# murk environment variable reference
The environment variables murk reads, and the CLI flags they mirror where one exists. This is the terse reference; the narrative version with resolution order and interactions lives in the Environment variables concept page.
## Identity and vault selection
| `MURK_KEY` | Your raw age private key (`AGE-SECRET-KEY-1…`), inline. Rejected for hardware-plugin identity strings (`AGE-PLUGIN-…`) — use `MURK_KEY_FILE` for those. |
| `MURK_KEY_FILE` | Path to a private-key file: a raw age key, an SSH PEM key, or an age plugin identity file. `murk init` writes this reference into `.env`. |
| `MURK_VAULT` | Vault filename, defaulting to `.murk`. Equivalent to passing `--vault` on every command (the one variable in the clap model). |
## Safety and agent context
| `MURK_STRICT` | Truthy fails closed rather than let a secret touch disk, and disables the automatic key lookup under `~/.config/murk/keys`. |
| `MURK_AGENT` | Marks the process as running for an AI agent. Forces strict mode unconditionally; `murk agent exec` sets it on its child. |
| `MURK_SELF_SCOPE` | Truthy holds your own key to the vault's agent allow-tag policy, as if you were an agent. Implied inside an agent context. |
| `MURK_NO_SIGNER_PIN` | Opts out of signer-registry pinning (TOFU) on load — an escape hatch for a deliberate signer-key change, not for everyday use. |
## Also honored
| `CI` | Truthy prints a one-line nudge toward the scoped-agent path when a pipeline decrypts with a personal key. Advisory only. |
| `EDITOR, VISUAL` | Editor launched by `murk edit`, checking `EDITOR` then `VISUAL`, falling back to `vi`. |
| `XDG_RUNTIME_DIR` | Preferred (typically tmpfs) scratch location for `murk edit`'s temporary file, over `/tmp`. |
| `HOME (USERPROFILE on Windows)` | Base directory for murk state: `~/.config/murk/keys`, `agent-keys`, and `signer-pins`. |