Environment variables

devhost passes each service its port, its hostname, and the ports of the other services, alongside any variables you set yourself. You can also read your own environment inside the manifest.

Set variables for a service

[services.web]
command = ["bun", "run", "dev"]
port = "auto"
env = { NODE_ENV = "development", API_URL = "{{ services.api.url }}" }

Each service inherits devhost’s environment, plus its env table, plus the variables below. To pass a value that another service gets at startup, such as an automatic port, use a service reference like the one above.

Variables devhost sets

Variable	Set when	Value
PORT	The service has a port	The port to listen on, including one chosen by port = "auto"
DEVHOST_BIND_HOST	Always	The address to listen on (the service’s bindHost, 127.0.0.1 by default)
DEVHOST_HOST	The service has a host	Its public hostname; the first one when host is a list
DEVHOST_PATH	The service has a host and a path	Its public path prefix, for mounting a router under it
DEVHOST_PORT_<NAME>	Any service in the manifest has a port	That service’s port. The name is upper-cased, with other characters as _: postgres-db becomes DEVHOST_PORT_POSTGRES_DB.
DEVHOST_SERVICE_NAME	Always	The service’s name in the manifest
DEVHOST_MANIFEST_PATH	Always	The absolute path of the root manifest

Bind your server to DEVHOST_BIND_HOST and PORT only. The other variables describe the service and its neighbors; never use them as a listening address. Other DEVHOST_* variables are internal and can change without notice.

• External services (managed = false) get none of these, because devhost does not start them.
• injectPort = false keeps devhost from setting PORT, while routing and health checks still use the configured port. Use it when one command starts several servers; see One command runs several dev servers.
• Setting PORT does not make $PORT work inside command, which runs without a shell; see Service commands and working directories.

Each process receives these values when it starts. When a reload or Restart Stack changes a port, devhost restarts the services whose variables change, so they never hold a stale port. A single-service restart keeps its port, so nothing else needs to restart. Chat sessions keep the environment they started with.

Environment variables in the manifest

Any string in the manifest can read your environment with {{ env.NAME }}, including names, hostnames, paths, cwd, commands, and env values:

name = "{{ env.USER }}-stack"

[services.web]
command = ["bun", "run", "dev"]
port = "auto"
host = "web-{{ env.USER }}.localhost"

• A name starts with a letter or underscore, followed by letters, digits, or underscores.
• An unset variable is an error when the manifest is read. A variable set to an empty string expands to nothing.
• Text that is not a valid placeholder stays as written, including a {{ that is never closed.

devhost reads the environment it was started with, and does not load .env files. Use a tool such as direnv to export variables per project.