hermes - 💡(How to fix) Fix Langfuse SDK plugin: placeholder API key silent failure [1 pull requests]

Bug Description

When HERMES_LANGFUSE_PUBLIC_KEY is set to a placeholder value (e.g., a dummy key or misconfigured secret), the Langfuse SDK plugin registers hooks successfully but never emits any traces. Critically, it produces zero errors, logs, or warnings — making the failure completely invisible to the operator.

Steps to Reproduce

1. Set HERMES_LANGFUSE_PUBLIC_KEY to a non-functional placeholder string
2. Start Hermes Agent with the Langfuse plugin enabled
3. Observe that the plugin initializes without errors and hooks are registered
4. Execute any agent interaction that should produce traces
5. Check Langfuse — no traces appear

Expected Behavior

The plugin should either:

• Validate the API key on initialization (e.g., a lightweight auth check against the Langfuse API) and fail loudly with a clear error, OR
• Emit a warning when traces fail to be ingested after N attempts

Actual Behavior

Silent failure. The plugin registers hooks, the agent operates normally, but zero traces are ever emitted. No error, no warning, no indication of misconfiguration.

Impact

Observability is the primary debugging surface for agent behavior. A silent trace gap means operators lose visibility into agent runs without any signal that something is wrong. This is especially dangerous in production deployments where trace completeness is assumed.

Environment

• Hermes Agent (current)
• Langfuse SDK plugin (any version where the API key is configurable)
• Reproducible with any non-valid placeholder key

/label ~observability