Env var reference
Complete list. See Environment variables for the narrative version.
Backend selection
| Var | Value | Effect |
|---|---|---|
LANGSMITH_TRACING | true/false | Enables LangSmith backend |
LANGSMITH_API_KEY | lsv2_... | LangSmith auth |
LANGSMITH_ENDPOINT | URL | LangSmith endpoint (default: https://api.smith.langchain.com) |
LANGSMITH_PROJECT | string | LangSmith project name |
OTEL_LANGFUSE_PUBLIC_API_KEY | pk-lf-... | Langfuse public key (plugin-specific) |
OTEL_LANGFUSE_SECRET_API_KEY | sk-lf-... | Langfuse secret key (plugin-specific) |
OTEL_LANGFUSE_ENDPOINT | URL | Langfuse OTLP endpoint |
LANGFUSE_PUBLIC_KEY | pk-lf-... | Langfuse public key (SDK-standard) |
LANGFUSE_SECRET_KEY | sk-lf-... | Langfuse secret key (SDK-standard) |
LANGFUSE_BASE_URL | URL | Langfuse base URL (SDK-standard) |
OTEL_SIGNOZ_ENDPOINT | URL | SigNoz OTLP endpoint (self-host: http://localhost:4328/v1/traces) |
OTEL_SIGNOZ_INGESTION_KEY | sz-... | SigNoz Cloud ingestion key |
OTEL_JAEGER_ENDPOINT | URL | Jaeger OTLP endpoint (http://localhost:4318/v1/traces) |
OTEL_TEMPO_ENDPOINT | URL | Tempo OTLP endpoint |
OTEL_PHOENIX_ENDPOINT | URL | Phoenix OTLP endpoint (http://localhost:6006/v1/traces) |
OTEL_PROJECT_NAME | string | Resource service.name + openinference.project.name |
Shaping overrides
| Var | Maps to | Default |
|---|---|---|
HERMES_OTEL_ENABLED | enabled | true |
HERMES_OTEL_SAMPLE_RATE | sample_rate | null (AlwaysOn) |
HERMES_OTEL_ROOT_SPAN_TTL_MS | root_span_ttl_ms | 600000 (10 min) |
HERMES_OTEL_FLUSH_INTERVAL_MS | flush_interval_ms | 60000 (60s) |
HERMES_OTEL_PREVIEW_MAX_CHARS | preview_max_chars | 1200 |
HERMES_OTEL_CAPTURE_PREVIEWS | capture_previews | true |
HERMES_OTEL_CAPTURE_CONVERSATION_HISTORY | capture_conversation_history | false |
HERMES_OTEL_CONVERSATION_HISTORY_MAX_CHARS | conversation_history_max_chars | 20000 |
HERMES_OTEL_PROJECT_NAME | project_name | (unset) |
HERMES_OTEL_SPAN_BATCH_MAX_QUEUE_SIZE | span_batch_max_queue_size | 2048 |
HERMES_OTEL_SPAN_BATCH_SCHEDULE_DELAY_MS | span_batch_schedule_delay_ms | 1000 |
HERMES_OTEL_SPAN_BATCH_MAX_EXPORT_BATCH_SIZE | span_batch_max_export_batch_size | 512 |
HERMES_OTEL_SPAN_BATCH_EXPORT_TIMEOUT_MS | span_batch_export_timeout_ms | 30000 |
HERMES_OTEL_FORCE_FLUSH_ON_SESSION_END | force_flush_on_session_end | true |
Logs
See OTel logs for behavior.
| Var | Maps to | Default |
|---|---|---|
HERMES_OTEL_CAPTURE_LOGS | capture_logs | false |
HERMES_OTEL_LOG_LEVEL | log_level | INFO |
HERMES_OTEL_LOG_ATTACH_LOGGER | log_attach_logger | (unset = root) |
Debug
| Var | Value | Effect |
|---|---|---|
HERMES_OTEL_DEBUG | true/false | Enables debug log at ~/.hermes/plugins/hermes_otel/debug.log |
Boolean accepted values
| True | False |
|---|---|
true / 1 / yes / on | false / 0 / no / off / "" |
Case-insensitive. Anything else → warning + fallback to default.