Providing context and warnings

We might mention news from The Verge as related context, but I should keep it brief. I also need to add a warning about editing extension.js—this could break with future updates and the extension may auto-revert changes. Forking isn't easy, especially since the Copilot Chat extension is closed-source. I’ll also clarify that modifying the extension is different from bypassing a paywall, but it still carries potential security risks. A proper disclaimer is needed.

Recommending stable alternatives

It’s important to recommend supported alternatives like using repository indexing remotely or knowledge bases (though they’ll be replaced by Copilot Spaces in 2025). I should also suggest ways to extend RAG context using VSCode workspace context, restructuring files, or reducing noise with .gitignore. A quick TL;DR with code snippet names and citations will help clarify details like the file limit error.

Clarifying limits and version variations

I should mention that the file limit can vary between 2000 and 2500 depending on the version, using both the Medium article (2000) and GitHub issue (2500, from 7 months ago) as references. I

Thought for 1m 19s

Here’s the gist of that post, in plain English:

What the author tried

Explores how Copilot Chat’s @workspace context works in VS Code and how it’s essentially a local RAG setup: your question is embedded, VS Code compares it to prebuilt file embeddings, then sends the most relevant snippets + your question to the LLM. (Medium)
Notes you can trigger or inspect this with “Build local workspace index” (⇧⌘P) and by checking Output → GitHub Copilot Chat with log level Trace. (Medium)

The pragmatic findings

Local indexing limit: Copilot Chat will say indexing is limited (the author saw ~2,000 files; other official threads mention ~2,500 for the local index). When you exceed it, a “sparse” index is used, which can degrade answers. (Medium)
Unofficial hack (do-at-your-own-risk): edit the installed Copilot Chat extension’s extension.js to raise caps (e.g., the functions for manual/auto index file caps), bump an embeddings-cache max size, toggle a search timeout flag, and tweak a “parallelism” value. Paths are given for macOS/Windows; you need to reload the window afterward. (This is brittle and may be overwritten by updates.) (Medium)
Where the cache lives: the post points to a workspace-specific embeddings cache JSON under your VS Code user storage; the author observed a size limit and experimented with raising it. (Medium)
A few gotchas: symlinks weren’t indexed; you’ll see a “still building” warning mid-index; adding to .gitignore may require a window reload. (Medium)

Safer, supported ways to expand context (vs. patching the extension)

Use GitHub’s repository indexing: when your repo is on GitHub, Copilot can use a richer remote index that isn’t constrained like the local one. (GitHub)
Prefer official context features: VS Code’s Workspace context docs explain how @workspace scopes and sources are used; trimming noise with .gitignore and multi-root workspaces helps. (Visual Studio Code)
Knowledge bases → Copilot Spaces: GitHub is retiring knowledge bases on Nov 1, 2025 in favor of Copilot Spaces; if you were considering KBs, plan for Spaces instead. (GitHub Docs)

Should you do the hack?

If you just want better answers on big repos, first try: (1) pushing the repo to GitHub to benefit from the remote index; (2) pruning/excluding non-code files; (3) splitting monorepos or using multi-root workspaces. Editing the extension is unsupported, may violate terms, and will likely break on updates—do it only in a disposable setup if you fully understand the risks. (GitHub Docs)

If you want, I can turn these notes into a quick checklist (with commands/paths for macOS/Windows) tailored to your setup.

https://medium.com/@cnkbekir/how-to-extend-github-...

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