Hey Uday,

I have banged my head against this exact wall before. Since you already confirmed standard ACLs and Record Rules are passing, and the user can actually write to the record, standard logic says they should see the history.

However, because you mentioned "The default company of the affected users is different from the company of the record," I am 99% sure this is the "Multi-Company Message Rule" biting you.

Here is what is likely happening and what you need to check:

1. The mail.message Company Trap We often forget that mail.message is a model itself, and it has a company_id field.

• The Scenario: When the record was created (or when those old messages were posted), they were likely stamped with Company A.

• The Problem: Even if your user (from Company B) has a record rule to see the Record itself, there is a global multi-company rule that applies to every model with a company_id field.

• The Conflict: If the user is logged in and their "Allowed Companies" (top right switch) is set to only Company B, Odoo’s standard multi-company security will strictly hide any mail.message rows belonging to Company A. They see the record shell, but the messages inside are filtered out by SQL.

The Fix/Test: Ask the affected user to tick the box for the Record's company in their top-right company switcher (so they are in "Company B + Company A" mode). I bet the chatter instantly appears.

2. Subtypes and "Internal" Groups If the multi-company check passes, the next "invisible" filter is the Message Subtype.

• Check the mail.message rows in the database. Do they have a subtype_id?

• Go to Settings > Technical > Email > Subtypes.

• Check the subtype for "Discussions" or "Note" related to your custom model.

• If the "Internal Only" boolean is checked on that subtype, users must be part of the specific Internal/Employee group to see them. If your custom users are "Portal" or "Public" or a custom restricted group, they won't see messages of that subtype.

3. The "Partner" Filter (Rare but possible) Sometimes, messages are created with specific partner_ids (private notifications). If the message was sent "Privately" to a specific list of partners and the current user isn't in that list, they won't see it, even if they have access to the document.

My money is on #1. Since they can post new messages (which likely get stamped with their current company, Company B), they can see their own new messages, but the old history (Company A) remains invisible until they switch their allowed company context.

Let me know if that was it!

If this helped, kindly upvote.
Best Regards,


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