Positron Notebooks: Assistant (Anthropic) claims false “Changes Applied” message with NO actual edits

[rodrigosf672]

Relevant notes

• Regression appeared in the latest build (today).
• Issue is specific to .ipynb files; other file types behave normally. This places it in the Notebooks workstream.
• Making the request more explicit/specific does not change the outcome. The Assistant still reports that changes were made even though the notebook content remains unchanged (see third screenshot).
• Observed tool calls:
  • In some flows, the model attempts copilot_editNotebook but the resulting edit does not apply.
  • In other flows, positron_editFile_internal is invoked, but again no change is applied to the actual notebook content.
  • In the failing Anthropic Notebook Assistant case, the model claims success even when the tool calls are missing entirely.

System details:

Positron Version: 2025.12.0 build 79  
Code - OSS Version: 1.105.0  
Commit: 3af147dca07686d2cfa80faf0796c04661c56616  
Date: 2025-11-14T07:19:22.022Z  
Electron: 37.6.0  
Chromium: 138.0.7204.251  
Node.js: 22.19.0  
V8: 13.8.258.32-electron.0  
OS: Darwin arm64 25.0.0

Session details

• Model: Claude Sonnet 4.5
• Modes affected: Agent and Edit
• Provider: Anthropic

Describe the issue:

When using Notebook Assistant with Anthropic models (Claude Sonnet 4.5), the Assistant consistently states that notebook edits were successfully applied — even though no actual modification occurs in the .ipynb file.

Behaviors observed:

• In many requests, no notebook edit tool call fires at all, yet the Assistant still says “changes were made.”
• In other cases, the model issues a copilot_editNotebook call or a positron_editFile_internal call, but the resulting notebook edit does not apply.
• No visible diff appears, and notebook content remains unchanged.

Expected behavior:

The Notebook Assistant should:

• Apply the requested changes to the .ipynb file,
• Only report success when the notebook was actually modified,
• Call one of the notebook-editing tools (copilot_editNotebook or Positron’s internal edit path) reliably, and
• Not produce false-positive “changes applied” messages.

Steps to reproduce:

1. Open any .ipynb file in Positron.
2. Open the Assistant in Agent or Edit mode.
3. Ask Claude Sonnet 4.5 to modify any cell (e.g., update Markdown or change a print statement).
4. Observe that:
   • The Assistant reports that edits were applied,
   • But the notebook content does not change,
   • No diff is shown, and
   • In many cases no tool call occurs, while in others the tool call fires but does not result in a real edit.

Screenshots

[cindyytong]

@rodrigosf672 we have not been able to produce this with Anthropic Sonnet 4.5 or Copilot. Can you confirm that you can reproduce this

[rodrigosf672]

@rodrigosf672 we have not been able to produce this with Anthropic Sonnet 4.5 or Copilot. Can you confirm that you can reproduce this

Yes, it remains reproducible in 2025.12.0 build 85

• Edit mode

• Agent mode

[cindyytong]

Thank you @rodrigosf672

[nstrayer]

May be solved when #10654 is merged.