[plan] Create "design-decision-gate" agentic workflow

[github-actions]

Context

From the Scout analysis of issue #25311, this workflow addresses Problem 3: Procrastination on Key Design Decisions.

"AI made me procrastinate on key design decisions. Because refactoring was cheap, I could always say 'I'll deal with this later.' [...] Deferring decisions corroded my ability to think clearly."

AI lowers the perceived cost of deferring decisions. Without a structured gate that forces design decisions before implementation, the codebase drifts into incoherence. The Scout identified this as the highest-leverage workflow.

Objective

Create a new gh-aw agentic workflow called design-decision-gate that enforces Architecture Decision Records (ADRs) before implementation work can merge.

Workflow Prompt

Create an agentic GitHub Actions workflow called "design-decision-gate" that
enforces design decisions before implementation work begins.

The workflow must:
1. Detect when a PR is labeled "implementation" or contains >100 lines of new code
   in core business logic directories (configurable via .design-gate.yml)
2. Check if the PR body or linked issue contains a structured "Design Decision Record"
   (ADR) with sections: Context, Decision, Alternatives Considered, Consequences
3. If no ADR is linked:
   a. Use an AI agent to analyze the PR diff and generate a DRAFT ADR based on
      what design decisions the code appears to be making
   b. Post a comment saying: "This PR appears to make design decisions without
      a recorded rationale. A draft ADR has been generated — please review,
      complete, and commit it to /docs/adr/ before this PR can merge."
   c. Set the PR check to "pending" until an ADR file is linked in the PR body
4. If an ADR exists, use an AI agent to verify the implementation matches the
   stated decision and flag any divergences
5. Store all ADRs as numbered Markdown files in /docs/adr/ for searchable history

This workflow should enforce a culture of "decide explicitly before you build."
The ADR format should follow the Michael Nygard template.

Files to Create

• .github/workflows/design-decision-gate.md — the workflow markdown file

Acceptance Criteria

• Workflow triggers on PRs labeled implementation or with >100 lines of new business logic
• Detects missing ADR and generates a draft using AI analysis of the PR diff
• Posts actionable comment guiding the author to complete and commit the ADR
• Blocks merge until ADR is linked in the PR body
• Verifies implementation matches existing ADR when one is present
• Configurable business logic paths via .design-gate.yml
• Compiled .lock.yml generated via make recompile
  Related to Blog analysis #25311

Generated by Plan Command for issue #25311 · ● 394.6K · ◷

• expires on Apr 10, 2026, 1:57 PM UTC

[github-actions]

🍪 Issue Monster has assigned this to Copilot!

I've identified this issue as a good candidate for automated resolution and assigned it to the Copilot coding agent.

The Copilot coding agent will analyze the issue and create a pull request with the fix.

Om nom nom! 🍪

🍪 Om nom nom by Issue Monster · ● 245.6K · ◷

[pelikhan]

@copilot label command or on ready for review