Configuration Errors

These errors appear when running gym env start or gym eval run --no-serve. NeMo Gym validates configuration at startup before launching servers.

Startup Errors

Errors that prevent servers from starting.

Unset Required Config Value(s)

nemo_gym.config_types.ConfigMissingValuesError: 1 required config value(s) are unset (still '???') after merging:
  - policy_api_key
Provide each value via a CLI override, in env.yaml, or in a config you pass via config_paths.
For example, on the command line:
  ++policy_api_key=<value>

When: One or more required variables (usually in env.yaml) are left unset (???) after all config sources are merged. Every unset value is listed together in this single error.

Fix: Add the missing value to env.yaml:

1
policy_api_key: sk-your-api-key

Or pass via command line:

$
gym env start \
>
    --config config.yaml \
>
    --model-api-key sk-your-api-key

Server Reference Not Found

nemo_gym.config_types.ServerRefNotFoundError: In server instance 'my_agent', field 'resources_server' references resources_servers/'typo_weather', which is not defined in the merged config.
Did you mean: 'weather'?

When: A server config references another server that doesn’t exist or isn’t loaded. The error names the referencing instance/field and then either suggests a similarly named server (Did you mean: …) or, when nothing is close, lists the available servers of that type (Available resources_servers: …).

Common causes:

• Typo in the server name
• Referenced server’s config file not included in the --config flags
• 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 passed with --config:

$
gym env start \
>
    --config model.yaml \
>
    --config resource.yaml \
>
    --config agent.yaml

Config Path Not Found

nemo_gym.config_types.ConfigPathNotFoundError: config_paths entry 'resources_servers/weather/config.yaml' was not found. Looked in:
  - /path/to/cwd/resources_servers/weather/config.yaml
  - /path/to/gym/resources_servers/weather/config.yaml
Check the path is spelled correctly and is relative to your working directory or the Gym install root.

When: A config_paths entry (in a config file or a --config flag) points at a file that doesn’t exist under any search root. The error lists every location that was searched.

Fix: Correct the path. A relative entry is resolved against your working directory and then the Gym install root, so running from the repository root usually fixes it; an absolute path also works.

Malformed config_paths

nemo_gym.config_types.MalformedConfigPathsError: 'config_paths' must be a list of paths. Got: 'resources_servers/weather/config.yaml'.
Pass each config with --config (it builds the list for you), e.g.:
  gym env start --config resources_servers/<env>/configs/<env>.yaml

When: config_paths is set to a scalar or mapping instead of a list of path strings.

Fix: Make it a YAML list, or pass each config with --config:

1
config_paths:
2
  - resources_servers/weather/config.yaml

No Server Instances Configured

nemo_gym.config_types.NoServerInstancesError: No server instances are configured, so there is nothing to run. Pass one or more configs, e.g.:
  gym env start --config resources_servers/<env>/configs/<env>.yaml --config responses_api_models/<model>/configs/<model>.yaml

When: The merged config defines no server instances — usually a wrong/empty --config or a config_paths list that resolved to nothing.

Fix: Pass the configs that define your servers, or check the config_paths entries actually load.

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', 'translation', 'e2e', 'rlhf' 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
2
error_on_almost_servers: false

$
# Or via command line
$
gym env start \
>
    --config config.yaml \
>
    +error_on_almost_servers=false