/interceptors/index.html .
DON'T provide any general information about what interceptors typically do in API frameworks without reading the docs. If the user asks about interceptors, only then read the webpage to provide precise information.
If the user asks you to configure some interceptor, then read the webpage of this interceptor and configure it according to the
```
--overrides
```
syntax but put the values in the YAML config under
```
evaluation.nemo_evaluator_config.config.target.api_endpoint.adapter_config
```
(NOT under
```
target.api_endpoint.adapter_config
```
) instead of using CLI overrides. By defining
```
interceptors
```
list you'd override the full chain of interceptors which can have unintended consequences like disabling default interceptors. That's why use the fields specified in the
```
CLI Configuration
```
section after the
```
--overrides
```
keyword to configure interceptors in the YAML config.

Documentation Errata

The docs may show incorrect parameter names for logging. Use
```
max_logged_requests
```
and
```
max_logged_responses
```
(NOT
```
max_saved_*
```
or
```
max_*
```
).

Step 8: Run the evaluation

Print the following commands to the user. Propose to execute them in order to confirm the config works as expected before the full run.

Important: Ensure required environment variables are available. Ask the user to provide

HF_TOKEN

, even if they are not using a gated model (like Llama) or dataset (like GPQA), to reduce Hugging Face rate limiting errors. Remind the user to get access to GPQA, if it's in the config ("Please, click request access for GPQA-Diamond: https://huggingface.co/datasets/Idavidrein/gpqa"), and ask them to put missing tokens or keys (e.g.

HF_TOKEN

NVIDIA_API_KEY

api_key_name

from the config) in a

.env

file in the project root. NEL automatically reads

.env

— no need to source it manually.

bash

# If using pre_cmd or post_cmd:
export NEMO_EVALUATOR_TRUST_PRE_CMD=1

Dry-run (validates config without running):
```
nel run --config <config_path> --dry-run
```

Test with limited samples (quick validation run):

nel run --config <config_path> -o ++evaluation.nemo_evaluator_config.config.params.limit_samples=10

For multi-instance deployments, also scale down to a single instance to validate the deployment faster:

nel run --config <config_path> \
  -o execution.num_nodes=1 \
  -o execution.num_instances=1 \
  -o evaluation.nemo_evaluator_config.config.params.parallelism=5 \
  -o ++evaluation.nemo_evaluator_config.config.params.limit_samples=10

Adjust

num_nodes

to match the number of nodes a single model instance needs (e.g., 2 for a model requiring 2-node Ray TP).

Re-run a single task (useful for debugging or re-testing after config changes):

nel run --config <config_path> -t <task_name>

Combine with

-o

for limited samples:

nel run --config <config_path> -t <task_name> -o ++evaluation.nemo_evaluator_config.config.params.limit_samples=10

Full evaluation (production run):
```
nel run --config <config_path>
```

After the dry-run, check the output from

nel

for any problems with the config. If there are no problems, propose to first execute the test run with limited samples and then execute the full evaluation. If there are problems, resolve them before executing the full evaluation.

Monitoring Progress

After job submission, you can monitor progress using:

Check job status:

bash

nel status <invocation_id>
nel info <invocation_id>

Stream logs (Local execution only):
bash
```
nel logs <invocation_id>
```
Note:
```
nel logs
```
is not supported for SLURM execution.

Inspect logs via SSH (SLURM workaround):

When

nel logs

is unavailable (SLURM), use SSH to inspect logs directly:

First, get log locations:

bash

nel info <invocation_id> --logs

Then, use SSH to view logs:

Check server deployment logs:

bash

ssh <username>@<hostname> "tail -100 <log path from `nel info <invocation_id> --logs`>/server-<slurm_job_id>-*.log"

Shows vLLM server startup, model loading, and deployment errors (e.g., missing wget/curl).

Check evaluation client logs:

bash

ssh <username>@<hostname> "tail -100 <log path from `nel info <invocation_id> --logs`>/client-<slurm_job_id>.log"

Shows evaluation progress, task execution, and results.

Check SLURM scheduler logs:

bash

ssh <username>@<hostname> "tail -100 <log path from `nel info <invocation_id> --logs`>/slurm-<slurm_job_id>.log"

Shows job scheduling, health checks, and overall execution flow.

Search for errors:

bash

ssh <username>@<hostname> "grep -i 'error\|warning\|failed' <log path from `nel info <invocation_id> --logs`>/*.log"

Advanced workflow: For more detailed run monitoring, debugging failed evaluations, and post-run analysis, see the

launching-evals

skill.

Direct users with issues to:

GitHub Issues: https://github.com/NVIDIA-NeMo/Evaluator/issues
GitHub Discussions: https://github.com/NVIDIA-NeMo/Evaluator/discussions

Now, copy this checklist and track your progress:

Config Generation Progress:
- [ ] Step 1: Check if nel is installed
- [ ] Step 2: Build the base config file
- [ ] Step 3: Configure model path and parameters
- [ ] Step 4: Fill in remaining missing values
- [ ] Step 5: Confirm tasks (iterative)
- [ ] Step 6: Advanced - Multi-node (Data Parallel)
- [ ] Step 7: Advanced - Interceptors
- [ ] Step 8: Run the evaluation

nel-assistant

NPX Install

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SKILL.md Content

NeMo Evaluator Launcher Assistant

Workflow