Claude Agent treats Copilot Instructions as separately attached file

[bamurtaugh]

Testing #297136

• I asked the Claude Agent about 1 attached file app.js
  • See Unexpected GH MCP auth modal when attaching context for Claude Agent #297427 for my exact steps
• ❓ Claude Agent also told me about my copilot-instructions.md, as if I had attached it and asked for info about it explicitly

[TylerLeonhardt]

Looks like we are including extra attachments that we shouldn't:

<system-reminder>
The user provided the following references:
- /Users/tyleonha/Code/Microsoft/vscode-copilot-chat/src/extension/log/vscode-node/extensionStateCommand.ts
- /Users/tyleonha/Code/Microsoft/vscode-copilot-chat/.github/copilot-instructions.md
- /Users/tyleonha/.claude/CLAUDE.md

IMPORTANT: this context may or may not be relevant to your tasks. You should not respond to this context unless it is highly relevant to your task.
</system-reminder>

We shouldn't include copilot-instructions.md & CLAUDE.md (CLAUDE.md for example is brought in via the system prompt) so these are coming from Core I think. I need to see if there's a switch for me to disable adding these as implicit references.

cc @roblourens @pwang347 if you have any ideas.

[bamurtaugh]

Cross-linking #290891 - @TylerLeonhardt do you think it makes sense to keep both of these issues open? They seem similar enough that one could be closed as a dupe of the other.

[TylerLeonhardt]

I think let's keep both. This bug tracks the real problem of these being automatically added. Like CLAUDE.md shouldn't be there because the Claude Agent handles CLAUDE.md internally.