Codex App import creates duplicate conversations for cumulative history prefixes

What version of the Codex App are you using?

26.901.51231 (8109)

What subscription do you have?

ChatGPT account. The exact plan is omitted because the problem concerns local conversation import.

What platform is your computer?

Darwin 25.6.0 arm64 arm

What issue are you seeing?

Importing a continued conversation creates several separate Codex conversations that contain cumulative prefixes of the same history.

For example:

• Conversation A contains message 1.
• Conversation B contains messages 1 and 2.
• Conversation C contains messages 1, 2, and 3.

A and B remain visible even though C already contains their complete history. Titles are often identical, so the sidebar fills with entries that look like duplicates. The older entries do not represent distinct branches or independent work.

What steps can reproduce the bug?

1. Start a conversation in another supported environment.
2. Continue the same conversation with another message.
3. Import the conversation history into Codex.
4. Inspect the imported conversation list.

Each intermediate state appears as a separate conversation rather than one conversation with the latest complete history.

What is the expected behavior?

Import the chain as one conversation containing the complete history.

If the source contains real branches, keep only distinct branch tips or represent the parent-child relationship without duplicating every shared prefix as a separate top-level conversation.

Additional information

The current behavior makes the conversation list hard to scan and makes it unclear whether two entries contain different work. Deduplicating by title is not sufficient. The importer needs to compare ancestry or message prefixes.

Start by locating the Codex App's conversation-history import path and the code that constructs imported conversation entries. Reproduce the cumulative-prefix case, then verify that the import keeps one complete conversation while preserving distinct branch tips without duplicate top-level entries.