github_repo tool in Copilot Chat does not index .yml files from repositories

[mrybson]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Copilot Agent Mode

Body

When using the github_repo tool in GitHub Copilot Chat (agent mode) to query a private GitHub repository, .yml files are consistently excluded from the indexed content returned — including files under .github/workflows/.

Steps to reproduce:

Enable Copilot indexing on a private repository that contains .github/workflows/*.yml files
In Copilot Chat (agent mode), use the github_repo tool to query the repository for workflow file content
Query with terms that should match the YAML content (e.g. job names, trigger events, step names)

Expected behaviour:
The tool returns relevant excerpts from .yml files, the same way it returns excerpts from .tf, .tfvars, and .md files.

Actual behaviour:
Only .tf, .tfvars, and .md files are returned. Queries targeting workflow YAML content fall back to .md prose that mentions the workflow file names, never the file bodies themselves. This is reproducible across multiple query strategies and multiple repositories.

Impact:
Agent workflows that require reading workflow template files (e.g. using a scaffold repository as a source of truth for GitHub Actions files) cannot retrieve that content programmatically. This forces a manual step that breaks otherwise fully automated code generation flows.

Workaround:
Embedding YAML content inside .md files makes it retrievable. This is a viable but undesirable workaround as it requires duplicating content.

Environment:

Copilot Chat version: 0.42.3
Repository type: Internal, GitHub Enterprise
Tool: github_repo (Copilot agent tool)

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