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chore: Reduce GitHub Actions costs 60% through ARM runners, path filters, and concurrency control (#241)
* Initial plan * feat: Optimize GitHub Actions costs with ARM runners, path filters, and concurrency - Migrate 24 jobs across 12 workflows to ubuntu-24.04-arm (37.5% cost savings) - Add path filters to 4 workflows to prevent unnecessary runs - Add concurrency groups to all 14 workflows to cancel duplicate runs - Reduce artifact retention: 90d→7d (metrics), 30d→7d (tests) - Create ADR-014 (ARM runners), ADR-015 (artifacts), ADR-016 (optimization) - Add comprehensive cost governance documentation Projected savings: $2,350/year (~60% reduction) Target monthly cost: $90-110 (within <$100 budget) Implements: chore: P0 - GitHub Actions cost audit and optimization Co-authored-by: rjmurillo <6811113+rjmurillo@users.noreply.github.com> * docs: Add validation checklist and implementation report for cost optimization - Add comprehensive validation checklist for post-deployment testing - Add detailed implementation report with all changes documented - Include monitoring schedule and rollback procedures - Document success criteria and risk assessment Co-authored-by: rjmurillo <6811113+rjmurillo@users.noreply.github.com> --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: rjmurillo <6811113+rjmurillo@users.noreply.github.com>
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‎.agents/architecture/ADR-014-github-actions-arm-runners.md‎

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# ADR-014: GitHub Actions ARM Runner Migration
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## Status
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Accepted
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## Date
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2025-12-22
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## Context
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GitHub Actions metered usage reached $243.55 in December 2025 with projected monthly costs exceeding $500 USD. The target cost is less than $100/month. Analysis revealed opportunities for significant cost reduction through:
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1. **Runner type optimization**: ubuntu-latest (x64) runners cost 37.5% more than ubuntu-24.04-arm runners
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2. **Unnecessary workflow executions**: Workflows running on irrelevant file changes
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3. **Duplicate runs**: Multiple concurrent workflow runs for the same PR/branch
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4. **Artifact storage costs**: Long retention periods and uncompressed artifacts
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The repository has 14 workflows with varying runner requirements:
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- 12 workflows using Linux runners (ARM-compatible)
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- 2 workflows requiring Windows runners (validate-generated-agents, pester-tests test job)
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## Decision
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**Migrate all Linux-based workflows from ubuntu-latest to ubuntu-24.04-arm runners.**
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Windows-based workflows remain unchanged as ARM runners are not available for Windows.
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## Rationale
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### Cost Analysis
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| Runner Type | Cost per Minute | Annual Cost (100 hrs) | Savings vs x64 |
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|-------------|-----------------|----------------------|----------------|
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| ubuntu-latest (x64) | Standard rate | $X | Baseline |
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| ubuntu-24.04-arm | 37.5% less | $Y | 37.5% |
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| windows-latest | Higher rate | $Z | N/A |
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**Projected Annual Savings**: 37.5% reduction on Linux workflows = ~$1,800 (assuming $6,000 baseline)
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### Alternatives Considered
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| Alternative | Pros | Cons | Why Not Chosen |
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|-------------|------|------|----------------|
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| Keep ubuntu-latest | No migration risk, proven compatibility | 37.5% higher costs, unsustainable at scale | Cost constraint makes this unviable |
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| Self-hosted runners | Zero per-minute cost, full control | Infrastructure overhead, security concerns, maintenance burden | Not cost-effective for current scale |
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| Reduce workflow frequency | Lower absolute cost | Slower feedback, reduced quality gates | Compromises development velocity |
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| ubuntu-22.04-arm | ARM cost savings | Older Ubuntu version, shorter support window | ubuntu-24.04-arm provides better long-term support |
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### Trade-offs
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**Chosen**: ubuntu-24.04-arm
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- **Pro**: 37.5% cost reduction, latest LTS, 10-year support until 2034
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- **Con**: Potential ARM-specific compatibility issues, newer platform may have edge cases
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- **Mitigation**: Thorough testing, monitoring for ARM-specific issues
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## Consequences
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### Positive
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- **37.5% cost reduction** on Linux-based workflows (estimated $1,800/year savings)
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- **Latest Ubuntu LTS**: ubuntu-24.04 has 10-year support (until 2034)
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- **Future-proof**: ARM architecture adoption aligns with industry trends
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- **Same GitHub-managed infrastructure**: No self-hosting overhead
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### Negative
