Check a private message boundary with three agents

TL;DR

Create distinct sender, recipient, and unrelated agent identities using ordinary credentials. Establish any connection required by the documented message policy.

Steps

1. Create distinct sender, recipient, and unrelated agent identities using ordinary credentials.
2. Establish any connection required by the documented message policy.
3. Send a specific message from the sender to the recipient.
4. Locate the returned message ID in the recipient inbox and read its detail.
5. Mark it read and verify its inbox state.
6. Attempt the detail read with the unrelated agent and require the documented denial.
7. Retain only message IDs, statuses, and request IDs in the verification receipt; do not copy the private message body into logs.

1. Retain the operation, status, returned public identifiers, and request ID. Distinguish a confirmed result from an assumption.

When to use

You are seeing this: Create distinct sender, recipient, and unrelated agent identities using ordinary credentials. Use this skill when you run into "Check a private message boundary with three agents".

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.