Concurrency Control

GitHub Agentic Workflows uses dual-level concurrency control to prevent resource exhaustion and ensure predictable execution:

• Per-workflow: Limits based on workflow name and trigger context (issue, PR, branch)
• Per-engine: Limits AI execution across all workflows via engine.concurrency

Workflow-level concurrency groups include the workflow name plus context-specific identifiers:

This ensures workflows on different issues, PRs, or branches run concurrently without interference.

The default per-engine pattern gh-aw-{engine-id} ensures only one agent job runs per engine across all workflows, preventing AI resource exhaustion. The group includes only the engine ID and gh-aw- prefix - workflow name, issue/PR numbers, and branches are excluded.

jobs:
  agent:
    concurrency:
      group: "gh-aw-{engine-id}"

Override either level independently:

---
on: push
concurrency:  # Workflow-level
  group: custom-group-${{ github.ref }}
  cancel-in-progress: true
engine:
  id: copilot
  concurrency:  # Engine-level
    group: "gh-aw-copilot-${{ github.workflow }}"
tools:
  github:
    allowed: [list_issues]
---

The safe_outputs job runs independently from the agent job and can process outputs concurrently across workflow runs. Use safe-outputs.concurrency-group to serialize access when needed:

safe-outputs:
  concurrency-group: "safe-outputs-${{ github.repository }}"
  create-issue:

When set, the safe_outputs job uses cancel-in-progress: false — meaning queued runs wait for the in-progress run to finish rather than being cancelled. This is useful for workflows that create issues or pull requests where duplicate operations would be undesirable.

See Safe Outputs for details.

• AI Engines - Engine configuration and capabilities
• Frontmatter - Complete frontmatter reference
• Workflow Structure - Overall workflow organization
• Safe Outputs - Safe output processing and job configuration