[dan-newton-sparta]

ASSET_MATERIALIZATION_PLANNED emitted a placeholder output dataset with no inputs and no facets. This change emits it as a pure run-start; the COMPLETE event still carries the full inputs, outputs, and facets.

Summary & Motivation

A planned/START event has no materialization metadata yet — no inputs, no schema, no column lineage. For lineage backends that build edges from every event this can produce an output-only edge with no input side. Emitting START as a pure run-start signal keeps the run-start semantics while deferring all dataset/facet information to COMPLETE, where it is actually known.

How I Tested These Changes

• Updated the adapter and end-to-end tests: START now asserts no inputs/outputs; COMPLETE still carries the output.
• uv run pytest green; ruff check, ruff format --check, and ty check . clean.
• Tested locally end to end: ingested the emitted OpenLineage events into OpenMetadata and used it to visualise the resulting lineage.

Changelog

Added a ### Changed entry under ## [Unreleased] in CHANGELOG.md.

Related changes

Part of a set of small improvements to Dagster → OpenLineage. The lineage-fidelity changes are each independent and mergeable on their own; the ownership pair is stacked (#354 builds on #353).

Lineage fidelity:

• feat(dagster-openlineage): decouple job namespace from dataset namespace #344 — decouple job namespace from dataset namespace
• fix(dagster-openlineage): emit asset run-start without a placeholder output #345 — emit asset run-start without a placeholder output
• feat(dagster-openlineage): derive asset inputs from column lineage #346 — derive asset inputs from column lineage
• feat(dagster-openlineage): add exclude_asset_keys to the storage wrapper #347 — add exclude_asset_keys to the storage wrapper

Ownership:

• feat(dagster-openlineage): emit jobType and per-asset ownership facets #353 — emit jobType and per-asset ownership facets
• feat(dagster-openlineage): read native asset owners in the sensor #354 — read native asset owners in the sensor (builds on feat(dagster-openlineage): emit jobType and per-asset ownership facets #353; until feat(dagster-openlineage): emit jobType and per-asset ownership facets #353 merges its diff includes feat(dagster-openlineage): emit jobType and per-asset ownership facets #353's commit)