Configuration Errors

These errors appear when running ng_run or ng_collect_rollouts. NeMo Gym validates configuration at startup before launching servers.

Startup Errors

Errors that prevent servers from starting.

Missing Mandatory Value

omegaconf.errors.MissingMandatoryValue: Missing mandatory value: policy_api_key

When: A required variable (usually in env.yaml) is not defined.

Fix: Add the missing value to env.yaml:

1
policy_api_key: sk-your-api-key

Or pass via command line:

$
ng_run "+config_paths=[config.yaml]" +policy_api_key=sk-your-api-key

Server Reference Not Found

AssertionError: Could not find ResourcesServerRef(type='resources_servers', name='typo_weather') 
in the list of available servers: [ResourcesServerRef(...), ...]

When: A server config references another server that doesn’t exist or isn’t loaded.

Common causes:

• Typo in the server name
• Referenced server’s config file not included in +config_paths
• Server defined in a different config file that wasn’t loaded

Fix:

1. Check server name spelling in your config
2. Ensure all required config files are in +config_paths:

$
ng_run "+config_paths=[model.yaml,resource.yaml,agent.yaml]"

Validation Errors

Errors where config structure is correct but values are invalid.

Almost-Servers Detected

Configuration Warnings: Almost-Servers Detected
  Almost-Server Detected: 'example_simple_agent'
  This server configuration failed validation:
- ResourcesServerInstanceConfig -> resources_servers -> example_server -> domain: 
  Input should be 'math', 'coding', 'agent', 'knowledge', 'instruction_following', 
  'long_context', 'safety', 'games', 'e2e' or 'other'

When: Config has the right structure (server type, entrypoint) but contains invalid field values.

Common causes:

• Invalid domain value for resources servers
• Invalid license value in dataset configs
• Missing required fields for the server type

Fix: Check the validation error path (for example, resources_servers -> example_server -> domain) and update the field with a valid value. Refer to configuration-reference for valid field values.

Bypass Strict Validation

To continue with invalid configs (invalid servers will be skipped):

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# In env.yaml
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error_on_almost_servers: false

$
# Or via command line
$
ng_run "+config_paths=[config.yaml]" +error_on_almost_servers=false