A duplicate start() takes the holder's handle from DBOS - #319
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czpython merged 1 commit intoAug 24, 2026
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The dedup collision arm caught DBOSQueueDeduplicatedError, looked the holder up through private API, and recursed when the holder reached terminal between the rejection and the lookup. DBOS 2.30's return-existing duplication policy does all three natively: on a held slot the enqueue returns the holder's handle, with the terminal race retried inside DBOS.
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August 24, 2026 10:26
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Workflow.start()claims a subject's run slot with DBOS queue deduplication. The collision arm hand-rolled what DBOS 2.30 now does natively: it caughtDBOSQueueDeduplicatedError, looked the holder up through private API (_get_dbos_instance()._sys_db.get_deduplicated_workflow), and recursed intostart()when the holder reached terminal between the rejection and the lookup.With
duplication_policy="return-existing"on the enqueue, a held slot returns the holder's handle instead of raising, and DBOS retries the terminal race internally (_core.py, theinit_workflowloop). A fresh enqueue ishandle.workflow_id == workflow_id— the minted id — and keeps its row creation and SCHEDULED event; a duplicate returns the holder's id bare, same as before.Net: the private
_sys_dbreach, the exception import, and the recursion are gone; behavior is unchanged and the existing dedup tests (test_duplicate_start_returns_the_live_run,test_duplicate_start_shares_the_run_across_accounts,test_failed_enqueue_claims_no_slot) pin it end to end.