[Feature Request] Review-specific custom instructions and custom agent selection for automatic Copilot PR reviews

[michalmela]

🏷️ Discussion Type

Product Feedback

Body

GitHub Copilot code review would be much more useful if repositories could configure review-only behavior, separate from general coding/chat behavior, and optionally choose a specific custom agent for automatic PR reviews.

Problem

Today, repository instructions can help shape Copilot behavior broadly, but code review has a distinct purpose from code generation, chat, or general cloud-agent tasks.

In practice, teams often need PR reviews to follow rules that are:

• specific to reviewing, not authoring code
• stricter than normal coding guidance
• tailored to a particular review persona
• stable and predictable across all automatic reviews

Examples:

• “Prioritize correctness, security, data loss risk, and backward compatibility over style.”
• “Do not suggest large refactors during review unless they are required to fix a bug.”
• “Review database migrations for rollback safety and lock risk.”
• “For API changes, focus on contract compatibility, auth implications, and observability.”
• “For generated files, skip style feedback and only flag correctness or reproducibility issues.”
• “In this repository, review comments should be concise and actionable, and avoid speculative suggestions.”

These instructions are often not appropriate as general Copilot instructions, because they would also affect coding/chat use cases where different behavior is desirable.

Requested capability

Please support a single review-specific configuration model for Copilot PR review that allows:

1. review-only custom instructions

   • A dedicated instruction source that applies only to Copilot code review
   • Not reused for chat, code completion, coding agent tasks, or PR authoring

2. optional custom agent selection for automatic PR review

   • Allow a repository or organization to specify which custom agent should perform automatic PR reviews
   • Ideally allow a default agent, with optional overrides later if needed

Why this should be one feature

These are two parts of the same operational need:

• teams want to define a review persona
• and ensure automatic reviews consistently use that persona

Review-only instructions without agent selection help, but still leave ambiguity about execution model.
Agent selection without review-only instructions helps, but does not provide a clean place for review-scoped policy.

Together, they provide a coherent configuration story for automated PR review.

Main use cases

This would help teams implement reliable automated review patterns such as:

• security reviewer

  • focus on auth, secrets, injection, permissions, unsafe deserialization, SSRF/XSS/CSRF classes of issues

• API reviewer

  • focus on schema compatibility, error semantics, pagination/filtering changes, versioning, deprecations

• database reviewer

  • focus on migration safety, indexes, rollback behavior, lock duration, data integrity

• reliability reviewer

  • focus on retries, timeouts, idempotency, concurrency, failure handling, observability

• frontend accessibility reviewer

  • focus on keyboard navigation, semantics, labeling, focus management, ARIA misuse

• docs/release reviewer

  • focus on changelog impact, operator-facing changes, upgrade notes, runbooks

Why existing mechanisms are not enough

Current instruction mechanisms are useful, but they do not fully address this use case:

• repo-wide instructions are too broad and affect non-review experiences
• path-specific instructions are scoped by files, not by activity/type of Copilot task
• custom agents exist in other Copilot contexts, but automatic PR review does not appear to expose a clean documented way to select a specific agent for reviews

What’s missing is the ability to say:

“When Copilot performs an automatic PR review for this repository, use this reviewer persona and these review-only instructions.”

Suggested UX

Any of these would solve the problem:

• a dedicated file such as .github/copilot-review-instructions.md
• a review-scoped instruction type under .github/instructions/
• repository settings for “Default Copilot review agent”
• optional branch/path/repo-level review agent configuration

Expected outcome

This would let teams make Copilot reviews:

• more predictable
• more relevant
• less noisy
• easier to align with compliance and engineering standards
• clearly separated from coding/chat behavior

Related discussions

https://github.com/orgs/community/discussions/185407 – also related to review-specific behavior, but skills would not solve the problem as described here

https://github.com/orgs/community/discussions/169109 – describes a problem with instructing the reviewer agent; the feature as described here could help clear the confusion expressed in this discussion

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[michalmela]

mostly resolved by REVIEW.md https://github.blog/changelog/2026-07-17-copilot-code-review-customization-and-configurability-improvements/#%f0%9f%93%84-expanded-custom-instructions-file-support