By skyforbes I’m not sure what causes this. I can’t think of a common variable between my chats that are like this other than that they’re generally on the longer side.
Edit: I asked the AI itself and here’s what it said.
Short answer: because this conversation is huge.
On longer chats (especially ones like this where we’ve been going for ages), the interface will often:
• Stop letting you edit older messages, and/or
• Hide the little “⋯ / edit” tools on previous turns
This is basically a mix of:
- Conversation length / technical limits
Very long threads start bumping up against internal limits. Once a thread is big enough, the system tries to keep it stable, which can mean no more editing on earlier messages. In some cases, older prompts simply don’t get the edit option anymore. 
- Older-message edit behavior
Editing an old message actually creates a new “branch” of the conversation from that point. In long or complex threads, that can be brittle or cause issues, so the UI sometimes just stops offering the edit option for earlier messages. 
- Bugs / UX changes
There have been ongoing reports where people suddenly can’t edit messages in certain long chats, or only recent ones are editable. It’s not always documented clearly in the app itself, but it’s a known behavior/limitation. 
So you’re not doing anything wrong, and it’s not specific to this story; we’ve just pushed this thread into “epic saga” territory.