Codebase indexing should be supported as it is in the Vscode extension

[numman-ali]

Describe the feature or problem you'd like to solve

Codebase Indexing https://docs.github.com/en/copilot/concepts/context/repository-indexing

Proposed solution

Overall there should be feature parity with the VS Code extension but at a minimum the codebase indexing should be supported first

This enables working with large codebases without friction

Example prompts or workflows

No response

Additional context

No response

[mamoreau-devolutions]

I'm trying GitHub Copilot CLI as an alternative to Claude Code for devs that like the terminal UI and don't wish to use VSCode. The main feature Claude Code doesn't have that GitHub Copilot in VSCode has is automatic remote workspace indexing for repositories hosted in GitHub.

If Copilot CLI doesn't use the code indexing capabilities that makes GitHub Copilot in VSCode shine, then there's no reason for our existing Claude Code users to even try Copilot CLI, unfortunately. We have a lot of large code repositories, and tests have shown a huge difference in performance between GitHub Copilot in VSCode against Claude Code for complex questions that require scanning a lot of files to produce a good answer.

Can we get Copilot CLI to support using code indexing? This is a strong selling point

[EvanBoyle]

@numman-ali @mamoreau-devolutions would love to hear your perception on how this would improve the quality of the agentic coding loop? What do you think this will improve in terms of agent capability?

[mamoreau-devolutions]

Isn't it sufficiently obvious from what has already been said? Excellent code search performance not only means the agent can run faster, but it also reduces token usage by spending less time ingesting unrelated data, and increases accuracy with fewer cases where the agent failed to find something that was there to be found. This is a shining feature inside VSCode, we just need the same in Copilot CLI