Configuration

Configuration is read from environment variables when the service starts. Empty values are treated as unset where a default is available.

Server and authentication

Variable	Default	Description
API_TOKEN	Required	Bearer token for POST /print. Must contain at least 32 characters.
HOST	0.0.0.0	Hostname or address on which the server listens.
PORT	3000	Server port from 1 through 65535.

Printer

Variable	Default	Description
PRINTER_NAME	CUPS default	CUPS queue to use.
PRINTER_TYPE	epson	Printer command set: epson or star.
PRINTER_WIDTH	48	Printable text width in characters.
PRINTER_DOT_WIDTH	576	Printable raster width in dots.
PRINTER_CHARACTER_SET	pc437_usa	Character set used to encode printer text.
PRINT_TIMEOUT_MS	15000	Maximum time allowed for submission to CUPS.
CUPS_SERVER	/run/cups/cups.sock in Compose	CUPS server or socket used by the CUPS client.

Optional interfaces

Variable	Default	Description
EXPOSE_DOCS	false	Exposes the Scalar API reference at /docs.
EXPOSE_LLMS_TXT	false	Exposes generated Markdown API documentation at /llms.txt.
EXPOSE_MCP	false	Exposes the MCP endpoint at /mcp.
MCP_TOKEN	Unset	Separate bearer token for MCP. Required and at least 32 characters when MCP is enabled.

Request and image limits

Variable	Default	Description
MAX_REQUEST_BODY_BYTES	10485760	Maximum HTTP request size in bytes.
MAX_BLOCKS_PER_PRINT_JOB	50	Maximum number of blocks in one print request.
MAX_TEXT_CHARS_PER_BLOCK	5000	Configurable text limit used by text-bearing blocks.
MAX_IMAGE_INPUT_PIXELS	25000000	Maximum decoded image pixel count.
ALLOW_REMOTE_IMAGE_URLS	false	Allows image blocks to fetch supported images over HTTPS.
MAX_REMOTE_IMAGE_BYTES	5242880	Maximum remote image download size in bytes.
REMOTE_IMAGE_TIMEOUT_MS	5000	Remote image request timeout.

The generated /openapi.json reflects configuration-dependent request limits for the running server.