Environment variables

All env vars the plugin reads. Most shaping vars are HERMES_OTEL_*-prefixed and override the corresponding config.yaml field.

Backend selection

Setting any of these enables the matching backend. First match wins (see Backends overview for priority order).

Var	Backend	Example
`LANGSMITH_TRACING`	LangSmith	`true`
`LANGSMITH_API_KEY`	LangSmith	`lsv2_...`
`LANGSMITH_ENDPOINT`	LangSmith (optional)	`https://api.smith.langchain.com`
`LANGSMITH_PROJECT`	LangSmith (optional)	`hermes-langsmith-otel`
`OTEL_LANGFUSE_PUBLIC_API_KEY`	Langfuse (plugin-specific)	`pk-lf-...`
`OTEL_LANGFUSE_SECRET_API_KEY`	Langfuse (plugin-specific)	`sk-lf-...`
`OTEL_LANGFUSE_ENDPOINT`	Langfuse (plugin-specific)	`https://cloud.langfuse.com/api/public/otel`
`LANGFUSE_PUBLIC_KEY`	Langfuse (SDK-standard)	`pk-lf-...`
`LANGFUSE_SECRET_KEY`	Langfuse (SDK-standard)	`sk-lf-...`
`LANGFUSE_BASE_URL`	Langfuse (SDK-standard)	`https://cloud.langfuse.com`
`OTEL_SIGNOZ_ENDPOINT`	SigNoz	`http://localhost:4328/v1/traces`
`OTEL_SIGNOZ_INGESTION_KEY`	SigNoz Cloud	`sz-...`
`OTEL_JAEGER_ENDPOINT`	Jaeger	`http://localhost:4318/v1/traces`
`OTEL_TEMPO_ENDPOINT`	Tempo	`http://localhost:4318/v1/traces`
`OTEL_PHOENIX_ENDPOINT`	Phoenix	`http://localhost:6006/v1/traces`
`OTEL_PROJECT_NAME`	All	`hermes-agent`

Each of these overrides the corresponding field in config.yaml. See config.yaml for defaults and field-level docs.

Env var	Maps to	Type
`HERMES_OTEL_ENABLED`	`enabled`	bool
`HERMES_OTEL_SAMPLE_RATE`	`sample_rate`	float 0..1
`HERMES_OTEL_ROOT_SPAN_TTL_MS`	`root_span_ttl_ms`	int (ms)
`HERMES_OTEL_FLUSH_INTERVAL_MS`	`flush_interval_ms`	int (ms)
`HERMES_OTEL_PREVIEW_MAX_CHARS`	`preview_max_chars`	int
`HERMES_OTEL_CAPTURE_PREVIEWS`	`capture_previews`	bool
`HERMES_OTEL_CAPTURE_CONVERSATION_HISTORY`	`capture_conversation_history`	bool
`HERMES_OTEL_CONVERSATION_HISTORY_MAX_CHARS`	`conversation_history_max_chars`	int
`HERMES_OTEL_PROJECT_NAME`	`project_name`	string
`HERMES_OTEL_SPAN_BATCH_MAX_QUEUE_SIZE`	`span_batch_max_queue_size`	int
`HERMES_OTEL_SPAN_BATCH_SCHEDULE_DELAY_MS`	`span_batch_schedule_delay_ms`	int (ms)
`HERMES_OTEL_SPAN_BATCH_MAX_EXPORT_BATCH_SIZE`	`span_batch_max_export_batch_size`	int
`HERMES_OTEL_SPAN_BATCH_EXPORT_TIMEOUT_MS`	`span_batch_export_timeout_ms`	int (ms)
`HERMES_OTEL_FORCE_FLUSH_ON_SESSION_END`	`force_flush_on_session_end`	bool

Var	Effect
`HERMES_OTEL_DEBUG`	`true` enables per-span debug log to `~/.hermes/plugins/hermes_otel/debug.log`. See Debug logging.

Anywhere the plugin reads a boolean env var, the following are accepted:

Anything else logs a warning and falls back to the default.

The easiest place is ~/.hermes/.env, which Hermes auto-loads on startup:

OTEL_PHOENIX_ENDPOINT=http://localhost:6006/v1/traces
OTEL_PROJECT_NAME=hermes-agent
HERMES_OTEL_CAPTURE_PREVIEWS=true
HERMES_OTEL_SAMPLE_RATE=0.25

Or export them in your shell profile (~/.bashrc, ~/.zshrc) for a global default.

tip

Prefer ~/.hermes/.env for per-machine config. Per-shell exports are fine for experimentation but drift from what you've committed to config.yaml.