[Bug] Detection step `runs-on` not inherited from `runs-on` or `runs-on-slim`

[petercort]

I have the following frontmatter specification

runs-on: ubuntu-latest-cool
runs-on-slim: ubuntu-latest-cool

I also updated the copilot-setup-steps.yaml to the same

jobs:
  copilot-setup-steps:
    runs-on: ubuntu-latest-cool

And when I run gh aw compile the all the steps reflect that image, except the Detection step

  detection:
    needs:
      - activation
      - agent
    if: >
      always() && needs.agent.result != 'skipped' && (needs.agent.outputs.output_types != '' || needs.agent.outputs.has_patch == 'true')
    runs-on: ubuntu-latest

[pelikhan]

/scout review the docs. I think this is

safe-outputs:
threat-detection:
runs-on: HERE!

if so, add a FAQ entry using the tech-docs-writer agent

[github-actions]

🔭 Recon complete! Scout has charted the territory. Map ready! 🗺️

[github-actions]

🔍 Scout Research Report

Triggered by @pelikhan

Executive Summary

Confirmed: safe-outputs.threat-detection.runs-on is a valid, documented configuration field. The detection job has its own runner configuration that does not automatically inherit from runs-on-slim: — only from the top-level runs-on field.

A FAQ entry has been added to docs/src/content/docs/reference/faq.md explaining this behavior and how to configure the detection job runner explicitly.

Click to expand detailed findings

Research Findings

safe-outputs.threat-detection.runs-on — Field Verification

The field is documented in docs/src/content/docs/reference/threat-detection.md under Configuration Fields:

Field	Type	Description
runs-on	string/array/object	Runner for the detection job (default: inherits from workflow runs-on)

Usage:

safe-outputs:
  create-issue:
  threat-detection:
    runs-on: ubuntu-latest-cool   # set runner for detection job explicitly

Root Cause of the Reported Issue

The compiled workflow shows runs-on: ubuntu-latest for the Detection step because:

• The top-level runs-on-slim: field applies to framework system jobs (activation, safe outputs, conclusion) — not to the threat detection job.
• The detection job inherits from the top-level runs-on field when safe-outputs.threat-detection.runs-on is not set.
• Setting runs-on-slim: ubuntu-latest-cool in the frontmatter does not propagate to the detection job automatically.

FAQ Entry Added

A new entry was added to docs/src/content/docs/reference/faq.md in the Configuration & Setup section:

Why is the Detection step using a different runner than my workflow?

The threat detection job runs as a separate GitHub Actions job with its own runner. By default, it inherits from the workflow-level runs-on field. However, if you customized runner configuration using runs-on-slim: (which applies to framework system jobs such as activation, safe outputs, and conclusion), the Detection step does not automatically pick it up.

Use safe-outputs.threat-detection.runs-on to explicitly set the detection job runner.

Key Sources

• docs/src/content/docs/reference/threat-detection.md — Configuration Fields table with runs-on field documented
• docs/src/content/docs/reference/safe-outputs.md — safe-outputs.runs-on for safe-output jobs; top-level runs-on-slim: for all framework jobs
• docs/src/content/docs/reference/faq.md — FAQ entry added

Suggested Next Steps

1. Compile docs (make build-docs) to verify the FAQ entry renders correctly — build was unavailable in this environment.
2. Consider whether the top-level runs-on-slim: behavior should also propagate to the detection job (separate improvement, tracked by the original issue).

References: §24893544178

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