Changes in version 0.2.0 (2026-04-29)                  

New features

  - JSON serialization for both core handoff objects:
    write_dependency_graph() / read_dependency_graph() and
    write_split_spec() / read_split_spec(). The on-disk format is
    documented under ?write_dependency_graph and ?write_split_spec,
    carries a schema_version field, and round-trips NA values
    faithfully. This makes splitGraph objects portable across R sessions
    and across language boundaries (Python, Julia, CLI tools — anything
    that can read JSON). Requires jsonlite (added to Suggests); a
    helpful error is raised if it is not installed.
  - A new vignette, adapter-cookbook, walks through three small adapter
    patterns: a base-R leave-one-group-out adapter (executed), a
    grouped-CV adapter built on rsample::group_vfold_cv()
    (illustrative), and an ordered-evaluation adapter built on
    rsample::rolling_origin() (illustrative). It also shows the JSON
    cross-language handoff path.
  - validate_graph() and validate_depgraph() now accept a documented
    validation_overrides argument. Currently supported override:
    allow_multi_subject_samples (default FALSE); when TRUE, samples
    linked to multiple subjects are not flagged by the semantic
    validator and derive_split_constraints(mode = "subject") keeps the
    first listed assignment instead of erroring. The override mechanism
    is now first-class and merges into any graph-level override for the
    duration of the call only.
  - derive_split_constraints(mode = "subject") honors
    allow_multi_subject_samples consistently with validate_graph(). When
    the override is active and ambiguity exists, the choice is recorded
    in metadata$warnings so it is not invisible.
  - query_paths() now applies a finite default safety cap on max_length
    (8 edges) so that igraph::all_simple_paths() cannot blow up on dense
    graphs. Pass max_length = Inf to opt out and search exhaustively, or
    any non-negative integer for an explicit cap. Negative values and
    non-numeric inputs are rejected with a clear error.

Improvements

  - build_dependency_graph() returns a more useful error when edge
    endpoints don't match any node ID and the mismatch looks like a
    prefix problem (e.g. edges built with from_prefix = TRUE but nodes
    built with prefix = FALSE). The error now points at the likely
    cause.
  - graph_from_metadata() warns when it constructs Outcome nodes from a
    numeric outcome_value column (which produces outcome:0 / outcome:1
    nodes that are usually not what the user wants). To silence the
    warning, pass outcome_id (character class label) instead, or coerce
    outcome_value to character first.
  - The data-model schema_version is now explicitly decoupled from the
    package version. Bumping the package will not bump the schema; only
    an explicit, documented schema change should.

Deprecations

These remain functional in 0.2.0 but emit .Deprecated() warnings and are
scheduled for removal in a future release. Use the canonical names
instead:

  - validate_graph(checks = …) → use levels = … and severities = ….
  - build_depgraph() → use build_dependency_graph().
  - validate_depgraph() → use validate_graph().
  - new_depgraph_nodes() → use graph_node_set().
  - new_depgraph_edges() → use graph_edge_set().
  - new_depgraph() → use dependency_graph().

Documentation

  - README and the main vignette now use outcome_id (character) in their
    quick-start example instead of numeric outcome_value, matching the
    new warning behavior.
  - The validation_overrides parameter and the
    allow_multi_subject_samples key are now documented on
    ?build_dependency_graph / ?validate_graph.

                 Changes in version 0.1.0 (2026-04-21)                  

Initial public release. Highlights:

  - Typed dependency-graph construction from canonical metadata via
    graph_from_metadata(), or from explicit node and edge tables via
    create_nodes() / create_edges() / build_dependency_graph().
  - Structural, semantic, and leakage-relevant validation
    (validate_graph()), typed query helpers, and projected
    sample-dependency detection.
  - Split-constraint derivation (derive_split_constraints()) for
    subject, batch, study, time, and composite modes, translated into a
    stable, tool-agnostic split_spec via as_split_spec() with preflight
    validation and leakage-risk summaries.
  - plot() method for dependency_graph with a typed, layered layout,
    per-type node colors, and an auto-generated node-type legend.
  - splitGraph emits split_spec objects without runtime dependencies on
    downstream tooling. Adapters are expected to live in consumer
    packages (e.g. packages built on top of rsample) so that splitGraph
    itself stays neutral.

See the README for a full feature overview and a runnable Quick Start.