[jason810496]

TS SDK: reject a Dag whose order-only edges form a cycle

• Depends on TS SDK: add task groups to the native Dag surface #73439 get merged first (only the last commit is new here).
• Diff for early review: jason810496/airflow@feature/ts-sdk/task-groups...feature/ts-sdk/dag-cycle-detection
• next: TS SDK: serialize a native Dag to Dag JSON #73441
• Part of the native TypeScript Dag stack, TS SDK: declare task dependencies by calling tasks #73435 to TS SDK: cover native TypeScript Dags end to end #73446, to be merged in order.

Why

A cycle through arguments cannot be written: a reference exists only once its producing call has returned. before and after join two references that already exist, so they can form one, and Airflow would reject the Dag long after the author left.

How

• An iterative three-colour DFS over the combined graph — wiring edges and order-only edges together — run when the Dag is read.
• The error names the tasks on the cycle, in order, so the edge to remove is visible without redrawing the graph.
• The check sees through groups: a group edge stands for every task the group holds, nested groups included.

What

• src/sdk/cycle.ts, and the check in the Dag's own close step.

---

Was generative AI tooling used to co-author this PR?

• Yes, with help of Claude Code Opus 5 following the guidelines

[jason810496]

Closing: cycle validation moves to the core side, where the Dag processor receives the Dags a language SDK sends, so the TypeScript SDK does not need its own check. #73441 now builds directly on #73439.