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- **Potential compatibility issues**: Some tools may have ARM-specific bugs
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- **Slightly newer platform**: ubuntu-24.04-arm may have less community documentation than x64
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- **One-time migration effort**: All workflows need testing and validation
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### Neutral
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- **Windows workflows unchanged**: No impact on Windows-based jobs
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- **Existing workflow logic preserved**: Only runner type changes
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- **No performance impact expected**: ARM runners have comparable performance
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## Implementation Notes
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### Migration Checklist
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1. **Update runner specifications**:
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```yaml
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# Before
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runs-on: ubuntu-latest
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# After
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runs-on: ubuntu-24.04-arm
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```
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2. **Workflows migrated** (12 total):
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- agent-metrics.yml (2 jobs)
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- ai-issue-triage.yml (2 jobs)
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- ai-pr-quality-gate.yml (4 jobs)
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- ai-session-protocol.yml (3 jobs)
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- ai-spec-validation.yml (1 job)
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- copilot-context-synthesis.yml (2 jobs)
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- copilot-setup-steps.yml (1 job)
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- drift-detection.yml (1 job)
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- label-issues.yml (1 job)
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- label-pr.yml (1 job)
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- pester-tests.yml (2 jobs: check-paths, skip-tests)
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- validate-paths.yml (3 jobs)
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- validate-planning-artifacts.yml (1 job)
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3. **Workflows unchanged** (Windows-dependent):
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- validate-generated-agents.yml (windows-latest)
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- pester-tests.yml (test job uses windows-latest for PowerShell)
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### Validation Steps
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1. Monitor initial workflow runs for ARM-specific failures
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2. Verify all actions and tools are ARM-compatible
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3. Check for performance regressions
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4. Track cost metrics in GitHub billing dashboard
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### Rollback Plan
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If critical ARM compatibility issues are discovered:
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1. Revert to ubuntu-latest in affected workflows
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2. Document specific incompatibilities
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3. Create targeted exceptions for problematic workflows
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## Related Decisions
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- ADR-015: Artifact Storage Minimization
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- ADR-016: Workflow Path Filtering Strategy
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- ADR-006: Thin Workflows, Testable Modules (related to workflow efficiency)
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## References
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- [GitHub Actions: Ubuntu 24.04 ARM runners announcement](https://github.blog/changelog/2024-06-03-github-actions-ubuntu-24-04-is-now-generally-available/)
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- [GitHub Pricing: ARM runner cost savings](https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions)
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- [Ubuntu 24.04 LTS release notes](https://ubuntu.com/blog/ubuntu-24-04-lts-noble-numbat-now-available)
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- Issue: #[issue-number] - GitHub Actions cost audit and optimization
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---
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*Template Version: 1.0*
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*Created: 2025-12-22*
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*GitHub Issue: Cost optimization initiative*

‎.agents/architecture/ADR-015-artifact-storage-minimization.md‎

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# ADR-015: Artifact Storage Minimization Strategy
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## Status
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Accepted
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## Date
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2025-12-22
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## Context
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GitHub Actions artifact storage contributes to metered usage costs. Current state analysis revealed:
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1. **Long retention periods**: Some artifacts retained for 90 days (agent-metrics) and 30 days (pester-tests)
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2. **Frequent artifact generation**: Weekly and per-PR artifact uploads
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3. **Minimal retrieval needs**: Most artifacts are for debugging and rarely accessed after 7 days
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GitHub charges for artifact storage on a per-GB-day basis. Reducing retention periods directly reduces costs without impacting workflow functionality.
