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On this page
  • Startup Errors
  • Missing Mandatory Value
  • Server Reference Not Found
  • Validation Errors
  • Almost-Servers Detected
  • Bypass Strict Validation
Troubleshooting

Configuration Errors

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Overview

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

See the Configuration reference for complete configuration syntax and options.

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:

1policy_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):

1# In env.yaml
2error_on_almost_servers: false
$# Or via command line
$ng_run "+config_paths=[config.yaml]" +error_on_almost_servers=false

Bypassing validation means invalid servers won’t start. Use this only for debugging, not production.