Stage parameters

stages is a list of dictionaries or nodus.StageSpec values. A nonempty list replaces the top-level source. Use Python or [[stages]] entries in a workload file. Do not combine framework with explicit stages: a recognized framework takes precedence in the current compiler.

Stage field	Type	Omission / purpose
`id`	Unique string, 1–64 characters	Required. Letters, digits, `_`, `-`, `.`. Cannot start with `.` or `-`
`source`	`{image: str, command: list[str], asset_id?: str}`	Give explicit executable argv and image. Missing image defaults to Python image server-side
`depends_on`	List of stage IDs	Empty. Dependency edges must be acyclic
`inputs`	List of input references below	Empty
`outputs`	Mapping from logical name to relative output path. Name and path constraints	Empty. Files must actually be produced
`requirements`	Requirements dictionary	Zero/empty fields inherit workload-level values
`continuity`	`nodus.ContinuitySpec`	Missing/empty mode inherits workload mode and resume behavior. Missing/empty `checkpoint_paths` inherits workload paths
`total_units`	Nonnegative integer progress-unit count	`0`. Describes units for compatible restartable work, not GPUs or replicas

A stage-specific nonempty continuity.mode does not receive the SDK top-level resume default: provide resume_on_interruption explicitly. Setting only that flag without a mode does not override inherited mode and resume behavior.

A nonempty stage checkpoint_paths list overrides workload paths independently of mode. New workloads default to ["state"]. Use ["."] to opt a stage into preserving the whole code folder. See checkpoint paths.

Input field	Meaning
`name`	Local logical input name
`from_stage`	Upstream stage ID. Also include it in `depends_on`
`from_output`	Declared output name on the upstream stage

Always declare producer outputs and complete input references so a typo can be caught before execution. Output paths are relative to the runner's working directory. Runtime integrations expose resolved inputs through NODUS_INPUT_<name>. The value is a local file path, not the original storage URI.

Stage requirements support model, compute_class, dataset_bytes, peak_memory_gb, disk_gb, vcpus, gpu, and notes. The optimization field remains accepted for compatibility but has no preference effect on new runs. See resources and the complete multi-stage example.