Ref Sp Dev Github Dependabot

GitHub Dependabot

Purpose

Provide portable defaults for configuring Dependabot so repositories stay current without drowning maintainers in low-signal update pull requests.

When to use this skill

• Creating or revising .github/dependabot.yml.
• Choosing which ecosystems and directories Dependabot should monitor.
• Reducing PR noise with schedules, grouping, cooldowns, or open PR limits.
• Configuring updates for GitHub Actions, private registries, or multi-directory repositories.
• Automating safe Dependabot PR handling, such as metadata-driven labels, approvals, automerge, or release-intent file generation.

Scope boundaries

This skill owns .github/dependabot.yml: ecosystems, schedules, grouping, ignore and allow rules, private registries, and update volume.

• ref-sp-dev-github-actions-ci — .github/workflows/*.yml. Same folder, different job: this config opens the dependency PRs; those workflows are what run on them.
• ref-sp-dev-semantic-versioning — what a version range actually permits, and which dependency field a package belongs in. Those rules decide what Dependabot is even allowed to propose.
• ref-sp-dev-package-management — keeping versions in step across manifests once an update lands.

Defaults

• Keep the config in .github/dependabot.yml and start it with version: 2.
• Add one updates block per ecosystem and directory boundary unless multi-directory grouping is intentional.
• Prefer weekly schedules by default; use daily only when catching up or when the ecosystem genuinely requires faster movement.
• Keep open-pull-requests-limit intentional so Dependabot does not swamp the review queue.
• Use groups to reduce noisy one-dependency-at-a-time PR streams, especially for development dependencies or low-risk patch updates.
• Use package-ecosystem: github-actions with directory: "/" when workflows depend on external actions or reusable workflows.
• Keep private registry credentials in Dependabot registry configuration and secrets, never hard-coded in the file.
• Use ignore and allow narrowly and document why when blocking major upgrades or noisy packages.
• Let required CI and branch protection decide whether Dependabot PRs can merge; automation should enable auto-merge only after metadata, update type, and dependency scope match the policy.
• If the release workflow requires explicit release-intent files, generate dependency-update changesets or release notes only through metadata-only automation that does not execute PR code.

Task Framing

Core Rules

Base file shape

• Keep the config at .github/dependabot.yml.
• Start the file with version: 2.
• Define updates explicitly; each block should clearly own one ecosystem and directory or set of directories.
• Do not overlap directories across multiple update blocks for the same ecosystem and target branch unless the split is intentional and non-overlapping.

Ecosystems and directories

• Use directory for one manifest root and directories only when a multi-directory update block is truly warranted.
• Keep directory values repo-root-relative.
• For GitHub Actions, use package-ecosystem: github-actions with directory: "/"; Dependabot will scan workflow files under .github/workflows and root action definitions.
• Use separate update blocks when different ecosystems or dependency surfaces need different schedules, grouping, or labels.

Scheduling and update volume

• Prefer weekly as the default schedule.
• Add day, time, and timezone when the review process needs predictable update windows.
• Use open-pull-requests-limit to match human review capacity.
• Use cooldown when high-churn packages create constant PR churn and delayed uptake is acceptable.
• If the repo is severely outdated, temporarily tighten schedules, then relax them once the backlog is under control.

Grouping, allow, and ignore

• Use groups to combine low-risk updates into fewer PRs.
• Prefer group names that describe the review unit, such as dev-dependencies, github-actions, or infrastructure.
• Use dependency-type, patterns, and update-types to make groups predictable.
• Use ignore for genuinely blocked upgrades or known noisy ranges, not as a substitute for doing upgrade work forever.
• Remember that if a dependency matches both allow and ignore, it is ignored.
• Use open-pull-requests-limit: 0 only as an explicit temporary disable, not as a quiet way to forget that the ecosystem exists.

Commit and PR shaping

• Use commit-message settings when the repo expects a consistent PR and commit style.
• Keep labels, assignees, and milestones aligned with the review process instead of accepting whatever the defaults happen to generate.
• Use pull-request-branch-name.separator only when it solves a concrete branch naming or tooling issue.
• Use dependabot/fetch-metadata or the GitHub API when automation needs to distinguish direct production dependencies, development dependencies, patch updates, minor updates, or major updates.
• Prefer enabling GitHub auto-merge for approved low-risk PR classes over force-merging directly; branch protection and required checks should remain the gate.
• Keep auto-merge policies narrow, such as patch-only development dependencies or grouped GitHub Actions updates, until the repo has evidence that broader automation is safe.

