Command Helper Secret Source

Resolve credentials by running your own helper command at startup — any secret store with a CLI works: keepassxc-cli, secret-tool (GNOME Keyring), pass, gpg, Vaultwarden's CLI, or a script that cats a tmpfs env file. The helper prints KEY=VALUE lines on stdout; Hermes applies them through the same orchestrator as Bitwarden and 1Password, so you can enable any combination of sources simultaneously.

How it works

1. You configure a helper command in config.yaml (never in .env — the command is configuration, .env holds values).
2. At startup, after .env loads, Hermes runs the helper ONCE via /bin/sh -c and parses its stdout as a dotenv blob.
3. The parsed keys flow through the standard precedence ladder: .env/shell win unless override_existing: true; mapped sources beat this bulk source on contested vars; first claim wins.

secrets:
  command:
    enabled: true
    command: "cat /run/user/1000/hermes-secrets.env"
    # or any vault CLI that dumps KEY=VALUE lines:
    # command: "pass show hermes/env"
    # command: "secret-tool lookup service hermes-env"

Config

Key	Default	What it does
enabled	false	Master switch.
command	""	Helper run via /bin/sh -c; must print KEY=VALUE lines on stdout.
helper_timeout_seconds	3	Hard timeout for one helper run. Deliberately tight — the helper must be fast and NON-interactive (no unlock prompts, no touch/PIN).
override_existing	false	Helper values overwrite .env/shell values. Off by default (unlike Bitwarden/1Password) since a local helper is not a central rotation authority.

Security model

• The helper command string is YOUR configuration — same trust level as the .env file you control.
• Output is hard-capped at 1 MiB; a runaway helper can't wedge startup (process group killed on timeout).
• The helper's stderr is discarded — vault CLI diagnostics can carry secret material, so they never reach Hermes' output. Failures log structured fields only (exit code / signal / errno), never the command string.
• Whitespace-only values are treated as "no value" — a placeholder entry never flows into an Authorization header.
• POSIX-only (needs /bin/sh). On Windows the source reports itself unconfigured and startup continues.

Failure modes

Startup is never blocked. Errors print one line plus a → remediation hint:

Symptom	Cause	Fix
secrets.command.command is empty	Enabled without a command	Set secrets.command.command in config.yaml
helper command failed	Non-zero exit, timeout, spawn failure	Run the helper manually in a shell to see its real error (Hermes discards its stderr on purpose)
helper output was not a KEY=VALUE map	Helper printed a bare value or garbage	Make the helper emit dotenv-shaped lines

When to use this vs a plugin

The command source is the escape hatch for vaults without a bundled integration. If you find yourself wrapping a complex CLI dance in a long script, consider a proper secret-source plugin instead — plugins get caching, provenance labels, and typed config.