File Writer

Overview

The File Writer node writes data to a file in the configured storage backend (local gateway filesystem or cloud storage). Use it to persist battle outputs, model responses, or intermediate workflow data as files for downstream consumption or export. The node emits an error port on write failure, allowing workflows to handle storage errors without halting. A valid storage destination (path and bucket/directory) must be configured before the node can execute.

Configuration

Field	Type	Required	Description
destination_path	string	Yes	Target file path relative to the storage root (e.g. results/battle-123/output.json). Supports template variables such as {{run_id}} and {{timestamp}}.
storage_bucket	string	Yes	Name of the storage bucket or root directory to write into. Must exist and be writable by the workflow's service credentials.
write_mode	enum	No	Controls behavior when the target file already exists. One of overwrite (default), append, or error_if_exists.
content_type	enum	No	MIME type hint for the stored file. One of text/plain, application/json, text/csv, or application/octet-stream. Defaults to application/json when the input data is an object.
create_dirs	boolean	No	When true, automatically creates any missing parent directories in destination_path. Defaults to false.

Inputs

Port	Type	Description
data	any	The content to write to the file. Accepts strings, objects (serialized to JSON), or binary buffers. If an object is received, it is serialized with JSON.stringify before writing.

Outputs

Port	Type	Description
output	object	Emitted on success. Contains { path: string, bytes_written: number, storage_bucket: string } describing the written file.
error	object	Emitted when the write fails (e.g. permission denied, bucket not found, disk full). Contains { message: string, code: string, destination_path: string }.

Example

{
  "nodeType": "file_writer",
  "config": {
    "destination_path": "battles/{{run_id}}/judge-output.json",
    "storage_bucket": "battle-artifacts",
    "write_mode": "overwrite",
    "create_dirs": true
  }
}