feat: add Devin PR conflict resolver workflow

[keithwillcode]

What does this PR do?

Adds a GitHub Actions workflow that automatically detects PRs with merge conflicts and spins up Devin sessions to resolve them. This follows the same pattern established in #26618 (Cubic AI to Devin integration).

How it works:

1. Triggers on push to main branch (when main updates could cause conflicts in open PRs)
2. Also supports manual trigger via workflow_dispatch
3. Uses GraphQL API to fetch all open PRs with their mergeable status, draft status, labels, and fork information in a single batched query (with pagination support)
4. Skips draft PRs and PRs that already have the devin-conflict-resolution label
5. For PRs with conflicts (mergeable === 'CONFLICTING'):
   • Creates a new Devin session with instructions to resolve conflicts
   • Adds the devin-conflict-resolution label to prevent duplicate sessions
   • Posts a comment on the PR with the Devin session link

Fork PR Support:

• Detects PRs from external contributor forks via headRepository field
• Only processes fork PRs where the contributor enabled "Allow edits from maintainers" (maintainerCanModify: true)
• Provides fork-specific instructions to Devin: clone the fork repo, add upstream remote, fetch and merge from upstream

Updates since last revision

• Added response.ok check before parsing Devin API response to properly handle HTTP error status codes (authentication errors, server errors) separately from successful responses that might be missing expected fields
• Improved error logging to include the PR number for easier debugging when API calls fail

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A - workflow only.
• I confirm automated tests are in place that prove my fix is effective or that my feature works. N/A - GitHub Actions workflow, can be tested via manual trigger.

How should this be tested?

1. Setup required: Ensure DEVIN_API_KEY secret is added to the repository (Settings → Secrets and variables → Actions)
2. Manual test: Trigger the workflow manually via Actions → "Devin PR Conflict Resolver" → "Run workflow"
3. Production test: Push a change to main that would cause conflicts in an open PR, verify the workflow detects it and creates a Devin session
4. Draft PR test: Verify that draft PRs with conflicts are skipped (check workflow logs)
5. Label test: Verify that PRs with the devin-conflict-resolution label are skipped
6. Fork PR test: Verify that fork PRs with maintainerCanModify: true are processed with fork-specific instructions, and fork PRs without maintainer access are skipped

Human Review Checklist

• Verify DEVIN_API_KEY secret exists in the repository
• Consider if pagination (100 PRs per page) handles the repo's PR volume
• Review duplicate detection logic - uses devin-conflict-resolution label
• Verify the Devin prompt provides sufficient context for conflict resolution
• Confirm the devin-conflict-resolution label will be auto-created or exists in the repo
• Review fork handling logic - relies on maintainerCanModify flag from GitHub API
• Verify fork-specific Devin instructions are correct (clone fork, add upstream, merge from upstream)

---

Link to Devin run: https://app.devin.ai/sessions/ca72c54a713e41a8a871a52a0a6d82c3
Requested by: @keithwillcode

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR that start with 'DevinAI' or '@devin'.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

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4 Skipped Deployments

Project	Deployment	Review	Updated (UTC)
api-v2	Ignored	Preview	Jan 12, 2026 2:26pm
cal	Ignored		Jan 12, 2026 2:26pm
cal-companion	Ignored	Preview	Jan 12, 2026 2:26pm
cal-eu	Ignored		Jan 12, 2026 2:26pm

[keithwillcode]

DevinAI, is this going to be able to handle conflicts on PRs that are forks from external contributors?

[devin-ai-integration]

Good question. Currently, no - the workflow won't be able to resolve conflicts on PRs from external forks because:

1. The prompt tells Devin to clone calcom/cal.com and push to the PR branch
2. For fork PRs, the branch exists on the contributor's fork (e.g., contributor/cal.com)
3. Devin wouldn't have write access to push to external contributors' forks

Options to handle this:

1. Skip fork PRs - Add a check to skip PRs where headRepository.owner.login !== owner and just log that fork PRs need manual conflict resolution

2. Use GitHub's "Allow edits from maintainers" - If the contributor enabled this option, maintainers can push to their fork branch. But this requires the contributor to have enabled it and uses a different git remote.

3. Comment only for fork PRs - Instead of creating a Devin session, just post a comment asking the contributor to resolve conflicts themselves

I'd recommend option 1 (skip fork PRs) for now since it's the safest. Want me to implement that?

[devin-ai-integration]

Implemented fork PR support:

1. Updated GraphQL query to fetch headRepository (owner/name) and maintainerCanModify fields
2. Fork PRs where the contributor enabled "Allow edits from maintainers" will be processed
3. Fork PRs without maintainer access are skipped with a log message
4. Devin gets fork-specific instructions: clone the fork repo, add upstream remote, fetch and merge from upstream

The workflow will now handle both regular PRs and fork PRs (when maintainer push access is enabled).

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name=".github/workflows/devin-conflict-resolver.yml">

<violation number="1" location=".github/workflows/devin-conflict-resolver.yml:161">
P2: Check `response.ok` before parsing the response body to explicitly handle HTTP error status codes from the Devin API. This distinguishes API failures (authentication errors, server errors) from successful responses that might be missing expected fields.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[github-actions]

Devin AI is addressing Cubic AI's review feedback

A Devin session has been created to address the issues identified by Cubic AI.

View Devin Session

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.


<file name=".github/workflows/devin-conflict-resolver.yml">

<violation number="1" location=".github/workflows/devin-conflict-resolver.yml:190">
P2: Missing HTTP response status check before parsing Devin API response. If the API returns an error (4xx/5xx), the code will silently fail without logging the actual HTTP status. Check `response.ok` first to provide clearer error messages for debugging.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[github-actions]

Devin AI is addressing Cubic AI's review feedback

A Devin session has been created to address the issues identified by Cubic AI.

View Devin Session

[keithwillcode]

DevinAI let's add a safety net of maximum 15 PRs to resolve conflicts on

[devin-ai-integration]

Added a maximum 15 PRs safety net. If more than 15 PRs have conflicts, the workflow will only process the first 15 and log a warning message.

[pedroccastro]

Looks good to me! 🚀