Environment variables

Most shaping vars are HERMES_OTEL_*-prefixed and override the corresponding field in ~/.hermes/hermes_otel.yaml; backend vars (OTEL_PHOENIX_ENDPOINT, LANGSMITH_TRACING, …) select a single backend when no backends: list is configured.

The complete list

Every variable, grouped by purpose, is in the env var reference — backend selection, the HERMES_OTEL_* overrides (generated from the config dataclass), paths and debug. This page only covers where to set them and how they combine with the yaml file.

Precedence

For every field: HERMES_OTEL_<FIELD> env var → value in ~/.hermes/hermes_otel.yaml → built-in default. Maps (headers, global_tags, resource_attributes) and backends are yaml-only. Booleans accept true/1/yes/on and false/0/no/off (case-insensitive); anything else logs a warning and is ignored.

Where to set them

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.