Copilot Chat “Keep / Undo pending edits” causes irreversible loss of code across Codespaces sessions

[pramodsurya]

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Bug

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I experienced destructive behavior using GitHub Copilot Chat in VS Code Codespaces.

Copilot Chat maintains a long-lived edit session across days and machines. When prompted to “Keep & Continue” or “Undo & Continue” pending edits, both options resulted in overwriting or deleting valid code changes already present in the workspace.

This caused irreversible loss of work done across multiple sessions.

Exact Reproduction Steps

1. Open a Codespace on Machine A (Office)
2. Use Copilot Chat to edit files
3. Do not explicitly select “Keep” or “Undo”
4. Close Codespace
5. Open the same Codespace on Machine B (Home)
6. Continue editing using Copilot Chat
7. Close Codespace
8. Reopen Codespace on Machine A
9. Copilot Chat prompts:
10. “Start new chat? Keep or Undo pending edits”
11. Select either option

Observed Result

Selecting Keep re-applies stale Copilot diffs and overwrites newer changes
Selecting Undo reverts all Copilot-associated changes, deleting valid work already present on disk
No warning that this action is destructive
No recovery prompt or diff preview
Work is lost even though files existed and were visible before the prompt

Expected Result

Copilot Chat should never overwrite or revert workspace files without explicit, file-level confirmation
“Undo” should only discard Copilot’s internal session, not mutate the filesystem
Copilot edit sessions should not persist across machines/days without explicit user intent

Impact

High severity – data loss.
This makes Copilot Chat unsafe for professional use in Codespaces across multiple devices.

Environment

VS Code (latest)
GitHub Codespaces
GitHub Copilot Chat enabled
Same Codespace accessed from multiple machines

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