Add branch parameter to assign-to-agent safe output type

[Copilot]

The assign-to-agent safe output type now supports an optional branch parameter to specify the base branch for agent work.

Changes

• TypeScript/JavaScript: Added branch?: string field to AssignToAgentItem interface and MCP tools schema
• Go: Added DefaultBranch field to AssignToAgentConfig for YAML frontmatter configuration
• Handler: Modified assign_to_agent.cjs to:
  • Accept branch from agent output or use default from config
  • Call Copilot REST API directly (POST https://api.github.com/agents/swe/v1/jobs/{owner}/{repo}) with pull_request.base_ref parameter
  • Fall back to standard GraphQL assignment if REST API fails
  • Include branch in summary and staged preview outputs
• Issue Monster workflow: Updated instructions to extract branch from issue body using patterns like "base branch: develop" and pass to agent assignment

Implementation Details

After reviewing the gh CLI source code (pkg/cmd/agent-task/capi/job.go), discovered that agent task creation uses the Copilot REST API endpoint rather than GraphQL. The implementation now makes a direct REST API call, which is more reliable than shelling out to the gh CLI and provides better integration with the existing codebase.

Usage

// Agent can now specify target branch
safeoutputs/assign_to_agent(issue_number=123, agent="copilot", branch="develop")

# Or configure default in frontmatter
safe-outputs:
  assign-to-agent:
    name: copilot
    branch: main  # Default branch for all assignments

When a branch is specified for an issue, the handler calls the Copilot API with the payload:

{
  "problem_statement": "Work on issue #123",
  "event_type": "gh_cli",
  "pull_request": {
    "base_ref": "refs/heads/develop"
  }
}

This ensures the agent task is created with the correct base branch, and PRs are created from the specified branch.

Original prompt

At @copilot, update the assign-to-agent safe-output type to support also assigning a branch. Update the Issue Monster agentic-workflow to mine the base-branch of the fix so that you assign it to the correct branch.

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[pelikhan]

@copilot this function API call must take the branch and apply it in the API call.

[Copilot]

Fixed in 3ec5193. When a branch is specified, the handler now calls gh agent-task create #<issue_number> --base <branch> which properly passes the branch parameter to the agent task creation API. Falls back to standard GraphQL assignment if the CLI command fails.

[pelikhan]

@copilot review the agent-task source to discover how to update the graphql calls

[Copilot]

@copilot review the agent-task source to discover how to update the graphql calls

Reviewed gh CLI source code and discovered the solution in 248e31e. The gh agent-task command uses a REST API (Copilot API), not GraphQL.

The implementation now calls POST https://api.github.com/agents/swe/v1/jobs/{owner}/{repo} with payload:

{
  "pull_request": {
    "base_ref": "refs/heads/{branch}"
  }
}

This matches how gh CLI implements it in pkg/cmd/agent-task/capi/job.go CreateJob() method. Direct REST API call is more reliable than shelling out to gh CLI.