Cloud Tasks batch create is GA: one Sume idempotency key per task

When you enqueue Sume generations with the new Cloud Tasks batch create, put a distinct Idempotency-Key header on each task, derived from the business item and not from the batch. Google's release notes list batch create, batch delete and per-task retry parameters as generally available on September 30, 2026. A batch call that fails halfway is easy to repeat, and stable per-item keys are what make the repeat safe.

What Google shipped

From the Cloud Tasks release notes:

Why the key belongs to the item

Cloud Tasks delivers at least once, so a handler can run twice. Sume's rule is simple: the same key with the same body returns the original job, and the same key with a different body returns 409 idempotency_conflict. If the key came from the batch, a re-created batch would collide on unrelated items. If it came from a random value generated in the handler, a retry would get a new key and a second paid job.

A key such as campaign-42-item-7-v1 survives handler retries, batch re-creation and operator re-runs. Change the version suffix only when you truly want a new generation.

Match retry parameters to Sume's errors

Per-task retry parameters let you set different limits per task. Sume's responses split cleanly:

• 429 rate_limited: retry, honouring retry-after.
• 429 queue_full: retry with a longer minimum back-off, because your queue capacity is max(3, 5 times concurrency).
• 402 insufficient_credits: return a non-retryable status from the handler so the task is not re-sent.
• 202 accepted: store the job id and return success; the job continues without the task.

Do not wait inside the task handler

The handler should create the job and return. Sume's sync and subscribe modes wait at most 30 seconds through wait_timeout_seconds and then ask you to poll. A client timeout does not cancel the job, so never resubmit after one. Use webhook mode and process job.completed separately, or poll /status with next_poll_after_seconds.

If you have up to 100 items of one Format, bulk-runs is a single call with a concurrency setting. Cloud Tasks is the better fit when items arrive over time or need different schedules.