How does Copilot CLI read and understand repository context?

Copilot CLI builds its understanding of your codebase from several sources - the directory you run it in, the files it reads during a session, project configuration files, and the copilot-instructions.md file.

# Copilot CLI reads context progressively during a session
# It does NOT index the entire codebase upfront

# To give Copilot specific context:
"Look at src/auth/login.ts and explain the authentication flow"
# → Copilot reads that file and builds context from it

# For large codebases, guide Copilot to the relevant files:
"The bug is in the payment processing module in src/payments/"
# → Copilot narrows its file reading to that directory

# copilot-instructions.md reduces the need for repeated context:
# Instead of explaining your stack every session, put it in the file

Context limits: like all LLM-based tools, Copilot CLI has a context window limit. For very large files or repositories, it reads selectively. Providing clear, targeted prompts and maintaining a well-written copilot-instructions.md reduces the risk of Copilot operating with incomplete context.

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