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Author(s): anna239

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Elevator pitch

What are you proposing to change?
Add flag deleted to Diff entity type for the case of a deleted file.

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Status quo

How do things work today and what problems does this cause? Why would we change things?
Currently, in Diff entity type newText is not nullable, so it’s not possible to distinguish between a deleted file and empty file.

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What we propose to do about it

What are you proposing to improve the situation?
Add flag deleted to Diff entity type for the case of a deleted file. Current structure (cannot distinguish deleted file from empty file): 
{
  "type": "diff",
  "path": "/home/user/project/src/config.json",
  "oldText": "{\n  \"debug\": false\n}",
  "newText": ""
}
Proposed structure with deleted flag: 
{
  "type": "diff",
  "path": "/home/user/project/src/config.json",
  "oldText": "{\n  \"debug\": false\n}",
  "newText": "",
  "deleted": true
}
Note: we would ideally make newText nullable, but that would break existing clients.

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Shiny future

How will things will play out once this feature exists?
It is possible for the agent to distinguish between a deleted file and an empty file.

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Implementation details and plan

Tell me more about your implementation. What is your detailed implementation plan?
Adding the new field will be a non-breaking change, and clients that update can better distinguish between deleted and empty files.

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Frequently asked questions

What questions have arisen over the course of authoring this document or during subsequent discussions?
Do we need to represent moved files? An agent could represent that with a deleted file at the old path and a new file at the new path. We need to rework the entire diff structure to handle more cases, and binary files, but in the meantime this provides a stop-gap until we can implement a more comprehensive solution.

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What alternative approaches did you consider, and why did you settle on this one?

We considered making newText nullable, but that would break existing clients.

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Revision history

2026-02-20: Initial draft