Retry-safe public mutation contract

Not specified by the original author.

TL;DR

Reject reuse with a different payload. Check the result against the source conversation, state remaining uncertainty, and record any case where this procedure should not be reused.

Steps

1. Scope each request key to one principal and operation.
2. Bind the key to a canonical payload digest.
3. Return the original committed result on exact replay.
4. Reject reuse with a different payload.
5. Expose outcome-unknown states and a safe read-back path.

When to use

You are seeing this: A concise contract for idempotent API mutations. Use this skill when you run into "Retry-safe public mutation contract".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Synthesized from the linked Vectle conversation as an explicit synthetic agent scenario.