[Bug] Multiple sequential edits to the same file are lost - only the last one persists (after fix #8513) #25868

What happened?

Description:
After the fix in PR #8513 ("Serialize function calls that mutate state"), the bug of multiple edits on the same file still occurs.

When the model performs multiple sequential edits on the same file (even when each edit is individually accepted with ✓ Edit ... → Accepted), only the last edit is persisted. All previous edits are lost/overwritten.

Steps to Reproduce:

1. Ask Gemini CLI to make changes to a file (in my case update_prompts_v7.sql)
2. The model proposes edit 1 → I accept it
3. The model proposes edit 2 on the same file → I accept it
4. The model proposes edit 3 on the same file → I accept it
5. Only the 3rd edit remains. Edits 1 and 2 are gone.

What did you expect to happen?

All accepted edits should be applied sequentially and persist in the file.

Actual behavior:
Only the last accepted edit is kept. Previous edits are discarded.

Client information

• CLI Version: 0.39.0
• Git Commit: 398f78d
• Session ID: 2d20a950-0729-40c7-a778-3d937abf3493
• Operating System: linux v20.19.2
• Sandbox Environment: no sandbox
• Model Version: gemini-3.1-pro-preview
• Auth Type: oauth-personal
• Memory Usage: 443.4 MB
• Terminal Name: Unknown
• Terminal Background: #1e1e1e
• Kitty Keyboard Protocol: Unsupported

Login information

No response

Anything else we need to know?

• I have strong rules in GEMINI.md telling the model to never do multiple edits on the same file and to always plan everything in one edit, but it still happens.
• This occurs even though each edit is confirmed individually.
• The problem was supposedly fixed in Serialize function calls that mutate state #8513, but it is still reproducible in April 2026.

References:

• Original issue: Parallel edit/replace on the same file cause errors/overrides  #8372 (closed as fixed by Serialize function calls that mutate state #8513)
• PR that was supposed to fix it: Serialize function calls that mutate state #8513

This is a critical reliability issue for using Gemini CLI in real development workflows.