eugeneo17 opened a new pull request, #71730:
URL: https://github.com/apache/airflow/pull/71730

   closes: #53402
   
   TriggerDagRunOperator gains an opt-in auto_clear_failed_tasks flag (default 
False) that lets a parent-task retry resume a failed child run from its point 
of failure instead of dead-ending.
   
   **Motivation**
   Chained-DAG pipelines commonly pin the child's trigger_run_id (or its 
logical_date) so the child run is idempotent, one run per business date/key, so 
a parent retry doesn't spawn duplicate child runs. But with 
wait_for_completion=True, that same stability makes retries a dead end: once 
the pinned child run has failed, re-running the parent task raises 
DagRunAlreadyExists, and the only escape today is reset_dag_run=True, which 
wipes the whole child and re-runs tasks that already succeeded. There is no way 
to resume a failed child from where it stopped without manual cleanup.
   
   **What this does**
   On the parent task's retry, when the pinned child run already exists in a 
terminal failed state, auto_clear_failed_tasks=True clears only the failed 
tasks (and their downstream) of that run and re-runs them, preserving 
already-successful tasks - the child resumes rather than restarts or errors.
   
   The failed-only clear is delivered server-side via a new Execution API 
version (2026-11-13, AddOnlyFailedToClearDagRunPayload); the only_failed flag 
is threaded operator → task-runner → supervisor → SDK client, and on a 409 
conflict the client routes the trigger to the /clear endpoint with 
only_failed=true.
   reset_dag_run keeps precedence: if both are set the whole run is cleared, 
and at most one clear ever happens.
   It is version-gated, against a core older than 2026-11-13 the operator 
raises NotImplementedError rather than silently downgrading to a whole-run 
clear.
   
   **Scope and notes**
   Synchronous only (wait_for_completion=True); not supported with 
deferrable=True (setting both raises ValueError).
   Because previously-successful child tasks are not re-run and failed ones 
are, the triggered DAG's tasks should be idempotent - called out in the 
operator docstring and the operator guide.
   A healed child run's final state reads success, so run-level alerting won't 
see the transient failure (per-attempt logs are preserved). Emitting a 
metric/event when a heal fires would close that gap and is proposed as a 
follow-up rather than part of this PR.
   
   **Testing**
   Unit tests for the operator, the Task SDK 
(comms/supervisor/task-runner/client), and the Execution API version + payload. 
Includes a regression test asserting the failed-only clear is reached when 
reset_dag_run=False (the auto_clear path), which fails against a client that 
gates the clear on reset_dag_run alone.
   
   Was generative AI tooling used to co-author this PR?
   [X] Yes (please specify the tool below)
   Generated-by: Claude Code (Opus 4.8) following [the 
guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions)


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