JSON logs no longer include levelname, Datadog status mapping breaks

[MonkeyLeeT]

Bug Description

• PR #3199 switched the CLI logging to a custom JsonFormatter (livekit-agents/livekit/agents/cli/log.py).
• That formatter only copies fields referenced in logging.PercentStyle.default_format, plus two hard- coded keys (level and name). It never emits the standard levelname.
• The formatter also drops levelname from extras via _RESERVED_ATTRS, so applications can’t re-add it in handlers.
• Result: production JSON logs now only contain level, not levelname. Datadog (and any tooling that expects the canonical Python field) can’t determine log status anymore.
  • As a workaround, we added ad hoc remapper logic to look at level field, but not in canonical way.

Expected Behavior

levelname is still in output json record

Reproduction Steps

Upgrade to 1.3.0+, then run agent with prod environment and json logger, and configure logging override as below

logging.PercentStyle.default_format = (
    "%(levelname)s %(message)s %(processName) %(threadName)s"
)

observe that levelname is not present in the json output

Operating System

Linux

Models Used

No response

Package Versions

livekit-agents=1.3.2

Session/Room/Call IDs

No response

Proposed Solution

Always include the levelname attribute in JSON output (the previous dependency did this by default), or provide a supported hook to restore it across processes. Otherwise every consumer has to monkeypatch json formatter before app runs, which is brittle.

Additional Context

No response

Screenshots and Recordings

No response

[longcw]

does levelname exist in the json logs before agents 1.3? I tested with 1.2.18 and it's "level": "INFO".

[MonkeyLeeT]

does levelname exist in the json logs before agents 1.3? I tested with 1.2.18 and it's "level": "INFO".

It does, you need to override the default formatting as below to expose it in final json.

    logging.PercentStyle.default_format = (
        "%(levelname)s %(message)s %(processName) %(threadName)s"
    )

But this is not working now after 1.2.18.

[MonkeyLeeT]

@longcw Any update here?

[MonkeyLeeT]

@longcw A friendly ping here.

[longcw]

the issue is that the setting of logging.PercentStyle.default_format is not used, fixed in https://github.com/livekit/agents/pull/4169