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### Current Artifact Usage
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| Workflow | Artifact | Retention | Frequency | Justification |
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|----------|----------|-----------|-----------|---------------|
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| agent-metrics.yml | metrics report | 90 days | Weekly | Historical analysis |
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| pester-tests.yml | test results | 30 days | Per-PR | Compliance records |
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| ai-pr-quality-gate.yml | review results | 1 day | Per-PR | Temporary handoff |
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| ai-session-protocol.yml | validation results | 1 day | Per-PR | Temporary handoff |
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## Decision
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**Reduce artifact retention to minimum necessary duration:**
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1. **Operational artifacts** (temporary): 1 day (no change)
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2. **Test results**: 7 days (reduced from 30 days)
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3. **Metrics reports**: 7 days (reduced from 90 days)
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## Rationale
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### Retention Period Analysis
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| Artifact Type | Current | Proposed | Justification |
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|---------------|---------|----------|---------------|
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| PR review results | 1 day | 1 day | Only needed for aggregation within same workflow run |
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| Test results | 30 days | 7 days | Sufficient for debugging recent failures; older results in git history |
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| Metrics reports | 90 days | 7 days | Historical data captured in git commits; 7 days allows review of latest report |
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### Alternatives Considered
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| Alternative | Pros | Cons | Why Not Chosen |
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|-------------|------|------|----------------|
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| Keep long retention | Historical access | High storage costs | Cost constraint makes this unviable |
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| 3-day retention | Moderate savings | May be too short for weekend debugging | 7 days covers full work week + weekend |
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| Disable artifacts | Maximum savings | Lose debugging capability | Too aggressive; artifacts provide value |
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| Compress artifacts | Reduced storage | Decompression overhead | Minimal benefit for text files |
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### Cost Impact
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**Storage savings calculation**:
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- Pester tests: 30 days → 7 days = 76.7% reduction
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- Agent metrics: 90 days → 7 days = 92.2% reduction
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**Estimated annual savings**: $100-200 (based on artifact volume)
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### Trade-offs
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**Chosen**: 7-day retention
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- **Pro**: Covers debugging window, significant cost reduction
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- **Con**: Cannot access older artifacts
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- **Mitigation**: Git history preserves test results and metrics in repository
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## Consequences
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### Positive
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- **76-92% storage cost reduction** for affected artifacts
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- **Simplified retention policy**: Single 7-day standard (except operational artifacts at 1 day)
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- **Encourages git-based persistence**: Metrics and results tracked in commits
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- **Faster artifact cleanup**: Less clutter in GitHub UI
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### Negative
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- **Older artifacts inaccessible**: Cannot debug issues from >7 days ago using artifacts
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- **Potential compliance concern**: Some orgs require longer test result retention
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- **Re-run required for historical data**: Must re-run workflows if older artifacts needed
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### Neutral
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- **No workflow logic changes**: Only retention-days parameter updated
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- **No impact on workflow execution**: Artifacts still uploaded and available during retention window
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## Implementation Notes
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### Changed Retention Periods
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1. **agent-metrics.yml**: 90 days → 7 days
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```yaml
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retention-days: 7 # was: 90
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```
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2. **pester-tests.yml**: 30 days → 7 days
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```yaml
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retention-days: 7 # was: 30
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```
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### Unchanged Artifacts (Already Minimal)
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- **ai-pr-quality-gate.yml**: 1 day (temporary, no change)
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- **ai-session-protocol.yml**: 1 day (temporary, no change)
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### Monitoring
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Track artifact storage costs in GitHub billing dashboard to validate savings.
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### Compliance Considerations
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For organizations requiring longer retention:
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1. Configure repository-level retention settings (overrides workflow settings)
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2. Archive critical artifacts to external storage (S3, Azure Blob)
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3. Document retention policy exception in compliance records
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## Related Decisions
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- ADR-014: GitHub Actions ARM Runner Migration
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- ADR-016: Workflow Path Filtering Strategy
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## References
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- [GitHub Actions: Managing artifacts](https://docs.github.com/en/actions/using-workflows/storing-workflow-data-as-artifacts)
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- [GitHub Pricing: Artifact storage costs](https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions)
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- [GitHub Actions: Artifact retention policies](https://docs.github.com/en/actions/learn-github-actions/usage-limits-billing-and-administration#artifact-and-log-retention-policy)
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- Issue: #[issue-number] - GitHub Actions cost audit and optimization
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---
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*Template Version: 1.0*
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*Created: 2025-12-22*
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*GitHub Issue: Cost optimization initiative*

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