[Code Quality] Cache PR file-lists and diffs in top-4 review workflows to reduce REST API consumption

[github-actions]

Description

The four top PR-review workflows — Matt Pocock Skills Reviewer, Impeccable Skills Reviewer, PR Code Quality Reviewer, and Test Quality Sentinel — each independently fetch PR diffs and file lists on every run. Together they account for ~54% of daily REST API consumption (~91K of ~170K calls/day). REST API usage has grown +46% in 30 days, driven by this fan-out pattern.

Each PR triggers ~19 independent runs of these workflows, and each run independently re-fetches the same PR diff/file list, leading to massive redundancy.

Suggested Changes

• Identify the specific gh api or MCP calls in each of the four review workflows that fetch PR diffs and file lists
• Introduce a shared cache-memory key (e.g., pr-files-{pr_number}-{head_sha}) that stores the file list and diff summary
• On subsequent runs for the same PR head SHA, read from cache instead of re-fetching
• Fall back to fresh fetch if cache is cold or SHA changed
• Validate that the cached data is sufficient for each workflow's analysis

Files Affected

• .github/workflows/ — Matt Pocock Skills Reviewer workflow
• .github/workflows/ — Impeccable Skills Reviewer workflow
• .github/workflows/ — PR Code Quality Reviewer workflow
• .github/workflows/ — Test Quality Sentinel workflow

Success Criteria

• Same-PR same-SHA repeat runs hit cache for file list/diff instead of making fresh API calls
• Daily REST API consumption for the top-4 workflows decreases by ≥20%
• No degradation in review quality or accuracy
• Cache invalidates correctly when PR head SHA changes

Source

Extracted from DeepReport Intelligence Briefing - 2026-07-24 discussion #47817: "Cache PR file-lists/diffs in the top-4 review workflows — Medium; the named lever against +46%/30d REST growth."
Also corroborated by GitHub API Consumption Report - 2026-07-25 discussion #47983: top three workflows account for ~39% of daily REST API quota.

Priority

Medium — clear ROI lever against ongoing REST API growth trend

🔍 Task mining by Discussion Task Miner - Code Quality Improvement Agent · sonnet46 · 54.2 AIC · ⌖ 8.34 AIC · ⊞ 7.2K · ◷

• expires on Jul 26, 2026, 5:20 PM UTC-08:00