## TL;DR
Fix this in the Salesforce writeback by acting on the exact message first: checkpoint the signed quote writeback payload before syncing, on a login expiry sign in again and replay the saved payload to Salesforce, then confirm the opportunity shows the signed quote. Do not rerun the whole job unchanged, because the same inputs produce the same failure. Prove the fix on one item, then rerun the full scope and reconcile the counts.

```text
OAuth token expired mid proposal sync agent lost Salesforce writeback for signed quote
```

## Use this when
- The operation in the Salesforce writeback fails with this exact message: OAuth token expired mid proposal sync agent lost Salesforce writeback for signed quote.
- The same failure repeats on retry with unchanged inputs.
- A proposal, quote or send is blocked until this item completes.

## Not for this skill when
- The message is a permission or outage notice from the platform. Resolve that first, then return here if this error remains.
- The operation completes and you only disagree with its output. That is a quality review, not this failure.

## Steps
1. Reproduce the failure with the smallest scope that still shows it in the Salesforce writeback, and copy the full message plus the proposal, quote or account involved into the run notes. Verify: the error is reproduced on demand with a named item, not only seen in a log.
2. Apply the specific fix for this error: checkpoint the signed quote writeback payload before syncing, on a login expiry sign in again and replay the saved payload to Salesforce, then confirm the opportunity shows the signed quote. Verify: the opportunity shows the signed quote after the replay and the writeback log shows one successful write.
3. Check the neighbouring items that share the same template, integration, pricebook or account, because this class of failure rarely affects only one item. Verify: the neighbouring items are listed and each is marked affected or clear.
4. Compare the result against the source system in the Salesforce writeback so a silent partial success is caught before sign off. Verify: counts and key values match the source or every difference is named and explained.
5. Rerun the original operation in the Salesforce writeback on the previously failing scope, watching for the same message rather than assuming success from a quiet log. Verify: the operation completes and the original message does not appear.
6. Record the fix, the triggering input and the verification result on the item so the next occurrence is recognised immediately. Verify: the record names the error, the fix applied and the evidence of success.

## Why it happens
the login expired during sync and the writeback payload existed only in the failed call, so the signed state never reached Salesforce.

## Variant phrasings

### OAuth token expired mid proposal sync agent lost Salesforce writeback for signed quote
The verbatim form searchers paste from the terminal or console. Treat it identically: same fix, same single item proof, then the full rerun.

### How to fix: OAuth token expired mid proposal sync agent lost Salesforce writeback for signed quote
The how-to phrasing for the same failure in the Salesforce writeback. The steps above apply unchanged; start at the reproduction step rather than skipping to the rerun.

### Troubleshooting this failure in the Salesforce writeback
The symptom-first phrasing used when the console hides the full message. Surface the full message first, confirm it matches the code block above, then follow the steps.

Compatibility: the Salesforce writeback at current versions, plus the platform API or console the query names; no extra tooling beyond the source system access needed to verify counts.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_c2x30rhhy6QfeBaMDYvulw