Making auto-merge actually work

Enabling Dependabot auto-merge with gh pr merge --auto needs three independent things in place. Missing any one fails only part of the time, which makes it look flaky rather than broken:

• Write-scoped workflow token — contents: write + pull-requests: write on the merging job (job design owned by ref-sp-dev-github-actions-ci). Missing → GraphQL: Resource not accessible by integration (mergePullRequest).
• The repo "Allow auto-merge" setting — Settings → General → Pull Requests. Off → GraphQL: Auto merge is not allowed for this repository (enablePullRequestAutoMerge). This is a repository setting, not YAML; no workflow change can fix it.
• A branch protection rule with an unmet requirement — auto-merge can only be enabled on a PR that cannot merge immediately (a required status check or review still pending, or "require branches up to date" / "require linear history" leaving it behind base). With nothing to wait on, there is no deferred merge to enable.

gh pr merge --auto takes one of two paths depending on PR state, which is why a missing setting can appear to "sometimes work":

• Immediately mergeable → direct mergePullRequest. Needs only the token, not the setting. A lone Dependabot PR usually hits this and succeeds.
• Not immediately mergeable (behind base after another PR merged, a lockfile conflict, a pending required check) → enablePullRequestAutoMerge. Needs the token and the setting. Concurrent Dependabot PRs routinely hit this, so "it fails only when two race" points at the setting being off, not at the YAML.

Private registries and restricted ecosystems

• Put registry definitions in top-level registries and reference them from specific updates blocks.
• Store registry credentials in repository or organization secrets, not plaintext config.
• Use replaces-base carefully because it changes how the ecosystem resolves packages.
• Avoid enabling insecure external code execution unless the package manager truly needs it and the security tradeoff is understood.

Actions and workflow dependencies

• Keep GitHub Actions dependencies under Dependabot coverage when the repository uses external actions or reusable workflows.
• Prefer repository-style action references that Dependabot can update.
• Remember that local ./.github/... references and docker:// action references are not Dependabot-updateable in the same way.
• Treat Actions updates as part of CI maintenance, not as a separate afterthought.

Dependabot release automation

• If the repo uses Changesets or another explicit release-intent model, decide whether dependency updates should create user-visible release notes before adding automation.
• For routine dependency maintenance, prefer a generic patch changeset only when the package itself should publish because dependency versions changed.
• Use pull_request_target only for metadata-only operations such as labels, comments, or writing a simple release-intent file; never install dependencies or run code from the Dependabot branch in that privileged context.
• Avoid adding a fine-grained PAT solely for Dependabot automerge unless the native GITHUB_TOKEN, branch protection, and auto-merge model cannot express the required workflow.

Gotchas

• Forks do not automatically enable Dependabot version updates just because the file exists; the fork owner must enable them.
• target-branch affects version updates only; security updates still target the default branch.
• groups combine matching dependencies in the first matching group, so ordering matters.
• directory and directories are not interchangeable; use the plural form only when the ecosystem supports it and the grouping is intentional.
• Dependabot can update GitHub Actions referenced by repository syntax, but not arbitrary local action paths or docker:// references.
• Dependabot PR workflows are constrained like forked PRs: assume no ordinary Actions secrets and a limited token unless the workflow deliberately uses a trusted event.
• pull_request_target runs with the base repository context. It is useful for Dependabot metadata automation, but unsafe if it checks out and runs PR-controlled code.
• Auto-generating release-intent files for dependency updates can create noisy releases if every dev-only update publishes a package version.
• "Allow auto-merge" gates only the deferred-merge feature (enablePullRequestAutoMerge), not an immediate merge; with the setting off a directly-mergeable PR still merges via mergePullRequest, so auto-merge looks like it works until a non-fast-forward PR needs to queue.
• Auto-merge is silently disabled if someone without write access pushes to the PR head branch or switches its base — for example a fork contributor pushing after a maintainer enabled it.

Validation

• The file uses version: 2 and one clear update block per dependency surface.
• Ecosystem and directory scopes do not overlap accidentally.
• PR volume matches review capacity through schedules, grouping, and PR limits.
• Private registry access is explicit and credential handling stays secret-backed.
• Workflow dependencies are covered if the repository depends on GitHub Actions.
• Dependabot automation conditions on actor, repository, dependency metadata, update type, and dependency scope before approving or enabling auto-merge.
• Dependabot auto-merge has all three prerequisites in place: a write-scoped token, the repo "Allow auto-merge" setting, and a branch protection rule that gives auto-merge a requirement to wait on.
• Any generated changeset or release-intent file matches the package's real release policy and does not run untrusted PR code.

References

• Dependabot Options Reference: https://docs.github.com/en/code-security/dependabot/working-with-dependabot/dependabot-options-reference
• Configuring Dependabot Version Updates: https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuring-dependabot-version-updates
• About Dependabot Version Updates: https://docs.github.com/en/code-security/dependabot/dependabot-version-updates
• Automating Dependabot with GitHub Actions (the auto-merge workflow pattern): https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions
• Automatically merging a pull request (auto-merge prerequisites and auto-disable rules): https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/automatically-merging-a-pull-request
• Managing auto-merge for pull requests (the "Allow auto-merge" repo setting): https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-auto-merge-for-pull-requests-in-your-repository
• Read ./references/checklist.md for a quick Dependabot review pass.
• Read ./references/config-patterns.md when deciding how to split ecosystems, group updates, or wire private registries.
• Read ./assets/trigger-eval-queries.example.json when testing trigger quality for Dependabot prompts.
• Review ./evals/evals.json when validating output quality for update-scope and PR-noise guidance.