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Cross-repo reviews help cubic catch changes that need a matching update in another repository. Link related repositories so reviews can check shared APIs, schemas, docs, or release work. Both repositories must be installed in the same cubic GitHub installation. You need a Member or Admin role to add, edit, or remove repository links. Viewers can see the configured links but cannot change them. See Roles and permissions for details.
Cross-repo reviews are available on every plan.

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How it works

When cubic reviews a pull request in either linked repository, it:
  1. Checks whether the link applies - Uses the changed files and your guidance to decide whether the linked repository matters for the PR.
  2. Reads the linked repository when needed - If the link applies, cubic inspects the shared code or contract being changed.
  3. Posts cross-repo findings - Adds comments to the reviewed PR with citations to affected files in the linked repository.
  4. Tracks companion fixes - If the reviewed PR description references a PR in the linked repository, cubic updates the finding when the companion PR addresses it.
Cross-repo checks run as part of the normal review. You do not need to start a separate review.

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Setting up cross-repo reviews

Cross-repo reviews card in AI review settings with several configured links
  1. Open AI review settings and select the repository you want to configure.
  2. Find the Cross-repo reviews card and select Add link.
  3. Choose the related repository from the picker. Only repositories in the same installation appear.
  4. Write one or two sentences describing what the repositories share and which changes need coordinated updates, then select Link repository.
Repository links work in both directions. Configure a pair once, and cubic can use the link when reviewing either repository.
Open the Cross-repo reviews card for either linked repository. Select the pencil icon to update the review guidance, or select the trash icon and confirm to remove the link. Because links work in both directions, editing or removing a link affects reviews in both repositories.

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Limits and access

  • Each repository can link to up to 5 other repositories. To link more, contact us.
  • Guidance is capped at 80 words. cubic reads it verbatim, so concise guidance works best.
  • Both repositories must be in the same GitHub installation. Cross-installation links are not supported.
  • Archived repositories, repositories cubic no longer has access to, and repositories that have moved installations show an inaccessible badge and are skipped during review.

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Writing good guidance

Guidance tells code review agents when another repository matters. Name the shared surface and the kinds of changes that need coordination.

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Good examples

Frontend and backend share an HTTP API; route or response-shape changes need coordinated updates on both sides.
Both services read from the same Postgres database. Schema migrations and column renames require matching updates in both repositories.
The shared @acme/types package is consumed by both repositories. Breaking changes to exported types require updates wherever they’re imported.

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What doesn’t work

They’re related.
This is too vague to be useful. cubic may skip the linked repository or check it too often.
Name the shared surface (API, schema, types, events) and the coordination rule (what changes need a matching update). Specific guidance makes relevance checks more accurate.

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Referencing companion PRs

Companion PR references are optional. They let cubic track fixes across repositories, but cubic can find cross-repo issues without them. When your change spans two repositories, add the companion PR to the reviewed PR description. cubic recognizes two formats:
  • Full URL: https://github.com/myorg/backend/pull/456
  • Shorthand: myorg/backend#456
The referenced PR must be in a repository linked from Cross-repo reviews. Bare #456 shorthand is intentionally not matched because same-repo references cannot be companions. Editing the PR description re-runs discovery, so you can add or remove companion references at any time.

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What you’ll see in reviews

A cross-repo finding comment on a PR citing files in three related repositories Cross-repo findings appear inline on the reviewed PR, the same way other AI review comments do. Each finding includes a citation pointing at the affected file in the linked repository, so you can jump to the code that needs a matching change. When the companion PR pushes new commits that address the cited issue, cubic edits the original comment to show the addressed state and the commit SHA that fixed it. If a comment cites multiple cross-repo concerns and only some are addressed, the comment shows a partial resolution so you know what remains.

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Troubleshooting

cubic checks a linked repository only when the link applies to the PR. Confirm that your guidance names the surface changing in the PR. For example, guidance that only mentions “API routes” does not apply to a CSS-only change. If the guidance is already specific, the linked repository may not be affected.
Confirm two things: the referenced PR is in a linked repository, and the reference in the reviewed PR description uses one of the recognized formats (full GitHub URL or owner/repo#number). Bare #number shorthand is ignored because it can’t point at another repository.