## TL;DR
Persist a per item done marker or idempotency key before the side effect, check that marker at the start of each item, and make the retry path skip finished items. Start in the Slack app config, the channel list in the new workspace, and the integration log, work on one affected item, and prove the fix there before running the full set. Most cases of this failure clear once the value named in step 2 is corrected at its source rather than retried.

```text
dashboard agent checkpoint restore duplicated scheduled deliveries: Looker plan sent twice to Slack channel
```

## Use this when
- You see this exact message or symptom in Slack: dashboard agent checkpoint restore duplicated scheduled deliveries: Looker plan sent twice to Slack channel
- One run, record, build, or object is affected and you can name it
- A retry without changing anything reproduces the same text

## Not for this skill when
- Slack fails with a different message and none of the signals here appear
- Nothing has failed yet and you are doing first time setup or general planning
- Every service from this vendor is down for all users, which is a vendor outage to wait out first

## Steps
1. Reproduce the failure once in the Slack app config, the channel list in the new workspace, and the integration log and search the log or history for the exact text in the block above, recording the time, the workspace or project, and the one object it names. Verify: you have one failing run or object identified, not a similar older failure
2. Inspect the channel id stored in the integration config, the app installation in the new workspace, and the alert routing rules, and check the done marker store, the idempotency key sent with the call, and the duplicate check that runs before each item. Verify: you can point to the specific value, field, or identity that does not match what this operation needs
3. Apply the fix at that source: persist a per item done marker or idempotency key before the side effect, check that marker at the start of each item, and make the retry path skip finished items. Verify: the corrected value or setting is visible in Slack itself, not only in a local config file
4. Re-run the original operation on the single affected item first: reinstall or re-point the app at a channel that exists in the new workspace and send one test alert. Verify: that one item completes with no trace of the error text from the block above
5. Put a guardrail on the agent run before widening it: cap retries and runtime for this step, require the agent to cite the record it acted on, and stop the run if the same item fails twice with the same text. Verify: a deliberately repeated failure stops the run and is reported instead of looping or being marked as success
6. Check the downstream result a user or the next job would see: the test churn alert appearing in the intended channel and the integration log showing a successful post. Verify: the downstream result agrees with the source for the test item, in value and in timestamp
7. Repeat for the full set, watch the first few items in the same log you started from, and write the root cause and the changed setting into the run notes. Verify: the full run finishes, the notes name the error and the changed setting, and no earlier item regressed

## Variant phrasings
### dashboard agent checkpoint restore duplicated scheduled deliveries: Looker plan sent twice to Slack channel
The subject-first phrasing of the same failure. The fix is the same, start at step 1 and confirm the object the log names.
### Slack version of this failure
The tool-first phrasing searchers use once they know which system raised it. It is the same underlying problem, not a separate bug.
### Why does dashboard agent checkpoint restore duplicated scheduled deliveries: Looker plan sent twice to Slack channel keep happening after a retry
The repeat-occurrence phrasing. A retry without the step 2 and step 3 checks almost always reproduces it, because the cause sits in the object state, not in the attempt.

Compatibility: Slack apps and chat.postMessage API, workspace migrations, current Slack API. The steps assume you can read the job or build log and change the named object in Slack.

## Why it happens
In Slack, this failure usually means the run has no durable record of work already done, so a retry or a new sync repeats items it already finished. The visible message is raised at the point where the bad state is consumed, which is rarely where it was created, so fixing the message text or retrying the last step changes nothing. Correcting the state at its source, then re-running one item and comparing the downstream result against the source, is what separates a real fix from a run that only looks successful.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_Yq9DPKoPCXlKNmlWSQMV1A